ssh-rsa.c revision 124208
1/* 2 * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org> 3 * 4 * Permission to use, copy, modify, and distribute this software for any 5 * purpose with or without fee is hereby granted, provided that the above 6 * copyright notice and this permission notice appear in all copies. 7 * 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15 */ 16#include "includes.h" 17RCSID("$OpenBSD: ssh-rsa.c,v 1.30 2003/06/18 11:28:11 markus Exp $"); 18 19#include <openssl/evp.h> 20#include <openssl/err.h> 21 22#include "xmalloc.h" 23#include "log.h" 24#include "buffer.h" 25#include "bufaux.h" 26#include "key.h" 27#include "compat.h" 28#include "ssh.h" 29 30static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *); 31 32/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 33int 34ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp, 35 u_char *data, u_int datalen) 36{ 37 const EVP_MD *evp_md; 38 EVP_MD_CTX md; 39 u_char digest[EVP_MAX_MD_SIZE], *sig; 40 u_int slen, dlen, len; 41 int ok, nid; 42 Buffer b; 43 44 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 45 error("ssh_rsa_sign: no RSA key"); 46 return -1; 47 } 48 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 49 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 50 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 51 return -1; 52 } 53 EVP_DigestInit(&md, evp_md); 54 EVP_DigestUpdate(&md, data, datalen); 55 EVP_DigestFinal(&md, digest, &dlen); 56 57 slen = RSA_size(key->rsa); 58 sig = xmalloc(slen); 59 60 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 61 memset(digest, 'd', sizeof(digest)); 62 63 if (ok != 1) { 64 int ecode = ERR_get_error(); 65 error("ssh_rsa_sign: RSA_sign failed: %s", 66 ERR_error_string(ecode, NULL)); 67 xfree(sig); 68 return -1; 69 } 70 if (len < slen) { 71 u_int diff = slen - len; 72 debug("slen %u > len %u", slen, len); 73 memmove(sig + diff, sig, len); 74 memset(sig, 0, diff); 75 } else if (len > slen) { 76 error("ssh_rsa_sign: slen %u slen2 %u", slen, len); 77 xfree(sig); 78 return -1; 79 } 80 /* encode signature */ 81 buffer_init(&b); 82 buffer_put_cstring(&b, "ssh-rsa"); 83 buffer_put_string(&b, sig, slen); 84 len = buffer_len(&b); 85 if (lenp != NULL) 86 *lenp = len; 87 if (sigp != NULL) { 88 *sigp = xmalloc(len); 89 memcpy(*sigp, buffer_ptr(&b), len); 90 } 91 buffer_free(&b); 92 memset(sig, 's', slen); 93 xfree(sig); 94 95 return 0; 96} 97 98int 99ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, 100 u_char *data, u_int datalen) 101{ 102 Buffer b; 103 const EVP_MD *evp_md; 104 EVP_MD_CTX md; 105 char *ktype; 106 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 107 u_int len, dlen, modlen; 108 int rlen, ret, nid; 109 110 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 111 error("ssh_rsa_verify: no RSA key"); 112 return -1; 113 } 114 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { 115 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", 116 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); 117 return -1; 118 } 119 buffer_init(&b); 120 buffer_append(&b, signature, signaturelen); 121 ktype = buffer_get_string(&b, NULL); 122 if (strcmp("ssh-rsa", ktype) != 0) { 123 error("ssh_rsa_verify: cannot handle type %s", ktype); 124 buffer_free(&b); 125 xfree(ktype); 126 return -1; 127 } 128 xfree(ktype); 129 sigblob = buffer_get_string(&b, &len); 130 rlen = buffer_len(&b); 131 buffer_free(&b); 132 if (rlen != 0) { 133 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 134 xfree(sigblob); 135 return -1; 136 } 137 /* RSA_verify expects a signature of RSA_size */ 138 modlen = RSA_size(key->rsa); 139 if (len > modlen) { 140 error("ssh_rsa_verify: len %u > modlen %u", len, modlen); 141 xfree(sigblob); 142 return -1; 143 } else if (len < modlen) { 144 u_int diff = modlen - len; 145 debug("ssh_rsa_verify: add padding: modlen %u > len %u", 146 modlen, len); 147 sigblob = xrealloc(sigblob, modlen); 148 memmove(sigblob + diff, sigblob, len); 149 memset(sigblob, 0, diff); 150 len = modlen; 151 } 152 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 153 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 154 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 155 xfree(sigblob); 156 return -1; 157 } 158 EVP_DigestInit(&md, evp_md); 159 EVP_DigestUpdate(&md, data, datalen); 160 EVP_DigestFinal(&md, digest, &dlen); 161 162 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 163 memset(digest, 'd', sizeof(digest)); 164 memset(sigblob, 's', len); 165 xfree(sigblob); 166 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 167 return ret; 168} 169 170/* 171 * See: 172 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ 173 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn 174 */ 175/* 176 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) 177 * oiw(14) secsig(3) algorithms(2) 26 } 178 */ 179static const u_char id_sha1[] = { 180 0x30, 0x21, /* type Sequence, length 0x21 (33) */ 181 0x30, 0x09, /* type Sequence, length 0x09 */ 182 0x06, 0x05, /* type OID, length 0x05 */ 183 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ 184 0x05, 0x00, /* NULL */ 185 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ 186}; 187/* 188 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 189 * rsadsi(113549) digestAlgorithm(2) 5 } 190 */ 191static const u_char id_md5[] = { 192 0x30, 0x20, /* type Sequence, length 0x20 (32) */ 193 0x30, 0x0c, /* type Sequence, length 0x09 */ 194 0x06, 0x08, /* type OID, length 0x05 */ 195 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ 196 0x05, 0x00, /* NULL */ 197 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ 198}; 199 200static int 201openssh_RSA_verify(int type, u_char *hash, u_int hashlen, 202 u_char *sigbuf, u_int siglen, RSA *rsa) 203{ 204 u_int ret, rsasize, oidlen = 0, hlen = 0; 205 int len; 206 const u_char *oid = NULL; 207 u_char *decrypted = NULL; 208 209 ret = 0; 210 switch (type) { 211 case NID_sha1: 212 oid = id_sha1; 213 oidlen = sizeof(id_sha1); 214 hlen = 20; 215 break; 216 case NID_md5: 217 oid = id_md5; 218 oidlen = sizeof(id_md5); 219 hlen = 16; 220 break; 221 default: 222 goto done; 223 break; 224 } 225 if (hashlen != hlen) { 226 error("bad hashlen"); 227 goto done; 228 } 229 rsasize = RSA_size(rsa); 230 if (siglen == 0 || siglen > rsasize) { 231 error("bad siglen"); 232 goto done; 233 } 234 decrypted = xmalloc(rsasize); 235 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, 236 RSA_PKCS1_PADDING)) < 0) { 237 error("RSA_public_decrypt failed: %s", 238 ERR_error_string(ERR_get_error(), NULL)); 239 goto done; 240 } 241 if (len != hlen + oidlen) { 242 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); 243 goto done; 244 } 245 if (memcmp(decrypted, oid, oidlen) != 0) { 246 error("oid mismatch"); 247 goto done; 248 } 249 if (memcmp(decrypted + oidlen, hash, hlen) != 0) { 250 error("hash mismatch"); 251 goto done; 252 } 253 ret = 1; 254done: 255 if (decrypted) 256 xfree(decrypted); 257 return ret; 258} 259