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fix(provenance): anchor with \Z, so a trailing newline is not part of an identifier #154

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Merged
imran-siddique merged 1 commit into from
Aug 12, 2026
Merged

fix(provenance): anchor with \Z, so a trailing newline is not part of an identifier #154

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6 changes: 4 additions & 2 deletions src/agentrust_trace/provenance.py
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,10 @@
#: Closed on purpose: the value of the field is that a verifier can key on it.
KINDS = ("publisher-asserted", "observer-attested", "tee-attested")

_DIGEST_RE = re.compile(r"^sha256:[0-9a-f]{64}$")
_PUBLISHER_RE = re.compile(r"^(did:[a-z0-9]+:.+|spiffe://[^/]+/.+)$")
# `\Z`, not `$`: in Python `$` also matches immediately before a single trailing newline,
# so `^...$` accepts "did:web:acme.example\n" and every digest with a newline glued to it.
_DIGEST_RE = re.compile(r"^sha256:[0-9a-f]{64}\Z")
_PUBLISHER_RE = re.compile(r"^(did:[a-z0-9]+:.+|spiffe://[^/]+/.+)\Z")


class ProvenanceError(ValueError):
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42 changes: 42 additions & 0 deletions tests/test_provenance.py
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Original file line number Diff line number Diff line change
Expand Up @@ -316,3 +316,45 @@ def test_a_well_formed_record_still_verifies() -> None:
key = generate_key()
signed = sign_record(_record(), key)
verify_record(signed, key_to_jwk(key))


# --- anchoring: a trailing newline is not part of an identifier ------------


@pytest.mark.parametrize(
"field,value",
[
("publisher", "did:web:acme.example\n"),
("artifact.digest", DIGEST + "\n"),
("endpoint.spki_sha256", DIGEST + "\n"),
("tool_catalog.hash", DIGEST + "\n"),
],
)
def test_a_trailing_newline_does_not_satisfy_a_pattern(field: str, value: str) -> None:
"""`$` in Python matches before a single trailing newline; these need `\\Z`.

Four fields are anchored with the same two patterns. Before this, every one of them
accepted its own value with a newline glued to the end, and `verify_record` returned
cleanly on all four. Only `tool_catalog.hash` had anything downstream to catch it,
and only because `check_tool_catalog` recomputes and compares.
"""
key = generate_key()
record = {
"format": FORMAT,
"kind": "publisher-asserted",
"identity": {"artifact": _artifact()},
"publisher": "did:web:acme.example",
"tool_catalog": {"hash": tool_catalog_hash(TOOLS), "tool_count": len(TOOLS)},
"issued_at": 1760000000,
}
if field == "publisher":
record["publisher"] = value
elif field == "artifact.digest":
record["identity"]["artifact"]["digest"] = value
elif field == "endpoint.spki_sha256":
record["identity"] = {"endpoint": {"url": "https://acme.example/mcp", "spki_sha256": value}}
else:
record["tool_catalog"]["hash"] = value

with pytest.raises(ProvenanceError):
verify_record(sign_record(record, key), key_to_jwk(key))
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