ssh-rsa.c revision 99060
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" 26RCSID("$OpenBSD: ssh-rsa.c,v 1.21 2002/06/23 03:30:17 deraadt 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#include "ssh.h" 39 40/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 41int 42ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp, 43 u_char *data, u_int datalen) 44{ 45 const EVP_MD *evp_md; 46 EVP_MD_CTX md; 47 u_char digest[EVP_MAX_MD_SIZE], *sig, *ret; 48 u_int slen, dlen, len; 49 int ok, nid; 50 Buffer b; 51 52 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 53 error("ssh_rsa_sign: no RSA key"); 54 return -1; 55 } 56 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 57 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 58 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 59 return -1; 60 } 61 EVP_DigestInit(&md, evp_md); 62 EVP_DigestUpdate(&md, data, datalen); 63 EVP_DigestFinal(&md, digest, &dlen); 64 65 slen = RSA_size(key->rsa); 66 sig = xmalloc(slen); 67 68 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 69 memset(digest, 'd', sizeof(digest)); 70 71 if (ok != 1) { 72 int ecode = ERR_get_error(); 73 error("ssh_rsa_sign: RSA_sign failed: %s", 74 ERR_error_string(ecode, NULL)); 75 xfree(sig); 76 return -1; 77 } 78 if (len < slen) { 79 int diff = slen - len; 80 debug("slen %u > len %u", slen, len); 81 memmove(sig + diff, sig, len); 82 memset(sig, 0, diff); 83 } else if (len > slen) { 84 error("ssh_rsa_sign: slen %u slen2 %u", slen, len); 85 xfree(sig); 86 return -1; 87 } 88 /* encode signature */ 89 buffer_init(&b); 90 buffer_put_cstring(&b, "ssh-rsa"); 91 buffer_put_string(&b, sig, slen); 92 len = buffer_len(&b); 93 ret = xmalloc(len); 94 memcpy(ret, buffer_ptr(&b), len); 95 buffer_free(&b); 96 memset(sig, 's', slen); 97 xfree(sig); 98 99 if (lenp != NULL) 100 *lenp = len; 101 if (sigp != NULL) 102 *sigp = ret; 103 return 0; 104} 105 106int 107ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, 108 u_char *data, u_int datalen) 109{ 110 Buffer b; 111 const EVP_MD *evp_md; 112 EVP_MD_CTX md; 113 char *ktype; 114 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 115 u_int len, dlen, modlen; 116 int rlen, ret, nid; 117 118 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 119 error("ssh_rsa_verify: no RSA key"); 120 return -1; 121 } 122 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { 123 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", 124 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); 125 return -1; 126 } 127 buffer_init(&b); 128 buffer_append(&b, signature, signaturelen); 129 ktype = buffer_get_string(&b, NULL); 130 if (strcmp("ssh-rsa", ktype) != 0) { 131 error("ssh_rsa_verify: cannot handle type %s", ktype); 132 buffer_free(&b); 133 xfree(ktype); 134 return -1; 135 } 136 xfree(ktype); 137 sigblob = buffer_get_string(&b, &len); 138 rlen = buffer_len(&b); 139 buffer_free(&b); 140 if (rlen != 0) { 141 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 142 xfree(sigblob); 143 return -1; 144 } 145 /* RSA_verify expects a signature of RSA_size */ 146 modlen = RSA_size(key->rsa); 147 if (len > modlen) { 148 error("ssh_rsa_verify: len %u > modlen %u", len, modlen); 149 xfree(sigblob); 150 return -1; 151 } else if (len < modlen) { 152 int diff = modlen - len; 153 debug("ssh_rsa_verify: add padding: modlen %u > len %u", 154 modlen, len); 155 sigblob = xrealloc(sigblob, modlen); 156 memmove(sigblob + diff, sigblob, len); 157 memset(sigblob, 0, diff); 158 len = modlen; 159 } 160 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 161 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 162 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 163 xfree(sigblob); 164 return -1; 165 } 166 EVP_DigestInit(&md, evp_md); 167 EVP_DigestUpdate(&md, data, datalen); 168 EVP_DigestFinal(&md, digest, &dlen); 169 170 ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 171 memset(digest, 'd', sizeof(digest)); 172 memset(sigblob, 's', len); 173 xfree(sigblob); 174 if (ret == 0) { 175 int ecode = ERR_get_error(); 176 error("ssh_rsa_verify: RSA_verify failed: %s", 177 ERR_error_string(ecode, NULL)); 178 } 179 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 180 return ret; 181} 182