1 /* $OpenBSD: ssh-ecdsa.c,v 1.4 2010/09/10 01:04:10 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 46 int 47 ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp, 48 const u_char *data, u_int datalen) 49 { 50 ECDSA_SIG *sig; 51 const EVP_MD *evp_md; 52 EVP_MD_CTX md; 53 u_char digest[EVP_MAX_MD_SIZE]; 54 u_int len, dlen; 55 Buffer b, bb; 56 57 if (key == NULL || key->ecdsa == NULL || 58 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) { 59 error("%s: no ECDSA key", __func__); 60 return -1; 61 } 62 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid); 63 EVP_DigestInit(&md, evp_md); 64 EVP_DigestUpdate(&md, data, datalen); 65 EVP_DigestFinal(&md, digest, &dlen); 66 67 sig = ECDSA_do_sign(digest, dlen, key->ecdsa); 68 memset(digest, 'd', sizeof(digest)); 69 70 if (sig == NULL) { 71 error("%s: sign failed", __func__); 72 return -1; 73 } 74 75 buffer_init(&bb); 76 buffer_put_bignum2(&bb, sig->r); 77 buffer_put_bignum2(&bb, sig->s); 78 ECDSA_SIG_free(sig); 79 80 buffer_init(&b); 81 buffer_put_cstring(&b, key_ssh_name_plain(key)); 82 buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb)); 83 buffer_free(&bb); 84 len = buffer_len(&b); 85 if (lenp != NULL) 86 *lenp = len; 87 if (sigp != NULL) { 88 *sigp = xmalloc(len); 89 memcpy(*sigp, buffer_ptr(&b), len); 90 } 91 buffer_free(&b); 92 93 return 0; 94 } 95 int 96 ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen, 97 const u_char *data, u_int datalen) 98 { 99 ECDSA_SIG *sig; 100 const EVP_MD *evp_md; 101 EVP_MD_CTX md; 102 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 103 u_int len, dlen; 104 int rlen, ret; 105 Buffer b, bb; 106 char *ktype; 107 108 if (key == NULL || key->ecdsa == NULL || 109 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) { 110 error("%s: no ECDSA key", __func__); 111 return -1; 112 } 113 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid); 114 115 /* fetch signature */ 116 buffer_init(&b); 117 buffer_append(&b, signature, signaturelen); 118 ktype = buffer_get_string(&b, NULL); 119 if (strcmp(key_ssh_name_plain(key), ktype) != 0) { 120 error("%s: cannot handle type %s", __func__, ktype); 121 buffer_free(&b); 122 xfree(ktype); 123 return -1; 124 } 125 xfree(ktype); 126 sigblob = buffer_get_string(&b, &len); 127 rlen = buffer_len(&b); 128 buffer_free(&b); 129 if (rlen != 0) { 130 error("%s: remaining bytes in signature %d", __func__, rlen); 131 xfree(sigblob); 132 return -1; 133 } 134 135 /* parse signature */ 136 if ((sig = ECDSA_SIG_new()) == NULL) 137 fatal("%s: ECDSA_SIG_new failed", __func__); 138 if ((sig->r = BN_new()) == NULL || 139 (sig->s = BN_new()) == NULL) 140 fatal("%s: BN_new failed", __func__); 141 142 buffer_init(&bb); 143 buffer_append(&bb, sigblob, len); 144 buffer_get_bignum2(&bb, sig->r); 145 buffer_get_bignum2(&bb, sig->s); 146 if (buffer_len(&bb) != 0) 147 fatal("%s: remaining bytes in inner sigblob", __func__); 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 } 167 168 #endif /* OPENSSL_HAS_ECC */ 169