tests: Refactor simulator signer handling

Store signers with their keyids so they are easier to remove.
The signers structure now looks like:
{
  "role1": {
    "keyidA": SSlibSigner,
    "keyidB": SSlibSigner,
  }
}

Add convenience method for adding a signer.

Signed-off-by: Jussi Kukkonen <jkukkonen@vmware.com>

tests/repository_simulator.py

@@ -98,7 +98,8 @@ def __init__(self):
         self.signed_roots: List[bytes] = []
 
         # signers are used on-demand at fetch time to sign metadata
-        self.signers: Dict[str, List[SSlibSigner]] = {}
+        # keys are roles, values are dicts of {keyid: signer}
+        self.signers: Dict[str, Dict[str, SSlibSigner]] = {}
 
         # target downloads are served from this dict
         self.target_files: Dict[str, RepositoryTarget] = {}
@@ -139,6 +140,11 @@ def create_key(self) -> Tuple[Key, SSlibSigner]:
         sslib_key = generate_ed25519_key()
         return Key.from_securesystemslib_key(sslib_key), SSlibSigner(sslib_key)
 
+    def add_signer(self, role:str, signer: SSlibSigner):
+        if role not in self.signers:
+            self.signers[role] = {}
+        self.signers[role][signer.key_dict["keyid"]] = signer
+
     def _initialize(self):
         """Setup a minimal valid repository"""
 
@@ -159,18 +165,16 @@ def _initialize(self):
         for role in TOP_LEVEL_ROLE_NAMES:
             key, signer = self.create_key()
             root.add_key(role, key)
-            # store the private key
-            if role not in self.signers:
-                self.signers[role] = []
-            self.signers[role].append(signer)
+            self.add_signer(role, signer)
+
         self.md_root = Metadata(root, OrderedDict())
         self.publish_root()
 
     def publish_root(self):
         """Sign and store a new serialized version of root"""
         self.md_root.signatures.clear()
-        for signer in self.signers["root"]:
-            self.md_root.sign(signer)
+        for signer in self.signers["root"].values():
+            self.md_root.sign(signer, append=True)
 
         self.signed_roots.append(self.md_root.to_bytes(JSONSerializer()))
         logger.debug("Published root v%d", self.root.version)
@@ -242,7 +246,7 @@ def _fetch_metadata(self, role: str, version: Optional[int] = None) -> bytes:
                 raise FetcherHTTPError(f"Unknown {role} version {version}", 404)
 
             md.signatures.clear()
-            for signer in self.signers[role]:
+            for signer in self.signers[role].values():
                 md.sign(signer, append=True)
 
             logger.debug(
@@ -320,9 +324,7 @@ def add_delegation(
         # By default add one new key for the role
         key, signer = self.create_key()
         delegator.add_key(role.name, key)
-        if role.name not in self.signers:
-            self.signers[role.name] = []
-        self.signers[role.name].append(signer)
+        self.add_signer(role.name, signer)
 
         # Add metadata for the role
         self.md_delegates[role.name] = Metadata(targets, OrderedDict())

tests/test_updater_with_simulator.py

@@ -156,10 +156,10 @@ def test_keys_and_signatures(self):
         # Update top level metadata
         self._run_refresh()
 
-        # New targets: signed with a new key that is not in roles keys
-        old_signer = self.sim.signers["targets"].pop()
+        # New targets: signed with only a new key that is not in roles keys
+        old_signers = self.sim.signers.pop("targets")
         key, signer = self.sim.create_key()
-        self.sim.signers["targets"] = [signer]
+        self.sim.add_signer("targets", signer)
         self.sim.targets.version += 1
         self.sim.update_snapshot()
 
@@ -182,8 +182,9 @@ def test_keys_and_signatures(self):
         with self.assertRaises(UnsignedMetadataError):
             self._run_refresh()
 
-        # New targets: sign with both new and old key
-        self.sim.signers["targets"] = [signer, old_signer]
+        # New targets: sign with both new and any original keys
+        for signer in old_signers.values():
+            self.sim.add_signer("targets", signer)
         self.sim.targets.version += 1
         self.sim.update_snapshot()