Coverage for ledger/signature.py: 96%

1# The MIT License (MIT) 

2# 

3# Copyright (c) 2021 RSK Labs Ltd 

4# 

5# Permission is hereby granted, free of charge, to any person obtaining a copy of 

6# this software and associated documentation files (the "Software"), to deal in 

7# the Software without restriction, including without limitation the rights to 

8# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies 

9# of the Software, and to permit persons to whom the Software is furnished to do 

10# so, subject to the following conditions: 

11# 

12# The above copyright notice and this permission notice shall be included in all 

13# copies or substantial portions of the Software. 

14# 

15# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 

16# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 

17# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 

18# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 

19# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 

20# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 

21# SOFTWARE. 

22 

23# Parses a signature received from a powHSM dongle 

24 

25class HSM2DongleSignature: 

26 def __init__(self, signature_bytes): 

27 def error(): 

28 raise ValueError("Invalid DER-encoded signature: %s" % signature_bytes.hex()) 

29 

30 # Decode signature_bytes, which should be in DER format 

31 # Format: 

32 # 

33 # 0x30 TOTAL_LENGTH 

34 # 0x02 R_LENGTH [R bytes] 

35 # 0x02 S_LENGTH [S bytes] 

36 # [potential rubbish] 

37 # 

38 # IMPORTANT: due to a bug, sometimes the first byte is 0x31 and not 0x30. 

39 # Deal with it. 

40 if ( 

41 len(signature_bytes) < 2 

42 or signature_bytes[0] not in [0x30, 0x31] 

43 or len(signature_bytes[2:]) < signature_bytes[1] 

44 ): 

45 error() 

46 

47 # R 

48 if ( 

49 len(signature_bytes[2:]) < 2 

50 or signature_bytes[2] != 0x02 

51 or len(signature_bytes[4:]) < signature_bytes[3] 

52 ): 

53 error() 

54 r_len = signature_bytes[3] 

55 rbytes = signature_bytes[4:4 + r_len] 

56 

57 # S 

58 if ( 

59 len(signature_bytes[4 + r_len:]) < 2 

60 or signature_bytes[4 + r_len] != 0x02 

61 or len(signature_bytes[6 + r_len:]) < signature_bytes[5 + r_len] 

62 ): 

63 error() 

64 s_len = signature_bytes[5 + r_len] 

65 sbytes = signature_bytes[6 + r_len:6 + r_len + s_len] 

66 

67 self._r = rbytes.hex() 

68 self._s = sbytes.hex() 

69 

70 @property 

71 def r(self): 

72 return self._r 

73 

74 @property 

75 def s(self): 

76 return self._s 

77 

78 def __repr__(self): 

79 return f"{type(self).__name__}<0x{self.r}, 0x{self.s}>" 

80 

81 # Self explanatory 

82 def __eq__(self, other): 

83 return ( 

84 type(self) == type(other) 

85 and self.r == other.r 

86 and self.s == other.s 

87 )