_ Git - BearSSL/blob - encode_rsa_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_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 }