Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/cryptography/hazmat/backends/openssl/hmac.py: 50%

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 

14if typing.TYPE_CHECKING: 

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

16 

17 

18class _HMACContext(hashes.HashContext): 

19 def __init__( 

20 self, 

21 backend: "Backend", 

22 key: bytes, 

23 algorithm: hashes.HashAlgorithm, 

24 ctx=None, 

25 ): 

26 self._algorithm = algorithm 

27 self._backend = backend 

28 

29 if ctx is None: 

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

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

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

33 evp_md = self._backend._evp_md_from_algorithm(algorithm) 

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

35 raise UnsupportedAlgorithm( 

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

37 algorithm.name 

38 ), 

39 _Reasons.UNSUPPORTED_HASH, 

40 ) 

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

42 res = self._backend._lib.HMAC_Init_ex( 

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

44 ) 

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

46 

47 self._ctx = ctx 

48 self._key = key 

49 

50 @property 

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

52 return self._algorithm 

53 

54 def copy(self) -> "_HMACContext": 

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

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

57 copied_ctx = self._backend._ffi.gc( 

58 copied_ctx, self._backend._lib.HMAC_CTX_free 

59 ) 

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

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

62 return _HMACContext( 

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

64 ) 

65 

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

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

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

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

70 

71 def finalize(self) -> bytes: 

72 buf = self._backend._ffi.new( 

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

74 ) 

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

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

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

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

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

80 

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

82 digest = self.finalize() 

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

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