_ Git - BearSSL/blob - src/x509/encode_ec_pk8der.c

   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
  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 }