1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
#!/usr/bin/env python3
"""Detach CMS encrypted data.
Detach encrypted data from a CMS envelopedData or authEnvelopedData
message into a separate file.
"""
import argparse
import asn1
# Parse command-line arguments
#
parser = argparse.ArgumentParser(
description=__doc__,
formatter_class=argparse.RawDescriptionHelpFormatter,
)
parser.add_argument("-d", "--data", metavar="FILE",
help="Write detached data (without envelope) to FILE")
parser.add_argument("-e", "--envelope", metavar="FILE",
help="Write envelope (without data) to FILE")
parser.add_argument("-o", "--overwrite", action="store_true",
help="Overwrite output files")
parser.add_argument("file", help="Input envelope file")
args = parser.parse_args()
if args.data is None and args.envelope is None:
parser.error("at least one of --data and --envelope is required")
outmode = "wb" if args.overwrite else "xb"
# Create decoder
#
decoder = asn1.Decoder()
with open(args.file, mode="rb") as fh:
decoder.start(fh.read())
# Create encoder
#
encoder = asn1.Encoder()
encoder.start()
# Detach encrypted data
#
data = None
datastack = [
asn1.Numbers.Sequence, 0, asn1.Numbers.Sequence, asn1.Numbers.Sequence
]
stack = []
while stack or not decoder.eof():
if decoder.eof():
encoder.leave()
decoder.leave()
stack.pop()
else:
tag = decoder.peek()
if tag.typ == asn1.Types.Constructed:
encoder.enter(nr=tag.nr, cls=tag.cls)
decoder.enter()
stack.append(tag.nr)
else:
(tag, value) = decoder.read()
if stack == datastack and tag.nr == 0:
data = value
else:
encoder.write(value, nr=tag.nr, cls=tag.cls)
envelope = encoder.output()
if data is None:
parser.error("Input file does not contain any encrypted data")
# Write envelope (without data), if applicable
#
if args.envelope:
with open(args.envelope, mode=outmode) as fh:
fh.write(envelope)
# Write data (without envelope), if applicable
#
if args.data:
with open(args.data, mode=outmode) as fh:
fh.write(data)
|
