Add tests for SSlib Signer

Signed-off-by: Martin Vrachev <mvrachev@vmware.com>

tests/test_signer.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python
+
+"""
+Program Name:
+    test_signer.py
+
+Author:
+    Martin Vrachev <mvrachev@vmware.com>
+
+Started:
+    February, 04 2021
+
+Copyright
+    See LICENSE for licensing information.
+
+Purpose:
+    Test cases for 'signer.py'.
+"""
+
+import unittest
+import securesystemslib.formats
+import securesystemslib.keys as KEYS
+from securesystemslib.signer import Signature, SSlibSigner
+from securesystemslib.exceptions import FormatError, UnsupportedAlgorithmError
+
+class TestSSlibSigner(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        cls.rsakey_dict = KEYS.generate_rsa_key()
+        cls.ed25519key_dict = KEYS.generate_ed25519_key()
+        cls.ecdsakey_dict = KEYS.generate_ecdsa_key()
+        cls.DATA_STR = 'SOME DATA REQUIRING AUTHENTICITY.'
+        cls.DATA = securesystemslib.formats.encode_canonical(
+                cls.DATA_STR).encode('utf-8')
+
+
+    def test_sslib_sign(self):
+        dicts = [self.rsakey_dict, self.ecdsakey_dict, self.ed25519key_dict]
+        for scheme_dict in dicts:
+            # Test generation of signatures.
+            sslib_signer = SSlibSigner(scheme_dict)
+            sig_obj = sslib_signer.sign(self.DATA)
+
+            # Verify signature
+            verified = KEYS.verify_signature(scheme_dict, sig_obj.to_dict(),
+                    self.DATA)
+            self.assertTrue(verified, "Incorrect signature.")
+
+            # Removing private key from 'scheme_dict' - should raise a ValueError.
+            private = scheme_dict['keyval']['private']
+            scheme_dict['keyval']['private'] = ''
+            sslib_signer.key_dict = scheme_dict
+
+            with self.assertRaises((ValueError, FormatError)):
+                sslib_signer.sign(self.DATA)
+
+            scheme_dict['keyval']['private'] = private
+
+            # Test for invalid signature scheme.
+            valid_scheme = scheme_dict['scheme']
+            scheme_dict['scheme'] = 'invalid_scheme'
+            sslib_signer = SSlibSigner(scheme_dict)
+
+            with self.assertRaises((UnsupportedAlgorithmError, FormatError)):
+                sslib_signer.sign(self.DATA)
+
+            scheme_dict['scheme'] = valid_scheme
+
+            # Supplying an incorrect number of arguments.
+            with self.assertRaises(TypeError):
+                sslib_signer.sign()
+
+
+
+    def test_signature_from_to_json(self):
+        signature_dict = {
+            "sig": "30460221009342e4566528fcecf6a7a5d53ebacdb1df151e242f55f8775883469cb01dbc6602210086b426cc826709acfa2c3f9214610cb0a832db94bbd266fd7c5939a48064a851",
+            "keyid": "11fa391a0ed7a447cbfeb4b2667e286fc248f64d5e6d0eeed2e5e23f97f9f714"
+        }
+        sig_obj = Signature.from_dict(signature_dict)
+
+        self.assertEqual(signature_dict, sig_obj.to_dict())
+
+
+# Run the unit tests.
+if __name__ == '__main__':
+    unittest.main()