_ Git - BearSSL/blob - src/x509/encode_ec_rawder.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 inner.h */
  28 const unsigned char *
  29 br_get_curve_OID(int curve)
  30 {
  31         static const unsigned char OID_secp256r1[] = {
  32                 0x08, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x03, 0x01, 0x07
  33         };
  34         static const unsigned char OID_secp384r1[] = {
  35                 0x05, 0x2b, 0x81, 0x04, 0x00, 0x22
  36         };
  37         static const unsigned char OID_secp521r1[] = {
  38                 0x05, 0x2b, 0x81, 0x04, 0x00, 0x23
  39         };
  40
  41         switch (curve) {
  42         case BR_EC_secp256r1:  return OID_secp256r1;
  43         case BR_EC_secp384r1:  return OID_secp384r1;
  44         case BR_EC_secp521r1:  return OID_secp521r1;
  45         default:
  46                 return NULL;
  47         }
  48 }
  49
  50 /* see inner.h */
  51 size_t
  52 br_encode_ec_raw_der_inner(void *dest,
  53         const br_ec_private_key *sk, const br_ec_public_key *pk,
  54         int include_curve_oid)
  55 {
  56         /*
  57          * ASN.1 format:
  58          *
  59          *   ECPrivateKey ::= SEQUENCE {
  60          *     version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
  61          *     privateKey     OCTET STRING,
  62          *     parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
  63          *     publicKey  [1] BIT STRING OPTIONAL
  64          *   }
  65          *
  66          * The tages '[0]' and '[1]' are explicit. The 'ECParameters'
  67          * is a CHOICE; in our case, it will always be an OBJECT IDENTIFIER
  68          * that identifies the curve.
  69          *
  70          * The value of the 'privateKey' field is the raw unsigned big-endian
  71          * encoding of the private key (integer modulo the curve subgroup
  72          * order); there is no INTEGER tag, and the leading bit may be 1.
  73          * Also, leading bytes of value 0x00 are _not_ removed.
  74          *
  75          * The 'publicKey' contents are the raw encoded public key point,
  76          * normally uncompressed (leading byte of value 0x04, followed
  77          * by the unsigned big-endian encodings of the X and Y coordinates,
  78          * padded to the full field length if necessary).
  79          */
  80
  81         size_t len_version, len_privateKey, len_parameters, len_publicKey;
  82         size_t len_publicKey_bits, len_seq;
  83         const unsigned char *oid;
  84
  85         if (include_curve_oid) {
  86                 oid = br_get_curve_OID(sk->curve);
  87                 if (oid == NULL) {
  88                         return 0;
  89                 }
  90         } else {
  91                 oid = NULL;
  92         }
  93         len_version = 3;
  94         len_privateKey = 1 + len_of_len(sk->xlen) + sk->xlen;
  95         if (include_curve_oid) {
  96                 len_parameters = 4 + oid[0];
  97         } else {
  98                 len_parameters = 0;
  99         }
 100         if (pk == NULL) {
 101                 len_publicKey = 0;
 102                 len_publicKey_bits = 0;
 103         } else {
 104                 len_publicKey_bits = 2 + len_of_len(pk->qlen) + pk->qlen;
 105                 len_publicKey = 1 + len_of_len(len_publicKey_bits)
 106                         + len_publicKey_bits;
 107         }
 108         len_seq = len_version + len_privateKey + len_parameters + len_publicKey;
 109         if (dest == NULL) {
 110                 return 1 + len_of_len(len_seq) + len_seq;
 111         } else {
 112                 unsigned char *buf;
 113                 size_t lenlen;
 114
 115                 buf = dest;
 116                 *buf ++ = 0x30;  /* SEQUENCE tag */
 117                 lenlen = br_asn1_encode_length(buf, len_seq);
 118                 buf += lenlen;
 119
 120                 /* version */
 121                 *buf ++ = 0x02;
 122                 *buf ++ = 0x01;
 123                 *buf ++ = 0x01;
 124
 125                 /* privateKey */
 126                 *buf ++ = 0x04;
 127                 buf += br_asn1_encode_length(buf, sk->xlen);
 128                 memcpy(buf, sk->x, sk->xlen);
 129                 buf += sk->xlen;
 130
 131                 /* parameters */
 132                 if (include_curve_oid) {
 133                         *buf ++ = 0xA0;
 134                         *buf ++ = oid[0] + 2;
 135                         *buf ++ = 0x06;
 136                         memcpy(buf, oid, oid[0] + 1);
 137                         buf += oid[0] + 1;
 138                 }
 139
 140                 /* publicKey */
 141                 if (pk != NULL) {
 142                         *buf ++ = 0xA1;
 143                         buf += br_asn1_encode_length(buf, len_publicKey_bits);
 144                         *buf ++ = 0x03;
 145                         buf += br_asn1_encode_length(buf, pk->qlen + 1);
 146                         *buf ++ = 0x00;
 147                         memcpy(buf, pk->q, pk->qlen);
 148                         /* buf += pk->qlen; */
 149                 }
 150
 151                 return 1 + lenlen + len_seq;
 152         }
 153 }
 154
 155 /* see bearssl_x509.h */
 156 size_t
 157 br_encode_ec_raw_der(void *dest,
 158         const br_ec_private_key *sk, const br_ec_public_key *pk)
 159 {
 160         return br_encode_ec_raw_der_inner(dest, sk, pk, 1);
 161 }