contrib/suci-keytool.py: Convenience tool for SUCI key generation

This adds a small utility program that can be used for generating
keys used for SUCI in 5G SA networks, as well as for dumping them
in a format that's compatible with what is needed on the USIM.

Change-Id: I9e92bbba7f700e160ea9c58da5f23fa4c31d40c6

contrib/suci-keytool.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+
+# small utility program to deal with 5G SUCI key material, at least for the ECIES Protection Scheme
+# Profile A (curve25519) and B (secp256r1)
+
+# (C) 2024 by Harald Welte <laforge@osmocom.org>
+# SPDX-License-Identifier: GPL-2.0+
+
+import argparse
+
+from osmocom.utils import b2h
+from Cryptodome.PublicKey import ECC
+# if used with pycryptodome < v3.21.0 you will get the following error when using curve25519:
+# "Cryptodome.PublicKey.ECC.UnsupportedEccFeature: Unsupported ECC purpose (OID: 1.3.101.110)"
+
+def gen_key(opts):
+    # FIXME: avoid overwriting key files
+    mykey = ECC.generate(curve=opts.curve)
+    data = mykey.export_key(format='PEM')
+    with open(opts.key_file, "wt") as f:
+        f.write(data)
+
+def dump_pkey(opts):
+
+    #with open("curve25519-1.key", "r") as f:
+
+    with open(opts.key_file, "r") as f:
+        data = f.read()
+        mykey = ECC.import_key(data)
+
+        der = mykey.public_key().export_key(format='raw', compress=opts.compressed)
+        print(b2h(der))
+
+arg_parser = argparse.ArgumentParser(description="""Generate or export SUCI keys for 5G SA networks""")
+arg_parser.add_argument('--key-file', help='The key file to use', required=True)
+
+subparsers = arg_parser.add_subparsers(dest='command', help="The command to perform", required=True)
+
+parser_genkey = subparsers.add_parser('generate-key', help='Generate a new key pair')
+parser_genkey.add_argument('--curve', help='The ECC curve to use', choices=['secp256r1','curve25519'], required=True)
+
+parser_dump_pkey = subparsers.add_parser('dump-pub-key', help='Dump the public key')
+parser_dump_pkey.add_argument('--compressed', help='Use point compression', action='store_true')
+
+if __name__ == '__main__':
+
+    opts = arg_parser.parse_args()
+
+    if opts.command == 'generate-key':
+        gen_key(opts)
+    elif opts.command == 'dump-pub-key':
+        dump_pkey(opts)