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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 1.24 2002/08/02 21:23:41 markus 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 | /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ | |
41 | int | |
42 | ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp, | |
43 | u_char *data, u_int datalen) | |
44 | { | |
45 | const EVP_MD *evp_md; | |
46 | EVP_MD_CTX md; | |
47 | u_char digest[EVP_MAX_MD_SIZE], *sig; | |
48 | u_int slen, dlen, len; | |
49 | int ok, nid; | |
50 | Buffer b; | |
51 | ||
52 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { | |
53 | error("ssh_rsa_sign: no RSA key"); | |
54 | return -1; | |
55 | } | |
56 | nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; | |
57 | if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { | |
58 | error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid); | |
59 | return -1; | |
60 | } | |
61 | EVP_DigestInit(&md, evp_md); | |
62 | EVP_DigestUpdate(&md, data, datalen); | |
63 | EVP_DigestFinal(&md, digest, &dlen); | |
64 | ||
65 | slen = RSA_size(key->rsa); | |
66 | sig = xmalloc(slen); | |
67 | ||
68 | ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa); | |
69 | memset(digest, 'd', sizeof(digest)); | |
70 | ||
71 | if (ok != 1) { | |
72 | int ecode = ERR_get_error(); | |
73 | error("ssh_rsa_sign: RSA_sign failed: %s", | |
74 | ERR_error_string(ecode, NULL)); | |
75 | xfree(sig); | |
76 | return -1; | |
77 | } | |
78 | if (len < slen) { | |
79 | u_int diff = slen - len; | |
80 | debug("slen %u > len %u", slen, len); | |
81 | memmove(sig + diff, sig, len); | |
82 | memset(sig, 0, diff); | |
83 | } else if (len > slen) { | |
84 | error("ssh_rsa_sign: slen %u slen2 %u", slen, len); | |
85 | xfree(sig); | |
86 | return -1; | |
87 | } | |
88 | /* encode signature */ | |
89 | buffer_init(&b); | |
90 | buffer_put_cstring(&b, "ssh-rsa"); | |
91 | buffer_put_string(&b, sig, slen); | |
92 | len = buffer_len(&b); | |
93 | if (lenp != NULL) | |
94 | *lenp = len; | |
95 | if (sigp != NULL) { | |
96 | *sigp = xmalloc(len); | |
97 | memcpy(*sigp, buffer_ptr(&b), len); | |
98 | } | |
99 | buffer_free(&b); | |
100 | memset(sig, 's', slen); | |
101 | xfree(sig); | |
102 | ||
103 | return 0; | |
104 | } | |
105 | ||
106 | int | |
107 | ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen, | |
108 | u_char *data, u_int datalen) | |
109 | { | |
110 | Buffer b; | |
111 | const EVP_MD *evp_md; | |
112 | EVP_MD_CTX md; | |
113 | char *ktype; | |
114 | u_char digest[EVP_MAX_MD_SIZE], *sigblob; | |
115 | u_int len, dlen, modlen; | |
116 | int rlen, ret, nid; | |
117 | ||
118 | if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) { | |
119 | error("ssh_rsa_verify: no RSA key"); | |
120 | return -1; | |
121 | } | |
122 | if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { | |
123 | error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits", | |
124 | BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); | |
125 | return -1; | |
126 | } | |
127 | buffer_init(&b); | |
128 | buffer_append(&b, signature, signaturelen); | |
129 | ktype = buffer_get_string(&b, NULL); | |
130 | if (strcmp("ssh-rsa", ktype) != 0) { | |
131 | error("ssh_rsa_verify: cannot handle type %s", ktype); | |
132 | buffer_free(&b); | |
133 | xfree(ktype); | |
134 | return -1; | |
135 | } | |
136 | xfree(ktype); | |
137 | sigblob = buffer_get_string(&b, &len); | |
138 | rlen = buffer_len(&b); | |
139 | buffer_free(&b); | |
140 | if (rlen != 0) { | |
141 | error("ssh_rsa_verify: remaining bytes in signature %d", rlen); | |
142 | xfree(sigblob); | |
143 | return -1; | |
144 | } | |
145 | /* RSA_verify expects a signature of RSA_size */ | |
146 | modlen = RSA_size(key->rsa); | |
147 | if (len > modlen) { | |
148 | error("ssh_rsa_verify: len %u > modlen %u", len, modlen); | |
149 | xfree(sigblob); | |
150 | return -1; | |
151 | } else if (len < modlen) { | |
152 | u_int diff = modlen - len; | |
153 | debug("ssh_rsa_verify: add padding: modlen %u > len %u", | |
154 | modlen, len); | |
155 | sigblob = xrealloc(sigblob, modlen); | |
156 | memmove(sigblob + diff, sigblob, len); | |
157 | memset(sigblob, 0, diff); | |
158 | len = modlen; | |
159 | } | |
160 | nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1; | |
161 | if ((evp_md = EVP_get_digestbynid(nid)) == NULL) { | |
162 | error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid); | |
163 | xfree(sigblob); | |
164 | return -1; | |
165 | } | |
166 | EVP_DigestInit(&md, evp_md); | |
167 | EVP_DigestUpdate(&md, data, datalen); | |
168 | EVP_DigestFinal(&md, digest, &dlen); | |
169 | ||
170 | ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa); | |
171 | memset(digest, 'd', sizeof(digest)); | |
172 | memset(sigblob, 's', len); | |
173 | xfree(sigblob); | |
174 | if (ret == 0) { | |
175 | int ecode = ERR_get_error(); | |
176 | error("ssh_rsa_verify: RSA_verify failed: %s", | |
177 | ERR_error_string(ecode, NULL)); | |
178 | } | |
179 | debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : ""); | |
180 | return ret; | |
181 | } |