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# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utility functions."""
import sys
from optparse import OptionParser
import rsa.key
def private_to_public() -> None:
"""Reads a private key and outputs the corresponding public key."""
# Parse the CLI options
parser = OptionParser(
usage="usage: %prog [options]",
description="Reads a private key and outputs the "
"corresponding public key. Both private and public keys use "
"the format described in PKCS#1 v1.5",
)
parser.add_option(
"-i",
"--input",
dest="infilename",
type="string",
help="Input filename. Reads from stdin if not specified",
)
parser.add_option(
"-o",
"--output",
dest="outfilename",
type="string",
help="Output filename. Writes to stdout of not specified",
)
parser.add_option(
"--inform",
dest="inform",
help="key format of input - default PEM",
choices=("PEM", "DER"),
default="PEM",
)
parser.add_option(
"--outform",
dest="outform",
help="key format of output - default PEM",
choices=("PEM", "DER"),
default="PEM",
)
(cli, cli_args) = parser.parse_args(sys.argv)
# Read the input data
if cli.infilename:
print(
"Reading private key from %s in %s format" % (cli.infilename, cli.inform),
file=sys.stderr,
)
with open(cli.infilename, "rb") as infile:
in_data = infile.read()
else:
print("Reading private key from stdin in %s format" % cli.inform, file=sys.stderr)
in_data = sys.stdin.read().encode("ascii")
assert type(in_data) == bytes, type(in_data)
# Take the public fields and create a public key
priv_key = rsa.key.PrivateKey.load_pkcs1(in_data, cli.inform)
pub_key = rsa.key.PublicKey(priv_key.n, priv_key.e)
# Save to the output file
out_data = pub_key.save_pkcs1(cli.outform)
if cli.outfilename:
print(
"Writing public key to %s in %s format" % (cli.outfilename, cli.outform),
file=sys.stderr,
)
with open(cli.outfilename, "wb") as outfile:
outfile.write(out_data)
else:
print("Writing public key to stdout in %s format" % cli.outform, file=sys.stderr)
sys.stdout.write(out_data.decode("ascii"))
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