ergosteurandClaude Opus 5
fd022a195c
A fork of ssh-copy-id that installs keys on Windows OpenSSH servers, for both regular users and members of Administrators, while keeping the standard behaviour on *nix targets. Windows design constraints: - Dispatches everything as `cmd.exe /c "<inner>"`, since a host's sshd DefaultShell is unpredictable. PowerShell is never assumed present. - Uses exactly one quote pair with no quotes inside <inner>. A PowerShell DefaultShell re-escapes nested quotes as \", which cmd.exe cannot parse. Staying quote-free means cd'ing to the base directory first and using short relative paths, and deduping on the whitespace-free base64 blob. - No hard-coded drive letters; %USERPROFILE% and %ProgramData% only. - Administrators are written to administrators_authorized_keys with the SYSTEM + Administrators ACL that Windows sshd requires, because the stock Match Group administrators block makes it the only file consulted for those accounts. - Group and ACL checks match on SIDs, not names, so they work on non-English Windows locales. - All steps share one multiplexed connection, so password-auth hosts prompt once rather than once per step. Two cmd.exe parsing traps are worked around, both of which corrupted the remote file with no error output: - `echo KEY>>file && echo DONE` leaves the space before `&&` inside the echoed text, appending a trailing space that defeats exact-match dedup and duplicates the key on every run. Uses `(echo KEY)>>file` instead. - An unparenthesised `if not exist ... & ...` swallows the rest of the command chain when the directory already exists, silently skipping everything after it. Verified on Linux, Windows Administrator, and Windows regular-user targets, each for both first install and duplicate detection. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
109 lines
5.2 KiB
Markdown
109 lines
5.2 KiB
Markdown
# ssh-scripts
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SSH key / authentication tooling. These notes travel with the repo.
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## ssh-copy-id-win
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A personal fork of `ssh-copy-id` that supports Windows OpenSSH servers (both
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regular users and Administrators) while keeping full *nix behaviour.
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**This repo is the source of truth**; `~/.local/bin/ssh-copy-id-win` is a
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*deployed copy* on the fish PATH. They are separate files, so edits here do not
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take effect until redeployed:
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```
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cp ./ssh-copy-id-win ~/.local/bin/ssh-copy-id-win # deploy
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diff ./ssh-copy-id-win ~/.local/bin/ssh-copy-id-win # check for drift
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```
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Edit the repo copy, not the deployed one. If they ever disagree, the deployed
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copy is the one that has been running.
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```
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ssh-copy-id-win [-i identity] [-p port] [-o ssh_opt] [-A|-U] [-n] [user@]host
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-A / -U force the Administrator / regular-user path on Windows
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-n dry run, prints the exact remote command
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```
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### Design constraints (do not regress these)
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* **cmd.exe only.** Everything is dispatched as `cmd.exe /c "<inner>"` because a
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host's sshd `DefaultShell` is unpredictable. PowerShell is never assumed to
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exist on a target.
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* **Exactly one quote pair, zero quotes inside `<inner>`.** If the remote default
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shell is PowerShell, sshd runs `powershell -c "cmd.exe /c \"<inner>\""` and
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PowerShell re-escapes nested quotes as `\"`, which cmd.exe does not understand.
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To stay quote-free the script `cd /d %USERPROFILE%` (or `%ProgramData%`) first
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and then uses short relative paths that cannot contain spaces, and dedups on
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the base64 key blob alone since that field is whitespace-free.
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* **No hard-coded drive letters.** `%USERPROFILE%` and `%ProgramData%` only.
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* **Admins need the ProgramData file.** Stock Windows `sshd_config` has a
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`Match Group administrators` block making
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`%ProgramData%\ssh\administrators_authorized_keys` the *only* file consulted
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for admin accounts. It also requires a restrictive ACL (SYSTEM +
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Administrators), which the script reapplies after every write.
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* **Locale independence.** Never match English text in Windows command output.
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Admin detection uses the `S-1-5-32-544` SID; ACLs are granted by SID
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(`*S-1-5-32-544`, `*S-1-5-18`).
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* **One connection.** All steps share a multiplexed `ControlMaster` connection so
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password-auth hosts prompt once, not once per step.
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### Two cmd.exe traps that fail silently
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Both of these produced a *corrupt file with no error message*, and both cost
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real debugging time. They are also commented in the script header.
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1. **Trailing space from a mid-line redirect.**
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`echo KEY>>file && echo DONE` — cmd lifts the redirect out of the middle, so
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the space before `&&` ends up inside the echoed text. Every key landed as
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`...comment ` with a trailing space, so the next run's exact-match dedup never
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matched and appended a duplicate. Forever.
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Use `(echo KEY)>>file` instead.
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2. **`if` swallowing the rest of the chain.**
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`if not exist ssh mkdir ssh & findstr ... && echo A || echo B` — when the
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directory *already exists*, cmd treats the entire remainder as the if-body and
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skips all of it, so the command produces no output at all.
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Parenthesise it: `(if not exist ssh mkdir ssh) & ...`
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## Testing
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Verified paths: Linux, Windows Administrator, Windows regular user — each for
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both first-install and duplicate detection.
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The three targets used were a Linux host, a domain Windows host reached as a
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member of Administrators (key auth), and the same Windows host reached as an
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ordinary domain user (**password auth only**). Specific hostnames and accounts
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are deliberately kept out of this repo.
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Conventions when working on this:
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* **Password-auth hosts cannot be tested from inside a Claude Code session.**
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The Bash tool and the `!` prefix give ssh no TTY, so it dies with exit 255. Ask
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the user to run those in a real terminal.
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* Test additive changes with a throwaway `ssh-keygen` key rather than the real
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one — it never risks locking you out of the box you are testing on.
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* When rewriting a remote `authorized_keys`, stage to `%TEMP%` and `copy /y` over
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the target, so the original survives a failed write.
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* Where `pwsh` 7 happens to be installed on a target it is fine for *debugging
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only* — the script must never depend on it. `pwsh -EncodedCommand` (base64
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UTF-16LE) sidesteps all quoting layers; `certutil -encodehex <in> <out>` gives
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byte-level output for spotting trailing whitespace and CRLF issues, and needs
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nothing beyond cmd.
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* Test against a **non-English Windows locale** if you can. Command output is
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localised, which is exactly why group and ACL checks match on SIDs
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(`S-1-5-32-544`, `S-1-5-18`) rather than on names like "Administrators".
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* Always verify a written key by *authenticating with it*, not just by reading
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the file back.
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## Local environment
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The user's shell is **fish**, but the Bash tool runs bash/zsh. Checking `$PATH`,
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aliases, or functions through the Bash tool reflects the wrong shell — verify
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with `fish -c '...'`, and persist path changes with `fish_add_path`.
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Note `ssh-copy-id` upstream picks its default key with
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`ls -dt ~/.ssh/id*.pub | head -1` — i.e. by **mtime**, newest first — whereas
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`ssh` itself uses fixed default filenames (`id_rsa`, `id_ecdsa`, `id_ed25519`,
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...). The two can disagree, which is confusing when a `touch` reorders things.
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