Add unit tests for timestamping_enricher

src/auto_archiver/modules/timestamping_enricher/timestamping_enricher.py

@@ -6,11 +6,11 @@ from importlib.metadata import version
 from asn1crypto.cms import ContentInfo
 from certvalidator import CertificateValidator, ValidationContext
 from asn1crypto import pem
+from asn1crypto.core import Asn1Value
 import certifi
 
 from auto_archiver.core import Enricher
 from auto_archiver.core import Metadata, ArchivingContext, Media
-from auto_archiver.core import Extractor
 
 
 class TimestampingEnricher(Enricher):
@@ -45,13 +45,10 @@ class TimestampingEnricher(Enricher):
         from slugify import slugify
         for tsa_url in self.tsa_urls:
             try:
-                signing_settings = SigningSettings(tsp_server=tsa_url, digest_algorithm=DigestAlgorithm.SHA256)
-                signer = TSPSigner()
                 message = bytes(data_to_sign, encoding='utf8')
-                # send TSQ and get TSR from the TSA server
-                signed = signer.sign(message=message, signing_settings=signing_settings)
+                signed = self.sign_data(tsa_url, message)
                 # fail if there's any issue with the certificates, uses certifi list of trusted CAs
-                TSPVerifier(certifi.where()).verify(signed, message=message)
+                self.verify_signed(signed, message)
                 # download and verify timestamping certificate
                 cert_chain = self.download_and_verify_certificate(signed)
                 # continue with saving the timestamp token
@@ -72,9 +69,22 @@ class TimestampingEnricher(Enricher):
         else:
             logger.warning(f"No successful timestamps for {url=}")
 
+    def verify_signed(self, signed: bytes, message: bytes) -> None:
+        verifier = TSPVerifier(certifi.where())
+        verifier.verify(signed, message=message)
+
+    def sign_data(self, tsa_url: str, bytes_data: bytes) -> bytes:
+        signing_settings = SigningSettings(tsp_server=tsa_url, digest_algorithm=DigestAlgorithm.SHA256)
+        signer = TSPSigner()
+        # send TSQ and get TSR from the TSA server
+        return signer.sign(message=bytes_data, signing_settings=signing_settings)
+    
+    def load_tst_certs(self, signed: bytes) -> list[Asn1Value]:
+        return ContentInfo.load(signed)["content"]["certificates"]
+    
     def download_and_verify_certificate(self, signed: bytes) -> list[Media]:
         # returns the leaf certificate URL, fails if not set
-        tst = ContentInfo.load(signed)
+        certificates = self.load_tst_certs(signed)
 
         trust_roots = []
         with open(certifi.where(), 'rb') as f:
@@ -82,7 +92,6 @@ class TimestampingEnricher(Enricher):
                 trust_roots.append(der_bytes)
         context = ValidationContext(trust_roots=trust_roots)
 
-        certificates = tst["content"]["certificates"]
         first_cert = certificates[0].dump()
         intermediate_certs = []
         for i in range(1, len(certificates)): # cannot use list comprehension [1:]