alef 0.81.0

//! Executable proof that the generated `install.sh` selects its PIE interpreter by digest,
//! never by what happens to be on `PATH`.
//!
//! The script used to reuse an already-installed `pie` whenever it reported >= 1.3.7. That
//! made the pin and the SHA-256 check apply only on a machine that happened to have no PIE:
//! everywhere else an arbitrary, unverified binary ran instead, and two machines executed two
//! different PIEs. This is the inverse of the injection defects elsewhere in this change --
//! there, hostile input reached a trusted sink; here the sink was trusted and the *binary* was
//! unverified.
//!
//! [`preinstalled_pie_on_path_is_never_executed`] is the marker-file negative control: a fake
//! `pie` sits first on `PATH`, announces a version that would have satisfied the old gate, and
//! drops a marker file if it is ever run. The marker must not exist.
//! [`the_removed_version_sniffing_gate_would_have_executed_the_fake_pie`] runs the *pre-fix*
//! bootstrap through the identical sandbox and requires the marker to appear, so a harness
//! that stopped being able to observe the bypass fails loudly instead of passing vacuously.
//! ~keep

use super::project::render_install_sh;
use std::path::Path;

/// Marker the fake `pie` drops if it is ever executed.
const PIE_EXECUTED_MARKER: &str = "FAKE_PIE_WAS_EXECUTED";

/// The pre-fix interpreter-selection gate, verbatim. Kept here rather than in the generator so
/// the RED control exercises the exact shell the generator used to emit.
const REMOVED_VERSION_SNIFFING_GATE: &str = r#"
need_pie_install=true
if command -v pie >/dev/null 2>&1; then
  current="$(pie --version 2>&1 | grep -oE '[0-9]+\.[0-9]+\.[0-9]+' | head -1 || echo '0.0.0')"
  if printf '%s\n%s\n' "1.3.7" "$current" | sort -V -C; then
    need_pie_install=false
  fi
fi
if [[ "$need_pie_install" == "false" ]]; then
  PIE="pie"
  "$PIE" install "pkg:1.0.0"
  exit 0
fi
"#;

fn write_executable(path: &Path, body: &str) {
    use std::os::unix::fs::PermissionsExt as _;
    std::fs::write(path, body).expect("write script");
    let mut permissions = std::fs::metadata(path).expect("metadata").permissions();
    permissions.set_mode(0o755);
    std::fs::set_permissions(path, permissions).expect("chmod");
}

/// Build a `PATH` whose FIRST entry holds a hostile `pie` that reports a version the removed
/// gate would have accepted and drops [`PIE_EXECUTED_MARKER`] into `root` if executed, plus a
/// `curl` that "downloads" a stub instead of reaching the network.
fn poisoned_path(root: &Path) -> String {
    let bin = root.join("bin");
    std::fs::create_dir_all(&bin).expect("create sandbox bin dir");
    write_executable(
        &bin.join("pie"),
        &format!(
            "#!/bin/sh\ntouch '{}'\necho 'PIE 9.9.9'\nexit 0\n",
            root.join(PIE_EXECUTED_MARKER).display()
        ),
    );
    write_executable(
        &bin.join("curl"),
        concat!(
            "#!/bin/sh\n",
            "out=''\n",
            "while [ $# -gt 0 ]; do\n",
            "  case \"$1\" in --output) out=\"$2\"; shift 2;; *) shift;; esac\n",
            "done\n",
            "printf 'not-the-real-phar' > \"$out\"\n"
        ),
    );
    format!("{}:/usr/bin:/bin", bin.display())
}

/// Run `script` under `bash` with the poisoned `PATH` and `HOME` rooted at `root`.
fn run_bootstrap(root: &Path, script: &str) -> std::process::Output {
    let path = poisoned_path(root);
    let script_path = root.join("bootstrap.sh");
    std::fs::write(&script_path, script).expect("write bootstrap script");
    std::process::Command::new("/bin/bash")
        .arg(&script_path)
        .current_dir(root)
        .env_clear()
        .env("PATH", path)
        .env("HOME", root)
        .output()
        .expect("/bin/bash should start")
}

/// Everything the generated script does before it would invoke `"$PIE"`, plus a line that
/// invokes it -- i.e. the interpreter-selection decision and its consequence, isolated from
/// the `php`/`composer` steps a unit test cannot run.
fn bootstrap_section(content: &str) -> String {
    let start = content.find("PIE_VERSION=").expect("PIE_VERSION pin present");
    let end = content
        .find("# Install the extension binary into the running PHP's extension dir.")
        .expect("bootstrap section ends before the extension install");
    format!(
        "set -euo pipefail\n{}\n\"$PIE\" install \"pkg:1.0.0\"\n",
        &content[start..end]
    )
}

/// NEGATIVE CONTROL. A hostile `pie` first on `PATH`, announcing a version the removed gate
/// accepted, must never be selected. The marker file is the assertion: string-matching the
/// generated script would only prove the text changed, not that the binary cannot be reached.
#[test]
fn preinstalled_pie_on_path_is_never_executed() {
    let root = tempfile::tempdir().expect("tempdir");
    let content = render_install_sh("test/pkg", "ext", "1.0.0");
    let output = run_bootstrap(root.path(), &bootstrap_section(&content));

    assert!(
        !root.path().join(PIE_EXECUTED_MARKER).exists(),
        "the preinstalled `pie` on PATH was executed; stderr:\n{}",
        String::from_utf8_lossy(&output.stderr)
    );
    assert!(
        !output.status.success(),
        "a stub download must not pass the digest check; stdout:\n{}",
        String::from_utf8_lossy(&output.stdout)
    );
    assert!(
        String::from_utf8_lossy(&output.stderr).contains("checksum mismatch"),
        "the script must reach the digest comparison rather than short-circuiting to the \
         preinstalled binary; stderr:\n{}",
        String::from_utf8_lossy(&output.stderr)
    );
}

/// RED harness proof: the removed gate, run through the identical sandbox, DOES execute the
/// fake `pie`. Without this, the test above could pass because the fake `pie` is unrunnable.
#[test]
fn the_removed_version_sniffing_gate_would_have_executed_the_fake_pie() {
    let root = tempfile::tempdir().expect("tempdir");
    let script = format!("set -euo pipefail\n{REMOVED_VERSION_SNIFFING_GATE}");
    let output = run_bootstrap(root.path(), &script);

    assert!(
        root.path().join(PIE_EXECUTED_MARKER).exists(),
        "the pre-fix gate must execute the fake `pie`, otherwise the control test proves \
         nothing; stderr:\n{}",
        String::from_utf8_lossy(&output.stderr)
    );
}

/// The generated script must carry no interpreter-selection branch at all: no `command -v
/// pie`, no version comparison, no `PIE="pie"` fallback to whatever is on `PATH`.
#[test]
fn the_generated_script_has_no_path_based_interpreter_fallback() {
    let content = render_install_sh("test/pkg", "ext", "1.0.0");
    for forbidden in [
        "command -v pie",
        "need_pie_install",
        "PIE=\"pie\"",
        "sort -V -C",
        "1.3.7",
    ] {
        assert!(
            !content.contains(forbidden),
            "install.sh must not reintroduce a PATH-based PIE fallback ({forbidden:?}), got:\n{content}"
        );
    }
    assert!(
        content.contains("PIE=\"$pie_dir/pie\""),
        "the interpreter must always be the verified PHAR, got:\n{content}"
    );
    // The digest gate must precede the only assignment of `$PIE`, so no code path reaches an
    // interpreter that was not compared against the pin.
    let verify = content.find("checksum mismatch").expect("digest gate present");
    let assign = content.find("PIE=\"$pie_dir/pie\"").expect("interpreter assigned");
    assert!(verify < assign, "the digest must be checked before `$PIE` is chosen");
}