Markus Fritsche
99568666d3
The quotesu setup notes exposed internal host details and aren't useful to readers, so remove the directory. The quoting-hell demo now requires the target host as an argument (any host running sicd) instead of defaulting to an internal name, and its labels say sic rather than the old rs. Example hostnames in the README/SKILL/main.go are now the neutral placeholder host1. 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
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Run a command on a remote host without a shell re-parsing its arguments.
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`ssh host touch 'a b'` creates two files: `ssh` joins its arguments with spaces
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and hands the result to the remote login shell, which splits it again. `sic host
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touch 'a b'` creates one file named `a b`. `sic` sends the argument vector to a
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daemon on the host as length-prefixed fields, and the daemon calls `execvp` on
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it. No shell parses the arguments.
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## Components
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- **`sic`** — client. Takes argv on the command line, frames it as netstrings,
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pipes the frame over `ssh` to `sicd`.
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- **`sicd`** — daemon on the target host. Reads netstrings from stdin and runs
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the command.
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Both are single static Go binaries (`cmd/sic`, `cmd/sicd`). A Python reference
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implementation of the daemon is in `gateway/sicd`.
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## Wire format
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Each field is a netstring: `<length>:<bytes>,`. A frame is a mode field, zero or
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more argument fields, and an empty terminator:
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```
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<mode> <arg>* 0:,
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```
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`argv = ["touch", "a b"]` is `4:exec,5:touch,3:a b,0:,`. The length prefix means
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no byte needs escaping and no delimiter can collide with the payload.
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| mode | selector | behaviour |
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|------|----------|-----------|
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| `exec` (default) | `4:exec,` | `execvp(argv)`, no shell. Arguments are passed through unchanged. |
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| `sh` | `2:sh,` | one field passed to `sh -c`. Pipes, redirects, and globs work. |
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## Usage
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```
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sic <host> <command> [arg ...]
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sic --sh <host> '<shell string>'
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sic <host> -- <command> [arg ...] # explicit separator
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```
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```
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sic host1 echo hello world
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sic host1 touch 'a b' # one file named "a b"
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sic host1 echo '$HOME' # literal, no expansion
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sic --sh host1 'echo hi | wc -c'
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```
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## Build
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```
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go build -o bin/sic ./cmd/sic
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go build -o bin/sicd ./cmd/sicd
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```
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## Install
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Client:
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```
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cp bin/sic ~/bin/sic
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```
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Daemon on each target host. `sicd` runs what it is sent, so it must only be
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reachable over an authenticated transport. Pin it to a dedicated ssh key so the
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target can run nothing else with that key:
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```
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scp bin/sicd host:/tmp/sicd
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ssh host 'sudo install -m755 /tmp/sicd /usr/local/bin/sicd'
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# ~/.ssh/authorized_keys on the target:
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# command="sicd",no-port-forwarding,no-pty ssh-ed25519 AAAA...
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```
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Do not listen on a TCP or message-bus port.
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## Test
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```
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printf '4:exec,2:id,0:,' | ssh host sicd
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sic host echo hello world
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```
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## See also
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- `docs/design.md` — wire format, exec modes, transport and security, prior art.
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- `demos/quoting-hell.py` — six cases run both ways, plain `ssh` versus `sic`.
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- `SKILL.md`, `SKILL-bg.md` — agent skill definitions (foreground and background).
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