atlas-iac/testing/tests/test_hermes_receive_pack_scan.py

"""Quarantine content-scanning contracts for brokered Git pushes."""

from __future__ import annotations

import hashlib
import io
import zlib

import pytest

from testing.tests.test_hermes_scm_broker_support import (
    _blob_pack,
    _load,
    _object_entry,
    _pack_of,
    _receive_command,
)

ZERO = b"0" * 40
COMMIT = b"1" * 40
TOKEN = "runtime-sentinel"
FORMS = (b"runtime-sentinel",)


def _request(pack: bytes, ref: bytes = b"refs/heads/hermes/scan") -> bytes:
    return _receive_command(ZERO, COMMIT, ref, pack)


def test_clean_push_with_real_content_passes():
    scan = _load("receive_pack_scan")
    pack = _blob_pack(
        b"# services/example/deployment.yaml\napiVersion: apps/v1\n",
        b"tree 5b3a\nparent none\n",
    )
    scan.validate_receive_pack(_request(pack), TOKEN, FORMS)


@pytest.mark.parametrize(
    "payload",
    [
        b"-----BEGIN OPENSSH PRIVATE KEY-----\nb3BlbnNzaA==\n",
        b"-----BEGIN RSA PRIVATE KEY-----\nMIIE\n",
        b"key = ghp_" + b"a1" * 12,
        b"aws_access_key_id = AKIAABCDEFGHIJKLMNOP",
        b"jwt eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIn0.c2lnbmF0dXJlLXNlZ21lbnQ",
        b"hook https://hooks.slack.com/services/T000/B000/tokentokentokentoken",
        b"AGE-SECRET-KEY-1QQPCXR7QQPCXR7QQPCXR7QQPCXR7",
        b"PuTTY-User-Key-File-3: ssh-ed25519",
        b"Authorization: Bearer abc123-tokenvalue",
        b"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIF2c hermes@atlas",
        b"gitea gta_" + b"z9" * 12,
    ],
)
def test_credential_shaped_object_content_is_rejected(payload):
    scan = _load("receive_pack_scan")
    with pytest.raises(scan.PolicyError, match="credential-shaped"):
        scan.validate_receive_pack(_request(_blob_pack(payload)), TOKEN, FORMS)


def test_runtime_token_hidden_by_compression_is_still_caught():
    scan = _load("receive_pack_scan")
    pack = _blob_pack(b"config value: runtime-sentinel\n")
    # The compressed wire bytes do not contain the token; only the
    # decompressed payload does.
    assert b"runtime-sentinel" not in pack
    with pytest.raises(scan.PolicyError, match="runtime credential material"):
        scan.validate_receive_pack(_request(pack), TOKEN, FORMS)


def _size_varint(value: int) -> bytes:
    out = bytearray()
    while True:
        byte = value & 0x7F
        value >>= 7
        if value:
            out.append(byte | 0x80)
        else:
            out.append(byte)
            return bytes(out)


def _typed_header(type_code: int, size: int) -> bytes:
    byte = (type_code << 4) | (size & 0x0F)
    size >>= 4
    header = bytearray()
    while size:
        header.append(byte | 0x80)
        byte = size & 0x7F
        size >>= 7
    header.append(byte)
    return bytes(header)


def test_secret_assembled_only_by_delta_resolution_is_caught():
    scan = _load("receive_pack_scan")
    base = b"docs: AKIAABCD"
    completion = b"EFGHIJKLMNOP"
    delta = (
        _size_varint(len(base))
        + _size_varint(len(base) + len(completion))
        + bytes([0x80 | 0x10, len(base)])
        + bytes([len(completion)])
        + completion
    )
    base_sha = hashlib.sha1(b"blob %d\x00" % len(base) + base).digest()
    delta_entry = _typed_header(7, len(delta)) + base_sha + zlib.compress(delta)
    pack = _pack_of([_object_entry(3, base), delta_entry])
    # Neither the base nor the delta insert alone matches; the resolved
    # payload is the only place the credential exists.
    with pytest.raises(scan.PolicyError, match="runtime credential|credential-shaped"):
        scan.validate_receive_pack(_request(pack), TOKEN, FORMS)


def test_thin_pack_deltas_are_rejected_outright():
    scan = _load("receive_pack_scan")
    delta = _size_varint(4) + _size_varint(1) + bytes([1]) + b"x"
    entry = _typed_header(7, len(delta)) + b"\xbb" * 20 + zlib.compress(delta)
    with pytest.raises(scan.PolicyError, match="push full packs"):
        scan.validate_receive_pack(_request(_pack_of([entry])), TOKEN, FORMS)


def test_trailing_bytes_after_the_pack_are_rejected():
    scan = _load("receive_pack_scan")
    body = _request(_pack_of([])) + b"extra"
    with pytest.raises(scan.PolicyError, match="bytes after its pack"):
        scan.validate_receive_pack(body, TOKEN, FORMS)


@pytest.mark.parametrize(
    ("line", "match"),
    [
        (b"shallow " + COMMIT, "ref command is invalid"),
        (COMMIT + b" " + COMMIT + b" refs/heads/hermes/x", "feature-branch creation"),
        (ZERO + b" " + ZERO + b" refs/heads/hermes/x", "feature-branch creation"),
        (ZERO + b" " + COMMIT + b" refs/heads/main", "namespaced feature branches"),
        (ZERO + b" " + COMMIT + b" refs/tags/v1", "namespaced feature branches"),
        (ZERO + b" " + COMMIT + b" refs/heads/hermes/\xff", "canonical ASCII"),
        (b"zz" * 20 + b" " + COMMIT + b" refs/heads/hermes/x", "ref command is invalid"),
    ],
)
def test_push_commands_outside_the_narrow_grant_are_rejected(line, match):
    scan = _load("receive_pack_scan")
    framed = f"{len(line) + 5:04x}".encode() + line + b"\n" + b"0000"
    with pytest.raises(scan.PolicyError, match=match):
        scan.validate_receive_pack(framed + _pack_of([]), TOKEN, FORMS)


def test_command_stream_bounds_are_enforced():
    scan = _load("receive_pack_scan")
    with pytest.raises(scan.PolicyError, match="no ref command"):
        scan.validate_receive_pack(b"0000" + _pack_of([]), TOKEN, FORMS)
    with pytest.raises(scan.PolicyError, match="omitted its command terminator"):
        scan.validate_receive_pack(b"", TOKEN, FORMS)
    line = ZERO + b" " + COMMIT + b" refs/heads/hermes/x\n"
    framed = f"{len(line) + 4:04x}".encode() + line
    many = framed * (scan.MAX_PUSH_COMMANDS + 1) + b"0000" + _pack_of([])
    with pytest.raises(scan.PolicyError, match="too many ref commands"):
        scan.validate_receive_pack(many, TOKEN, FORMS)
    with pytest.raises(scan.PolicyError, match="framing is invalid"):
        scan.validate_receive_pack(b"zzzz", TOKEN, FORMS)
    with pytest.raises(scan.PolicyError, match="framing is invalid"):
        scan.validate_receive_pack(b"0003", TOKEN, FORMS)
    with pytest.raises(scan.PolicyError, match="framing is invalid"):
        scan.validate_receive_pack(b"0009abc", TOKEN, FORMS)


def test_credential_forms_in_command_lines_are_rejected():
    scan = _load("receive_pack_scan")
    line = ZERO + b" " + COMMIT + b" refs/heads/hermes/x runtime-sentinel\n"
    framed = f"{len(line) + 4:04x}".encode() + line + b"0000"
    with pytest.raises(scan.PolicyError, match="runtime credential material"):
        scan.validate_receive_pack(framed + _pack_of([]), TOKEN, FORMS)


def test_scan_crosses_chunk_boundaries_with_carry(monkeypatch):
    scan = _load("receive_pack_scan")
    monkeypatch.setattr(scan, "SCAN_CHUNK", 8)
    monkeypatch.setattr(scan, "SCAN_CARRY", 48)
    payload = b"x" * 20 + b" AKIAABCDEFGHIJKLMNOP " + b"y" * 20
    with pytest.raises(scan.PolicyError, match="credential-shaped"):
        scan._scan_payload(io.BytesIO(payload), FORMS)
    scan._scan_payload(io.BytesIO(b"clean " * 40), FORMS)
    scan._scan_payload(io.BytesIO(b""), FORMS)


def test_scan_loose_object_reports_type_and_scans_content():
    scan = _load("receive_pack_scan")
    clean = zlib.compress(b"blob 5\x00clean")
    assert scan.scan_loose_object(clean, FORMS) == 3
    secret = b"-----BEGIN EC PRIVATE KEY-----"
    dirty = zlib.compress(b"blob %d\x00" % len(secret) + secret)
    with pytest.raises(scan.PolicyError, match="credential-shaped"):
        scan.scan_loose_object(dirty, FORMS)
    leaked = b"the runtime-sentinel value"
    with pytest.raises(scan.PolicyError, match="runtime credential material"):
        scan.scan_loose_object(
            zlib.compress(b"blob %d\x00" % len(leaked) + leaked), FORMS
        )


def test_content_patterns_extend_the_shared_standalone_corpus():
    scan = _load("receive_pack_scan")
    policy = _load("gitea_api_policy")
    assert len(scan.CONTENT_SECRET_PATTERNS) == len(policy.STANDALONE_SECRET_PATTERNS) + 3
    assert all(
        isinstance(pattern.pattern, bytes) for pattern in scan.CONTENT_SECRET_PATTERNS
    )


def test_validation_rewinds_the_stream_for_upstream_forwarding():
    scan = _load("receive_pack_scan")
    body = _request(_blob_pack(b"safe content"))
    stream = io.BytesIO(body)
    scan.validate_receive_pack(stream, TOKEN, FORMS)
    assert stream.tell() == 0
    with pytest.raises(scan.PolicyError):
        scan.validate_receive_pack(io.BytesIO(b"zzzz"), TOKEN, FORMS)