Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/cryptography/hazmat/backends/openssl/cmac.py: 24%

1# This file is dual licensed under the terms of the Apache License, Version 

2# 2.0, and the BSD License. See the LICENSE file in the root of this repository 

3# for complete details. 

4 

5import typing 

6 

7from cryptography.exceptions import ( 

8 InvalidSignature, 

9 UnsupportedAlgorithm, 

10 _Reasons, 

11) 

12from cryptography.hazmat.primitives import constant_time 

13from cryptography.hazmat.primitives.ciphers.modes import CBC 

14 

15if typing.TYPE_CHECKING: 

16 from cryptography.hazmat.primitives import ciphers 

17 from cryptography.hazmat.backends.openssl.backend import Backend 

18 

19 

20class _CMACContext: 

21 def __init__( 

22 self, 

23 backend: "Backend", 

24 algorithm: "ciphers.BlockCipherAlgorithm", 

25 ctx=None, 

26 ) -> None: 

27 if not backend.cmac_algorithm_supported(algorithm): 

28 raise UnsupportedAlgorithm( 

29 "This backend does not support CMAC.", 

30 _Reasons.UNSUPPORTED_CIPHER, 

31 ) 

32 

33 self._backend = backend 

34 self._key = algorithm.key 

35 self._algorithm = algorithm 

36 self._output_length = algorithm.block_size // 8 

37 

38 if ctx is None: 

39 registry = self._backend._cipher_registry 

40 adapter = registry[type(algorithm), CBC] 

41 

42 evp_cipher = adapter(self._backend, algorithm, CBC) 

43 

44 ctx = self._backend._lib.CMAC_CTX_new() 

45 

46 self._backend.openssl_assert(ctx != self._backend._ffi.NULL) 

47 ctx = self._backend._ffi.gc(ctx, self._backend._lib.CMAC_CTX_free) 

48 

49 key_ptr = self._backend._ffi.from_buffer(self._key) 

50 res = self._backend._lib.CMAC_Init( 

51 ctx, 

52 key_ptr, 

53 len(self._key), 

54 evp_cipher, 

55 self._backend._ffi.NULL, 

56 ) 

57 self._backend.openssl_assert(res == 1) 

58 

59 self._ctx = ctx 

60 

61 def update(self, data: bytes) -> None: 

62 res = self._backend._lib.CMAC_Update(self._ctx, data, len(data)) 

63 self._backend.openssl_assert(res == 1) 

64 

65 def finalize(self) -> bytes: 

66 buf = self._backend._ffi.new("unsigned char[]", self._output_length) 

67 length = self._backend._ffi.new("size_t *", self._output_length) 

68 res = self._backend._lib.CMAC_Final(self._ctx, buf, length) 

69 self._backend.openssl_assert(res == 1) 

70 

71 self._ctx = None 

72 

73 return self._backend._ffi.buffer(buf)[:] 

74 

75 def copy(self) -> "_CMACContext": 

76 copied_ctx = self._backend._lib.CMAC_CTX_new() 

77 copied_ctx = self._backend._ffi.gc( 

78 copied_ctx, self._backend._lib.CMAC_CTX_free 

79 ) 

80 res = self._backend._lib.CMAC_CTX_copy(copied_ctx, self._ctx) 

81 self._backend.openssl_assert(res == 1) 

82 return _CMACContext(self._backend, self._algorithm, ctx=copied_ctx) 

83 

84 def verify(self, signature: bytes) -> None: 

85 digest = self.finalize() 

86 if not constant_time.bytes_eq(digest, signature): 

87 raise InvalidSignature("Signature did not match digest.")