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Harden cmux ssh for mixed-version remote sessions

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This commit is contained in:
Lawrence Chen 2026-02-24 22:09:27 -08:00
parent 2b7928aa60
commit daa340fa87
8 changed files with 142 additions and 31 deletions
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7
daemon/remote/README.md
View file

@ -8,7 +8,7 @@ Go remote daemon for `cmux ssh` bootstrap, capability negotiation, and CLI relay
2. `cmuxd-remote serve --stdio`
3. `cmuxd-remote cli <command> [args...]` — relay cmux commands to the local app over the reverse TCP forward
When invoked as `cmux` (via symlink created during bootstrap), the binary auto-dispatches to the `cli` subcommand. This is busybox-style argv[0] detection.
When invoked as `cmux` (via wrapper/symlink installed during bootstrap), the binary auto-dispatches to the `cli` subcommand. This is busybox-style argv[0] detection.
## RPC methods (newline-delimited JSON over stdio)
@ -17,7 +17,7 @@ When invoked as `cmux` (via symlink created during bootstrap), the binary auto-d
## CLI relay
The `cli` subcommand (or `cmux` symlink) connects to the local cmux app's socket through an SSH reverse TCP forward and relays commands. It supports both v1 text protocol and v2 JSON-RPC commands.
The `cli` subcommand (or `cmux` wrapper/symlink) connects to the local cmux app's socket through an SSH reverse TCP forward and relays commands. It supports both v1 text protocol and v2 JSON-RPC commands.
Socket discovery order:
1. `--socket <path>` flag
@ -31,5 +31,6 @@ For TCP addresses, the CLI retries for up to 15 seconds on connection refused, r
1. `workspace.remote.configure` bootstraps this binary over SSH when missing.
2. Client sends `hello` before enabling remote port probing/forwarding.
3. Daemon status/capabilities are exposed in `workspace.remote.status -> remote.daemon`.
4. Bootstrap creates `~/.cmux/bin/cmux` symlink pointing to the daemon binary.
4. Bootstrap installs `~/.cmux/bin/cmux` wrapper and keeps a default daemon target (`~/.cmux/bin/cmuxd-remote-current`).
5. A background `ssh -N -R` process reverse-forwards a TCP port to the local cmux Unix socket. The relay address is written to `~/.cmux/socket_addr` on the remote.
6. Relay startup writes `~/.cmux/relay/<port>.daemon_path` so the wrapper can route each shell to the correct daemon binary when multiple local cmux instances/versions coexist.

12
daemon/remote/cmd/cmuxd-remote/cli.go
View file

@ -93,6 +93,9 @@ func runCLI(args []string) int {
i++
case "--json":
jsonOutput = true
case "--help", "-h":
cliUsage()
return 0
default:
remaining = append(remaining, args[i:]...)
goto doneFlags
@ -104,6 +107,12 @@ doneFlags:
cliUsage()
return 2
}
cmdName := remaining[0]
cmdArgs := remaining[1:]
if cmdName == "help" {
cliUsage()
return 0
}
// refreshAddr is set when the address came from socket_addr file (not env/flag),
// allowing retry loops to pick up updated relay ports.
@ -117,9 +126,6 @@ doneFlags:
return 1
}
cmdName := remaining[0]
cmdArgs := remaining[1:]
// Special case: "rpc" passthrough
if cmdName == "rpc" {
return runRPC(socketPath, cmdArgs, jsonOutput, refreshAddr)

14
daemon/remote/cmd/cmuxd-remote/cli_test.go
View file

@ -381,6 +381,20 @@ func TestCLINoArgs(t *testing.T) {
}
}
func TestCLIHelpFlag(t *testing.T) {
code := runCLI([]string{"--help"})
if code != 0 {
t.Fatalf("--help should return 0, got %d", code)
}
}
func TestCLIHelpCommand(t *testing.T) {
code := runCLI([]string{"help"})
if code != 0 {
t.Fatalf("help should return 0, got %d", code)
}
}
func TestFlagToParamKey(t *testing.T) {
tests := []struct {
input, expected string