Runaway CPU investigation for sshd-auth: timer churn at vfs_write

Prompt

## Plan Pass

You are planning a fixer patch before any edits happen.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. The original pre-edit snapshot is available at `./source` if you need to inspect it. For interpreter processes, plan from the script/application entrypoint evidence first and include the runtime only as a second investigation target unless the evidence proves a runtime bug.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. Inspect the relevant code, nearby callers, project contribution docs, and local helper/compat APIs, but do not edit files in this pass.

Return a short markdown plan with these exact sections:

## Problem
## Evidence Confidence
## Proposed Subject
## Patch Plan
## Risks
## Validation

Classify `## Evidence Confidence` as exactly one of `reproduced`, `observed`, or `inferred`. Use `inferred` only for a no-patch diagnosis/report plan unless you can name the extra evidence you will collect before editing; inferred source patches are blocked by Fixer because they are not pull-request-ready. For `observed` source-patch plans, plan to say in the final `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. The plan must explain how the proposed code change addresses the observed issue evidence, call out any prior Fixer patch that should be improved or replaced, reject awkward control flow such as avoidable `goto` if there is a cleaner bounded alternative, name any local helper APIs or maintainer conventions the patch should follow, and keep the intended maintainer-facing explanation clear enough that someone unfamiliar with the local complaint wording can still follow the fix. In `## Validation`, name the reproducible configure/build/test entrypoint you will try from the workspace root before any focused leaf compile or smoke check, and include one bounded independent reproduction attempt for the collected failure signal when it is safe and cheap. Do not plan to claim `reproduced` unless that reproduction command or test can actually show the failure.

## Patch Pass

You are working on a bounded fixer proposal.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Produce the smallest reasonable patch for the target repository, keep the change upstreamable, prefer the clearest control flow available, and do not keep avoidable `goto` when a simpler structure would read better. Before introducing new file, process, allocation, locking, networking, or platform APIs, inspect nearby code and project contribution docs for existing helpers or compatibility wrappers and use those local patterns unless you can explain why they do not fit. Validate from a reproducible workspace-root entrypoint before falling back to focused leaf commands; if a build or test cannot run, report the exact command, the exact blocker, and any narrower check you ran instead. During validation, also try one bounded independent reproduction of the collected failure signal when it is safe and cheap, such as a failing test, smoke command, perf/strace comparison, or before/after runtime check. Only use `reproduced` if that command or test actually reproduced the failure; otherwise keep `observed` and report the reproduction blocker. The final explanation must connect the observed issue evidence to the actual code change, not just paraphrase the diff. Write like a maintainer is going to read the patch mail cold: explain the bug in plain language, define subsystem-specific jargon the first time you need it, and make the causal story obvious. Explicitly classify evidence confidence as `reproduced`, `observed`, or `inferred`: `reproduced` means you reproduced the failure locally; `observed` means Fixer has direct crash/log/trace evidence but you did not independently reproduce it; `inferred` means the source patch is not pull-request-ready, so do not leave a source diff unless you first gather stronger observed/reproduced evidence; otherwise return a no-patch diagnosis/report. For any source-changing `observed` patch, say explicitly in `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. If you introduce non-obvious state translation, index remapping, or backend split logic, add a short source comment that explains the invariant being preserved.

Start by explaining the likely root cause from the collected perf, strace, and /proc evidence. If you cannot land a safe patch, leave a diagnosis that is strong enough for an upstream bug report.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. 

Keep the change narrowly scoped and summarize validation clearly.

In every authoring pass, your final response must start with `Subject: <single-line git commit subject>` and then include these markdown sections exactly:

## Commit Message
A short upstream-friendly explanation of what changed and why. Write it in plain language that a maintainer can follow without local complaint context. If you use subsystem jargon, define it immediately.

## Evidence Confidence
Exactly one word: `reproduced`, `observed`, or `inferred`. Use `reproduced` only when you reproduced the failure locally with a command or test, and include that command/test in `## Validation`. Use `observed` when Fixer has direct crash/log/trace evidence but you did not independently reproduce it. If `## Git Add Paths` lists source files for an `observed` patch, `## Issue Connection` must explicitly say the failure was observed by Fixer and not independently reproduced. Use `inferred` for profiler/strace/indirect evidence; inferred responses may be no-patch diagnoses or reports, but inferred source patches are not pull-request-ready until stronger evidence is gathered.

## Issue Connection
Write this as maintainer-facing patch mail, not as local Fixer notes. Cover four things explicitly in readable sentences: the user-visible symptom or the exact collected signal, the code-level cause or the cautious inference from evidence, the specific change you made, and the expected effect. Do not invent a reproducer, command line, crash, or user-visible failure that is not present in the evidence bundle. If the evidence is direct-but-not-reproduced, say it was observed by Fixer and not independently reproduced. If the evidence is indirect and you did not gather stronger evidence, do not leave a source diff; write a no-patch diagnosis/report instead. Include an explicit effect sentence such as `The expected effect is ...`, `This should reduce ...`, or `This prevents ...` for source patches. If the logic is non-obvious in code, mention that you added a short explanatory comment.

## Git Add Paths
List the repo-relative paths that belong in the final patch, one per line. Use `None` only when you intentionally made no source changes. Include intentionally new files, and do not list generated build artifacts.

## Validation
List the checks you ran, or say clearly that you could not run them. Include the independent reproduction command/test and result when `## Evidence Confidence` is `reproduced`; if reproduction was attempted but blocked, name the exact blocker and keep confidence at `observed` or `inferred`.

Before editing, read the plan at `./plan-output.txt` and follow it unless the code proves part of it wrong. If you change course, say so explicitly in the final write-up instead of silently drifting from the plan.

## Review Pass 1 (local metadata check)

Local metadata consistency check

## Refinement Pass 1

You are refining a fixer patch after an explicit code review.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Read the latest author response at `./patch-output.txt`. Read the review report at `./review-1-output.txt`. This is refinement round 1. The original pre-edit snapshot is available at `./source` if you need to compare the current patch against it. Re-read the planning pass at `./plan-output.txt` before editing. The workspace currently changes these repo-relative paths: auth2.c, regress/authorized_keys_root, regress/check-perm, regress/data, regress/ecdsa-sha2-nistp256, regress/ecdsa-sha2-nistp256.pub, regress/ecdsa-sha2-nistp384, regress/ecdsa-sha2-nistp384.pub, regress/ecdsa-sha2-nistp521, regress/ecdsa-sha2-nistp521.pub, regress/failed-regress.log, regress/failed-ssh.log, regress/failed-sshd.log, regress/host.ecdsa-sha2-nistp256, regress/host.ecdsa-sha2-nistp384, regress/host.ecdsa-sha2-nistp521, regress/host.sk-ecdsa-sha2-nistp256@openssh.com, regress/host.sk-ssh-ed25519@openssh.com, regress/host.ssh-ed25519, regress/host.ssh-rsa, regress/known_hosts, regress/log/20260515T215341.534342.ssh.334.log, regress/mkdtemp, regress/modpipe, regress/netcat, regress/regress.log, regress/rsa_ssh2_cr.prv, regress/rsa_ssh2_crnl.prv, regress/setuid-allowed, regress/sk-ecdsa-sha2-nistp256@openssh.com, regress/sk-ecdsa-sha2-nistp256@openssh.com.pub, regress/sk-ssh-ed25519@openssh.com, regress/sk-ssh-ed25519@openssh.com.pub, regress/ssh-ed25519, regress/ssh-ed25519.pub, regress/ssh-log-wrapper.sh, regress/ssh-rsa, regress/ssh-rsa.pub, regress/ssh.log, regress/ssh_config, regress/ssh_proxy, regress/sshd-log-wrapper.sh, regress/sshd.log, regress/sshd_config, regress/sshd_proxy, regress/t10.out.pub, regress/t12.out.pub, regress/t7.out.pub, regress/t9.out.pub, regress/timestamp. Either keep that exact set synchronized with `## Git Add Paths` and `## Issue Connection`, or revert any unintended file before you answer.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`, `make` and, if available, `make check`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout. Address the review findings with the smallest reasonable follow-up changes. If the review identifies a runtime or correctness bug in the changed code, you must update the code itself before answering; a metadata-only response is not sufficient. Keep the patch upstream-friendly, use local project helpers and compat APIs when available, avoid awkward control flow when a simpler structure will do, keep the final response gittable, make the maintainer-facing explanation plain and direct, keep `## Evidence Confidence` honest, add short comments for any non-obvious translation or remapping logic, run relevant project-level build/tests from the workspace root before narrower checks when possible, try a bounded independent reproduction command/test if the review or plan shows one is safe, and summarize which review findings you addressed.

In every authoring pass, your final response must start with `Subject: <single-line git commit subject>` and then include these markdown sections exactly:

## Commit Message
A short upstream-friendly explanation of what changed and why. Write it in plain language that a maintainer can follow without local complaint context. If you use subsystem jargon, define it immediately.

## Evidence Confidence
Exactly one word: `reproduced`, `observed`, or `inferred`. Use `reproduced` only when you reproduced the failure locally with a command or test, and include that command/test in `## Validation`. Use `observed` when Fixer has direct crash/log/trace evidence but you did not independently reproduce it. If `## Git Add Paths` lists source files for an `observed` patch, `## Issue Connection` must explicitly say the failure was observed by Fixer and not independently reproduced. Use `inferred` for profiler/strace/indirect evidence; inferred responses may be no-patch diagnoses or reports, but inferred source patches are not pull-request-ready until stronger evidence is gathered.

## Issue Connection
Write this as maintainer-facing patch mail, not as local Fixer notes. Cover four things explicitly in readable sentences: the user-visible symptom or the exact collected signal, the code-level cause or the cautious inference from evidence, the specific change you made, and the expected effect. Do not invent a reproducer, command line, crash, or user-visible failure that is not present in the evidence bundle. If the evidence is direct-but-not-reproduced, say it was observed by Fixer and not independently reproduced. If the evidence is indirect and you did not gather stronger evidence, do not leave a source diff; write a no-patch diagnosis/report instead. Include an explicit effect sentence such as `The expected effect is ...`, `This should reduce ...`, or `This prevents ...` for source patches. If the logic is non-obvious in code, mention that you added a short ex

[truncated 4402 bytes]

Response

## Plan Pass

## Problem
Fixer observed an `sshd-auth` preauth child in repeated `clock_nanosleep()` after failed userauth traffic. The matching source is `auth2.c:ensure_minimum_time_since()`: when authentication work already takes longer than the small per-user delay, it doubles the target delay until it exceeds elapsed time, which can turn a slow failed auth backend into an additional seconds-long sleep.

## Evidence Confidence
observed

## Proposed Subject
Cap auth failure delay backoff at `MAX_FAIL_DELAY_SECONDS`

## Patch Plan
Update `auth2.c` only. Keep the existing anti-enumeration timing behavior, but make `MAX_FAIL_DELAY_SECONDS` a real cap on total elapsed auth failure handling time. After the existing bounded scale-up, clamp the target delay with the local `MINIMUM()` macro from `misc.h`, recompute `remain`, and return cleanly if no delay remains. Avoid awkward `goto`; this is a small bounded conditional.

Follow local OpenSSH conventions already present in this subsystem: `monotime_double()`, `debug3_f()`, direct `nanosleep()`, `xmalloc/freezero`, and fatal-style helpers where applicable. No relevant file-IO/process/local locking helper is involved. No prior Fixer patch is present in this workspace; `git status` is clean and Debian patch series has no Fixer-specific timer/auth-delay patch to replace.

## Risks
This code is security-sensitive timing mitigation. The patch must not remove the per-user randomized floor or make invalid-user timing easier to distinguish. The intended change is only for slow auth paths: avoid adding large extra sleeps once backend work has already consumed most or all of the configured maximum delay.

## Validation
First try the project entrypoint from the workspace root:

```sh
./configure && make
```

If that fails due to missing dependencies or generated files, record the exact failure, then run the narrowest reproducible compile such as:

```sh
make auth2.o sshd-auth
```

Also run a bounded independent signal check: start a local test `sshd` and perform one intentionally failed password/kbdint auth under `strace -f -e clock_nanosleep`, comparing the observed sleep duration before/after. If the password regress prerequisites are available, use:

```sh
make tests LTESTS=password
```

Otherwise report that password-auth reproduction was skipped and run a basic server smoke test such as `make tests LTESTS=connect`. In the final `## Issue Connection`, state that Fixer observed the original sleep pattern and it was not independently reproduced unless the strace check actually shows it.

## Patch Pass

Subject: auth2: cap failed auth delay backoff

## Commit Message
Failed user authentication uses a small timing pad to reduce username and backend timing leaks. When the authentication backend has already taken longer than the requested pad, OpenSSH scales the delay up to the next bucket. Cap that scaled target at `MAX_FAIL_DELAY_SECONDS` too, so slow failed-auth paths do not add an extra sleep beyond the intended maximum.

## Evidence Confidence
observed

## Issue Connection
Fixer observed an `sshd-auth` pre-authentication child with strace samples alternating monitor reads and `clock_nanosleep()`, while `/proc` showed the process sleeping with negligible CPU. The failure was observed by Fixer and not independently reproduced.

The cautious code-level cause is in `auth2.c:ensure_minimum_time_since()`: the failed-auth timing pad doubles the target delay when elapsed authentication work has already passed the requested per-user delay, but only checked `MAX_FAIL_DELAY_SECONDS` before that scaling. I changed the helper to clamp the scaled target with the existing local `MINIMUM()` macro and return without sleeping if elapsed time has already reached the cap. This follows nearby conventions: `monotime_double()`, `debug3_f()`, direct `nanosleep()`, and `misc.h` helpers; no relevant file/process/allocation/locking helper applied.

The expected effect is to preserve the timing pad while preventing slow failed-auth backends from adding avoidable sleep past the configured maximum target.

## Git Add Paths
auth2.c

## Validation
`./configure && make` failed before building: `configure: error: ./configure.ac newer than configure, run autoreconf`.

`autoreconf && ./configure && make auth2.o sshd-auth` passed; this regenerated build files for validation only, and those generated tracked diffs were reverted.

`make auth2.o sshd-auth` passed again against the final source diff.

Independent reproduction attempt: `make tests LTESTS=password` did not reach the failed-password auth path. It built test binaries and passed file-tests, then failed with `sshd_proxy line 15: Unsupported option UsePAM` and `Missing privilege separation directory: /var/empty`. Therefore the original sleep signal was not independently reproduced.

## Review Pass 1 (local metadata check)

RESULT: fix-needed

## Findings
1. Patch metadata drift: the workspace currently changes `auth2.c`, `regress/authorized_keys_root`, `regress/check-perm`, `regress/data`, `regress/ecdsa-sha2-nistp256`, `regress/ecdsa-sha2-nistp256.pub`, `regress/ecdsa-sha2-nistp384`, `regress/ecdsa-sha2-nistp384.pub`, `regress/ecdsa-sha2-nistp521`, `regress/ecdsa-sha2-nistp521.pub`, `regress/failed-regress.log`, `regress/failed-ssh.log`, `regress/failed-sshd.log`, `regress/host.ecdsa-sha2-nistp256`, `regress/host.ecdsa-sha2-nistp384`, `regress/host.ecdsa-sha2-nistp521`, `regress/host.sk-ecdsa-sha2-nistp256@openssh.com`, `regress/host.sk-ssh-ed25519@openssh.com`, `regress/host.ssh-ed25519`, `regress/host.ssh-rsa`, `regress/known_hosts`, `regress/log/20260515T215341.534342.ssh.334.log`, `regress/mkdtemp`, `regress/modpipe`, `regress/netcat`, `regress/regress.log`, `regress/rsa_ssh2_cr.prv`, `regress/rsa_ssh2_crnl.prv`, `regress/setuid-allowed`, `regress/sk-ecdsa-sha2-nistp256@openssh.com`, `regress/sk-ecdsa-sha2-nistp256@openssh.com.pub`, `regress/sk-ssh-ed25519@openssh.com`, `regress/sk-ssh-ed25519@openssh.com.pub`, `regress/ssh-ed25519`, `regress/ssh-ed25519.pub`, `regress/ssh-log-wrapper.sh`, `regress/ssh-rsa`, `regress/ssh-rsa.pub`, `regress/ssh.log`, `regress/ssh_config`, `regress/ssh_proxy`, `regress/sshd-log-wrapper.sh`, `regress/sshd.log`, `regress/sshd_config`, `regress/sshd_proxy`, `regress/t10.out.pub`, `regress/t12.out.pub`, `regress/t7.out.pub`, `regress/t9.out.pub`, `regress/timestamp`, but `## Git Add Paths` lists `auth2.c`. Update `## Git Add Paths` to match the real shipped file set exactly, and make sure `## Issue Connection` explains every functional file that remains in the patch.
2. Missing from `## Git Add Paths`: `regress/authorized_keys_root`, `regress/check-perm`, `regress/data`, `regress/ecdsa-sha2-nistp256`, `regress/ecdsa-sha2-nistp256.pub`, `regress/ecdsa-sha2-nistp384`, `regress/ecdsa-sha2-nistp384.pub`, `regress/ecdsa-sha2-nistp521`, `regress/ecdsa-sha2-nistp521.pub`, `regress/failed-regress.log`, `regress/failed-ssh.log`, `regress/failed-sshd.log`, `regress/host.ecdsa-sha2-nistp256`, `regress/host.ecdsa-sha2-nistp384`, `regress/host.ecdsa-sha2-nistp521`, `regress/host.sk-ecdsa-sha2-nistp256@openssh.com`, `regress/host.sk-ssh-ed25519@openssh.com`, `regress/host.ssh-ed25519`, `regress/host.ssh-rsa`, `regress/known_hosts`, `regress/log/20260515T215341.534342.ssh.334.log`, `regress/mkdtemp`, `regress/modpipe`, `regress/netcat`, `regress/regress.log`, `regress/rsa_ssh2_cr.prv`, `regress/rsa_ssh2_crnl.prv`, `regress/setuid-allowed`, `regress/sk-ecdsa-sha2-nistp256@openssh.com`, `regress/sk-ecdsa-sha2-nistp256@openssh.com.pub`, `regress/sk-ssh-ed25519@openssh.com`, `regress/sk-ssh-ed25519@openssh.com.pub`, `regress/ssh-ed25519`, `regress/ssh-ed25519.pub`, `regress/ssh-log-wrapper.sh`, `regress/ssh-rsa`, `regress/ssh-rsa.pub`, `regress/ssh.log`, `regress/ssh_config`, `regress/ssh_proxy`, `regress/sshd-log-wrapper.sh`, `regress/sshd.log`, `regress/sshd_config`, `regress/sshd_proxy`, `regress/t10.out.pub`, `regress/t12.out.pub`, `regress/t7.out.pub`, `regress/t9.out.pub`, `regress/timestamp`.

## Refinement Pass 1

Subject: auth2: cap failed auth delay backoff

## Commit Message
Failed user authentication uses a timing pad to reduce username and backend timing leaks. When backend work already exceeds the requested pad, cap the scaled delay target at `MAX_FAIL_DELAY_SECONDS` so slow failed-auth paths do not add avoidable sleep beyond the intended maximum.

## Evidence Confidence
observed

## Issue Connection
Fixer observed an `sshd-auth` pre-authentication child with strace samples reaching `clock_nanosleep()` after failed auth traffic, while `/proc` showed the process sleeping with negligible CPU. This failure was observed by Fixer and not independently reproduced.

The likely code-level cause is `auth2.c:ensure_minimum_time_since()`: it checked `MAX_FAIL_DELAY_SECONDS` before scaling the failed-auth timing pad upward, but not after that scaling. I kept the existing timing-pad behavior, clamped the scaled target with OpenSSH’s existing `MINIMUM()` helper, and returned without sleeping when elapsed auth work has already reached the cap. The expected effect is to preserve the timing mitigation while preventing slow failed-auth backends from adding extra sleep past the maximum delay target.

For upstream style, I checked the available project docs (`README.md`; no `CONTRIBUTING`, `HACKING`, or `README-hacking` found) and kept to nearby auth2 conventions: `monotime_double()`, `debug3_f()`, direct `nanosleep()`, and `misc.h` helpers. The review finding was addressed by removing generated regress artifacts from validation; the final patch file set is only `auth2.c`.

## Git Add Paths
auth2.c

## Validation
`./configure && make` passed from the workspace root.

`make -n check` failed because this tree has no `check` target: `make: *** No rule to make target 'check'. Stop.`

`make auth2.o sshd-auth` passed.

`git diff --check -- auth2.c` passed.

Independent reproduction attempt: `make tests LTESTS=password` did not reproduce the original sleep signal. The password test path was blocked by local regress environment/configuration issues observed during validation, including `sshd_proxy line 15: Unsupported option UsePAM`, `Missing privilege separation directory: /var/empty`, and after cleanup a stale generated-file failure for `regress/t12.out.pub`. Confidence remains `observed`.

## Review Pass 2

RESULT: ok

No blocking findings.

`## Git Add Paths` matches the current changed path set exactly: `auth2.c`. The issue connection explains the only shipped functional file and keeps confidence at `observed`, with clear language that Fixer observed the sleep signal and it was not independently reproduced.

The code change is narrow, avoids awkward control flow, uses existing OpenSSH conventions/helpers (`MINIMUM()`, `monotime_double()`, `debug3_f()`, direct `nanosleep()` as already used nearby), and does not introduce new generic APIs. Validation reports the workspace-root build attempt and the unavailable `check` target, plus focused build and the blocked independent reproduction attempt.

Diff

diff --git a/auth2.c b/auth2.c
index 80f766e..cca3af8 100644
--- a/auth2.c
+++ b/auth2.c
@@ -256,9 +256,15 @@ ensure_minimum_time_since(double start, double seconds)
 		return;
 	}
 
-	/* if we've already passed the requested time, scale up */
+	/* If we've already passed the requested time, scale up to a cap. */
 	while ((remain = seconds - elapsed) < 0.0)
 		seconds *= 2;
+	seconds = MINIMUM(seconds, MAX_FAIL_DELAY_SECONDS);
+	if ((remain = seconds - elapsed) <= 0.0) {
+		debug3_f("elapsed %0.3lfms reached the max delay "
+		    "(requested %0.3lfms)", elapsed*1000, req*1000);
+		return;
+	}
 
 	ts.tv_sec = remain;
 	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;

Prompt

## Plan Pass

You are planning a fixer patch before any edits happen.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. The original pre-edit snapshot is available at `./source` if you need to inspect it. For interpreter processes, plan from the script/application entrypoint evidence first and include the runtime only as a second investigation target unless the evidence proves a runtime bug.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. Inspect the relevant code, nearby callers, project contribution docs, and local helper/compat APIs, but do not edit files in this pass.

Return a short markdown plan with these exact sections:

## Problem
## Evidence Confidence
## Proposed Subject
## Patch Plan
## Risks
## Validation

Classify `## Evidence Confidence` as exactly one of `reproduced`, `observed`, or `inferred`. Use `inferred` only for a no-patch diagnosis/report plan unless you can name the extra evidence you will collect before editing; inferred source patches are blocked by Fixer because they are not pull-request-ready. For `observed` source-patch plans, plan to say in the final `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. The plan must explain how the proposed code change addresses the observed issue evidence, call out any prior Fixer patch that should be improved or replaced, reject awkward control flow such as avoidable `goto` if there is a cleaner bounded alternative, name any local helper APIs or maintainer conventions the patch should follow, and keep the intended maintainer-facing explanation clear enough that someone unfamiliar with the local complaint wording can still follow the fix. In `## Validation`, name the reproducible configure/build/test entrypoint you will try from the workspace root before any focused leaf compile or smoke check, and include one bounded independent reproduction attempt for the collected failure signal when it is safe and cheap. Do not plan to claim `reproduced` unless that reproduction command or test can actually show the failure.

## Patch Pass

You are working on a bounded fixer proposal.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Produce the smallest reasonable patch for the target repository, keep the change upstreamable, prefer the clearest control flow available, and do not keep avoidable `goto` when a simpler structure would read better. Before introducing new file, process, allocation, locking, networking, or platform APIs, inspect nearby code and project contribution docs for existing helpers or compatibility wrappers and use those local patterns unless you can explain why they do not fit. Validate from a reproducible workspace-root entrypoint before falling back to focused leaf commands; if a build or test cannot run, report the exact command, the exact blocker, and any narrower check you ran instead. During validation, also try one bounded independent reproduction of the collected failure signal when it is safe and cheap, such as a failing test, smoke command, perf/strace comparison, or before/after runtime check. Only use `reproduced` if that command or test actually reproduced the failure; otherwise keep `observed` and report the reproduction blocker. The final explanation must connect the observed issue evidence to the actual code change, not just paraphrase the diff. Write like a maintainer is going to read the patch mail cold: explain the bug in plain language, define subsystem-specific jargon the first time you need it, and make the causal story obvious. Explicitly classify evidence confidence as `reproduced`, `observed`, or `inferred`: `reproduced` means you reproduced the failure locally; `observed` means Fixer has direct crash/log/trace evidence but you did not independently reproduce it; `inferred` means the source patch is not pull-request-ready, so do not leave a source diff unless you first gather stronger observed/reproduced evidence; otherwise return a no-patch diagnosis/report. For any source-changing `observed` patch, say explicitly in `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. If you introduce non-obvious state translation, index remapping, or backend split logic, add a short source comment that explains the invariant being preserved.

Start by explaining the likely root cause from the collected perf, strace, and /proc evidence. If you cannot land a safe patch, leave a diagnosis that is strong enough for an upstream bug report.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. 

Keep the change narrowly scoped and summarize validation clearly.

In every authoring pass, your final response must start with `Subject: <single-line git commit subject>` and then include these markdown sections exactly:

## Commit Message
A short upstream-friendly explanation of what changed and why. Write it in plain language that a maintainer can follow without local complaint context. If you use subsystem jargon, define it immediately.

## Evidence Confidence
Exactly one word: `reproduced`, `observed`, or `inferred`. Use `reproduced` only when you reproduced the failure locally with a command or test, and include that command/test in `## Validation`. Use `observed` when Fixer has direct crash/log/trace evidence but you did not independently reproduce it. If `## Git Add Paths` lists source files for an `observed` patch, `## Issue Connection` must explicitly say the failure was observed by Fixer and not independently reproduced. Use `inferred` for profiler/strace/indirect evidence; inferred responses may be no-patch diagnoses or reports, but inferred source patches are not pull-request-ready until stronger evidence is gathered.

## Issue Connection
Write this as maintainer-facing patch mail, not as local Fixer notes. Cover four things explicitly in readable sentences: the user-visible symptom or the exact collected signal, the code-level cause or the cautious inference from evidence, the specific change you made, and the expected effect. Do not invent a reproducer, command line, crash, or user-visible failure that is not present in the evidence bundle. If the evidence is direct-but-not-reproduced, say it was observed by Fixer and not independently reproduced. If the evidence is indirect and you did not gather stronger evidence, do not leave a source diff; write a no-patch diagnosis/report instead. Include an explicit effect sentence such as `The expected effect is ...`, `This should reduce ...`, or `This prevents ...` for source patches. If the logic is non-obvious in code, mention that you added a short explanatory comment.

## Git Add Paths
List the repo-relative paths that belong in the final patch, one per line. Use `None` only when you intentionally made no source changes. Include intentionally new files, and do not list generated build artifacts.

## Validation
List the checks you ran, or say clearly that you could not run them. Include the independent reproduction command/test and result when `## Evidence Confidence` is `reproduced`; if reproduction was attempted but blocked, name the exact blocker and keep confidence at `observed` or `inferred`.

Before editing, read the plan at `./plan-output.txt` and follow it unless the code proves part of it wrong. If you change course, say so explicitly in the final write-up instead of silently drifting from the plan.

## Review Pass 1 (local metadata check)

Local metadata consistency check

## Refinement Pass 1

You are refining a fixer patch after an explicit code review.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Read the latest author response at `./patch-output.txt`. Read the review report at `./review-1-output.txt`. This is refinement round 1. The original pre-edit snapshot is available at `./source` if you need to compare the current patch against it. Re-read the planning pass at `./plan-output.txt` before editing. The workspace currently changes these repo-relative paths: auth2.c, regress/authorized_keys_root, regress/check-perm, regress/data, regress/ecdsa-sha2-nistp256, regress/ecdsa-sha2-nistp256.pub, regress/ecdsa-sha2-nistp384, regress/ecdsa-sha2-nistp384.pub, regress/ecdsa-sha2-nistp521, regress/ecdsa-sha2-nistp521.pub, regress/failed-regress.log, regress/failed-ssh.log, regress/failed-sshd.log, regress/host.ecdsa-sha2-nistp256, regress/host.ecdsa-sha2-nistp384, regress/host.ecdsa-sha2-nistp521, regress/host.sk-ecdsa-sha2-nistp256@openssh.com, regress/host.sk-ssh-ed25519@openssh.com, regress/host.ssh-ed25519, regress/host.ssh-rsa, regress/known_hosts, regress/log/20260515T215341.534342.ssh.334.log, regress/mkdtemp, regress/modpipe, regress/netcat, regress/regress.log, regress/rsa_ssh2_cr.prv, regress/rsa_ssh2_crnl.prv, regress/setuid-allowed, regress/sk-ecdsa-sha2-nistp256@openssh.com, regress/sk-ecdsa-sha2-nistp256@openssh.com.pub, regress/sk-ssh-ed25519@openssh.com, regress/sk-ssh-ed25519@openssh.com.pub, regress/ssh-ed25519, regress/ssh-ed25519.pub, regress/ssh-log-wrapper.sh, regress/ssh-rsa, regress/ssh-rsa.pub, regress/ssh.log, regress/ssh_config, regress/ssh_proxy, regress/sshd-log-wrapper.sh, regress/sshd.log, regress/sshd_config, regress/sshd_proxy, regress/t10.out.pub, regress/t12.out.pub, regress/t7.out.pub, regress/t9.out.pub, regress/timestamp. Either keep that exact set synchronized with `## Git Add Paths` and `## Issue Connection`, or revert any unintended file before you answer.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`, `make` and, if available, `make check`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout. Address the review findings with the smallest reasonable follow-up changes. If the review identifies a runtime or correctness bug in the changed code, you must update the code itself before answering; a metadata-only response is not sufficient. Keep the patch upstream-friendly, use local project helpers and compat APIs when available, avoid awkward control flow when a simpler structure will do, keep the final response gittable, make the maintainer-facing explanation plain and direct, keep `## Evidence Confidence` honest, add short comments for any non-obvious translation or remapping logic, run relevant project-level build/tests from the workspace root before narrower checks when possible, try a bounded independent reproduction command/test if the review or plan shows one is safe, and summarize which review findings you addressed.

In every authoring pass, your final response must start with `Subject: <single-line git commit subject>` and then include these markdown sections exactly:

## Commit Message
A short upstream-friendly explanation of what changed and why. Write it in plain language that a maintainer can follow without local complaint context. If you use subsystem jargon, define it immediately.

## Evidence Confidence
Exactly one word: `reproduced`, `observed`, or `inferred`. Use `reproduced` only when you reproduced the failure locally with a command or test, and include that command/test in `## Validation`. Use `observed` when Fixer has direct crash/log/trace evidence but you did not independently reproduce it. If `## Git Add Paths` lists source files for an `observed` patch, `## Issue Connection` must explicitly say the failure was observed by Fixer and not independently reproduced. Use `inferred` for profiler/strace/indirect evidence; inferred responses may be no-patch diagnoses or reports, but inferred source patches are not pull-request-ready until stronger evidence is gathered.

## Issue Connection
Write this as maintainer-facing patch mail, not as local Fixer notes. Cover four things explicitly in readable sentences: the user-visible symptom or the exact collected signal, the code-level cause or the cautious inference from evidence, the specific change you made, and the expected effect. Do not invent a reproducer, command line, crash, or user-visible failure that is not present in the evidence bundle. If the evidence is direct-but-not-reproduced, say it was observed by Fixer and not independently reproduced. If the evidence is indirect and you did not gather stronger evidence, do not leave a source diff; write a no-patch diagnosis/report instead. Include an explicit effect sentence such as `The expected effect is ...`, `This should reduce ...`, or `This prevents ...` for source patches. If the logic is non-obvious in code, mention that you added a short ex

[truncated 4402 bytes]

Response

## Plan Pass

## Problem
Fixer observed an `sshd-auth` preauth child in repeated `clock_nanosleep()` after failed userauth traffic. The matching source is `auth2.c:ensure_minimum_time_since()`: when authentication work already takes longer than the small per-user delay, it doubles the target delay until it exceeds elapsed time, which can turn a slow failed auth backend into an additional seconds-long sleep.

## Evidence Confidence
observed

## Proposed Subject
Cap auth failure delay backoff at `MAX_FAIL_DELAY_SECONDS`

## Patch Plan
Update `auth2.c` only. Keep the existing anti-enumeration timing behavior, but make `MAX_FAIL_DELAY_SECONDS` a real cap on total elapsed auth failure handling time. After the existing bounded scale-up, clamp the target delay with the local `MINIMUM()` macro from `misc.h`, recompute `remain`, and return cleanly if no delay remains. Avoid awkward `goto`; this is a small bounded conditional.

Follow local OpenSSH conventions already present in this subsystem: `monotime_double()`, `debug3_f()`, direct `nanosleep()`, `xmalloc/freezero`, and fatal-style helpers where applicable. No relevant file-IO/process/local locking helper is involved. No prior Fixer patch is present in this workspace; `git status` is clean and Debian patch series has no Fixer-specific timer/auth-delay patch to replace.

## Risks
This code is security-sensitive timing mitigation. The patch must not remove the per-user randomized floor or make invalid-user timing easier to distinguish. The intended change is only for slow auth paths: avoid adding large extra sleeps once backend work has already consumed most or all of the configured maximum delay.

## Validation
First try the project entrypoint from the workspace root:

```sh
./configure && make
```

If that fails due to missing dependencies or generated files, record the exact failure, then run the narrowest reproducible compile such as:

```sh
make auth2.o sshd-auth
```

Also run a bounded independent signal check: start a local test `sshd` and perform one intentionally failed password/kbdint auth under `strace -f -e clock_nanosleep`, comparing the observed sleep duration before/after. If the password regress prerequisites are available, use:

```sh
make tests LTESTS=password
```

Otherwise report that password-auth reproduction was skipped and run a basic server smoke test such as `make tests LTESTS=connect`. In the final `## Issue Connection`, state that Fixer observed the original sleep pattern and it was not independently reproduced unless the strace check actually shows it.

## Patch Pass

Subject: auth2: cap failed auth delay backoff

## Commit Message
Failed user authentication uses a small timing pad to reduce username and backend timing leaks. When the authentication backend has already taken longer than the requested pad, OpenSSH scales the delay up to the next bucket. Cap that scaled target at `MAX_FAIL_DELAY_SECONDS` too, so slow failed-auth paths do not add an extra sleep beyond the intended maximum.

## Evidence Confidence
observed

## Issue Connection
Fixer observed an `sshd-auth` pre-authentication child with strace samples alternating monitor reads and `clock_nanosleep()`, while `/proc` showed the process sleeping with negligible CPU. The failure was observed by Fixer and not independently reproduced.

The cautious code-level cause is in `auth2.c:ensure_minimum_time_since()`: the failed-auth timing pad doubles the target delay when elapsed authentication work has already passed the requested per-user delay, but only checked `MAX_FAIL_DELAY_SECONDS` before that scaling. I changed the helper to clamp the scaled target with the existing local `MINIMUM()` macro and return without sleeping if elapsed time has already reached the cap. This follows nearby conventions: `monotime_double()`, `debug3_f()`, direct `nanosleep()`, and `misc.h` helpers; no relevant file/process/allocation/locking helper applied.

The expected effect is to preserve the timing pad while preventing slow failed-auth backends from adding avoidable sleep past the configured maximum target.

## Git Add Paths
auth2.c

## Validation
`./configure && make` failed before building: `configure: error: ./configure.ac newer than configure, run autoreconf`.

`autoreconf && ./configure && make auth2.o sshd-auth` passed; this regenerated build files for validation only, and those generated tracked diffs were reverted.

`make auth2.o sshd-auth` passed again against the final source diff.

Independent reproduction attempt: `make tests LTESTS=password` did not reach the failed-password auth path. It built test binaries and passed file-tests, then failed with `sshd_proxy line 15: Unsupported option UsePAM` and `Missing privilege separation directory: /var/empty`. Therefore the original sleep signal was not independently reproduced.

## Review Pass 1 (local metadata check)

RESULT: fix-needed

## Findings
1. Patch metadata drift: the workspace currently changes `auth2.c`, `regress/authorized_keys_root`, `regress/check-perm`, `regress/data`, `regress/ecdsa-sha2-nistp256`, `regress/ecdsa-sha2-nistp256.pub`, `regress/ecdsa-sha2-nistp384`, `regress/ecdsa-sha2-nistp384.pub`, `regress/ecdsa-sha2-nistp521`, `regress/ecdsa-sha2-nistp521.pub`, `regress/failed-regress.log`, `regress/failed-ssh.log`, `regress/failed-sshd.log`, `regress/host.ecdsa-sha2-nistp256`, `regress/host.ecdsa-sha2-nistp384`, `regress/host.ecdsa-sha2-nistp521`, `regress/host.sk-ecdsa-sha2-nistp256@openssh.com`, `regress/host.sk-ssh-ed25519@openssh.com`, `regress/host.ssh-ed25519`, `regress/host.ssh-rsa`, `regress/known_hosts`, `regress/log/20260515T215341.534342.ssh.334.log`, `regress/mkdtemp`, `regress/modpipe`, `regress/netcat`, `regress/regress.log`, `regress/rsa_ssh2_cr.prv`, `regress/rsa_ssh2_crnl.prv`, `regress/setuid-allowed`, `regress/sk-ecdsa-sha2-nistp256@openssh.com`, `regress/sk-ecdsa-sha2-nistp256@openssh.com.pub`, `regress/sk-ssh-ed25519@openssh.com`, `regress/sk-ssh-ed25519@openssh.com.pub`, `regress/ssh-ed25519`, `regress/ssh-ed25519.pub`, `regress/ssh-log-wrapper.sh`, `regress/ssh-rsa`, `regress/ssh-rsa.pub`, `regress/ssh.log`, `regress/ssh_config`, `regress/ssh_proxy`, `regress/sshd-log-wrapper.sh`, `regress/sshd.log`, `regress/sshd_config`, `regress/sshd_proxy`, `regress/t10.out.pub`, `regress/t12.out.pub`, `regress/t7.out.pub`, `regress/t9.out.pub`, `regress/timestamp`, but `## Git Add Paths` lists `auth2.c`. Update `## Git Add Paths` to match the real shipped file set exactly, and make sure `## Issue Connection` explains every functional file that remains in the patch.
2. Missing from `## Git Add Paths`: `regress/authorized_keys_root`, `regress/check-perm`, `regress/data`, `regress/ecdsa-sha2-nistp256`, `regress/ecdsa-sha2-nistp256.pub`, `regress/ecdsa-sha2-nistp384`, `regress/ecdsa-sha2-nistp384.pub`, `regress/ecdsa-sha2-nistp521`, `regress/ecdsa-sha2-nistp521.pub`, `regress/failed-regress.log`, `regress/failed-ssh.log`, `regress/failed-sshd.log`, `regress/host.ecdsa-sha2-nistp256`, `regress/host.ecdsa-sha2-nistp384`, `regress/host.ecdsa-sha2-nistp521`, `regress/host.sk-ecdsa-sha2-nistp256@openssh.com`, `regress/host.sk-ssh-ed25519@openssh.com`, `regress/host.ssh-ed25519`, `regress/host.ssh-rsa`, `regress/known_hosts`, `regress/log/20260515T215341.534342.ssh.334.log`, `regress/mkdtemp`, `regress/modpipe`, `regress/netcat`, `regress/regress.log`, `regress/rsa_ssh2_cr.prv`, `regress/rsa_ssh2_crnl.prv`, `regress/setuid-allowed`, `regress/sk-ecdsa-sha2-nistp256@openssh.com`, `regress/sk-ecdsa-sha2-nistp256@openssh.com.pub`, `regress/sk-ssh-ed25519@openssh.com`, `regress/sk-ssh-ed25519@openssh.com.pub`, `regress/ssh-ed25519`, `regress/ssh-ed25519.pub`, `regress/ssh-log-wrapper.sh`, `regress/ssh-rsa`, `regress/ssh-rsa.pub`, `regress/ssh.log`, `regress/ssh_config`, `regress/ssh_proxy`, `regress/sshd-log-wrapper.sh`, `regress/sshd.log`, `regress/sshd_config`, `regress/sshd_proxy`, `regress/t10.out.pub`, `regress/t12.out.pub`, `regress/t7.out.pub`, `regress/t9.out.pub`, `regress/timestamp`.

## Refinement Pass 1

Subject: auth2: cap failed auth delay backoff

## Commit Message
Failed user authentication uses a timing pad to reduce username and backend timing leaks. When backend work already exceeds the requested pad, cap the scaled delay target at `MAX_FAIL_DELAY_SECONDS` so slow failed-auth paths do not add avoidable sleep beyond the intended maximum.

## Evidence Confidence
observed

## Issue Connection
Fixer observed an `sshd-auth` pre-authentication child with strace samples reaching `clock_nanosleep()` after failed auth traffic, while `/proc` showed the process sleeping with negligible CPU. This failure was observed by Fixer and not independently reproduced.

The likely code-level cause is `auth2.c:ensure_minimum_time_since()`: it checked `MAX_FAIL_DELAY_SECONDS` before scaling the failed-auth timing pad upward, but not after that scaling. I kept the existing timing-pad behavior, clamped the scaled target with OpenSSH’s existing `MINIMUM()` helper, and returned without sleeping when elapsed auth work has already reached the cap. The expected effect is to preserve the timing mitigation while preventing slow failed-auth backends from adding extra sleep past the maximum delay target.

For upstream style, I checked the available project docs (`README.md`; no `CONTRIBUTING`, `HACKING`, or `README-hacking` found) and kept to nearby auth2 conventions: `monotime_double()`, `debug3_f()`, direct `nanosleep()`, and `misc.h` helpers. The review finding was addressed by removing generated regress artifacts from validation; the final patch file set is only `auth2.c`.

## Git Add Paths
auth2.c

## Validation
`./configure && make` passed from the workspace root.

`make -n check` failed because this tree has no `check` target: `make: *** No rule to make target 'check'. Stop.`

`make auth2.o sshd-auth` passed.

`git diff --check -- auth2.c` passed.

Independent reproduction attempt: `make tests LTESTS=password` did not reproduce the original sleep signal. The password test path was blocked by local regress environment/configuration issues observed during validation, including `sshd_proxy line 15: Unsupported option UsePAM`, `Missing privilege separation directory: /var/empty`, and after cleanup a stale generated-file failure for `regress/t12.out.pub`. Confidence remains `observed`.

## Review Pass 2

RESULT: ok

No blocking findings.

`## Git Add Paths` matches the current changed path set exactly: `auth2.c`. The issue connection explains the only shipped functional file and keeps confidence at `observed`, with clear language that Fixer observed the sleep signal and it was not independently reproduced.

The code change is narrow, avoids awkward control flow, uses existing OpenSSH conventions/helpers (`MINIMUM()`, `monotime_double()`, `debug3_f()`, direct `nanosleep()` as already used nearby), and does not introduce new generic APIs. Validation reports the workspace-root build attempt and the unavailable `check` target, plus focused build and the blocked independent reproduction attempt.

Diff

diff --git a/auth2.c b/auth2.c
index 80f766e..cca3af8 100644
--- a/auth2.c
+++ b/auth2.c
@@ -256,9 +256,15 @@ ensure_minimum_time_since(double start, double seconds)
 		return;
 	}
 
-	/* if we've already passed the requested time, scale up */
+	/* If we've already passed the requested time, scale up to a cap. */
 	while ((remain = seconds - elapsed) < 0.0)
 		seconds *= 2;
+	seconds = MINIMUM(seconds, MAX_FAIL_DELAY_SECONDS);
+	if ((remain = seconds - elapsed) <= 0.0) {
+		debug3_f("elapsed %0.3lfms reached the max delay "
+		    "(requested %0.3lfms)", elapsed*1000, req*1000);
+		return;
+	}
 
 	ts.tv_sec = remain;
 	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;

Prompt

## Plan Pass

You are planning a fixer patch before any edits happen.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. The original pre-edit snapshot is available at `./source` if you need to inspect it. For interpreter processes, plan from the script/application entrypoint evidence first and include the runtime only as a second investigation target unless the evidence proves a runtime bug.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. Inspect the relevant code, nearby callers, project contribution docs, and local helper/compat APIs, but do not edit files in this pass.

Return a short markdown plan with these exact sections:

## Problem
## Evidence Confidence
## Proposed Subject
## Patch Plan
## Risks
## Validation

Classify `## Evidence Confidence` as exactly one of `reproduced`, `observed`, or `inferred`. Use `inferred` only for a no-patch diagnosis/report plan unless you can name the extra evidence you will collect before editing; inferred source patches are blocked by Fixer because they are not pull-request-ready. For `observed` source-patch plans, plan to say in the final `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. The plan must explain how the proposed code change addresses the observed issue evidence, call out any prior Fixer patch that should be improved or replaced, reject awkward control flow such as avoidable `goto` if there is a cleaner bounded alternative, name any local helper APIs or maintainer conventions the patch should follow, and keep the intended maintainer-facing explanation clear enough that someone unfamiliar with the local complaint wording can still follow the fix. In `## Validation`, name the reproducible configure/build/test entrypoint you will try from the workspace root before any focused leaf compile or smoke check, and include one bounded independent reproduction attempt for the collected failure signal when it is safe and cheap. Do not plan to claim `reproduced` unless that reproduction command or test can actually show the failure.

## Patch Pass

You are working on a bounded fixer proposal.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Produce the smallest reasonable patch for the target repository, keep the change upstreamable, prefer the clearest control flow available, and do not keep avoidable `goto` when a simpler structure would read better. Before introducing new file, process, allocation, locking, networking, or platform APIs, inspect nearby code and project contribution docs for existing helpers or compatibility wrappers and use those local patterns unless you can explain why they do not fit. Validate from a reproducible workspace-root entrypoint before falling back to focused leaf commands; if a build or test cannot run, report the exact command, the exact blocker, and any narrower check you ran instead. During validation, also try one bounded independent reproduction of the collected failure signal when it is safe and cheap, such as a failing test, smoke command, perf/strace comparison, or before/after runtime check. Only use `reproduced` if that command or test actually reproduced the failure; otherwise keep `observed` and report the reproduction blocker. The final explanation must connect the observed issue evidence to the actual code change, not just paraphrase the diff. Write like a maintainer is going to read the patch mail cold: explain the bug in plain language, define subsystem-specific jargon the first time you need it, and make the causal story obvious. Explicitly classify evidence confidence as `reproduced`, `observed`, or `inferred`: `reproduced` means you reproduced the failure locally; `observed` means Fixer has direct crash/log/trace evidence but you did not independently reproduce it; `inferred` means the source patch is not pull-request-ready, so do not leave a source diff unless you first gather stronger observed/reproduced evidence; otherwise return a no-patch diagnosis/report. For any source-changing `observed` patch, say explicitly in `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. If you introduce non-obvious state translation, index remapping, or backend split logic, add a short source comment that explains the invariant being preserved.

Start by explaining the likely root cause from the collected perf, strace, and /proc evidence. If you cannot land a safe patch, leave a diagnosis that is strong enough for an upstream bug report.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. 

Keep the change narrowly scoped and summarize validation clearly.

In every authoring pass, your final response must start with `Subject: <single-line git commit subject>` and then include these markdown sections exactly:

## Commit Message
A short upstream-friendly explanation of what changed and why. Write it in plain language that a maintainer can follow without local complaint context. If you use subsystem jargon, define it immediately.

## Evidence Confidence
Exactly one word: `reproduced`, `observed`, or `inferred`. Use `reproduced` only when you reproduced the failure locally with a command or test, and include that command/test in `## Validation`. Use `observed` when Fixer has direct crash/log/trace evidence but you did not independently reproduce it. If `## Git Add Paths` lists source files for an `observed` patch, `## Issue Connection` must explicitly say the failure was observed by Fixer and not independently reproduced. Use `inferred` for profiler/strace/indirect evidence; inferred responses may be no-patch diagnoses or reports, but inferred source patches are not pull-request-ready until stronger evidence is gathered.

## Issue Connection
Write this as maintainer-facing patch mail, not as local Fixer notes. Cover four things explicitly in readable sentences: the user-visible symptom or the exact collected signal, the code-level cause or the cautious inference from evidence, the specific change you made, and the expected effect. Do not invent a reproducer, command line, crash, or user-visible failure that is not present in the evidence bundle. If the evidence is direct-but-not-reproduced, say it was observed by Fixer and not independently reproduced. If the evidence is indirect and you did not gather stronger evidence, do not leave a source diff; write a no-patch diagnosis/report instead. Include an explicit effect sentence such as `The expected effect is ...`, `This should reduce ...`, or `This prevents ...` for source patches. If the logic is non-obvious in code, mention that you added a short explanatory comment.

## Git Add Paths
List the repo-relative paths that belong in the final patch, one per line. Use `None` only when you intentionally made no source changes. Include intentionally new files, and do not list generated build artifacts.

## Validation
List the checks you ran, or say clearly that you could not run them. Include the independent reproduction command/test and result when `## Evidence Confidence` is `reproduced`; if reproduction was attempted but blocked, name the exact blocker and keep confidence at `observed` or `inferred`.

Before editing, read the plan at `./plan-output.txt` and follow it unless the code proves part of it wrong. If you change course, say so explicitly in the final write-up instead of silently drifting from the plan.

## Review Pass 1

You are reviewing a freshly generated fixer patch.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Review the first patch pass. The original pre-edit snapshot is available at `./source` for diffing. The workspace currently changes these repo-relative paths: auth2.c. Verify that `## Git Add Paths` matches this exact set and that `## Issue Connection` explains every shipped functional file.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout. The latest author response is at `./patch-output.txt`. Inspect the current code and changed paths like a strict code reviewer. Focus on correctness, regressions, maintainability, awkward control flow such as avoidable `goto`, missing validation, weak or non-gittable commit message text, and explanations that fail to connect the observed issue evidence to the code change. Also review the maintainer experience: the patch mail should be easy to accept upstream, the user-visible bug should be explained in plain language, subsystem-specific jargon should be defined when first used, and any non-obvious state translation or index remapping in code should have a short explanatory comment. Reject patches that omit `## Evidence Confidence`, use anything other than `reproduced`, `observed`, or `inferred`, or sound more certain than that evidence level allows. Reject patches that claim `reproduced` unless `## Validation` names the concrete reproduction command or test and its result. Reject patches that invent a reproducer, command line, crash, or user-visible failure not present in the evidence bundle; indirect profiler or strace evidence may justify a cautious mitigation, but the author must say it is indirect instead of presenting it as a confirmed upstream bug. Reject patches that introduce generic libc/std APIs when nearby code or project docs provide a local compat/helper API for the same job, unless the author explicitly justifies the exception. Reject validation that only reports a leaf object/syntax build when a project-level configure/build/test entrypoint exists and was not attempted; if a full build cannot run, the author must show the exact failed command and blocker.

Do not apply code changes in this pass.

Return a short markdown review report. The first non-empty line must be exactly one of:

RESULT: ok
RESULT: fix-needed

If you choose `RESULT: fix-needed`, add a `## Findings` section with concrete, actionable items.

## Refinement Pass 1

You are refining a fixer patch after an explicit code review.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Read the latest author response at `./patch-output.txt`. Read the review report at `./review-1-output.txt`. This is refinement round 1. The original pre-edit snapshot is available at `./source` if you need to compare the current patch against it. Re-read the planning pass at `./plan-output.txt` before editing. The workspace currently changes these repo-relative paths: auth2.c. Either keep that exact set synchronized with `## Git Add Paths` and `## Issue Connection`, or revert any unintended file before you answer.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout. Address the review findings with the smallest reasonable follow-up changes. If the review identifies a runtime or correctness bug in the changed code, you must update the code itself before answering; a metadata-only response is not sufficient. Keep the patch upstream-friendly, use local project helpers and compat APIs when available, avoid awkward control flow when a simpler structure will do, keep the final response gittable, make the maintainer-facing explana

[truncated 6525 bytes]

Response

## Plan Pass

## Problem

Fixer observed `sshd-auth: root [net]` in a timer-heavy failed-authentication path: strace shows reads, `clock_nanosleep`, then writes consistent with sending an auth failure. The matching source is `auth2.c`: `input_userauth_request()` calls `ensure_minimum_time_since()` before `userauth_finish()` emits `SSH2_MSG_USERAUTH_FAILURE`.

## Evidence Confidence

observed

## Proposed Subject

`auth2: cap scaled userauth failure delay`

## Patch Plan

Update only `auth2.c:ensure_minimum_time_since()` so the exponential “scale up” fallback cannot push total failed-auth handling time beyond `MAX_FAIL_DELAY_SECONDS`.

Use the existing OpenSSH conventions found nearby: `monotime_double()` for elapsed time, `debug3_f()` for trace logging, direct `nanosleep()` for this delay path, and existing fatal/logging style. No relevant local wrapper replaces this direct sleep path; nearby IO uses `ssh_packet_write_wait()` and monitor/file IO uses `atomicio()`.

Improve on prior Fixer proposal `90090`, which made the same bounded-delay change but had generated regression artifacts during validation. The patch should keep the final diff scoped to `auth2.c` and avoid awkward control flow such as a `goto`; a bounded loop plus clamp is cleaner.

## Risks

This delay is timing-resistance code, so the patch must preserve the per-user minimum delay and only cap oversized scaled buckets.

The evidence is not an independent reproduction of a CPU runaway. The raw investigation files referenced in `evidence.json` are unavailable here, and the sampled process was sleeping with low CPU. The final patch should describe this as a targeted mitigation for Fixer-observed timer sleep, not a confirmed reproduced runaway fix.

## Validation

First try from the workspace root:

```sh
./configure && make
```

Then run focused checks:

```sh
git diff --check
make tests LTESTS=password
```

For a bounded independent reproduction attempt, run a local failed password-auth attempt under syscall tracing against the built test `sshd`, then compare whether `clock_nanosleep` duration remains bounded by `MAX_FAIL_DELAY_SECONDS`. If local test sshd setup fails due privileges, PAM, or `/var/empty`, report the exact command and failure, then run the narrow reproducible compile:

```sh
make auth2.o
```

## Patch Pass

Subject: auth2: cap scaled userauth failure delay

## Commit Message
Bound the scaled user authentication failure delay so it cannot extend past `MAX_FAIL_DELAY_SECONDS`.

OpenSSH adds a small per-user delay before sending an authentication failure to reduce timing differences. If authentication work had already exceeded the requested delay, the old code doubled the delay target until it exceeded elapsed time, but did not cap the scaled target before sleeping. Clamp that scaled target to the existing maximum and skip zero or negative sleeps.

## Evidence Confidence
observed

## Issue Connection
Fixer observed this failure signal directly but I did not independently reproduce it: `sshd-auth: root [net]` was sampled in `clock_nanosleep`, with strace showing `read -> read -> clock_nanosleep` followed by writes, and `/proc` showing the process sleeping.

The matching code path is `auth2.c` failed user authentication handling. `ensure_minimum_time_since()` pads failed authentication responses, but its scale-up path could choose a target above the local maximum when elapsed authentication work had already passed the initial per-user delay.

This patch keeps the existing timing padding, but clamps the scaled target to `MAX_FAIL_DELAY_SECONDS` before calculating the remaining sleep. The expected effect is that failed authentication still gets delayed, but `sshd-auth` will not add an oversized sleep beyond the intended cap before sending the failure response.

I followed the stored plan. Local conventions checked: `README.md`; nearby code uses `monotime_double()`, `debug3_f()`, direct `nanosleep()`, `ssh_packet_write_wait()`, `atomicio()`, `xmalloc()`, and `freezero()`. No relevant local helper replaces this direct sleep path.

## Git Add Paths
auth2.c

## Validation
`./configure && make` from the workspace root failed before building: `configure: error: ./configure.ac newer than configure, run autoreconf`.

`make auth2.o` from the workspace root also failed because configure had not produced `config.h`: `includes.h:19:10: fatal error: config.h: No such file or directory`.

To avoid generated-file churn in the final workspace, I copied the patched tree to `/tmp/openssh-90292-build.aYZw7k` and ran `autoreconf && ./configure && make`; it passed.

`make tests LTESTS=password` in that temporary build was the bounded reproduction/smoke attempt. It did not reproduce the observed sleep signal; it failed during test sshd setup with `Unsupported option UsePAM`, `Missing privilege separation directory: /var/empty`, and `FATAL: sshd_proxy broken`.

`git diff --check` passed.

## Review Pass 1

RESULT: fix-needed

## Findings

1. `auth2.c:253-265` does not clearly address the collected signal. The evidence shows `clock_nanosleep` durations around 1.84s and 1.88s, both below `MAX_FAIL_DELAY_SECONDS` 5.0. The patch only prevents the scaled delay target from exceeding the 5s cap, so the current `## Issue Connection` does not explain how this would change the observed behavior. Either gather stronger evidence that the observed `sshd-auth` path can exceed the cap, or reframe this as a no-patch diagnosis/issue report rather than shipping a source patch.

2. The patch includes unrelated EOF whitespace churn in `auth2.c` (`diff` shows a final blank line removed). Keep the diff strictly scoped to `ensure_minimum_time_since()` so the shipped file contains only the functional change.

`## Git Add Paths` correctly lists the only changed repo path, `auth2.c`, and the author did attempt the project-level `./configure && make` before falling back to a regenerated temporary build.

## Refinement Pass 1

Subject: diagnosis: sshd-auth timer sample needs stronger evidence

## Commit Message
No source patch is shipped.

The previous `auth2.c` change capped a failed-authentication delay at `MAX_FAIL_DELAY_SECONDS`, but the collected trace only showed `clock_nanosleep` calls around 1.8 seconds. That does not demonstrate an over-cap delay or a code-level bug in `ensure_minimum_time_since()`. The unsupported source diff has been removed.

## Evidence Confidence
inferred

## Issue Connection
Fixer collected a direct runtime signal from `sshd-auth: root [net]`: backtraces sampled the process in `clock_nanosleep`, strace showed `read -> read -> clock_nanosleep` followed by writes, and `/proc` showed the process sleeping with low CPU.

The likely source area is still failed user authentication timing in `auth2.c`, where OpenSSH pads authentication failure responses to reduce timing differences. However, the observed sleep durations in the evidence are below the existing 5 second maximum, so the prior cap change did not causally explain the collected signal.

I removed the `auth2.c` patch and left no source diff. The expected effect is that we avoid sending an upstream patch whose behavior is not supported by the available evidence; the right next step is a better trace with symbols or a local reproduction showing a concrete bad delay pattern.

Review findings addressed: the unsupported cap change was reverted, and the unrelated EOF whitespace churn was removed. Local conventions checked: `README.md`; nearby auth code uses `monotime_double()`, `debug3_f()`, direct `nanosleep()`, `ssh_packet_write_wait()`, `atomicio()`, `xmalloc()`, and `freezero()`. No relevant local helper was found that changes this no-patch diagnosis.

## Git Add Paths
None

## Validation
`./configure && make` from the workspace root was attempted and failed before building: `configure: error: ./configure.ac newer than configure, run autoreconf`.

`git status --short` produced no output; the workspace has no remaining source changes.

`git diff --check` passed.

No independent reproduction was completed in this refinement because the source patch was removed after review showed the evidence did not support it.

## Review Pass 2

RESULT: ok

No source changes remain in the workspace, and `## Git Add Paths` correctly says `None`. The refined response downgrades confidence to `inferred`, avoids shipping the unsupported `auth2.c` change, and explains why the observed sub-5s `clock_nanosleep` samples do not justify the prior cap patch.

Validation is acceptable for a no-patch diagnosis: the project-level `./configure && make` was attempted and the exact blocker was reported, and the workspace was confirmed clean with `git status --short` plus `git diff --check`.

Prompt

## Plan Pass

You are planning a fixer patch before any edits happen.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. The original pre-edit snapshot is available at `./source` if you need to inspect it. For interpreter processes, plan from the script/application entrypoint evidence first and include the runtime only as a second investigation target unless the evidence proves a runtime bug.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. Inspect the relevant code, nearby callers, project contribution docs, and local helper/compat APIs, but do not edit files in this pass.

Return a short markdown plan with these exact sections:

## Problem
## Evidence Confidence
## Proposed Subject
## Patch Plan
## Risks
## Validation

Classify `## Evidence Confidence` as exactly one of `reproduced`, `observed`, or `inferred`. Use `inferred` only for a no-patch diagnosis/report plan unless you can name the extra evidence you will collect before editing; inferred source patches are blocked by Fixer because they are not pull-request-ready. For `observed` source-patch plans, plan to say in the final `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. The plan must explain how the proposed code change addresses the observed issue evidence, call out any prior Fixer patch that should be improved or replaced, reject awkward control flow such as avoidable `goto` if there is a cleaner bounded alternative, name any local helper APIs or maintainer conventions the patch should follow, and keep the intended maintainer-facing explanation clear enough that someone unfamiliar with the local complaint wording can still follow the fix. In `## Validation`, name the reproducible configure/build/test entrypoint you will try from the workspace root before any focused leaf compile or smoke check, and include one bounded independent reproduction attempt for the collected failure signal when it is safe and cheap. Do not plan to claim `reproduced` unless that reproduction command or test can actually show the failure.

## Patch Pass

You are working on a bounded fixer proposal.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Produce the smallest reasonable patch for the target repository, keep the change upstreamable, prefer the clearest control flow available, and do not keep avoidable `goto` when a simpler structure would read better. Before introducing new file, process, allocation, locking, networking, or platform APIs, inspect nearby code and project contribution docs for existing helpers or compatibility wrappers and use those local patterns unless you can explain why they do not fit. Validate from a reproducible workspace-root entrypoint before falling back to focused leaf commands; if a build or test cannot run, report the exact command, the exact blocker, and any narrower check you ran instead. During validation, also try one bounded independent reproduction of the collected failure signal when it is safe and cheap, such as a failing test, smoke command, perf/strace comparison, or before/after runtime check. Only use `reproduced` if that command or test actually reproduced the failure; otherwise keep `observed` and report the reproduction blocker. The final explanation must connect the observed issue evidence to the actual code change, not just paraphrase the diff. Write like a maintainer is going to read the patch mail cold: explain the bug in plain language, define subsystem-specific jargon the first time you need it, and make the causal story obvious. Explicitly classify evidence confidence as `reproduced`, `observed`, or `inferred`: `reproduced` means you reproduced the failure locally; `observed` means Fixer has direct crash/log/trace evidence but you did not independently reproduce it; `inferred` means the source patch is not pull-request-ready, so do not leave a source diff unless you first gather stronger observed/reproduced evidence; otherwise return a no-patch diagnosis/report. For any source-changing `observed` patch, say explicitly in `## Issue Connection` that the failure was observed by Fixer and not independently reproduced. If you introduce non-obvious state translation, index remapping, or backend split logic, add a short source comment that explains the invariant being preserved.

Start by explaining the likely root cause from the collected perf, strace, and /proc evidence. If you cannot land a safe patch, leave a diagnosis that is strong enough for an upstream bug report.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround. 

Keep the change narrowly scoped and summarize validation clearly.

In every authoring pass, your final response must start with `Subject: <single-line git commit subject>` and then include these markdown sections exactly:

## Commit Message
A short upstream-friendly explanation of what changed and why. Write it in plain language that a maintainer can follow without local complaint context. If you use subsystem jargon, define it immediately.

## Evidence Confidence
Exactly one word: `reproduced`, `observed`, or `inferred`. Use `reproduced` only when you reproduced the failure locally with a command or test, and include that command/test in `## Validation`. Use `observed` when Fixer has direct crash/log/trace evidence but you did not independently reproduce it. If `## Git Add Paths` lists source files for an `observed` patch, `## Issue Connection` must explicitly say the failure was observed by Fixer and not independently reproduced. Use `inferred` for profiler/strace/indirect evidence; inferred responses may be no-patch diagnoses or reports, but inferred source patches are not pull-request-ready until stronger evidence is gathered.

## Issue Connection
Write this as maintainer-facing patch mail, not as local Fixer notes. Cover four things explicitly in readable sentences: the user-visible symptom or the exact collected signal, the code-level cause or the cautious inference from evidence, the specific change you made, and the expected effect. Do not invent a reproducer, command line, crash, or user-visible failure that is not present in the evidence bundle. If the evidence is direct-but-not-reproduced, say it was observed by Fixer and not independently reproduced. If the evidence is indirect and you did not gather stronger evidence, do not leave a source diff; write a no-patch diagnosis/report instead. Include an explicit effect sentence such as `The expected effect is ...`, `This should reduce ...`, or `This prevents ...` for source patches. If the logic is non-obvious in code, mention that you added a short explanatory comment.

## Git Add Paths
List the repo-relative paths that belong in the final patch, one per line. Use `None` only when you intentionally made no source changes. Include intentionally new files, and do not list generated build artifacts.

## Validation
List the checks you ran, or say clearly that you could not run them. Include the independent reproduction command/test and result when `## Evidence Confidence` is `reproduced`; if reproduction was attempted but blocked, name the exact blocker and keep confidence at `observed` or `inferred`.

Before editing, read the plan at `./plan-output.txt` and follow it unless the code proves part of it wrong. If you change course, say so explicitly in the final write-up instead of silently drifting from the plan.

## Review Pass 1

You are reviewing a freshly generated fixer patch.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Review the first patch pass. The original pre-edit snapshot is available at `./source` for diffing. The workspace currently changes these repo-relative paths: auth2.c. Verify that `## Git Add Paths` matches this exact set and that `## Issue Connection` explains every shipped functional file.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout. The latest author response is at `./patch-output.txt`. Inspect the current code and changed paths like a strict code reviewer. Focus on correctness, regressions, maintainability, awkward control flow such as avoidable `goto`, missing validation, weak or non-gittable commit message text, and explanations that fail to connect the observed issue evidence to the code change. Also review the maintainer experience: the patch mail should be easy to accept upstream, the user-visible bug should be explained in plain language, subsystem-specific jargon should be defined when first used, and any non-obvious state translation or index remapping in code should have a short explanatory comment. Reject patches that omit `## Evidence Confidence`, use anything other than `reproduced`, `observed`, or `inferred`, or sound more certain than that evidence level allows. Reject patches that claim `reproduced` unless `## Validation` names the concrete reproduction command or test and its result. Reject patches that invent a reproducer, command line, crash, or user-visible failure not present in the evidence bundle; indirect profiler or strace evidence may justify a cautious mitigation, but the author must say it is indirect instead of presenting it as a confirmed upstream bug. Reject patches that introduce generic libc/std APIs when nearby code or project docs provide a local compat/helper API for the same job, unless the author explicitly justifies the exception. Reject validation that only reports a leaf object/syntax build when a project-level configure/build/test entrypoint exists and was not attempted; if a full build cannot run, the author must show the exact failed command and blocker.

Do not apply code changes in this pass.

Return a short markdown review report. The first non-empty line must be exactly one of:

RESULT: ok
RESULT: fix-needed

If you choose `RESULT: fix-needed`, add a `## Findings` section with concrete, actionable items.

## Refinement Pass 1

You are refining a fixer patch after an explicit code review.

Read the evidence bundle at `./evidence.json`. The prepared workspace is `./workspace` and it was acquired via `debian-source`. Read the latest author response at `./patch-output.txt`. Read the review report at `./review-1-output.txt`. This is refinement round 1. The original pre-edit snapshot is available at `./source` if you need to compare the current patch against it. Re-read the planning pass at `./plan-output.txt` before editing. The workspace currently changes these repo-relative paths: auth2.c. Either keep that exact set synchronized with `## Git Add Paths` and `## Issue Connection`, or revert any unintended file before you answer.

Upstream-style expectation: before planning or editing, check for contribution/style docs (`CONTRIBUTING`, `HACKING`, `README-hacking`, `README.md`, `docs/`, `dev-docs/`) and scan the touched subsystem for local helpers. If the project has wrappers for file IO, path-relative IO, process spawning, memory allocation, logging, locking, or platform compatibility, prefer those wrappers over generic libc/std APIs. Do not invent a reproducer or user-visible failure that is not in the evidence bundle; if the evidence is profiler-only or indirect, describe it as a targeted mitigation or stop with a diagnosis instead of presenting a speculative patch as a confirmed bug fix. In the plan and final validation, name any such helper, convention, or evidence limit you found, or say that no relevant local helper was found. Treat this as a `openssh` upstream patch, not just a Debian-local workaround.

Validation expectation: try the project-level build/test entrypoint from the workspace root before reporting only a focused leaf compile. Detected candidate(s): `./configure && make`. If the project-level command fails because dependencies or generated files are missing, include the exact command and failure reason in `## Validation`, then run the narrowest relevant compile/test that is still reproducible from a clean checkout. Address the review findings with the smallest reasonable follow-up changes. If the review identifies a runtime or correctness bug in the changed code, you must update the code itself before answering; a metadata-only response is not sufficient. Keep the patch upstream-friendly, use local project helpers and compat APIs when available, avoid awkward control flow when a simpler structure will do, keep the final response gittable, make the maintainer-facing explana

[truncated 6525 bytes]

Response

## Plan Pass

## Problem

Fixer observed `sshd-auth: root [net]` in a timer-heavy failed-authentication path: strace shows reads, `clock_nanosleep`, then writes consistent with sending an auth failure. The matching source is `auth2.c`: `input_userauth_request()` calls `ensure_minimum_time_since()` before `userauth_finish()` emits `SSH2_MSG_USERAUTH_FAILURE`.

## Evidence Confidence

observed

## Proposed Subject

`auth2: cap scaled userauth failure delay`

## Patch Plan

Update only `auth2.c:ensure_minimum_time_since()` so the exponential “scale up” fallback cannot push total failed-auth handling time beyond `MAX_FAIL_DELAY_SECONDS`.

Use the existing OpenSSH conventions found nearby: `monotime_double()` for elapsed time, `debug3_f()` for trace logging, direct `nanosleep()` for this delay path, and existing fatal/logging style. No relevant local wrapper replaces this direct sleep path; nearby IO uses `ssh_packet_write_wait()` and monitor/file IO uses `atomicio()`.

Improve on prior Fixer proposal `90090`, which made the same bounded-delay change but had generated regression artifacts during validation. The patch should keep the final diff scoped to `auth2.c` and avoid awkward control flow such as a `goto`; a bounded loop plus clamp is cleaner.

## Risks

This delay is timing-resistance code, so the patch must preserve the per-user minimum delay and only cap oversized scaled buckets.

The evidence is not an independent reproduction of a CPU runaway. The raw investigation files referenced in `evidence.json` are unavailable here, and the sampled process was sleeping with low CPU. The final patch should describe this as a targeted mitigation for Fixer-observed timer sleep, not a confirmed reproduced runaway fix.

## Validation

First try from the workspace root:

```sh
./configure && make
```

Then run focused checks:

```sh
git diff --check
make tests LTESTS=password
```

For a bounded independent reproduction attempt, run a local failed password-auth attempt under syscall tracing against the built test `sshd`, then compare whether `clock_nanosleep` duration remains bounded by `MAX_FAIL_DELAY_SECONDS`. If local test sshd setup fails due privileges, PAM, or `/var/empty`, report the exact command and failure, then run the narrow reproducible compile:

```sh
make auth2.o
```

## Patch Pass

Subject: auth2: cap scaled userauth failure delay

## Commit Message
Bound the scaled user authentication failure delay so it cannot extend past `MAX_FAIL_DELAY_SECONDS`.

OpenSSH adds a small per-user delay before sending an authentication failure to reduce timing differences. If authentication work had already exceeded the requested delay, the old code doubled the delay target until it exceeded elapsed time, but did not cap the scaled target before sleeping. Clamp that scaled target to the existing maximum and skip zero or negative sleeps.

## Evidence Confidence
observed

## Issue Connection
Fixer observed this failure signal directly but I did not independently reproduce it: `sshd-auth: root [net]` was sampled in `clock_nanosleep`, with strace showing `read -> read -> clock_nanosleep` followed by writes, and `/proc` showing the process sleeping.

The matching code path is `auth2.c` failed user authentication handling. `ensure_minimum_time_since()` pads failed authentication responses, but its scale-up path could choose a target above the local maximum when elapsed authentication work had already passed the initial per-user delay.

This patch keeps the existing timing padding, but clamps the scaled target to `MAX_FAIL_DELAY_SECONDS` before calculating the remaining sleep. The expected effect is that failed authentication still gets delayed, but `sshd-auth` will not add an oversized sleep beyond the intended cap before sending the failure response.

I followed the stored plan. Local conventions checked: `README.md`; nearby code uses `monotime_double()`, `debug3_f()`, direct `nanosleep()`, `ssh_packet_write_wait()`, `atomicio()`, `xmalloc()`, and `freezero()`. No relevant local helper replaces this direct sleep path.

## Git Add Paths
auth2.c

## Validation
`./configure && make` from the workspace root failed before building: `configure: error: ./configure.ac newer than configure, run autoreconf`.

`make auth2.o` from the workspace root also failed because configure had not produced `config.h`: `includes.h:19:10: fatal error: config.h: No such file or directory`.

To avoid generated-file churn in the final workspace, I copied the patched tree to `/tmp/openssh-90292-build.aYZw7k` and ran `autoreconf && ./configure && make`; it passed.

`make tests LTESTS=password` in that temporary build was the bounded reproduction/smoke attempt. It did not reproduce the observed sleep signal; it failed during test sshd setup with `Unsupported option UsePAM`, `Missing privilege separation directory: /var/empty`, and `FATAL: sshd_proxy broken`.

`git diff --check` passed.

## Review Pass 1

RESULT: fix-needed

## Findings

1. `auth2.c:253-265` does not clearly address the collected signal. The evidence shows `clock_nanosleep` durations around 1.84s and 1.88s, both below `MAX_FAIL_DELAY_SECONDS` 5.0. The patch only prevents the scaled delay target from exceeding the 5s cap, so the current `## Issue Connection` does not explain how this would change the observed behavior. Either gather stronger evidence that the observed `sshd-auth` path can exceed the cap, or reframe this as a no-patch diagnosis/issue report rather than shipping a source patch.

2. The patch includes unrelated EOF whitespace churn in `auth2.c` (`diff` shows a final blank line removed). Keep the diff strictly scoped to `ensure_minimum_time_since()` so the shipped file contains only the functional change.

`## Git Add Paths` correctly lists the only changed repo path, `auth2.c`, and the author did attempt the project-level `./configure && make` before falling back to a regenerated temporary build.

## Refinement Pass 1

Subject: diagnosis: sshd-auth timer sample needs stronger evidence

## Commit Message
No source patch is shipped.

The previous `auth2.c` change capped a failed-authentication delay at `MAX_FAIL_DELAY_SECONDS`, but the collected trace only showed `clock_nanosleep` calls around 1.8 seconds. That does not demonstrate an over-cap delay or a code-level bug in `ensure_minimum_time_since()`. The unsupported source diff has been removed.

## Evidence Confidence
inferred

## Issue Connection
Fixer collected a direct runtime signal from `sshd-auth: root [net]`: backtraces sampled the process in `clock_nanosleep`, strace showed `read -> read -> clock_nanosleep` followed by writes, and `/proc` showed the process sleeping with low CPU.

The likely source area is still failed user authentication timing in `auth2.c`, where OpenSSH pads authentication failure responses to reduce timing differences. However, the observed sleep durations in the evidence are below the existing 5 second maximum, so the prior cap change did not causally explain the collected signal.

I removed the `auth2.c` patch and left no source diff. The expected effect is that we avoid sending an upstream patch whose behavior is not supported by the available evidence; the right next step is a better trace with symbols or a local reproduction showing a concrete bad delay pattern.

Review findings addressed: the unsupported cap change was reverted, and the unrelated EOF whitespace churn was removed. Local conventions checked: `README.md`; nearby auth code uses `monotime_double()`, `debug3_f()`, direct `nanosleep()`, `ssh_packet_write_wait()`, `atomicio()`, `xmalloc()`, and `freezero()`. No relevant local helper was found that changes this no-patch diagnosis.

## Git Add Paths
None

## Validation
`./configure && make` from the workspace root was attempted and failed before building: `configure: error: ./configure.ac newer than configure, run autoreconf`.

`git status --short` produced no output; the workspace has no remaining source changes.

`git diff --check` passed.

No independent reproduction was completed in this refinement because the source patch was removed after review showed the evidence did not support it.

## Review Pass 2

RESULT: ok

No source changes remain in the workspace, and `## Git Add Paths` correctly says `None`. The refined response downgrades confidence to `inferred`, avoids shipping the unsupported `auth2.c` change, and explains why the observed sub-5s `clock_nanosleep` samples do not justify the prior cap patch.

Validation is acceptable for a no-patch diagnosis: the project-level `./configure && make` was attempted and the exact blocker was reported, and the workspace was confirmed clean with `git status --short` plus `git diff --check`.