1 /*
2 * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 /* see bearssl_x509.h */
28 size_t
br_encode_ec_pkcs8_der(void * dest,const br_ec_private_key * sk,const br_ec_public_key * pk)29 br_encode_ec_pkcs8_der(void *dest,
30 const br_ec_private_key *sk, const br_ec_public_key *pk)
31 {
32 /*
33 * ASN.1 format:
34 *
35 * OneAsymmetricKey ::= SEQUENCE {
36 * version Version,
37 * privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
38 * privateKey PrivateKey,
39 * attributes [0] Attributes OPTIONAL,
40 * ...,
41 * [[2: publicKey [1] PublicKey OPTIONAL ]],
42 * ...
43 * }
44 *
45 * We don't include attributes or public key (the public key
46 * is included in the private key value instead). The
47 * 'version' field is an INTEGER that we will set to 0
48 * (meaning 'v1', compatible with previous versions of PKCS#8).
49 * The 'privateKeyAlgorithm' structure is an AlgorithmIdentifier
50 * whose OID should be id-ecPublicKey, with, as parameters, the
51 * curve OID. The 'privateKey' is an OCTET STRING, whose value
52 * is the "raw DER" encoding of the key pair.
53 */
54
55 /*
56 * OID id-ecPublicKey (1.2.840.10045.2.1), DER-encoded (with
57 * the tag).
58 */
59 static const unsigned char OID_ECPUBKEY[] = {
60 0x06, 0x07, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02, 0x01
61 };
62
63 size_t len_version, len_privateKeyAlgorithm, len_privateKeyValue;
64 size_t len_privateKey, len_seq;
65 const unsigned char *oid;
66
67 oid = br_get_curve_OID(sk->curve);
68 if (oid == NULL) {
69 return 0;
70 }
71 len_version = 3;
72 len_privateKeyAlgorithm = 2 + sizeof OID_ECPUBKEY + 2 + oid[0];
73 len_privateKeyValue = br_encode_ec_raw_der_inner(NULL, sk, pk, 0);
74 len_privateKey = 1 + len_of_len(len_privateKeyValue)
75 + len_privateKeyValue;
76 len_seq = len_version + len_privateKeyAlgorithm + len_privateKey;
77
78 if (dest == NULL) {
79 return 1 + len_of_len(len_seq) + len_seq;
80 } else {
81 unsigned char *buf;
82 size_t lenlen;
83
84 buf = dest;
85 *buf ++ = 0x30; /* SEQUENCE tag */
86 lenlen = br_asn1_encode_length(buf, len_seq);
87 buf += lenlen;
88
89 /* version */
90 *buf ++ = 0x02;
91 *buf ++ = 0x01;
92 *buf ++ = 0x00;
93
94 /* privateKeyAlgorithm */
95 *buf ++ = 0x30;
96 *buf ++ = (sizeof OID_ECPUBKEY) + 2 + oid[0];
97 memcpy(buf, OID_ECPUBKEY, sizeof OID_ECPUBKEY);
98 buf += sizeof OID_ECPUBKEY;
99 *buf ++ = 0x06;
100 memcpy(buf, oid, 1 + oid[0]);
101 buf += 1 + oid[0];
102
103 /* privateKey */
104 *buf ++ = 0x04;
105 buf += br_asn1_encode_length(buf, len_privateKeyValue);
106 br_encode_ec_raw_der_inner(buf, sk, pk, 0);
107
108 return 1 + lenlen + len_seq;
109 }
110 }
111