codekingpro/portable-devtools

1#  Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
2#
3#  Licensed under the Apache License, Version 2.0 (the "License");
4#  you may not use this file except in compliance with the License.
5#  You may obtain a copy of the License at
6#
7#      https://www.apache.org/licenses/LICENSE-2.0
8#
9#  Unless required by applicable law or agreed to in writing, software
10#  distributed under the License is distributed on an "AS IS" BASIS,
11#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12#  See the License for the specific language governing permissions and
13#  limitations under the License.
14
15"""Utility functions."""
16
17import sys
18from optparse import OptionParser
19
20import rsa.key
21
22
23def private_to_public() -> None:
24    """Reads a private key and outputs the corresponding public key."""
25
26    # Parse the CLI options
27    parser = OptionParser(
28        usage="usage: %prog [options]",
29        description="Reads a private key and outputs the "
30        "corresponding public key. Both private and public keys use "
31        "the format described in PKCS#1 v1.5",
32    )
33
34    parser.add_option(
35        "-i",
36        "--input",
37        dest="infilename",
38        type="string",
39        help="Input filename. Reads from stdin if not specified",
40    )
41    parser.add_option(
42        "-o",
43        "--output",
44        dest="outfilename",
45        type="string",
46        help="Output filename. Writes to stdout of not specified",
47    )
48
49    parser.add_option(
50        "--inform",
51        dest="inform",
52        help="key format of input - default PEM",
53        choices=("PEM", "DER"),
54        default="PEM",
55    )
56
57    parser.add_option(
58        "--outform",
59        dest="outform",
60        help="key format of output - default PEM",
61        choices=("PEM", "DER"),
62        default="PEM",
63    )
64
65    (cli, cli_args) = parser.parse_args(sys.argv)
66
67    # Read the input data
68    if cli.infilename:
69        print(
70            "Reading private key from %s in %s format" % (cli.infilename, cli.inform),
71            file=sys.stderr,
72        )
73        with open(cli.infilename, "rb") as infile:
74            in_data = infile.read()
75    else:
76        print("Reading private key from stdin in %s format" % cli.inform, file=sys.stderr)
77        in_data = sys.stdin.read().encode("ascii")
78
79    assert type(in_data) == bytes, type(in_data)
80
81    # Take the public fields and create a public key
82    priv_key = rsa.key.PrivateKey.load_pkcs1(in_data, cli.inform)
83    pub_key = rsa.key.PublicKey(priv_key.n, priv_key.e)
84
85    # Save to the output file
86    out_data = pub_key.save_pkcs1(cli.outform)
87
88    if cli.outfilename:
89        print(
90            "Writing public key to %s in %s format" % (cli.outfilename, cli.outform),
91            file=sys.stderr,
92        )
93        with open(cli.outfilename, "wb") as outfile:
94            outfile.write(out_data)
95    else:
96        print("Writing public key to stdout in %s format" % cli.outform, file=sys.stderr)
97        sys.stdout.write(out_data.decode("ascii"))
98