MCPInstall

ssh-doctor

by steipeteBackend & APIs

SSH triage: Remote Login, launchd sshd, pre-auth closes, stale sessions.

Installs
150
Last 24h
—
Trending rank
—
Security
Not audited

Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/steipete/agent-scripts --skill ssh-doctor
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads ssh-doctor automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

SSH Doctor

Use when SSH connects then closes before auth, Remote Login seems advertised but unusable, or local/remote Mac SSH needs diagnosis.

Rules

  • Do not print secrets, tokens, full env, or broad secret grep output.
  • Validate locally first: loopback failure means server-side sshd/launchd/config; loopback success plus remote failure means network/firewall/filter/listen path.
  • Report suspicious config lines before changing /etc/ssh/sshd_config.
  • Prefer non-interactive SSH:
ssh -o RequestTTY=no -o RemoteCommand=none HOST 'hostname; id -un'

Baseline

hostname; id -un; sw_vers
ipconfig getifaddr en0
ipconfig getifaddr en1 2>/dev/null || true
ipconfig getifaddr en7 2>/dev/null || true
sudo systemsetup -getremotelogin
sudo systemsetup -setremotelogin on
sudo launchctl print system/com.openssh.sshd 2>&1 | head -80
sudo launchctl kickstart -k system/com.openssh.sshd
sudo lsof -nP -iTCP:22 -sTCP:LISTEN
nc -vz 127.0.0.1 22
ssh -4 -F /dev/null -o RequestTTY=no -o RemoteCommand=none USER@127.0.0.1 'hostname; id -un'

Use BatchMode=yes only when password fallback would hang or prompt.

Config

sudo sshd -T 2>&1 | egrep -i '^(allowusers|denyusers|allowgroups|denygroups|listenaddress|maxstartups|logingracetime|usepam|passwordauthentication|pubkeyauthentication|authenticationmethods)'
sudo egrep -n '^[[:space:]]*(AllowUsers|DenyUsers|AllowGroups|DenyGroups|Match|MaxStartups|LoginGraceTime|ListenAddress|AuthenticationMethods|UsePAM|PasswordAuthentication|PubkeyAuthentication)\b' /etc/ssh/sshd_config /etc/ssh/sshd_config.d/* 2>/dev/null || true

Suspicious:

  • DenyUsers matching target user
  • restrictive AllowUsers / AllowGroups
  • Match block accidentally applying
  • tiny MaxStartups
  • tiny LoginGraceTime
  • ListenAddress missing target interface

Logs

sudo log show --last 30m --predicate 'process == "sshd" OR process == "launchd"' --style compact | tail -160

Important Mac symptom:

  • client: kex_exchange_identification: Connection closed by remote host
  • server log: Could not create new instance of inetd service: 67: Too many processes
  • launchctl print system/com.openssh.sshd: high copy count
  • many sshd-session: USER processes parented by PID 1

This means launchd accepted TCP but refused to spawn more sshd inetd copies.

Stale sshd-session Fix

Inspect first:

sudo launchctl print system/com.openssh.sshd 2>&1 | egrep 'active count|copy count|state =|last exit code|runs ='
ps -axo pid,ppid,uid,user,state,lstart,etime,comm,args | awk '/sshd-session:/ && !/awk/ {print}'
sudo lsof -nP -c sshd-session -iTCP 2>/dev/null | head -120

If stale sessions are clearly stranded and blocking new SSH, terminate by selected command-line match:

ps -axo pid=,args= | awk '/sshd-session: / && !/awk/ {print $1}' | xargs sudo kill -TERM
sleep 2
ps -axo pid=,args= | awk '/sshd-session: / && !/awk/ {print}'

If TERM leaves blockers, re-check ownership and active shells before using KILL.

Firewall

Only after loopback works but remote fails:

sudo /usr/libexec/ApplicationFirewall/socketfilterfw --getglobalstate
sudo /usr/libexec/ApplicationFirewall/socketfilterfw --listapps | grep -i ssh -A2 -B2 || true
sudo pfctl -sr 2>/dev/null | head -80
sudo pfctl -si 2>/dev/null | head -80

Also check listen address and target interface:

ifconfig | awk '/^[a-z0-9]+:/{iface=$1; sub(":","",iface)} iface ~ /^en[0-9]+$/ && /inet / {print iface, $2}'
sudo lsof -nP -iTCP:22 -sTCP:LISTEN

OP Profile Block

If asked to ensure ~/.profile has a Codex-managed OP_SERVICE_ACCOUNT_TOKEN copied from another host:

  • verify exact variable/markers without printing value
  • copy only the matching line/block
  • redirect through a chmod 600 temp file
  • never echo the token

Presence check:

awk 'BEGIN{b=0;e=0;x=0} /BEGIN Codex-managed OP_SERVICE_ACCOUNT_TOKEN/ {b=1} /END Codex-managed OP_SERVICE_ACCOUNT_TOKEN/ {e=1} /^[[:space:]]*(export[[:space:]]+)?OP_SERVICE_ACCOUNT_TOKEN=/ {x=1} END{print "marker_begin", b; print "marker_end", e; print "exact_var", x}' ~/.profile

Append from remote host:

tmpfile=$(mktemp /tmp/codex-op-token.XXXXXX)
chmod 600 "$tmpfile"
ssh -o RequestTTY=no -o RemoteCommand=none HOST 'awk '\''/^[[:space:]]*(export[[:space:]]+)?OP_SERVICE_ACCOUNT_TOKEN=/ {print; exit}'\'' ~/.profile' > "$tmpfile"
if [ -s "$tmpfile" ]; then
  {
    printf '\n# BEGIN Codex-managed OP_SERVICE_ACCOUNT_TOKEN\n'
    sed -n '1p' "$tmpfile"
    printf '# END Codex-managed OP_SERVICE_ACCOUNT_TOKEN\n'
  } >> ~/.profile
fi
rm -f "$tmpfile"

Closeout

Report:

  • root cause
  • exact commands changed
  • validation output, redacted as needed
  • whether remote should retry

FAQ

What does the ssh-doctor skill do?

SSH triage: Remote Login, launchd sshd, pre-auth closes, stale sessions.

How do I install ssh-doctor?

Run npx skills add https://github.com/steipete/agent-scripts --skill ssh-doctor in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/ssh-doctor/ (personal) or .claude/skills/ssh-doctor/ (project).

Which AI agents can use ssh-doctor?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is ssh-doctor safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains ssh-doctor?

It is published by steipete in steipete/agent-scripts. It has 150 recorded installs.

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