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 <sys/types.h> 28 29 #include <openssl/bn.h> 30 #include <openssl/ec.h> 31 #include <openssl/ecdsa.h> 32 #include <openssl/evp.h> 33 34 #include <string.h> 35 36 #include "xmalloc.h" 37 #include "buffer.h" 38 #include "compat.h" 39 #include "log.h" 40 #include "key.h" 41 42 int 43 ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp, 44 const u_char *data, u_int datalen) 45 { 46 ECDSA_SIG *sig; 47 const EVP_MD *evp_md; 48 EVP_MD_CTX md; 49 u_char digest[EVP_MAX_MD_SIZE]; 50 u_int len, dlen; 51 Buffer b, bb; 52 53 if (key == NULL || key->ecdsa == NULL || 54 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) { 55 error("%s: no ECDSA key", __func__); 56 return -1; 57 } 58 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid); 59 EVP_DigestInit(&md, evp_md); 60 EVP_DigestUpdate(&md, data, datalen); 61 EVP_DigestFinal(&md, digest, &dlen); 62 63 sig = ECDSA_do_sign(digest, dlen, key->ecdsa); 64 memset(digest, 'd', sizeof(digest)); 65 66 if (sig == NULL) { 67 error("%s: sign failed", __func__); 68 return -1; 69 } 70 71 buffer_init(&bb); 72 buffer_put_bignum2(&bb, sig->r); 73 buffer_put_bignum2(&bb, sig->s); 74 ECDSA_SIG_free(sig); 75 76 buffer_init(&b); 77 buffer_put_cstring(&b, key_ssh_name_plain(key)); 78 buffer_put_string(&b, buffer_ptr(&bb), buffer_len(&bb)); 79 buffer_free(&bb); 80 len = buffer_len(&b); 81 if (lenp != NULL) 82 *lenp = len; 83 if (sigp != NULL) { 84 *sigp = xmalloc(len); 85 memcpy(*sigp, buffer_ptr(&b), len); 86 } 87 buffer_free(&b); 88 89 return 0; 90 } 91 int 92 ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen, 93 const u_char *data, u_int datalen) 94 { 95 ECDSA_SIG *sig; 96 const EVP_MD *evp_md; 97 EVP_MD_CTX md; 98 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 99 u_int len, dlen; 100 int rlen, ret; 101 Buffer b, bb; 102 char *ktype; 103 104 if (key == NULL || key->ecdsa == NULL || 105 (key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) { 106 error("%s: no ECDSA key", __func__); 107 return -1; 108 } 109 evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid); 110 111 /* fetch signature */ 112 buffer_init(&b); 113 buffer_append(&b, signature, signaturelen); 114 ktype = buffer_get_string(&b, NULL); 115 if (strcmp(key_ssh_name_plain(key), ktype) != 0) { 116 error("%s: cannot handle type %s", __func__, ktype); 117 buffer_free(&b); 118 xfree(ktype); 119 return -1; 120 } 121 xfree(ktype); 122 sigblob = buffer_get_string(&b, &len); 123 rlen = buffer_len(&b); 124 buffer_free(&b); 125 if (rlen != 0) { 126 error("%s: remaining bytes in signature %d", __func__, rlen); 127 xfree(sigblob); 128 return -1; 129 } 130 131 /* parse signature */ 132 if ((sig = ECDSA_SIG_new()) == NULL) 133 fatal("%s: ECDSA_SIG_new failed", __func__); 134 if ((sig->r = BN_new()) == NULL || 135 (sig->s = BN_new()) == NULL) 136 fatal("%s: BN_new failed", __func__); 137 138 buffer_init(&bb); 139 buffer_append(&bb, sigblob, len); 140 buffer_get_bignum2(&bb, sig->r); 141 buffer_get_bignum2(&bb, sig->s); 142 if (buffer_len(&bb) != 0) 143 fatal("%s: remaining bytes in inner sigblob", __func__); 144 145 /* clean up */ 146 memset(sigblob, 0, len); 147 xfree(sigblob); 148 149 /* hash the data */ 150 EVP_DigestInit(&md, evp_md); 151 EVP_DigestUpdate(&md, data, datalen); 152 EVP_DigestFinal(&md, digest, &dlen); 153 154 ret = ECDSA_do_verify(digest, dlen, sig, key->ecdsa); 155 memset(digest, 'd', sizeof(digest)); 156 157 ECDSA_SIG_free(sig); 158 159 debug("%s: signature %s", __func__, 160 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 161 return ret; 162 } 163