1 /* $NetBSD: ssh-rsa.c,v 1.1.1.1 2009/06/07 22:19:24 christos Exp $ */ 2 /* $OpenBSD: ssh-rsa.c,v 1.39 2006/08/03 03:34:42 deraadt Exp $ */ 3 /* 4 * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include <sys/types.h> 20 21 #include <openssl/evp.h> 22 #include <openssl/err.h> 23 24 #include <string.h> 25 26 #include "xmalloc.h" 27 #include "log.h" 28 #include "buffer.h" 29 #include "key.h" 30 #include "compat.h" 31 #include "ssh.h" 32 33 static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *); 34 35 /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ 36 int 37 ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp, 38 const u_char *data, u_int datalen) 39 { 40 const EVP_MD *evp_md; 41 EVP_MD_CTX md; 42 u_char digest[EVP_MAX_MD_SIZE], *sig; 43 u_int slen, dlen, len; 44 int ok, nid; 45 Buffer b; 46 47 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 48 error("ssh_rsa_sign: no RSA key"); 49 return -1; 50 } 51 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 52 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 53 error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); 54 return -1; 55 } 56 EVP_DigestInit(&md, evp_md); 57 EVP_DigestUpdate(&md, data, datalen); 58 EVP_DigestFinal(&md, digest, &dlen); 59 60 slen = RSA_size(key->rsa); 61 sig = xmalloc(slen); 62 63 ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); 64 memset(digest, 'd', sizeof(digest)); 65 66 if (ok != 1) { 67 int ecode = ERR_get_error(); 68 69 error("ssh_rsa_sign: RSA_sign failed: %s", 70 ERR_error_string(ecode, NULL)); 71 xfree(sig); 72 return -1; 73 } 74 if (len < slen) { 75 u_int diff = slen - len; 76 debug("slen %u > len %u", slen, len); 77 memmove(sig + diff, sig, len); 78 memset(sig, 0, diff); 79 } else if (len > slen) { 80 error("ssh_rsa_sign: slen %u slen2 %u", slen, len); 81 xfree(sig); 82 return -1; 83 } 84 /* encode signature */ 85 buffer_init(&b); 86 buffer_put_cstring(&b, "ssh-rsa"); 87 buffer_put_string(&b, sig, slen); 88 len = buffer_len(&b); 89 if (lenp != NULL) 90 *lenp = len; 91 if (sigp != NULL) { 92 *sigp = xmalloc(len); 93 memcpy(*sigp, buffer_ptr(&b), len); 94 } 95 buffer_free(&b); 96 memset(sig, 's', slen); 97 xfree(sig); 98 99 return 0; 100 } 101 102 int 103 ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen, 104 const u_char *data, u_int datalen) 105 { 106 Buffer b; 107 const EVP_MD *evp_md; 108 EVP_MD_CTX md; 109 char *ktype; 110 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 111 u_int len, dlen, modlen; 112 int rlen, ret, nid; 113 114 if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { 115 error("ssh_rsa_verify: no RSA key"); 116 return -1; 117 } 118 if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { 119 error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", 120 BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); 121 return -1; 122 } 123 buffer_init(&b); 124 buffer_append(&b, signature, signaturelen); 125 ktype = buffer_get_string(&b, NULL); 126 if (strcmp("ssh-rsa", ktype) != 0) { 127 error("ssh_rsa_verify: cannot handle type %s", ktype); 128 buffer_free(&b); 129 xfree(ktype); 130 return -1; 131 } 132 xfree(ktype); 133 sigblob = buffer_get_string(&b, &len); 134 rlen = buffer_len(&b); 135 buffer_free(&b); 136 if (rlen != 0) { 137 error("ssh_rsa_verify: remaining bytes in signature %d", rlen); 138 xfree(sigblob); 139 return -1; 140 } 141 /* RSA_verify expects a signature of RSA_size */ 142 modlen = RSA_size(key->rsa); 143 if (len > modlen) { 144 error("ssh_rsa_verify: len %u > modlen %u", len, modlen); 145 xfree(sigblob); 146 return -1; 147 } else if (len < modlen) { 148 u_int diff = modlen - len; 149 debug("ssh_rsa_verify: add padding: modlen %u > len %u", 150 modlen, len); 151 sigblob = xrealloc(sigblob, 1, modlen); 152 memmove(sigblob + diff, sigblob, len); 153 memset(sigblob, 0, diff); 154 len = modlen; 155 } 156 nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; 157 if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { 158 error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); 159 xfree(sigblob); 160 return -1; 161 } 162 EVP_DigestInit(&md, evp_md); 163 EVP_DigestUpdate(&md, data, datalen); 164 EVP_DigestFinal(&md, digest, &dlen); 165 166 ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); 167 memset(digest, 'd', sizeof(digest)); 168 memset(sigblob, 's', len); 169 xfree(sigblob); 170 debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); 171 return ret; 172 } 173 174 /* 175 * See: 176 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ 177 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn 178 */ 179 /* 180 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) 181 * oiw(14) secsig(3) algorithms(2) 26 } 182 */ 183 static const u_char id_sha1[] = { 184 0x30, 0x21, /* type Sequence, length 0x21 (33) */ 185 0x30, 0x09, /* type Sequence, length 0x09 */ 186 0x06, 0x05, /* type OID, length 0x05 */ 187 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ 188 0x05, 0x00, /* NULL */ 189 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ 190 }; 191 /* 192 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 193 * rsadsi(113549) digestAlgorithm(2) 5 } 194 */ 195 static const u_char id_md5[] = { 196 0x30, 0x20, /* type Sequence, length 0x20 (32) */ 197 0x30, 0x0c, /* type Sequence, length 0x09 */ 198 0x06, 0x08, /* type OID, length 0x05 */ 199 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */ 200 0x05, 0x00, /* NULL */ 201 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */ 202 }; 203 204 static int 205 openssh_RSA_verify(int type, u_char *hash, u_int hashlen, 206 u_char *sigbuf, u_int siglen, RSA *rsa) 207 { 208 u_int ret, rsasize, oidlen = 0, hlen = 0; 209 int len; 210 const u_char *oid = NULL; 211 u_char *decrypted = NULL; 212 213 ret = 0; 214 switch (type) { 215 case NID_sha1: 216 oid = id_sha1; 217 oidlen = sizeof(id_sha1); 218 hlen = 20; 219 break; 220 case NID_md5: 221 oid = id_md5; 222 oidlen = sizeof(id_md5); 223 hlen = 16; 224 break; 225 default: 226 goto done; 227 } 228 if (hashlen != hlen) { 229 error("bad hashlen"); 230 goto done; 231 } 232 rsasize = RSA_size(rsa); 233 if (siglen == 0 || siglen > rsasize) { 234 error("bad siglen"); 235 goto done; 236 } 237 decrypted = xmalloc(rsasize); 238 if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, 239 RSA_PKCS1_PADDING)) < 0) { 240 error("RSA_public_decrypt failed: %s", 241 ERR_error_string(ERR_get_error(), NULL)); 242 goto done; 243 } 244 if (len < 0 || (u_int)len != hlen + oidlen) { 245 error("bad decrypted len: %d != %d + %d", len, hlen, oidlen); 246 goto done; 247 } 248 if (memcmp(decrypted, oid, oidlen) != 0) { 249 error("oid mismatch"); 250 goto done; 251 } 252 if (memcmp(decrypted + oidlen, hash, hlen) != 0) { 253 error("hash mismatch"); 254 goto done; 255 } 256 ret = 1; 257 done: 258 if (decrypted) 259 xfree(decrypted); 260 return ret; 261 } 262