tests: cover the three security boundaries that had none (#3950)

- hive-c0re::webhook_secret::verify_signature — the HMAC comparison
  verify_hmac (the only gate on the public webhook endpoint) delegates
  to. Correct-signature and mismatched-signature (wrong secret, tampered
  body) cases.
- hive-forge credential-helper get (host= check) — subprocess
  integration tests since the check is inlined in run(), which reads
  real stdin/env and prints real stdout. Host mismatch (error, token
  withheld), host match (credentials printed), and no host= line
  (backwards compat) cases.
- hive-priv::{validate_credential_name, validate_snapshot_name,
  ensure_plain_filename} — the only gate on the root-privileged socket.
  Empty/charset/dot/slash rejection, hive- prefix requirement, and
  ./../slash rejection respectively.

hive-c0re/src/webhook_secret.rs

@@ -97,3 +97,41 @@ fn hex_decode(s: &str) -> Option<Vec<u8>> {
     }
     Some(out)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{hex_encode, verify_signature};
+
+    /// Compute the `sha256=<hex>` header Forgejo would send for `secret` +
+    /// `body`, so the "matches" test below isn't asserting against a
+    /// hand-picked string that happens to look like a signature.
+    fn sign(secret: &str, body: &[u8]) -> String {
+        use hmac::{Hmac, KeyInit, Mac};
+        use sha2::Sha256;
+        let mut mac = Hmac::<Sha256>::new_from_slice(secret.as_bytes()).unwrap();
+        mac.update(body);
+        format!("sha256={}", hex_encode(&mac.finalize().into_bytes()))
+    }
+
+    /// `verify_hmac` (`dashboard/webhook.rs`) delegates the actual HMAC
+    /// comparison here — this is the only gate on an inbound Forgejo
+    /// webhook reachable via the public gateway. A signature computed
+    /// with the right secret over the right body must verify.
+    #[test]
+    fn verify_signature_accepts_the_correct_hmac() {
+        let header = sign("s3cr3t", b"payload");
+        assert!(verify_signature("s3cr3t", b"payload", &header).is_ok());
+    }
+
+    /// If `mac.verify_slice`'s result were ever inverted (accept on
+    /// mismatch), an unauthenticated actor could queue an operator
+    /// approval through the public webhook endpoint. Cover both ways a
+    /// signature can stop matching: wrong secret, and a body that no
+    /// longer matches the one that was signed.
+    #[test]
+    fn verify_signature_rejects_a_mismatched_hmac() {
+        let header = sign("s3cr3t", b"payload");
+        assert!(verify_signature("different-secret", b"payload", &header).is_err());
+        assert!(verify_signature("s3cr3t", b"tampered-payload", &header).is_err());
+    }
+}

hive-forge/tests/credential_helper.rs

@@ -0,0 +1,113 @@
+//! Integration coverage for `hive-forge credential-helper get` — the
+//! `host=` check in `verbs::credential_helper::run` exists to close a
+//! reported credential leak, and git invokes the helper fresh over
+//! stdin/env on every fetch/push. The check is inlined in `run()`
+//! (real stdin, real env, real stdout), so it can only be driven the way
+//! git actually drives it: run the compiled binary.
+
+use std::io::Write as _;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
+
+const TOKEN: &str = "test-token-value";
+
+/// A unique scratch `HYPERHIVE_STATE_DIR`, seeded with a `forge-token`
+/// file. Matches the manual-tmpdir pattern `hive-c0re`'s
+/// `dashboard::state_files` tests use — this crate carries no `tempfile`
+/// dependency to reach for instead.
+fn scratch_state_dir(tag: &str) -> PathBuf {
+    let ts = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .map_or(0, |d| d.as_nanos());
+    let dir = std::env::temp_dir().join(format!("hive-forge-cred-test-{tag}-{ts}"));
+    std::fs::create_dir_all(&dir).expect("create scratch state dir");
+    std::fs::write(dir.join("forge-token"), format!("{TOKEN}\n")).expect("seed forge-token");
+    dir
+}
+
+/// Run `hive-forge credential-helper get` against `base_url` +
+/// `state_dir`, feeding `request` as the git credential-protocol
+/// request body on stdin. Returns `(exit success, stdout, stderr)`.
+fn run_get(base_url: &str, state_dir: &Path, request: &str) -> (bool, String, String) {
+    let mut child = Command::new(env!("CARGO_BIN_EXE_hive-forge"))
+        .arg("credential-helper")
+        .arg("get")
+        .env("HIVE_FORGE_URL", base_url)
+        .env("HYPERHIVE_STATE_DIR", state_dir)
+        .env_remove("HIVE_LABEL")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .expect("spawn hive-forge credential-helper get");
+    child
+        .stdin
+        .take()
+        .expect("piped stdin")
+        .write_all(request.as_bytes())
+        .expect("write credential request to stdin");
+    let out = child.wait_with_output().expect("wait for hive-forge");
+    (
+        out.status.success(),
+        String::from_utf8_lossy(&out.stdout).into_owned(),
+        String::from_utf8_lossy(&out.stderr).into_owned(),
+    )
+}
+
+/// This is the check the module doc says exists to close a reported
+/// credential leak: refusing to hand the forge token to a host git
+/// didn't ask this invocation to serve. If the host comparison were ever
+/// inverted, a mismatched host would get the token instead of being
+/// refused.
+#[test]
+fn credential_helper_get_refuses_a_mismatched_host_and_withholds_the_token() {
+    let dir = scratch_state_dir("mismatch");
+    let (ok, stdout, stderr) = run_get(
+        "http://forge.internal.example",
+        &dir,
+        "protocol=https\nhost=not-the-forge.example\n",
+    );
+    assert!(!ok, "a mismatched host= must fail, stderr={stderr}");
+    assert!(
+        !stdout.contains(TOKEN),
+        "the token must never reach stdout on a host mismatch: stdout={stdout}"
+    );
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+/// The other side of the same check: a `host=` that matches the
+/// configured forge must still print the credentials, or every real git
+/// fetch/push would break.
+#[test]
+fn credential_helper_get_answers_when_host_matches() {
+    let dir = scratch_state_dir("match");
+    let (ok, stdout, stderr) = run_get(
+        "http://forge.internal.example",
+        &dir,
+        "protocol=https\nhost=forge.internal.example\n",
+    );
+    assert!(ok, "a matching host= must succeed, stderr={stderr}");
+    assert!(stdout.contains("username="), "stdout={stdout}");
+    assert!(
+        stdout.contains(&format!("password={TOKEN}")),
+        "stdout={stdout}"
+    );
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+/// Backwards compatibility: the request shape git sent before this check
+/// existed — no `host=` line at all — must still work.
+#[test]
+fn credential_helper_get_still_works_with_no_host_line() {
+    let dir = scratch_state_dir("nohost");
+    let (ok, stdout, stderr) = run_get("http://forge.internal.example", &dir, "protocol=https\n");
+    assert!(
+        ok,
+        "a request with no host= line must not be treated as a failure, stderr={stderr}"
+    );
+    assert!(
+        stdout.contains(&format!("password={TOKEN}")),
+        "stdout={stdout}"
+    );
+    let _ = std::fs::remove_dir_all(&dir);
+}

hive-priv/src/main.rs

@@ -3114,9 +3114,10 @@ mod tests {
     use super::{
         AgentTmpfilesEntry, BindMount, OwnedFd, PAUSED_MARKER_FILE, PrivRequest,
         agent_tmpfiles_content, check_fd_agreement, clear_runner_credentials,
-        contains_secret_shaped_run, git_overlay_flags, limits_dropin_body, matrix_token_filename,
-        partial_name, redact_secret_line, remove_marker_in, single_output_path, toplevel_attr,
-        validate_account_name, write_agent_dir_file, write_state_file_nofollow,
+        contains_secret_shaped_run, ensure_plain_filename, git_overlay_flags, limits_dropin_body,
+        matrix_token_filename, partial_name, redact_secret_line, remove_marker_in,
+        single_output_path, toplevel_attr, validate_account_name, validate_credential_name,
+        validate_snapshot_name, write_agent_dir_file, write_state_file_nofollow,
     };
     use std::path::PathBuf;
     use std::sync::atomic::{AtomicU32, Ordering};
@@ -3735,4 +3736,44 @@ mod tests {
         );
         std::fs::remove_dir_all(&dir).ok();
     }
+
+    /// The only gate on the root-privileged socket for a `--load-credential`
+    /// name. The doc comment is explicit that `.` is excluded on purpose
+    /// ("this name gets interpolated into filesystem paths") — a future
+    /// "let's allow dots for version numbers" loosening must fail this,
+    /// not just the `/` case below.
+    #[test]
+    fn validate_credential_name_rejects_dot_slash_and_empty_but_allows_the_charset() {
+        assert!(
+            validate_credential_name("").is_err(),
+            "empty must be rejected"
+        );
+        assert!(validate_credential_name("valid-name_123").is_ok());
+        assert!(
+            validate_credential_name("bad.name").is_err(),
+            "dot must be rejected — see the fn's doc comment"
+        );
+        assert!(validate_credential_name("bad/name").is_err());
+    }
+
+    /// A snapshot label must additionally carry the `hive-` prefix (it
+    /// doubles as the allow-list gating the btrfs snapshot/delete
+    /// shellouts) on top of [`validate_credential_name`]'s charset rule.
+    #[test]
+    fn validate_snapshot_name_requires_hive_prefix() {
+        assert!(validate_snapshot_name("not-hive-prefixed").is_err());
+        assert!(validate_snapshot_name("hive-valid").is_ok());
+    }
+
+    /// `ensure_plain_filename` is the gate between an agent-writable
+    /// directory and a root-privileged file write. `.`/`..` would resolve
+    /// to the directory itself or its parent; any `/` climbs into a path
+    /// component the caller never named.
+    #[test]
+    fn ensure_plain_filename_rejects_dot_dotdot_and_any_slash() {
+        assert!(ensure_plain_filename("test", ".").is_err());
+        assert!(ensure_plain_filename("test", "..").is_err());
+        assert!(ensure_plain_filename("test", "sub/dir").is_err());
+        assert!(ensure_plain_filename("test", "matrix-token").is_ok());
+    }
 }