Claude (noether)
4fcd8512ae
@reviewer re-probed the argc path (18 hand-built frames, all rejection paths clean) and cleared it as deployable. Three non-blocking follow-ups, all closed here: #1 doc rot -- the comments ARE the spec on a hand-rolled wire, and three still described removed formats: readNetstringStream (claimed v1-only; it now serves both paths), parseV2Content doc (empty-netstring terminator), runV2 doc (the two-generations-old command/NUL/payload split), and the test frame() helper. All rewritten to netstring(argc) + argc argv netstrings + payload. #2 canonical argc -- strconv.Atoi accepted "+1" and "001" (one value, two encodings). Reject leading +/-, leading zeros, and empty before Atoi, mirroring readNetstringStream length-token validation. New regression TestV2NonCanonicalArgcRejected (01/+1/-1 etc. exit 1, no exec). #3 argc-low reclassification -- documented where payload is defined: a low argc turns the sender's own trailing netstrings into child stdin; only ever the sender frame, no trust boundary. By design, now stated. Also fixed TestV2FrameElementCapRejected, which under the argc wire was tripping on a bad argc token rather than the count cap it claims -- now sends argc=5000 to hit maxArgs honestly. Build/vet clean, full daemon + client suites green. Daemon is deploy-ready at this commit. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
sic
Run a command on a remote host without a shell re-parsing its arguments.
ssh host touch 'a b' creates two files: ssh joins its arguments with spaces
and hands the result to the remote login shell, which splits it again. sic host touch 'a b' creates one file named a b. sic sends the argument vector to a
daemon on the host as length-prefixed fields, and the daemon calls execvp on
it. No shell parses the arguments.
Components
sic— client. Takes argv on the command line, frames it as netstrings, pipes the frame oversshtosicd.sicd— daemon on the target host. Reads netstrings from stdin and runs the command.
Both are single static Go binaries (cmd/sic, cmd/sicd). A Python reference
implementation of the daemon is in gateway/sicd.
Wire format
Each field is a netstring: <length>:<bytes>,. A frame is a mode field, zero or
more argument fields, and an empty terminator:
<mode> <arg>* 0:,
argv = ["touch", "a b"] is 4:exec,5:touch,3:a b,0:,. The length prefix means
no byte needs escaping and no delimiter can collide with the payload.
| mode | selector | behaviour |
|---|---|---|
exec (default) |
4:exec, |
execvp(argv), no shell. Arguments are passed through unchanged. |
sh |
2:sh, |
one field passed to sh -c. Pipes, redirects, and globs work. |
Usage
sic <host> <command> [arg ...]
sic --sh <host> '<shell string>'
sic <host> -- <command> [arg ...] # explicit separator
sic host1 echo hello world
sic host1 touch 'a b' # one file named "a b"
sic host1 echo '$HOME' # literal, no expansion
sic --sh host1 'echo hi | wc -c'
Build
go build -o bin/sic ./cmd/sic
go build -o bin/sicd ./cmd/sicd
Install
Client:
cp bin/sic ~/bin/sic
Daemon on each target host. sicd runs what it is sent, so it must only be
reachable over an authenticated transport. Pin it to a dedicated ssh key so the
target can run nothing else with that key:
scp bin/sicd host:/tmp/sicd
ssh host 'sudo install -m755 /tmp/sicd /usr/local/bin/sicd'
# ~/.ssh/authorized_keys on the target:
# command="sicd",no-port-forwarding,no-pty ssh-ed25519 AAAA...
Do not listen on a TCP or message-bus port.
Test
printf '4:exec,2:id,0:,' | ssh host sicd
sic host echo hello world
See also
docs/design.md— wire format, exec modes, transport and security, prior art.demos/quoting-hell.py— six cases run both ways, plainsshversussic.SKILL.md,SKILL-bg.md— agent skill definitions (foreground and background).