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Add client_secret redaction pass to credential scrubber #17

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Add client_secret redaction pass to credential scrubber #17

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1f5e2d0
Add client_secret redaction pass to _url.redact()
jamesgol Jul 25, 2026
52c7bf3
Handle quoted and alternate-spelling client_secret forms
jamesgol Aug 1, 2026
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4 changes: 4 additions & 0 deletions vulnhunter-agent/agent/_url.py
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,9 @@
_RAW_TOKEN_RE = re.compile(
r"(ghp_|gho_|ghu_|ghs_|ghr_|github_pat_|sk-ant-)[A-Za-z0-9_-]+"
)
_FORM_SECRET_RE = re.compile(
r"(?i)(client[_-]?secret\"?\s*[=:]\s*)[\"']?[^\s,}&\"']+[\"']?"
)

@schenksj schenksj Aug 1, 2026

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The exclusion class [^\s,}&\"']+ is meant to stop at a closing quote, but it also blocks the opening one — so any quoted value fails to match at all and passes through verbatim. Probing the regex directly:

ok    client_secret=SUPERSECRET&grant_type=x   -> client_secret=***&grant_type=x
ok    client_secret: SUPERSECRET               -> client_secret: ***
ok    CLIENT_SECRET=SUPERSECRET                -> CLIENT_SECRET=***
LEAK  {"client_secret": "SUPERSECRET"}         -> unchanged
LEAK  {"client_secret":"SUPERSECRET"}          -> unchanged
LEAK  client_secret = "SUPERSECRET"            -> unchanged   (TOML config form)
LEAK  client_secret='SUPERSECRET'              -> unchanged

This matters for the threat model in the PR description. RFC 6749 §5.2 specifies token-endpoint error responses as JSON, and agent/auth.py:134 interpolates response.text straight into AuthTokenError — so the most likely shape of the leak is exactly the shape not covered. The TOML form is live too: tests/test_audit.py:496 writes client_secret = "csecret" in a config fixture, and agent/audit.py:368 redacts every string in an audit record.

Suggested fix — consume the opening quote explicitly, and pick up the client-secret / clientSecret spellings that also leak today:

_FORM_SECRET_RE = re.compile(
    r"(?i)(client[_-]?secret\"?\s*[=:]\s*)[\"']?[^\s,}&\"']+[\"']?"
)

Please re-check idempotence after changing this. The current pattern happens to be idempotent because * isn't in the exclusion class, and that property is worth keeping — note that test_property_redact_is_idempotent (tests/test_url.py:164) only generates URL inputs, so it won't check this for you.



def redact(text: str) -> str:
Expand All @@ -42,6 +45,7 @@ def redact(text: str) -> str:
s = _BEARER_RE.sub(r"\1***", s)
s = _QUERY_TOKEN_RE.sub(r"\1***", s)
s = _RAW_TOKEN_RE.sub(r"\1***", s)
s = _FORM_SECRET_RE.sub(r"\1***", s)

@schenksj schenksj Aug 1, 2026

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Pass ordering is fine — this runs after the token-prefix pass and the patterns don't overlap, so no interaction to worry about.

This new pass is the line with no test behind it. Please add a test_client_secret_redacted alongside the existing per-pass cases in tests/verify_012_audit_redaction.py, parametrized over the forms in my other comment (form-encoded, JSON with and without a space after the colon, TOML key = "value", single-quoted, uppercase), asserting the secret is absent and *** is present — plus an idempotence assertion.

# Residual risk (VULN-012, CWE-532): redaction is pattern-based over
# enumerated token formats; a novel/unknown secret format not in the pass
# list above would still pass through to the audit stream.
Expand Down
23 changes: 23 additions & 0 deletions vulnhunter-agent/tests/verify_012_audit_redaction.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,8 @@
headers, access_token query params, and raw token prefixes.
"""

import pytest

from agent._url import redact


Expand Down Expand Up @@ -38,6 +40,27 @@ def test_raw_token_prefixes_redacted_prefix_preserved():
assert prefix in out, f"prefix {prefix} should be preserved for triage"


@pytest.mark.parametrize(
"text",
[
"client_secret=SUPERSECRET&grant_type=x",
"client_secret: SUPERSECRET",
"CLIENT_SECRET=SUPERSECRET",
'{"client_secret": "SUPERSECRET"}',
'{"client_secret":"SUPERSECRET"}',
'client_secret = "SUPERSECRET"',
"client_secret='SUPERSECRET'",
"client-secret=SUPERSECRET",
"clientSecret=SUPERSECRET",
],
)
def test_client_secret_redacted(text):
out = redact(text)
assert "SUPERSECRET" not in out
assert "***" in out
assert redact(out) == out # idempotent


def test_benign_text_unchanged():
assert redact("just a normal log line about issue #42") == (
"just a normal log line about issue #42"
Expand Down