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  }