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 #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 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int , RSA *); 41 42 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 43 int 44 ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp, 45 u_char *data, u_int datalen) 46 { 47 const EVP_MD *evp_md; 48 EVP_MD_CTX md; 49 u_char digest[EVP_MAX_MD_SIZE], *sig; 50 u_int slen, dlen, len; 51 int ok, nid; 52 Buffer b; 53 54 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 55 error("ssh_rsa_sign: no RSA key"); 56 return -1; 57 } 58 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 59 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 60 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 61 return -1; 62 } 63 EVP_DigestInit(&md, evp_md); 64 EVP_DigestUpdate(&md, data, datalen); 65 EVP_DigestFinal(&md, digest, &dlen); 66 67 slen = RSA_size(key->rsa); 68 sig = xmalloc(slen); 69 70 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 71 memset(digest, 'd', sizeof(digest)); 72 73 if (ok != 1) { 74 int ecode = ERR_get_error(); 75 error("ssh_rsa_sign: RSA_sign failed: %s", 76 ERR_error_string(ecode, NULL)); 77 xfree(sig); 78 return -1; 79 } 80 if (len < slen) { 81 u_int diff = slen - len; 82 debug("slen %u > len %u", slen, len); 83 memmove(sig + diff, sig, len); 84 memset(sig, 0, diff); 85 } else if (len > slen) { 86 error("ssh_rsa_sign: slen %u slen2 %u", slen, len); 87 xfree(sig); 88 return -1; 89 } 90 /* encode signature */ 91 buffer_init(&b); 92 buffer_put_cstring(&b, "ssh-rsa"); 93 buffer_put_string(&b, sig, slen); 94 len = buffer_len(&b); 95 if (lenp != NULL) 96 *lenp = len; 97 if (sigp != NULL) { 98 *sigp = xmalloc(len); 99 memcpy(*sigp, buffer_ptr(&b), len); 100 } 101 buffer_free(&b); 102 memset(sig, 's', slen); 103 xfree(sig); 104 105 return 0; 106 } 107 108 int 109 ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, 110 u_char *data, u_int datalen) 111 { 112 Buffer b; 113 const EVP_MD *evp_md; 114 EVP_MD_CTX md; 115 char *ktype; 116 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 117 u_int len, dlen, modlen; 118 int rlen, ret, nid; 119 120 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 121 error("ssh_rsa_verify: no RSA key"); 122 return -1; 123 } 124 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { 125 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", 126 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); 127 return -1; 128 } 129 buffer_init(&b); 130 buffer_append(&b, signature, signaturelen); 131 ktype = buffer_get_string(&b, NULL); 132 if (strcmp("ssh-rsa", ktype) != 0) { 133 error("ssh_rsa_verify: cannot handle type %s", ktype); 134 buffer_free(&b); 135 xfree(ktype); 136 return -1; 137 } 138 xfree(ktype); 139 sigblob = buffer_get_string(&b, &len); 140 rlen = buffer_len(&b); 141 buffer_free(&b); 142 if (rlen != 0) { 143 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 144 xfree(sigblob); 145 return -1; 146 } 147 /* RSA_verify expects a signature of RSA_size */ 148 modlen = RSA_size(key->rsa); 149 if (len > modlen) { 150 error("ssh_rsa_verify: len %u > modlen %u", len, modlen); 151 xfree(sigblob); 152 return -1; 153 } else if (len < modlen) { 154 u_int diff = modlen - len; 155 debug("ssh_rsa_verify: add padding: modlen %u > len %u", 156 modlen, len); 157 sigblob = xrealloc(sigblob, modlen); 158 memmove(sigblob + diff, sigblob, len); 159 memset(sigblob, 0, diff); 160 len = modlen; 161 } 162 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 163 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 164 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 165 xfree(sigblob); 166 return -1; 167 } 168 EVP_DigestInit(&md, evp_md); 169 EVP_DigestUpdate(&md, data, datalen); 170 EVP_DigestFinal(&md, digest, &dlen); 171 172 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 173 memset(digest, 'd', sizeof(digest)); 174 memset(sigblob, 's', len); 175 xfree(sigblob); 176 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 177 return ret; 178 } 179 180 /* 181 * See: 182 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ 183 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn 184 */ 185 /* 186 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) 187 * oiw(14) secsig(3) algorithms(2) 26 } 188 */ 189 static const u_char id_sha1[] = { 190 0x30, 0x21, /* type Sequence, length 0x21 (33) */ 191 0x30, 0x09, /* type Sequence, length 0x09 */ 192 0x06, 0x05, /* type OID, length 0x05 */ 193 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ 194 0x05, 0x00, /* NULL */ 195 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ 196 }; 197 /* 198 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 199 * rsadsi(113549) digestAlgorithm(2) 5 } 200 */ 201 static const u_char id_md5[] = { 202 0x30, 0x20, /* type Sequence, length 0x20 (32) */ 203 0x30, 0x0c, /* type Sequence, length 0x09 */ 204 0x06, 0x08, /* type OID, length 0x05 */ 205 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ 206 0x05, 0x00, /* NULL */ 207 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ 208 }; 209 210 static int 211 openssh_RSA_verify(int type, u_char *hash, u_int hashlen, 212 u_char *sigbuf, u_int siglen, RSA *rsa) 213 { 214 u_int ret, rsasize, oidlen = 0, hlen = 0; 215 int len; 216 const u_char *oid = NULL; 217 u_char *decrypted = NULL; 218 219 ret = 0; 220 switch (type) { 221 case NID_sha1: 222 oid = id_sha1; 223 oidlen = sizeof(id_sha1); 224 hlen = 20; 225 break; 226 case NID_md5: 227 oid = id_md5; 228 oidlen = sizeof(id_md5); 229 hlen = 16; 230 break; 231 default: 232 goto done; 233 break; 234 } 235 if (hashlen != hlen) { 236 error("bad hashlen"); 237 goto done; 238 } 239 rsasize = RSA_size(rsa); 240 if (siglen == 0 || siglen > rsasize) { 241 error("bad siglen"); 242 goto done; 243 } 244 decrypted = xmalloc(rsasize); 245 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, 246 RSA_PKCS1_PADDING)) < 0) { 247 error("RSA_public_decrypt failed: %s", 248 ERR_error_string(ERR_get_error(), NULL)); 249 goto done; 250 } 251 if (len != hlen + oidlen) { 252 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); 253 goto done; 254 } 255 if (memcmp(decrypted, oid, oidlen) != 0) { 256 error("oid mismatch"); 257 goto done; 258 } 259 if (memcmp(decrypted + oidlen, hash, hlen) != 0) { 260 error("hash mismatch"); 261 goto done; 262 } 263 ret = 1; 264 done: 265 if (decrypted) 266 xfree(decrypted); 267 return ret; 268 } 269