[PATCH 3/4] Fix signature verification for b4 pr

[Konstantin Ryabitsev <konstantin@linuxfoundation.org>]

We moved pgp sig verification code around, so fix it for the invocation
in b4 pr.

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
---
 b4/__init__.py | 76 +++++++++++++++++++++++++++++++-------------------
 b4/attest.py   |  4 +--
 b4/pr.py       | 14 ++++++----
 3 files changed, 57 insertions(+), 37 deletions(-)

diff --git a/b4/__init__.py b/b4/__init__.py
index ab5797d..ac0e85c 100644
--- a/b4/__init__.py
+++ b/b4/__init__.py
@@ -1753,35 +1753,11 @@ class LoreAttestationSignaturePGP(LoreAttestationSignature):
         os.unlink(savefile)
         output = out.decode()
 
-        gs_matches = re.search(r'^\[GNUPG:] GOODSIG ([0-9A-F]+)\s+.*$', output, re.M)
-        if gs_matches:
-            logger.debug('  GOODSIG')
-            self.good = True
-            keyid = gs_matches.groups()[0]
-            self.attestor = LoreAttestorPGP(keyid)
-            puid = '%s <%s>' % self.attestor.get_primary_uid()
-            vs_matches = re.search(r'^\[GNUPG:] VALIDSIG ([0-9A-F]+) (\d{4}-\d{2}-\d{2}) (\d+)', output, re.M)
-            if vs_matches:
-                logger.debug('  VALIDSIG')
-                self.valid = True
-                ymd = vs_matches.groups()[1]
-                self.sigdate = datetime.datetime.strptime(ymd, '%Y-%m-%d').replace(tzinfo=datetime.timezone.utc)
-                # Do we have a TRUST_(FULLY|ULTIMATE)?
-                ts_matches = re.search(r'^\[GNUPG:] TRUST_(FULLY|ULTIMATE)', output, re.M)
-                if ts_matches:
-                    logger.debug('  TRUST_%s', ts_matches.groups()[0])
-                    self.trusted = True
-                    self.passing = True
-                else:
-                    self.errors.add('Insufficient trust (model=%s): %s (%s)'
-                                    % (trustmodel, keyid, puid))
-            else:
-                self.errors.add('Signature not valid from key: %s (%s)' % (keyid, puid))
-        else:
-            # Are we missing a key?
-            matches = re.search(r'^\[GNUPG:] NO_PUBKEY ([0-9A-F]+)$', output, re.M)
-            if matches:
-                self.errors.add('Missing public key: %s' % matches.groups()[0])
+        self.good, self.valid, self.trusted, self.attestor, self.sigdate, self.errors = \
+            validate_gpg_signature(output, trustmodel)
+
+        if self.good and self.valid and self.trusted:
+            self.passing = True
 
         # A couple of final verifications
         self.verify_time_drift()
@@ -2319,6 +2295,48 @@ def get_parts_from_header(hstr: str) -> dict:
     return hdata
 
 
+def validate_gpg_signature(output, trustmodel):
+    good = False
+    valid = False
+    trusted = False
+    attestor = None
+    sigdate = None
+    errors = set()
+    gs_matches = re.search(r'^\[GNUPG:] GOODSIG ([0-9A-F]+)\s+.*$', output, re.M)
+    if gs_matches:
+        logger.debug('  GOODSIG')
+        good = True
+        keyid = gs_matches.groups()[0]
+        attestor = LoreAttestorPGP(keyid)
+        puid = '%s <%s>' % attestor.get_primary_uid()
+        vs_matches = re.search(r'^\[GNUPG:] VALIDSIG ([0-9A-F]+) (\d{4}-\d{2}-\d{2}) (\d+)', output, re.M)
+        if vs_matches:
+            logger.debug('  VALIDSIG')
+            valid = True
+            ymd = vs_matches.groups()[1]
+            sigdate = datetime.datetime.strptime(ymd, '%Y-%m-%d').replace(tzinfo=datetime.timezone.utc)
+            # Do we have a TRUST_(FULLY|ULTIMATE)?
+            ts_matches = re.search(r'^\[GNUPG:] TRUST_(FULLY|ULTIMATE)', output, re.M)
+            if ts_matches:
+                logger.debug('  TRUST_%s', ts_matches.groups()[0])
+                trusted = True
+            else:
+                errors.add('Insufficient trust (model=%s): %s (%s)' % (trustmodel, keyid, puid))
+        else:
+            errors.add('Signature not valid from key: %s (%s)' % (attestor.keyid, puid))
+    else:
+        # Are we missing a key?
+        matches = re.search(r'^\[GNUPG:] NO_PUBKEY ([0-9A-F]+)$', output, re.M)
+        if matches:
+            errors.add('Missing public key: %s' % matches.groups()[0])
+        # Is the key expired?
+        matches = re.search(r'^\[GNUPG:] EXPKEYSIG (.*)$', output, re.M)
+        if matches:
+            errors.add('Expired key: %s' % matches.groups()[0])
+
+    return good, valid, trusted, attestor, sigdate, errors
+
+
 def dkim_get_txt(name: bytes, timeout: int = 5):
     global _DKIM_DNS_CACHE
     if name not in _DKIM_DNS_CACHE:
diff --git a/b4/attest.py b/b4/attest.py
index 4391b19..a4012d7 100644
--- a/b4/attest.py
+++ b/b4/attest.py
@@ -39,7 +39,7 @@ def in_header_attest(lmsg: b4.LoreMessage, mode: str = 'pgp', replace: bool = Fa
         f'm={lmsg.attestation.mb}',
         f'p={lmsg.attestation.pb}',
     ]
-    hhname, hhval = b4.LoreAttestation.dkim_canonicalize_header(lmsg.attestation.hashes_header_name, '; '.join(hparts))
+    hhname, hhval = b4.dkim_canonicalize_header(lmsg.attestation.hashes_header_name, '; '.join(hparts))
     headers.append(f'{hhname}:{hhval}')
 
     logger.debug('Signing with mode=%s', mode)
@@ -59,7 +59,7 @@ def in_header_attest(lmsg: b4.LoreMessage, mode: str = 'pgp', replace: bool = Fa
             'b=',
         ]
 
-        shname, shval = b4.LoreAttestation.dkim_canonicalize_header(lmsg.attestation.sig_header_name, '; '.join(hparts))
+        shname, shval = b4.dkim_canonicalize_header(lmsg.attestation.sig_header_name, '; '.join(hparts))
         headers.append(f'{shname}:{shval}')
         payload = '\r\n'.join(headers).encode()
         ecode, out, err = b4.gpg_run_command(gpgargs, payload)
diff --git a/b4/pr.py b/b4/pr.py
index 40d3127..b7ed9e1 100644
--- a/b4/pr.py
+++ b/b4/pr.py
@@ -127,27 +127,29 @@ def attest_fetch_head(gitdir, lmsg):
         ecode, out = b4.git_run_command(gitdir, ['verify-tag', '--raw', 'FETCH_HEAD'], logstderr=True)
     elif otype == 'commit':
         ecode, out = b4.git_run_command(gitdir, ['verify-commit', '--raw', 'FETCH_HEAD'], logstderr=True)
-    lsig = b4.LoreAttestationSignature(out, 'git')
-    if lsig.good and lsig.valid and lsig.trusted:
+
+    good, valid, trusted, attestor, sigdate, errors = b4.validate_gpg_signature(out, 'pgp')
+
+    if good and valid and trusted:
         passing = True
 
     out = out.strip()
     if not len(out) and attpolicy != 'check':
-        lsig.errors.add('Remote %s is not signed!' % otype)
+        errors.add('Remote %s is not signed!' % otype)
 
     if passing:
-        trailer = lsig.attestor.get_trailer(lmsg.fromemail)
+        trailer = attestor.get_trailer(lmsg.fromemail)
         logger.info('  ---')
         logger.info('  %s %s', attpass, trailer)
         return
 
-    if lsig.errors:
+    if errors:
         logger.critical('  ---')
         if len(out):
             logger.critical('  Pull request is signed, but verification did not succeed:')
         else:
             logger.critical('  Pull request verification did not succeed:')
-        for error in lsig.errors:
+        for error in errors:
             logger.critical('    %s %s', attfail, error)
 
         if attpolicy == 'hardfail':
-- 
2.26.2