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 1.26 2002/08/27 17:13:56 stevesk Exp $"); 27 28 #pragma ident "%Z%%M% %I% %E% SMI" 29 30 #include <openssl/evp.h> 31 #include <openssl/err.h> 32 33 #include "xmalloc.h" 34 #include "log.h" 35 #include "buffer.h" 36 #include "bufaux.h" 37 #include "key.h" 38 #include "ssh-rsa.h" 39 #include "compat.h" 40 #include "ssh.h" 41 42 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int , RSA *); 43 44 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 45 int 46 ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp, 47 u_char *data, u_int datalen) 48 { 49 const EVP_MD *evp_md; 50 EVP_MD_CTX md; 51 u_char digest[EVP_MAX_MD_SIZE], *sig; 52 u_int slen, dlen, len; 53 int ok, nid; 54 Buffer b; 55 56 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 57 error("ssh_rsa_sign: no RSA key"); 58 return -1; 59 } 60 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 61 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 62 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 63 return -1; 64 } 65 EVP_DigestInit(&md, evp_md); 66 EVP_DigestUpdate(&md, data, datalen); 67 EVP_DigestFinal(&md, digest, &dlen); 68 69 slen = RSA_size(key->rsa); 70 sig = xmalloc(slen); 71 72 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 73 memset(digest, 'd', sizeof(digest)); 74 75 if (ok != 1) { 76 int ecode = ERR_get_error(); 77 error("ssh_rsa_sign: RSA_sign failed: %s", 78 ERR_error_string(ecode, NULL)); 79 xfree(sig); 80 return -1; 81 } 82 if (len < slen) { 83 u_int diff = slen - len; 84 debug("slen %u > len %u", slen, len); 85 memmove(sig + diff, sig, len); 86 memset(sig, 0, diff); 87 } else if (len > slen) { 88 error("ssh_rsa_sign: slen %u slen2 %u", 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 if (lenp != NULL) 98 *lenp = len; 99 if (sigp != NULL) { 100 *sigp = xmalloc(len); 101 memcpy(*sigp, buffer_ptr(&b), len); 102 } 103 buffer_free(&b); 104 memset(sig, 's', slen); 105 xfree(sig); 106 107 return 0; 108 } 109 110 int 111 ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, 112 u_char *data, u_int datalen) 113 { 114 Buffer b; 115 const EVP_MD *evp_md; 116 EVP_MD_CTX md; 117 char *ktype; 118 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 119 u_int len, dlen, modlen; 120 int rlen, ret, nid; 121 122 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 123 error("ssh_rsa_verify: no RSA key"); 124 return -1; 125 } 126 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { 127 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", 128 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); 129 return -1; 130 } 131 buffer_init(&b); 132 buffer_append(&b, signature, signaturelen); 133 ktype = buffer_get_string(&b, NULL); 134 if (strcmp("ssh-rsa", ktype) != 0) { 135 error("ssh_rsa_verify: cannot handle type %s", ktype); 136 buffer_free(&b); 137 xfree(ktype); 138 return -1; 139 } 140 xfree(ktype); 141 sigblob = buffer_get_string(&b, &len); 142 rlen = buffer_len(&b); 143 buffer_free(&b); 144 if (rlen != 0) { 145 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 146 xfree(sigblob); 147 return -1; 148 } 149 /* RSA_verify expects a signature of RSA_size */ 150 modlen = RSA_size(key->rsa); 151 if (len > modlen) { 152 error("ssh_rsa_verify: len %u > modlen %u", len, modlen); 153 xfree(sigblob); 154 return -1; 155 } else if (len < modlen) { 156 u_int diff = modlen - len; 157 debug("ssh_rsa_verify: add padding: modlen %u > len %u", 158 modlen, len); 159 sigblob = xrealloc(sigblob, modlen); 160 memmove(sigblob + diff, sigblob, len); 161 memset(sigblob, 0, diff); 162 len = modlen; 163 } 164 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 165 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 166 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 167 xfree(sigblob); 168 return -1; 169 } 170 EVP_DigestInit(&md, evp_md); 171 EVP_DigestUpdate(&md, data, datalen); 172 EVP_DigestFinal(&md, digest, &dlen); 173 174 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 175 memset(digest, 'd', sizeof(digest)); 176 memset(sigblob, 's', len); 177 xfree(sigblob); 178 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 179 return ret; 180 } 181 182 /* 183 * See: 184 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ 185 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn 186 */ 187 /* 188 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) 189 * oiw(14) secsig(3) algorithms(2) 26 } 190 */ 191 static const u_char id_sha1[] = { 192 0x30, 0x21, /* type Sequence, length 0x21 (33) */ 193 0x30, 0x09, /* type Sequence, length 0x09 */ 194 0x06, 0x05, /* type OID, length 0x05 */ 195 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ 196 0x05, 0x00, /* NULL */ 197 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ 198 }; 199 /* 200 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 201 * rsadsi(113549) digestAlgorithm(2) 5 } 202 */ 203 static const u_char id_md5[] = { 204 0x30, 0x20, /* type Sequence, length 0x20 (32) */ 205 0x30, 0x0c, /* type Sequence, length 0x09 */ 206 0x06, 0x08, /* type OID, length 0x05 */ 207 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ 208 0x05, 0x00, /* NULL */ 209 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ 210 }; 211 212 static int 213 openssh_RSA_verify(int type, u_char *hash, u_int hashlen, 214 u_char *sigbuf, u_int siglen, RSA *rsa) 215 { 216 u_int ret, rsasize, oidlen = 0, hlen = 0; 217 int len; 218 const u_char *oid = NULL; 219 u_char *decrypted = NULL; 220 221 ret = 0; 222 switch (type) { 223 case NID_sha1: 224 oid = id_sha1; 225 oidlen = sizeof(id_sha1); 226 hlen = 20; 227 break; 228 case NID_md5: 229 oid = id_md5; 230 oidlen = sizeof(id_md5); 231 hlen = 16; 232 break; 233 default: 234 goto done; 235 break; 236 } 237 if (hashlen != hlen) { 238 error("bad hashlen"); 239 goto done; 240 } 241 rsasize = RSA_size(rsa); 242 if (siglen == 0 || siglen > rsasize) { 243 error("bad siglen"); 244 goto done; 245 } 246 decrypted = xmalloc(rsasize); 247 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, 248 RSA_PKCS1_PADDING)) < 0) { 249 error("RSA_public_decrypt failed: %s", 250 ERR_error_string(ERR_get_error(), NULL)); 251 goto done; 252 } 253 if (len != hlen + oidlen) { 254 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); 255 goto done; 256 } 257 if (memcmp(decrypted, oid, oidlen) != 0) { 258 error("oid mismatch"); 259 goto done; 260 } 261 if (memcmp(decrypted + oidlen, hash, hlen) != 0) { 262 error("hash mismatch"); 263 goto done; 264 } 265 ret = 1; 266 done: 267 if (decrypted) 268 xfree(decrypted); 269 return ret; 270 } 271