ssh-rsa.c revision 113908
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 1.28 2003/02/12 09:33:04 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 "compat.h" 37#include "ssh.h" 38 39static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *); 40 41/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 42int 43ssh_rsa_sign(Key *key, 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; 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 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 58 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 59 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 60 return -1; 61 } 62 EVP_DigestInit(&md, evp_md); 63 EVP_DigestUpdate(&md, data, datalen); 64 EVP_DigestFinal(&md, digest, &dlen); 65 66 slen = RSA_size(key->rsa); 67 sig = xmalloc(slen); 68 69 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 70 memset(digest, 'd', sizeof(digest)); 71 72 if (ok != 1) { 73 int ecode = ERR_get_error(); 74 error("ssh_rsa_sign: RSA_sign failed: %s", 75 ERR_error_string(ecode, NULL)); 76 xfree(sig); 77 return -1; 78 } 79 if (len < slen) { 80 u_int diff = slen - len; 81 debug("slen %u > len %u", slen, len); 82 memmove(sig + diff, sig, len); 83 memset(sig, 0, diff); 84 } else if (len > slen) { 85 error("ssh_rsa_sign: slen %u slen2 %u", slen, len); 86 xfree(sig); 87 return -1; 88 } 89 /* encode signature */ 90 buffer_init(&b); 91 buffer_put_cstring(&b, "ssh-rsa"); 92 buffer_put_string(&b, sig, slen); 93 len = buffer_len(&b); 94 if (lenp != NULL) 95 *lenp = len; 96 if (sigp != NULL) { 97 *sigp = xmalloc(len); 98 memcpy(*sigp, buffer_ptr(&b), len); 99 } 100 buffer_free(&b); 101 memset(sig, 's', slen); 102 xfree(sig); 103 104 return 0; 105} 106 107int 108ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, 109 u_char *data, u_int datalen) 110{ 111 Buffer b; 112 const EVP_MD *evp_md; 113 EVP_MD_CTX md; 114 char *ktype; 115 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 116 u_int len, dlen, modlen; 117 int rlen, ret, nid; 118 119 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 120 error("ssh_rsa_verify: no RSA key"); 121 return -1; 122 } 123 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { 124 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", 125 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); 126 return -1; 127 } 128 buffer_init(&b); 129 buffer_append(&b, signature, signaturelen); 130 ktype = buffer_get_string(&b, NULL); 131 if (strcmp("ssh-rsa", ktype) != 0) { 132 error("ssh_rsa_verify: cannot handle type %s", ktype); 133 buffer_free(&b); 134 xfree(ktype); 135 return -1; 136 } 137 xfree(ktype); 138 sigblob = buffer_get_string(&b, &len); 139 rlen = buffer_len(&b); 140 buffer_free(&b); 141 if (rlen != 0) { 142 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 143 xfree(sigblob); 144 return -1; 145 } 146 /* RSA_verify expects a signature of RSA_size */ 147 modlen = RSA_size(key->rsa); 148 if (len > modlen) { 149 error("ssh_rsa_verify: len %u > modlen %u", len, modlen); 150 xfree(sigblob); 151 return -1; 152 } else if (len < modlen) { 153 u_int diff = modlen - len; 154 debug("ssh_rsa_verify: add padding: modlen %u > len %u", 155 modlen, len); 156 sigblob = xrealloc(sigblob, modlen); 157 memmove(sigblob + diff, sigblob, len); 158 memset(sigblob, 0, diff); 159 len = modlen; 160 } 161 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 162 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 163 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 164 xfree(sigblob); 165 return -1; 166 } 167 EVP_DigestInit(&md, evp_md); 168 EVP_DigestUpdate(&md, data, datalen); 169 EVP_DigestFinal(&md, digest, &dlen); 170 171 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 172 memset(digest, 'd', sizeof(digest)); 173 memset(sigblob, 's', len); 174 xfree(sigblob); 175 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 176 return ret; 177} 178 179/* 180 * See: 181 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ 182 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn 183 */ 184/* 185 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) 186 * oiw(14) secsig(3) algorithms(2) 26 } 187 */ 188static const u_char id_sha1[] = { 189 0x30, 0x21, /* type Sequence, length 0x21 (33) */ 190 0x30, 0x09, /* type Sequence, length 0x09 */ 191 0x06, 0x05, /* type OID, length 0x05 */ 192 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ 193 0x05, 0x00, /* NULL */ 194 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ 195}; 196/* 197 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 198 * rsadsi(113549) digestAlgorithm(2) 5 } 199 */ 200static const u_char id_md5[] = { 201 0x30, 0x20, /* type Sequence, length 0x20 (32) */ 202 0x30, 0x0c, /* type Sequence, length 0x09 */ 203 0x06, 0x08, /* type OID, length 0x05 */ 204 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ 205 0x05, 0x00, /* NULL */ 206 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ 207}; 208 209static int 210openssh_RSA_verify(int type, u_char *hash, u_int hashlen, 211 u_char *sigbuf, u_int siglen, RSA *rsa) 212{ 213 u_int ret, rsasize, oidlen = 0, hlen = 0; 214 int len; 215 const u_char *oid = NULL; 216 u_char *decrypted = NULL; 217 218 ret = 0; 219 switch (type) { 220 case NID_sha1: 221 oid = id_sha1; 222 oidlen = sizeof(id_sha1); 223 hlen = 20; 224 break; 225 case NID_md5: 226 oid = id_md5; 227 oidlen = sizeof(id_md5); 228 hlen = 16; 229 break; 230 default: 231 goto done; 232 break; 233 } 234 if (hashlen != hlen) { 235 error("bad hashlen"); 236 goto done; 237 } 238 rsasize = RSA_size(rsa); 239 if (siglen == 0 || siglen > rsasize) { 240 error("bad siglen"); 241 goto done; 242 } 243 decrypted = xmalloc(rsasize); 244 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, 245 RSA_PKCS1_PADDING)) < 0) { 246 error("RSA_public_decrypt failed: %s", 247 ERR_error_string(ERR_get_error(), NULL)); 248 goto done; 249 } 250 if (len != hlen + oidlen) { 251 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); 252 goto done; 253 } 254 if (memcmp(decrypted, oid, oidlen) != 0) { 255 error("oid mismatch"); 256 goto done; 257 } 258 if (memcmp(decrypted + oidlen, hash, hlen) != 0) { 259 error("hash mismatch"); 260 goto done; 261 } 262 ret = 1; 263done: 264 if (decrypted) 265 xfree(decrypted); 266 return ret; 267} 268