mirrors/hermes-agent
1
0
Fork 0
mirror of https://github.com/NousResearch/hermes-agent.git synced 2026-07-20 15:33:54 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 7

fix(webhook): reject a non-ASCII signature header instead of crashing the endpoint

Browse source 
_validate_signature backs the public webhook receiver. It compared each
attacker-supplied signature/token header (GitHub X-Hub-Signature-256,
GitLab X-Gitlab-Token, generic X-Webhook-Signature / -V2, and the Svix v1
header) against a computed hex/base64 digest with hmac.compare_digest on
two str values. compare_digest raises TypeError on a str containing
non-ASCII characters, and the header is raw client input on an
unauthenticated endpoint — so any internet client could POST a single
non-ASCII byte in the signature header and raise out of the handler,
returning a 500 instead of a clean 401. Fail-closed, but an on-demand
crash of the request path.

Route all five comparisons through a small _hmac_str_equal() helper that
encodes both sides to UTF-8 bytes before the constant-time compare
(compare_digest has no ASCII restriction on bytes). Semantics are
unchanged for valid signatures; a hostile non-ASCII header now fails
closed with a rejection instead of raising.

Adds regression tests: non-ASCII GitHub/GitLab/generic/V2 signature
headers return False (no raise), and a non-ASCII configured secret still
matches its exact token value.

Also maps drexux0@gmail.com in scripts/release.py AUTHOR_MAP.
This commit is contained in:
Drexuxux 2026-07-16 04:42:13 +03:00 • committed by Teknium
parent efb6c21498
commit 1b69c47e97
2 changed files with 53 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

24
gateway/platforms/webhook.py
View file

@ -125,6 +125,20 @@ def _is_loopback_host(host: Optional[str]) -> bool:
return host.strip().lower() in _LOOPBACK_HOSTS
def _hmac_str_equal(provided: str, expected: str) -> bool:
"""Timing-safe equality for two ``str`` values, tolerant of non-ASCII input.
``hmac.compare_digest`` raises ``TypeError`` when given a ``str`` that
contains non-ASCII characters. The ``provided`` value here is an
attacker-controlled signature/token header on a public, unauthenticated
webhook endpoint, so a single non-ASCII byte would otherwise raise out of
the request handler and return a 500 instead of rejecting the request.
Comparing as UTF-8 bytes keeps the constant-time guarantee while making a
hostile header fail closed with a clean rejection.
"""
return hmac.compare_digest(provided.encode(), expected.encode())
def check_webhook_requirements() -> bool:
"""Check if webhook adapter dependencies are available."""
return AIOHTTP_AVAILABLE
@ -969,12 +983,12 @@ class WebhookAdapter(BasePlatformAdapter):
expected = "sha256=" + hmac.new(
secret.encode(), body, hashlib.sha256
).hexdigest()
return hmac.compare_digest(gh_sig, expected)
return _hmac_str_equal(gh_sig, expected)
# GitLab: X-Gitlab-Token = <plain secret>
gl_token = request.headers.get("X-Gitlab-Token", "")
if gl_token:
return hmac.compare_digest(gl_token, secret)
return _hmac_str_equal(gl_token, secret)
# Generic V2: X-Webhook-Signature-V2 = <hex HMAC-SHA256 of "<timestamp>.<body>">
# X-Webhook-Timestamp = <unix seconds> (required for V2)
@ -1017,7 +1031,7 @@ class WebhookAdapter(BasePlatformAdapter):
expected_v2 = hmac.new(
secret.encode(), signed_content, hashlib.sha256
).hexdigest()
return hmac.compare_digest(v2_sig, expected_v2)
return _hmac_str_equal(v2_sig, expected_v2)
# Generic V1 (legacy): X-Webhook-Signature = <hex HMAC-SHA256 of body>
# (deprecated — no replay protection, since the signature only
@ -1041,7 +1055,7 @@ class WebhookAdapter(BasePlatformAdapter):
"'<timestamp>.<body>').",
route_name,
)
return hmac.compare_digest(generic_sig, expected)
return _hmac_str_equal(generic_sig, expected)
# No recognised signature header but secret is configured → reject
logger.debug(
@ -1095,7 +1109,7 @@ class WebhookAdapter(BasePlatformAdapter):
version, signature = part.split(",", 1)
except ValueError:
continue
if version == "v1" and hmac.compare_digest(signature, expected):
if version == "v1" and _hmac_str_equal(signature, expected):
return True
return False

34
tests/gateway/test_webhook_adapter.py
View file

@ -166,6 +166,40 @@ class TestValidateSignature:
req = _mock_request(headers={}) # no sig headers at all
assert adapter._validate_signature(req, b"{}", "my-secret") is False
def test_non_ascii_signature_headers_reject_without_raising(self):
"""The signature headers are attacker-controlled on a public, unauth
endpoint. A non-ASCII byte in one must be rejected (False), not crash
the handler: hmac.compare_digest raises TypeError on a non-ASCII str."""
adapter = _make_adapter()
body = b'{"action": "opened"}'
secret = "webhook-secret-42"
hostile = "ské-not-a-valid-signature"
for header in (
"X-Hub-Signature-256",
"X-Gitlab-Token",
"X-Webhook-Signature",
):
req = _mock_request(headers={header: hostile})
# Must return False, never raise.
assert adapter._validate_signature(req, body, secret) is False
def test_non_ascii_generic_v2_signature_rejected(self):
"""V2 branch (timestamp-bound) also rejects a non-ASCII signature."""
adapter = _make_adapter()
req = _mock_request(headers={
"X-Webhook-Signature-V2": "ské-bad",
"X-Webhook-Timestamp": str(int(time.time())),
})
assert adapter._validate_signature(req, b"{}", "secret") is False
def test_non_ascii_secret_still_validates_a_matching_token(self):
"""A non-ASCII configured secret must still match its exact GitLab
token value byte for byte (bytes comparison keeps this working)."""
adapter = _make_adapter()
secret = "gl-tökén-välue"
req = _mock_request(headers={"X-Gitlab-Token": secret})
assert adapter._validate_signature(req, b"{}", secret) is True
def test_validate_no_secret_allows_all(self):
"""When the secret is empty/falsy, the validator is never even called
by the handler (secret check is 'if secret and secret != _INSECURE...').