Mike Lockwood | 1305e95 | 2011-12-07 08:17:59 -0800 | [diff] [blame] | 1 | /* $OpenBSD: ssh-dss.c,v 1.27 2010/08/31 09:58:37 djm Exp $ */ |
| 2 | /* |
| 3 | * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * |
| 14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 15 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 16 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 17 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 18 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 19 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 20 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 21 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 23 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 24 | */ |
| 25 | |
| 26 | #include "includes.h" |
| 27 | |
| 28 | #include <sys/types.h> |
| 29 | |
| 30 | #include <openssl/bn.h> |
| 31 | #include <openssl/evp.h> |
| 32 | |
| 33 | #include <stdarg.h> |
| 34 | #include <string.h> |
| 35 | |
| 36 | #include "xmalloc.h" |
| 37 | #include "buffer.h" |
| 38 | #include "compat.h" |
| 39 | #include "log.h" |
| 40 | #include "key.h" |
| 41 | |
| 42 | #define INTBLOB_LEN 20 |
| 43 | #define SIGBLOB_LEN (2*INTBLOB_LEN) |
| 44 | |
| 45 | int |
| 46 | ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, |
| 47 | const u_char *data, u_int datalen) |
| 48 | { |
| 49 | DSA_SIG *sig; |
| 50 | const EVP_MD *evp_md = EVP_sha1(); |
| 51 | EVP_MD_CTX md; |
| 52 | u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; |
| 53 | u_int rlen, slen, len, dlen; |
| 54 | Buffer b; |
| 55 | |
| 56 | if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA && |
| 57 | key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) { |
| 58 | error("ssh_dss_sign: no DSA key"); |
| 59 | return -1; |
| 60 | } |
| 61 | EVP_DigestInit(&md, evp_md); |
| 62 | EVP_DigestUpdate(&md, data, datalen); |
| 63 | EVP_DigestFinal(&md, digest, &dlen); |
| 64 | |
| 65 | sig = DSA_do_sign(digest, dlen, key->dsa); |
| 66 | memset(digest, 'd', sizeof(digest)); |
| 67 | |
| 68 | if (sig == NULL) { |
| 69 | error("ssh_dss_sign: sign failed"); |
| 70 | return -1; |
| 71 | } |
| 72 | |
| 73 | rlen = BN_num_bytes(sig->r); |
| 74 | slen = BN_num_bytes(sig->s); |
| 75 | if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { |
| 76 | error("bad sig size %u %u", rlen, slen); |
| 77 | DSA_SIG_free(sig); |
| 78 | return -1; |
| 79 | } |
| 80 | memset(sigblob, 0, SIGBLOB_LEN); |
| 81 | BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); |
| 82 | BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); |
| 83 | DSA_SIG_free(sig); |
| 84 | |
| 85 | if (datafellows & SSH_BUG_SIGBLOB) { |
| 86 | if (lenp != NULL) |
| 87 | *lenp = SIGBLOB_LEN; |
| 88 | if (sigp != NULL) { |
| 89 | *sigp = xmalloc(SIGBLOB_LEN); |
| 90 | memcpy(*sigp, sigblob, SIGBLOB_LEN); |
| 91 | } |
| 92 | } else { |
| 93 | /* ietf-drafts */ |
| 94 | buffer_init(&b); |
| 95 | buffer_put_cstring(&b, "ssh-dss"); |
| 96 | buffer_put_string(&b, sigblob, SIGBLOB_LEN); |
| 97 | len = buffer_len(&b); |
| 98 | if (lenp != NULL) |
| 99 | *lenp = len; |
| 100 | if (sigp != NULL) { |
| 101 | *sigp = xmalloc(len); |
| 102 | memcpy(*sigp, buffer_ptr(&b), len); |
| 103 | } |
| 104 | buffer_free(&b); |
| 105 | } |
| 106 | return 0; |
| 107 | } |
| 108 | int |
| 109 | ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, |
| 110 | const u_char *data, u_int datalen) |
| 111 | { |
| 112 | DSA_SIG *sig; |
| 113 | const EVP_MD *evp_md = EVP_sha1(); |
| 114 | EVP_MD_CTX md; |
| 115 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; |
| 116 | u_int len, dlen; |
| 117 | int rlen, ret; |
| 118 | Buffer b; |
| 119 | |
| 120 | if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA && |
| 121 | key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) { |
| 122 | error("ssh_dss_verify: no DSA key"); |
| 123 | return -1; |
| 124 | } |
| 125 | |
| 126 | /* fetch signature */ |
| 127 | if (datafellows & SSH_BUG_SIGBLOB) { |
| 128 | sigblob = xmalloc(signaturelen); |
| 129 | memcpy(sigblob, signature, signaturelen); |
| 130 | len = signaturelen; |
| 131 | } else { |
| 132 | /* ietf-drafts */ |
| 133 | char *ktype; |
| 134 | buffer_init(&b); |
| 135 | buffer_append(&b, signature, signaturelen); |
| 136 | ktype = buffer_get_cstring(&b, NULL); |
| 137 | if (strcmp("ssh-dss", ktype) != 0) { |
| 138 | error("ssh_dss_verify: cannot handle type %s", ktype); |
| 139 | buffer_free(&b); |
| 140 | xfree(ktype); |
| 141 | return -1; |
| 142 | } |
| 143 | xfree(ktype); |
| 144 | sigblob = buffer_get_string(&b, &len); |
| 145 | rlen = buffer_len(&b); |
| 146 | buffer_free(&b); |
| 147 | if (rlen != 0) { |
| 148 | error("ssh_dss_verify: " |
| 149 | "remaining bytes in signature %d", rlen); |
| 150 | xfree(sigblob); |
| 151 | return -1; |
| 152 | } |
| 153 | } |
| 154 | |
| 155 | if (len != SIGBLOB_LEN) { |
| 156 | fatal("bad sigbloblen %u != SIGBLOB_LEN", len); |
| 157 | } |
| 158 | |
| 159 | /* parse signature */ |
| 160 | if ((sig = DSA_SIG_new()) == NULL) |
| 161 | fatal("ssh_dss_verify: DSA_SIG_new failed"); |
| 162 | if ((sig->r = BN_new()) == NULL) |
| 163 | fatal("ssh_dss_verify: BN_new failed"); |
| 164 | if ((sig->s = BN_new()) == NULL) |
| 165 | fatal("ssh_dss_verify: BN_new failed"); |
| 166 | if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || |
| 167 | (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) |
| 168 | fatal("ssh_dss_verify: BN_bin2bn failed"); |
| 169 | |
| 170 | /* clean up */ |
| 171 | memset(sigblob, 0, len); |
| 172 | xfree(sigblob); |
| 173 | |
| 174 | /* sha1 the data */ |
| 175 | EVP_DigestInit(&md, evp_md); |
| 176 | EVP_DigestUpdate(&md, data, datalen); |
| 177 | EVP_DigestFinal(&md, digest, &dlen); |
| 178 | |
| 179 | ret = DSA_do_verify(digest, dlen, sig, key->dsa); |
| 180 | memset(digest, 'd', sizeof(digest)); |
| 181 | |
| 182 | DSA_SIG_free(sig); |
| 183 | |
| 184 | debug("ssh_dss_verify: signature %s", |
| 185 | ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); |
| 186 | return ret; |
| 187 | } |