openpgp: Allow verifying a subset of signatures

Signed-off-by: Michał Górny <mgorny@gentoo.org>

2 files changed, 49 insertions, 0 deletions

diff --git a/gemato/openpgp.py b/gemato/openpgp.py
index 8c1db59..16a369e 100644
--- a/gemato/openpgp.py
+++ b/gemato/openpgp.py
@@ -167,12 +167,18 @@ class SystemGPGEnvironment:
 
     def verify_file(self,
                     f: typing.IO[str],
+                    require_all_good: bool = True,
                     ) -> OpenPGPSignatureList:
         """
         Perform an OpenPGP verification of Manifest data in open file @f.
         The file should be open in text mode and set at the beginning
         (or start of signed part). Raises an exception if the verification
         fails.
+
+        If require_all_good is True and the file contains multiple OpenPGP
+        signatures, all signatures have to be good and trusted in order
+        for the verificatin to succeed. Otherwise, a single good signature
+        is considered sufficient.
         """
 
         exitst, out, err = self._spawn_gpg(
@@ -231,6 +237,17 @@ class SystemGPGEnvironment:
             raise OpenPGPUnknownSigFailure(
                 err.decode('utf8', errors='backslashreplace'))
 
+        # bad signature causes failure even without require_all_good
+        for sig in sig_list:
+            if sig.sig_status == OpenPGPSignatureStatus.BAD:
+                raise OpenPGPVerificationFailure(
+                    err.decode("utf8", errors="backslashreplace"), sig)
+
+        if not require_all_good:
+            if any(x.sig_status == OpenPGPSignatureStatus.GOOD and
+                   x.valid_sig and x.trusted_sig for x in sig_list):
+                return sig_list
+
         for sig in sig_list:
             if sig.sig_status == OpenPGPSignatureStatus.GOOD:
                 pass
diff --git a/tests/test_openpgp.py b/tests/test_openpgp.py
index 6702471..22ef6cf 100644
--- a/tests/test_openpgp.py
+++ b/tests/test_openpgp.py
@@ -484,6 +484,38 @@ def test_verify_manifest(openpgp_env, manifest_var, key_var, expected):
         pytest.skip(str(e))
 
 
+def test_verify_one_out_of_two():
+    try:
+        with MockedSystemGPGEnvironment() as openpgp_env:
+            with io.BytesIO(VALID_PUBLIC_KEY) as f:
+                openpgp_env.import_key(f)
+
+            with io.StringIO(TWO_SIGNATURE_MANIFEST) as f:
+                sig = openpgp_env.verify_file(f, require_all_good=False)
+
+            assert sig == [
+                OpenPGPSignatureData(
+                    fingerprint="81E12C16BD8DCD60BE180845136880E72A7B1384",
+                    timestamp=datetime.datetime(2023, 1, 21, 17, 14, 44),
+                    expire_timestamp=None,
+                    primary_key_fingerprint="81E12C16BD8DCD60BE18"
+                                            "0845136880E72A7B1384",
+                    sig_status=OpenPGPSignatureStatus.GOOD,
+                    valid_sig=True,
+                    trusted_sig=True),
+                OpenPGPSignatureData(
+                    fingerprint="",
+                    timestamp=None,
+                    expire_timestamp=None,
+                    primary_key_fingerprint="",
+                    sig_status=OpenPGPSignatureStatus.NO_PUBLIC_KEY,
+                    valid_sig=False,
+                    trusted_sig=False),
+            ]
+    except OpenPGPNoImplementation as e:
+        pytest.skip(str(e))
+
+
 def test_verify_untrusted_key():
     try:
         with MockedSystemGPGEnvironment() as openpgp_env: