marfrit
35a8a07152
Client (sic) frames argv as netstrings and pipes it over ssh to a daemon (sicd) that execvp's it, so no shell re-parses the arguments. exec mode by default; opt-in sh mode for pipes/redirects/globs. Go client + daemon, Python reference daemon, design doc, quoting-hell demo, and foreground/background agent skills. Renamed from the climcp prototype. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EWpfhDgYNA21tETDP9ueBE
93 lines
2.6 KiB
Markdown
93 lines
2.6 KiB
Markdown
# 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 over `ssh` to `sicd`.
|
|
- **`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 quotesu echo hello world
|
|
sic quotesu touch 'a b' # one file named "a b"
|
|
sic quotesu echo '$HOME' # literal, no expansion
|
|
sic --sh quotesu '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, plain `ssh` versus `sic`.
|
|
- `SKILL.md`, `SKILL-bg.md` — agent skill definitions (foreground and background).
|