The CLI and TUI build an SSH ProxyCommand string by interpolating fields
from CreateSshSessionResponse into a shell command. Three fields -
sandbox_id, token, and the assembled gateway_url (composed from
gateway_scheme, gateway_host, gateway_port, connect_path) - were not
passed through shell_escape, even though exe_command and gateway_name
were. The resulting string is handed to `ssh -o ProxyCommand=...` which
OpenSSH routes through `/bin/sh -c`, so a hostile or compromised gateway
could inject shell metacharacters and execute arbitrary commands under
the developer's workstation account.
- Add build_proxy_command in openshell-core::forward that wraps every
interpolated value in shell_escape. Use it at all four ProxyCommand
sites: openshell-cli/src/ssh.rs (ssh_session_config) and the three
TUI sites in openshell-tui/src/lib.rs (shell connect, sandbox exec,
port-forward reconciliation).
- Add validate_ssh_session_response in openshell-core::forward, called
at each site immediately after response.into_inner(). Enforces a
conservative charset per field (sandbox_id, token, gateway_host,
gateway_scheme, gateway_port, connect_path, host_key_fingerprint) so
malformed responses fail loudly at the gRPC trust boundary before
shell escaping is attempted. Belt-and-suspenders with the escape.
- Harden render_ssh_config so `gateway` and `name` are shell-escaped
even though validate_gateway_name currently gates `gateway`.
- Document the charset contract on CreateSshSessionResponse in
proto/openshell.proto: servers must uphold these rules and clients
reject responses that violate them.
- Add regression unit tests covering adversarial values in every field
and a build_proxy_command test asserting no shell metacharacter
remains outside single-quoted regions.
Tracks OS-100.
Derek Carr