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 */
28size_t
29br_encode_rsa_pkcs8_der(void *dest, const br_rsa_private_key *sk,
30	const br_rsa_public_key *pk, const void *d, size_t dlen)
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 'version' field
46	 * is an INTEGER that we will set to 0 (meaning 'v1', compatible
47	 * with previous versions of PKCS#8). The 'privateKeyAlgorithm'
48	 * structure is an AlgorithmIdentifier whose OID should be
49	 * rsaEncryption, with NULL parameters. The 'privateKey' is an
50	 * OCTET STRING, whose value is the "raw DER" encoding of the
51	 * key pair.
52	 *
53	 * Since the private key value comes last, this function really
54	 * adds a header, which is mostly fixed (only some lengths have
55	 * to be modified.
56	 */
57
58	/*
59	 * Concatenation of:
60	 *  - DER encoding of an INTEGER of value 0 (the 'version' field)
61	 *  - DER encoding of a PrivateKeyAlgorithmIdentifier that uses
62	 *    the rsaEncryption OID, and NULL parameters
63	 *  - An OCTET STRING tag
64	 */
65	static const unsigned char PK8_HEAD[] = {
66		0x02, 0x01, 0x00,
67		0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
68		0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00,
69		0x04
70	};
71
72	size_t len_raw, len_seq;
73
74	len_raw = br_encode_rsa_raw_der(NULL, sk, pk, d, dlen);
75	len_seq = (sizeof PK8_HEAD) + len_of_len(len_raw) + len_raw;
76	if (dest == NULL) {
77		return 1 + len_of_len(len_seq) + len_seq;
78	} else {
79		unsigned char *buf;
80		size_t lenlen;
81
82		buf = dest;
83		*buf ++ = 0x30;  /* SEQUENCE tag */
84		lenlen = br_asn1_encode_length(buf, len_seq);
85		buf += lenlen;
86
87		/* version, privateKeyAlgorithm, privateKey tag */
88		memcpy(buf, PK8_HEAD, sizeof PK8_HEAD);
89		buf += sizeof PK8_HEAD;
90
91		/* privateKey */
92		buf += br_asn1_encode_length(buf, len_raw);
93		br_encode_rsa_raw_der(buf, sk, pk, d, dlen);
94
95		return 1 + lenlen + len_seq;
96	}
97}
98