Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/cryptography/hazmat/backends/openssl/hmac.py: 33%

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, hashes 

13 

14 

15if typing.TYPE_CHECKING: 

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

17 

18 

19class _HMACContext(hashes.HashContext): 

20 def __init__( 

21 self, 

22 backend: "Backend", 

23 key: bytes, 

24 algorithm: hashes.HashAlgorithm, 

25 ctx=None, 

26 ): 

27 self._algorithm = algorithm 

28 self._backend = backend 

29 

30 if ctx is None: 

31 ctx = self._backend._lib.HMAC_CTX_new() 

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

33 ctx = self._backend._ffi.gc(ctx, self._backend._lib.HMAC_CTX_free) 

34 evp_md = self._backend._evp_md_from_algorithm(algorithm) 

35 if evp_md == self._backend._ffi.NULL: 

36 raise UnsupportedAlgorithm( 

37 "{} is not a supported hash on this backend".format( 

38 algorithm.name 

39 ), 

40 _Reasons.UNSUPPORTED_HASH, 

41 ) 

42 key_ptr = self._backend._ffi.from_buffer(key) 

43 res = self._backend._lib.HMAC_Init_ex( 

44 ctx, key_ptr, len(key), evp_md, self._backend._ffi.NULL 

45 ) 

46 self._backend.openssl_assert(res != 0) 

47 

48 self._ctx = ctx 

49 self._key = key 

50 

51 @property 

52 def algorithm(self) -> hashes.HashAlgorithm: 

53 return self._algorithm 

54 

55 def copy(self) -> "_HMACContext": 

56 copied_ctx = self._backend._lib.HMAC_CTX_new() 

57 self._backend.openssl_assert(copied_ctx != self._backend._ffi.NULL) 

58 copied_ctx = self._backend._ffi.gc( 

59 copied_ctx, self._backend._lib.HMAC_CTX_free 

60 ) 

61 res = self._backend._lib.HMAC_CTX_copy(copied_ctx, self._ctx) 

62 self._backend.openssl_assert(res != 0) 

63 return _HMACContext( 

64 self._backend, self._key, self.algorithm, ctx=copied_ctx 

65 ) 

66 

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

68 data_ptr = self._backend._ffi.from_buffer(data) 

69 res = self._backend._lib.HMAC_Update(self._ctx, data_ptr, len(data)) 

70 self._backend.openssl_assert(res != 0) 

71 

72 def finalize(self) -> bytes: 

73 buf = self._backend._ffi.new( 

74 "unsigned char[]", self._backend._lib.EVP_MAX_MD_SIZE 

75 ) 

76 outlen = self._backend._ffi.new("unsigned int *") 

77 res = self._backend._lib.HMAC_Final(self._ctx, buf, outlen) 

78 self._backend.openssl_assert(res != 0) 

79 self._backend.openssl_assert(outlen[0] == self.algorithm.digest_size) 

80 return self._backend._ffi.buffer(buf)[: outlen[0]] 

81 

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

83 digest = self.finalize() 

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

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