1 /* 2 * Copyright (c) 2000 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #include "includes.h" 26 RCSID("$OpenBSD: ssh-rsa.c,v 1.16 2002/02/24 19:14:59 markus Exp $"); 27 28 #include <openssl/evp.h> 29 #include <openssl/err.h> 30 31 #include "xmalloc.h" 32 #include "log.h" 33 #include "buffer.h" 34 #include "bufaux.h" 35 #include "key.h" 36 #include "ssh-rsa.h" 37 #include "compat.h" 38 39 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 40 int 41 ssh_rsa_sign( 42 Key *key, 43 u_char **sigp, u_int *lenp, 44 u_char *data, u_int datalen) 45 { 46 const EVP_MD *evp_md; 47 EVP_MD_CTX md; 48 u_char digest[EVP_MAX_MD_SIZE], *sig, *ret; 49 u_int slen, dlen, len; 50 int ok, nid; 51 Buffer b; 52 53 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 54 error("ssh_rsa_sign: no RSA key"); 55 return -1; 56 } 57 if (datafellows & SSH_BUG_SIGBLOB) { 58 error("ssh_rsa_sign: SSH_BUG_SIGBLOB not supported"); 59 return -1; 60 } 61 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 62 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 63 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 64 return -1; 65 } 66 EVP_DigestInit(&md, evp_md); 67 EVP_DigestUpdate(&md, data, datalen); 68 EVP_DigestFinal(&md, digest, &dlen); 69 70 slen = RSA_size(key->rsa); 71 sig = xmalloc(slen); 72 73 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 74 memset(digest, 'd', sizeof(digest)); 75 76 if (ok != 1) { 77 int ecode = ERR_get_error(); 78 error("ssh_rsa_sign: RSA_sign failed: %s", ERR_error_string(ecode, NULL)); 79 xfree(sig); 80 return -1; 81 } 82 if (len < slen) { 83 int diff = slen - len; 84 debug("slen %d > len %d", slen, len); 85 memmove(sig + diff, sig, len); 86 memset(sig, 0, diff); 87 } else if (len > slen) { 88 error("ssh_rsa_sign: slen %d slen2 %d", slen, len); 89 xfree(sig); 90 return -1; 91 } 92 /* encode signature */ 93 buffer_init(&b); 94 buffer_put_cstring(&b, "ssh-rsa"); 95 buffer_put_string(&b, sig, slen); 96 len = buffer_len(&b); 97 ret = xmalloc(len); 98 memcpy(ret, buffer_ptr(&b), len); 99 buffer_free(&b); 100 memset(sig, 's', slen); 101 xfree(sig); 102 103 if (lenp != NULL) 104 *lenp = len; 105 if (sigp != NULL) 106 *sigp = ret; 107 return 0; 108 } 109 110 int 111 ssh_rsa_verify( 112 Key *key, 113 u_char *signature, u_int signaturelen, 114 u_char *data, u_int datalen) 115 { 116 Buffer b; 117 const EVP_MD *evp_md; 118 EVP_MD_CTX md; 119 char *ktype; 120 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 121 u_int len, dlen; 122 int rlen, ret, nid; 123 124 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 125 error("ssh_rsa_verify: no RSA key"); 126 return -1; 127 } 128 if (datafellows & SSH_BUG_SIGBLOB) { 129 error("ssh_rsa_verify: SSH_BUG_SIGBLOB not supported"); 130 return -1; 131 } 132 if (BN_num_bits(key->rsa->n) < 768) { 133 error("ssh_rsa_verify: n too small: %d bits", 134 BN_num_bits(key->rsa->n)); 135 return -1; 136 } 137 buffer_init(&b); 138 buffer_append(&b, signature, signaturelen); 139 ktype = buffer_get_string(&b, NULL); 140 if (strcmp("ssh-rsa", ktype) != 0) { 141 error("ssh_rsa_verify: cannot handle type %s", ktype); 142 buffer_free(&b); 143 xfree(ktype); 144 return -1; 145 } 146 xfree(ktype); 147 sigblob = buffer_get_string(&b, &len); 148 rlen = buffer_len(&b); 149 buffer_free(&b); 150 if (rlen != 0) { 151 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 152 xfree(sigblob); 153 return -1; 154 } 155 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 156 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 157 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 158 xfree(sigblob); 159 return -1; 160 } 161 EVP_DigestInit(&md, evp_md); 162 EVP_DigestUpdate(&md, data, datalen); 163 EVP_DigestFinal(&md, digest, &dlen); 164 165 ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 166 memset(digest, 'd', sizeof(digest)); 167 memset(sigblob, 's', len); 168 xfree(sigblob); 169 if (ret == 0) { 170 int ecode = ERR_get_error(); 171 error("ssh_rsa_verify: RSA_verify failed: %s", ERR_error_string(ecode, NULL)); 172 } 173 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 174 return ret; 175 } 176