Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.11/site-packages/Crypto/Util/Padding.py: 11%

1# 

2# Util/Padding.py : Functions to manage padding 

3# 

4# =================================================================== 

5# 

6# Copyright (c) 2014, Legrandin <helderijs@gmail.com> 

7# All rights reserved. 

8# 

9# Redistribution and use in source and binary forms, with or without 

10# modification, are permitted provided that the following conditions 

11# are met: 

12# 

13# 1. Redistributions of source code must retain the above copyright 

14# notice, this list of conditions and the following disclaimer. 

15# 2. Redistributions in binary form must reproduce the above copyright 

16# notice, this list of conditions and the following disclaimer in 

17# the documentation and/or other materials provided with the 

18# distribution. 

19# 

20# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 

21# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 

22# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 

23# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 

24# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 

25# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 

26# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 

27# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 

28# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 

29# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 

30# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 

31# POSSIBILITY OF SUCH DAMAGE. 

32# =================================================================== 

33 

34__all__ = [ 'pad', 'unpad' ] 

35 

36from Crypto.Util.py3compat import * 

37 

38 

39def pad(data_to_pad, block_size, style='pkcs7'): 

40 """Apply standard padding. 

41 

42 Args: 

43 data_to_pad (byte string): 

44 The data that needs to be padded. 

45 block_size (integer): 

46 The block boundary to use for padding. The output length is guaranteed 

47 to be a multiple of :data:`block_size`. 

48 style (string): 

49 Padding algorithm. It can be *'pkcs7'* (default), *'iso7816'* or *'x923'*. 

50 

51 Return: 

52 byte string : the original data with the appropriate padding added at the end. 

53 """ 

54 

55 padding_len = block_size - len(data_to_pad) % block_size 

56 

57 if style == 'pkcs7': 

58 padding = bchr(padding_len) * padding_len 

59 elif style == 'x923': 

60 padding = bchr(0)*(padding_len-1) + bchr(padding_len) 

61 elif style == 'iso7816': 

62 padding = bchr(128) + bchr(0) * (padding_len-1) 

63 else: 

64 raise ValueError("Unknown padding style") 

65 

66 return data_to_pad + padding 

67 

68 

69def unpad(padded_data, block_size, style='pkcs7'): 

70 """Remove standard padding. 

71 

72 Args: 

73 padded_data (byte string): 

74 A piece of data with padding that needs to be stripped. 

75 block_size (integer): 

76 The block boundary to use for padding. The input length 

77 must be a multiple of :data:`block_size`. 

78 style (string): 

79 Padding algorithm. It can be *'pkcs7'* (default), *'iso7816'* or *'x923'*. 

80 Return: 

81 byte string : data without padding. 

82 Raises: 

83 ValueError: if the padding is incorrect. 

84 """ 

85 

86 pdata_len = len(padded_data) 

87 

88 if pdata_len == 0: 

89 raise ValueError("Zero-length input cannot be unpadded") 

90 

91 if pdata_len % block_size: 

92 raise ValueError("Input data is not padded") 

93 

94 if style in ('pkcs7', 'x923'): 

95 padding_len = bord(padded_data[-1]) 

96 

97 if padding_len < 1 or padding_len > min(block_size, pdata_len): 

98 raise ValueError("Padding is incorrect.") 

99 

100 if style == 'pkcs7': 

101 if padded_data[-padding_len:] != bchr(padding_len)*padding_len: 

102 raise ValueError("PKCS#7 padding is incorrect.") 

103 else: 

104 if padded_data[-padding_len:-1] != bchr(0)*(padding_len-1): 

105 raise ValueError("ANSI X.923 padding is incorrect.") 

106 

107 elif style == 'iso7816': 

108 padding_len = pdata_len - padded_data.rfind(bchr(128)) 

109 

110 if padding_len < 1 or padding_len > min(block_size, pdata_len): 

111 raise ValueError("Padding is incorrect.") 

112 

113 if padding_len > 1 and padded_data[1-padding_len:] != bchr(0)*(padding_len-1): 

114 raise ValueError("ISO 7816-4 padding is incorrect.") 

115 else: 

116 raise ValueError("Unknown padding style") 

117 

118 return padded_data[:-padding_len] 

119