1 /* $OpenBSD: ssh-ecdsa.c,v 1.10 2014/02/03 23:28:00 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * Copyright (c) 2010 Damien Miller. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 29 #ifdef OPENSSL_HAS_ECC 30 31 #include <sys/types.h> 32 33 #include <openssl/bn.h> 34 #include <openssl/ec.h> 35 #include <openssl/ecdsa.h> 36 #include <openssl/evp.h> 37 38 #include <string.h> 39 40 #include "xmalloc.h" 41 #include "buffer.h" 42 #include "compat.h" 43 #include "log.h" 44 #include "key.h" 45 #include "digest.h" 46 47 int 48 ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp, 49 const u_char *data, u_int datalen) 50 { 51 ECDSA_SIG *sig; 52 int hash_alg; 53 u_char digest[SSH_DIGEST_MAX_LENGTH]; 54 u_int len, dlen; 55 Buffer b, bb; 56 57 if (key == NULL || key_type_plain(key->type) != KEY_ECDSA || 58 key->ecdsa == NULL) { 59 error("%s: no ECDSA key", __func__); 60 return -1; 61 } 62 63 hash_alg = key_ec_nid_to_hash_alg(key->ecdsa_nid); 64 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) { 65 error("%s: bad hash algorithm %d", __func__, hash_alg); 66 return -1; 67 } 68 if (ssh_digest_memory(hash_alg, data, datalen, 69 digest, sizeof(digest)) != 0) { 70 error("%s: digest_memory failed", __func__); 71 return -1; 72 } 73 74 sig = ECDSA_do_sign(digest, dlen, key->ecdsa); 75 explicit_bzero(digest, sizeof(digest)); 76 77 if (sig == NULL) { 78 error("%s: sign failed", __func__); 79 return -1; 80 } 81 82 buffer_init(&bb); 83 buffer_put_bignum2(&bb, sig->r); 84 buffer_put_bignum2(&bb, sig->s); 85 ECDSA_SIG_free(sig); 86 87 buffer_init(&b); 88 buffer_put_cstring(&b, key_ssh_name_plain(key)); 89 buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb)); 90 buffer_free(&bb); 91 len = buffer_len(&b); 92 if (lenp != NULL) 93 *lenp = len; 94 if (sigp != NULL) { 95 *sigp = xmalloc(len); 96 memcpy(*sigp, buffer_ptr(&b), len); 97 } 98 buffer_free(&b); 99 100 return 0; 101 } 102 int 103 ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen, 104 const u_char *data, u_int datalen) 105 { 106 ECDSA_SIG *sig; 107 int hash_alg; 108 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob; 109 u_int len, dlen; 110 int rlen, ret; 111 Buffer b, bb; 112 char *ktype; 113 114 if (key == NULL || key_type_plain(key->type) != KEY_ECDSA || 115 key->ecdsa == NULL) { 116 error("%s: no ECDSA key", __func__); 117 return -1; 118 } 119 120 /* fetch signature */ 121 buffer_init(&b); 122 buffer_append(&b, signature, signaturelen); 123 ktype = buffer_get_string(&b, NULL); 124 if (strcmp(key_ssh_name_plain(key), ktype) != 0) { 125 error("%s: cannot handle type %s", __func__, ktype); 126 buffer_free(&b); 127 free(ktype); 128 return -1; 129 } 130 free(ktype); 131 sigblob = buffer_get_string(&b, &len); 132 rlen = buffer_len(&b); 133 buffer_free(&b); 134 if (rlen != 0) { 135 error("%s: remaining bytes in signature %d", __func__, rlen); 136 free(sigblob); 137 return -1; 138 } 139 140 /* parse signature */ 141 if ((sig = ECDSA_SIG_new()) == NULL) 142 fatal("%s: ECDSA_SIG_new failed", __func__); 143 144 buffer_init(&bb); 145 buffer_append(&bb, sigblob, len); 146 buffer_get_bignum2(&bb, sig->r); 147 buffer_get_bignum2(&bb, sig->s); 148 if (buffer_len(&bb) != 0) 149 fatal("%s: remaining bytes in inner sigblob", __func__); 150 buffer_free(&bb); 151 152 /* clean up */ 153 explicit_bzero(sigblob, len); 154 free(sigblob); 155 156 /* hash the data */ 157 hash_alg = key_ec_nid_to_hash_alg(key->ecdsa_nid); 158 if ((dlen = ssh_digest_bytes(hash_alg)) == 0) { 159 error("%s: bad hash algorithm %d", __func__, hash_alg); 160 return -1; 161 } 162 if (ssh_digest_memory(hash_alg, data, datalen, 163 digest, sizeof(digest)) != 0) { 164 error("%s: digest_memory failed", __func__); 165 return -1; 166 } 167 168 ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa); 169 explicit_bzero(digest, sizeof(digest)); 170 171 ECDSA_SIG_free(sig); 172 173 debug("%s: signature %s", __func__, 174 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 175 return ret; 176 } 177 178 #endif /* OPENSSL_HAS_ECC */ 179