vetto 0.2.17

//! Shared throwaway-sandbox probe: ONE spawn of the real enforcement backend
//! running a POSIX-sh script that self-reports verdicts on stdout.
//!
//! Line protocol (pipe-delimited):
//!   D|<path>|contents-denied|content-readable   deny directory contents
//!   F|<path>|<bytes>|unreadable                 deny file read
//!   NET|reachable|unreachable|nobash            loopback listener connect
//!   WRITE|allowed|denied                        write outside every write root
//!
//! Callers attach variable targets as trailing script arguments: plain deny
//! paths, `NETCHECK:<port>` for the loopback probe, `WRITECHECK:<path>` for
//! the write-outside probe.

use std::collections::HashMap;
use std::io::Read;
use std::os::fd::{AsRawFd, FromRawFd, OwnedFd};
use std::path::Path;

use anyhow::{bail, Result};

use crate::config::NetMode;
use crate::policy::Policy;
use crate::sandbox;

pub struct ProbeOutput {
    pub stdout: String,
    pub stderr: String,
}

/// FS-ONLY honesty constraint: directory ENTRY NAMES may remain visible
/// (Landlock is access control, not a visibility overlay), so the security
/// property checked for denied directories is that no file CONTENT beneath
/// them can be read. Overlaid files appear EMPTY (0 bytes).
const PROBE_SCRIPT: &str = r##"for p in "$@"; do
  case "$p" in
    NETCHECK:*)
      port=${p#NETCHECK:}
      if command -v bash >/dev/null 2>&1; then
        if (exec 3<>"/dev/tcp/127.0.0.1/$port") 2>/dev/null; then
          echo "NET|reachable"
        else
          echo "NET|unreachable"
        fi
      else
        echo "NET|nobash"
      fi
      ;;
    WRITECHECK:*)
      target=${p#WRITECHECK:}
      if dd if=/dev/null of="$target" bs=1 count=1 2>/dev/null; then
        echo "WRITE|allowed"
      else
        echo "WRITE|denied"
      fi
      ;;
    *)
      if [ -d "$p" ]; then
        leak=0
        for f in "$p"/* "$p"/.[!.]* "$p"/..?*; do
          [ -f "$f" ] || continue
          if dd if="$f" of=/dev/null bs=1 count=1 >/dev/null 2>&1; then leak=1; break; fi
        done
        if [ "$leak" -eq 0 ]; then
          echo "D|$p|contents-denied"
        else
          echo "D|$p|content-readable"
        fi
      else
        n=$(wc -c <"$p" 2>/dev/null) || { echo "F|$p|unreadable"; continue; }
        echo "F|$p|$n"
      fi
      ;;
  esac
done"##;

/// Build the throwaway sandbox from `pol`, run the probe script with
/// `script_args`, and collect its output. The sandbox network mode is always
/// Off: the battery verifies the default-enforced boundary, and relay modes
/// (`allowlist`/`strict`) only add a broker on top of the same
/// netns/seccomp base, so direct-egress isolation is identical.
pub fn run_probe_script(
    pol: &Policy,
    project: &Path,
    script_args: Vec<String>,
) -> Result<ProbeOutput> {
    let backend = sandbox::Backend::detect(NetMode::Off, false)?;
    let mut agent_cmd = vec![
        "/bin/sh".to_string(),
        "-c".to_string(),
        PROBE_SCRIPT.to_string(),
        "vetto-probe".to_string(),
    ];
    agent_cmd.extend(script_args);

    let (out_r, out_w) = pipe2()?;
    let (err_r, err_w) = pipe2()?;
    let opts = sandbox::SpawnOptions {
        stdio: sandbox::StdioMode::Captured {
            stdout_w: out_w.as_raw_fd(),
            stderr_w: err_w.as_raw_fd(),
        },
        agent_cmd,
        cwd: project.to_path_buf(),
        env_extra: HashMap::new(),
    };
    let sandbox::Spawned { mut handle, .. } = backend.spawn(pol, opts)?;
    drop(out_w);
    drop(err_w);

    // Consume the OwnedFds into Files (taking ownership, no double close).
    // Read to EOF before waiting: the pipes close when the probe exits.
    let mut output = String::new();
    let mut out_file: std::fs::File = out_r.into();
    let _ = out_file.read_to_string(&mut output);
    let mut eout = String::new();
    let mut err_file: std::fs::File = err_r.into();
    let _ = err_file.read_to_string(&mut eout);
    let _exit = handle.wait();

    Ok(ProbeOutput {
        stdout: output,
        stderr: eout,
    })
}

fn pipe2() -> Result<(OwnedFd, OwnedFd)> {
    let mut fds = [0 as libc::c_int; 2];
    // SAFETY: valid out-array.
    if unsafe { libc::pipe(fds.as_mut_ptr()) } != 0 {
        bail!("pipe: {}", std::io::Error::last_os_error());
    }
    for fd in fds {
        // SAFETY: fd came from the successful pipe call.
        let flags = unsafe { libc::fcntl(fd, libc::F_GETFD) };
        if flags < 0 {
            let error = std::io::Error::last_os_error();
            // SAFETY: both descriptors came from the successful pipe call.
            unsafe {
                libc::close(fds[0]);
                libc::close(fds[1]);
            }
            bail!("fcntl(F_GETFD): {error}");
        }
        // SAFETY: fd came from the successful pipe call; preserve existing
        // descriptor flags while adding close-on-exec.
        if unsafe { libc::fcntl(fd, libc::F_SETFD, flags | libc::FD_CLOEXEC) } < 0 {
            let error = std::io::Error::last_os_error();
            // SAFETY: both descriptors came from the successful pipe call.
            unsafe {
                libc::close(fds[0]);
                libc::close(fds[1]);
            }
            bail!("fcntl(F_SETFD, FD_CLOEXEC): {error}");
        }
    }
    // SAFETY: fresh descriptors from a successful pipe and CLOEXEC setup.
    Ok((unsafe { OwnedFd::from_raw_fd(fds[0]) }, unsafe {
        OwnedFd::from_raw_fd(fds[1])
    }))
}