1 /* $NetBSD: ssh-ecdsa.c,v 1.3 2012/05/02 02:41:08 christos Exp $ */ 2 /* $OpenBSD: ssh-ecdsa.c,v 1.5 2012/01/08 13:17:11 miod Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * Copyright (c) 2010 Damien Miller. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 __RCSID("$NetBSD: ssh-ecdsa.c,v 1.3 2012/05/02 02:41:08 christos Exp $"); 30 #include <sys/types.h> 31 32 #include <openssl/bn.h> 33 #include <openssl/ec.h> 34 #include <openssl/ecdsa.h> 35 #include <openssl/evp.h> 36 37 #include <string.h> 38 39 #include "xmalloc.h" 40 #include "buffer.h" 41 #include "compat.h" 42 #include "log.h" 43 #include "key.h" 44 45 int 46 ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp, 47 const u_char *data, u_int datalen) 48 { 49 ECDSA_SIG *sig; 50 const EVP_MD *evp_md; 51 EVP_MD_CTX md; 52 u_char digest[EVP_MAX_MD_SIZE]; 53 u_int len, dlen; 54 Buffer b, bb; 55 56 if (key == NULL || key->ecdsa == NULL || 57 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) { 58 error("%s: no ECDSA key", __func__); 59 return -1; 60 } 61 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid); 62 EVP_DigestInit(&md, evp_md); 63 EVP_DigestUpdate(&md, data, datalen); 64 EVP_DigestFinal(&md, digest, &dlen); 65 66 sig = ECDSA_do_sign(digest, dlen, key->ecdsa); 67 memset(digest, 'd', sizeof(digest)); 68 69 if (sig == NULL) { 70 error("%s: sign failed", __func__); 71 return -1; 72 } 73 74 buffer_init(&bb); 75 buffer_put_bignum2(&bb, sig->r); 76 buffer_put_bignum2(&bb, sig->s); 77 ECDSA_SIG_free(sig); 78 79 buffer_init(&b); 80 buffer_put_cstring(&b, key_ssh_name_plain(key)); 81 buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb)); 82 buffer_free(&bb); 83 len = buffer_len(&b); 84 if (lenp != NULL) 85 *lenp = len; 86 if (sigp != NULL) { 87 *sigp = xmalloc(len); 88 memcpy(*sigp, buffer_ptr(&b), len); 89 } 90 buffer_free(&b); 91 92 return 0; 93 } 94 int 95 ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen, 96 const u_char *data, u_int datalen) 97 { 98 ECDSA_SIG *sig; 99 const EVP_MD *evp_md; 100 EVP_MD_CTX md; 101 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 102 u_int len, dlen; 103 int rlen, ret; 104 Buffer b, bb; 105 char *ktype; 106 107 if (key == NULL || key->ecdsa == NULL || 108 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) { 109 error("%s: no ECDSA key", __func__); 110 return -1; 111 } 112 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid); 113 114 /* fetch signature */ 115 buffer_init(&b); 116 buffer_append(&b, signature, signaturelen); 117 ktype = buffer_get_string(&b, NULL); 118 if (strcmp(key_ssh_name_plain(key), ktype) != 0) { 119 error("%s: cannot handle type %s", __func__, ktype); 120 buffer_free(&b); 121 xfree(ktype); 122 return -1; 123 } 124 xfree(ktype); 125 sigblob = buffer_get_string(&b, &len); 126 rlen = buffer_len(&b); 127 buffer_free(&b); 128 if (rlen != 0) { 129 error("%s: remaining bytes in signature %d", __func__, rlen); 130 xfree(sigblob); 131 return -1; 132 } 133 134 /* parse signature */ 135 if ((sig = ECDSA_SIG_new()) == NULL) 136 fatal("%s: ECDSA_SIG_new failed", __func__); 137 if ((sig->r = BN_new()) == NULL || 138 (sig->s = BN_new()) == NULL) 139 fatal("%s: BN_new failed", __func__); 140 141 buffer_init(&bb); 142 buffer_append(&bb, sigblob, len); 143 buffer_get_bignum2(&bb, sig->r); 144 buffer_get_bignum2(&bb, sig->s); 145 if (buffer_len(&bb) != 0) 146 fatal("%s: remaining bytes in inner sigblob", __func__); 147 buffer_free(&bb); 148 149 /* clean up */ 150 memset(sigblob, 0, len); 151 xfree(sigblob); 152 153 /* hash the data */ 154 EVP_DigestInit(&md, evp_md); 155 EVP_DigestUpdate(&md, data, datalen); 156 EVP_DigestFinal(&md, digest, &dlen); 157 158 ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa); 159 memset(digest, 'd', sizeof(digest)); 160 161 ECDSA_SIG_free(sig); 162 163 debug("%s: signature %s", __func__, 164 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 165 return ret; 166 } 167