1 /*
2 * Copyright (c) 2008 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthias Schmidt <matthias@dragonflybsd.org>, University of Marburg,
6 * Germany.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
17 * distribution.
18 * 3. Neither the name of The DragonFly Project nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific, prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
28 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
29 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
31 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include <openssl/x509.h>
37 #include <openssl/md5.h>
38 #include <openssl/ssl.h>
39 #include <openssl/err.h>
40 #include <openssl/pem.h>
41 #include <openssl/rand.h>
42
43 #include <strings.h>
44 #include <string.h>
45 #include <syslog.h>
46
47 #include "dma.h"
48
49 static int
init_cert_file(SSL_CTX * ctx,const char * path)50 init_cert_file(SSL_CTX *ctx, const char *path)
51 {
52 int error;
53
54 /* Load certificate into ctx */
55 error = SSL_CTX_use_certificate_chain_file(ctx, path);
56 if (error < 1) {
57 syslog(LOG_ERR, "SSL: Cannot load certificate `%s': %s", path, ssl_errstr());
58 return (-1);
59 }
60
61 /* Add private key to ctx */
62 error = SSL_CTX_use_PrivateKey_file(ctx, path, SSL_FILETYPE_PEM);
63 if (error < 1) {
64 syslog(LOG_ERR, "SSL: Cannot load private key `%s': %s", path, ssl_errstr());
65 return (-1);
66 }
67
68 /*
69 * Check the consistency of a private key with the corresponding
70 * certificate
71 */
72 error = SSL_CTX_check_private_key(ctx);
73 if (error < 1) {
74 syslog(LOG_ERR, "SSL: Cannot check private key: %s", ssl_errstr());
75 return (-1);
76 }
77
78 return (0);
79 }
80
81 static int
verify_server_fingerprint(const X509 * cert)82 verify_server_fingerprint(const X509 *cert)
83 {
84 unsigned char fingerprint[EVP_MAX_MD_SIZE] = {0};
85 unsigned int fingerprint_len = 0;
86 if(!X509_digest(cert, EVP_sha256(), fingerprint, &fingerprint_len)) {
87 syslog(LOG_WARNING, "failed to load fingerprint of server certicate: %s",
88 ssl_errstr());
89 return (1);
90 }
91 if(fingerprint_len != SHA256_DIGEST_LENGTH) {
92 syslog(LOG_WARNING, "sha256 fingerprint has unexpected length of %d bytes",
93 fingerprint_len);
94 return (1);
95 }
96 if(memcmp(fingerprint, config.fingerprint, SHA256_DIGEST_LENGTH) != 0) {
97 syslog(LOG_WARNING, "fingerprints do not match");
98 return (1);
99 }
100 syslog(LOG_DEBUG, "successfully verified server certificate fingerprint");
101 return (0);
102 }
103
104 int
smtp_init_crypto(int fd,int feature,struct smtp_features * features)105 smtp_init_crypto(int fd, int feature, struct smtp_features* features)
106 {
107 SSL_CTX *ctx = NULL;
108 #if (OPENSSL_VERSION_NUMBER >= 0x00909000L)
109 const SSL_METHOD *meth = NULL;
110 #else
111 SSL_METHOD *meth = NULL;
112 #endif
113 X509 *cert;
114 int error;
115
116 /* XXX clean up on error/close */
117 /* Init SSL library */
118 SSL_library_init();
119 SSL_load_error_strings();
120
121 // Allow any possible version
122 #if (OPENSSL_VERSION_NUMBER >= 0x10100000L)
123 meth = TLS_client_method();
124 #else
125 meth = SSLv23_client_method();
126 #endif
127
128 ctx = SSL_CTX_new(meth);
129 if (ctx == NULL) {
130 syslog(LOG_WARNING, "remote delivery deferred: SSL init failed: %s", ssl_errstr());
131 return (1);
132 }
133
134 /* User supplied a certificate */
135 if (config.certfile != NULL) {
136 error = init_cert_file(ctx, config.certfile);
137 if (error) {
138 syslog(LOG_WARNING, "remote delivery deferred");
139 return (1);
140 }
141 }
142
143 /*
144 * If the user wants STARTTLS, we have to send EHLO here
145 */
146 if (((feature & SECURETRANSFER) != 0) &&
147 (feature & STARTTLS) != 0) {
148 /* TLS init phase, disable SSL_write */
149 config.features |= NOSSL;
150
151 if (perform_server_greeting(fd, features) == 0) {
152 send_remote_command(fd, "STARTTLS");
153 if (read_remote(fd, 0, NULL) != 2) {
154 if ((feature & TLS_OPP) == 0) {
155 syslog(LOG_ERR, "remote delivery deferred: STARTTLS not available: %s", neterr);
156 return (1);
157 } else {
158 syslog(LOG_INFO, "in opportunistic TLS mode, STARTTLS not available: %s", neterr);
159 return (0);
160 }
161 }
162 } else {
163 syslog(LOG_ERR, "remote delivery deferred: could not perform server greeting: %s",
164 neterr);
165 return (1);
166 }
167
168 /* End of TLS init phase, enable SSL_write/read */
169 config.features &= ~NOSSL;
170 }
171
172 config.ssl = SSL_new(ctx);
173 if (config.ssl == NULL) {
174 syslog(LOG_NOTICE, "remote delivery deferred: SSL struct creation failed: %s",
175 ssl_errstr());
176 return (1);
177 }
178
179 /* Set ssl to work in client mode */
180 SSL_set_connect_state(config.ssl);
181
182 /* Set fd for SSL in/output */
183 error = SSL_set_fd(config.ssl, fd);
184 if (error == 0) {
185 syslog(LOG_NOTICE, "remote delivery deferred: SSL set fd failed: %s",
186 ssl_errstr());
187 return (1);
188 }
189
190 /* Open SSL connection */
191 error = SSL_connect(config.ssl);
192 if (error != 1) {
193 syslog(LOG_ERR, "remote delivery deferred: SSL handshake failed fatally: %s",
194 ssl_errstr());
195 return (1);
196 }
197
198 /* Get peer certificate */
199 cert = SSL_get_peer_certificate(config.ssl);
200 if (cert == NULL) {
201 syslog(LOG_WARNING, "remote delivery deferred: Peer did not provide certificate: %s",
202 ssl_errstr());
203 return (1);
204 }
205 if(config.fingerprint != NULL && verify_server_fingerprint(cert)) {
206 X509_free(cert);
207 return (1);
208 }
209 X509_free(cert);
210
211 return (0);
212 }
213
214 /*
215 * hmac_md5() taken out of RFC 2104. This RFC was written by H. Krawczyk,
216 * M. Bellare and R. Canetti.
217 *
218 * text pointer to data stream
219 * text_len length of data stream
220 * key pointer to authentication key
221 * key_len length of authentication key
222 * digest caller digest to be filled int
223 */
224 void
hmac_md5(unsigned char * text,int text_len,unsigned char * key,int key_len,unsigned char * digest)225 hmac_md5(unsigned char *text, int text_len, unsigned char *key, int key_len,
226 unsigned char* digest)
227 {
228 MD5_CTX context;
229 unsigned char k_ipad[65]; /* inner padding -
230 * key XORd with ipad
231 */
232 unsigned char k_opad[65]; /* outer padding -
233 * key XORd with opad
234 */
235 unsigned char tk[16];
236 int i;
237 /* if key is longer than 64 bytes reset it to key=MD5(key) */
238 if (key_len > 64) {
239
240 MD5_CTX tctx;
241
242 MD5_Init(&tctx);
243 MD5_Update(&tctx, key, key_len);
244 MD5_Final(tk, &tctx);
245
246 key = tk;
247 key_len = 16;
248 }
249
250 /*
251 * the HMAC_MD5 transform looks like:
252 *
253 * MD5(K XOR opad, MD5(K XOR ipad, text))
254 *
255 * where K is an n byte key
256 * ipad is the byte 0x36 repeated 64 times
257 *
258 * opad is the byte 0x5c repeated 64 times
259 * and text is the data being protected
260 */
261
262 /* start out by storing key in pads */
263 bzero( k_ipad, sizeof k_ipad);
264 bzero( k_opad, sizeof k_opad);
265 bcopy( key, k_ipad, key_len);
266 bcopy( key, k_opad, key_len);
267
268 /* XOR key with ipad and opad values */
269 for (i=0; i<64; i++) {
270 k_ipad[i] ^= 0x36;
271 k_opad[i] ^= 0x5c;
272 }
273 /*
274 * perform inner MD5
275 */
276 MD5_Init(&context); /* init context for 1st
277 * pass */
278 MD5_Update(&context, k_ipad, 64); /* start with inner pad */
279 MD5_Update(&context, text, text_len); /* then text of datagram */
280 MD5_Final(digest, &context); /* finish up 1st pass */
281 /*
282 * perform outer MD5
283 */
284 MD5_Init(&context); /* init context for 2nd
285 * pass */
286 MD5_Update(&context, k_opad, 64); /* start with outer pad */
287 MD5_Update(&context, digest, 16); /* then results of 1st
288 * hash */
289 MD5_Final(digest, &context); /* finish up 2nd pass */
290 }
291
292 /*
293 * CRAM-MD5 authentication
294 */
295 int
smtp_auth_md5(int fd,char * login,char * password)296 smtp_auth_md5(int fd, char *login, char *password)
297 {
298 unsigned char digest[BUF_SIZE];
299 char buffer[BUF_SIZE], ascii_digest[33];
300 char *temp;
301 int len, i;
302 static char hextab[] = "0123456789abcdef";
303
304 temp = calloc(BUF_SIZE, 1);
305 memset(buffer, 0, sizeof(buffer));
306 memset(digest, 0, sizeof(digest));
307 memset(ascii_digest, 0, sizeof(ascii_digest));
308
309 /* Send AUTH command according to RFC 2554 */
310 send_remote_command(fd, "AUTH CRAM-MD5");
311 if (read_remote(fd, sizeof(buffer), buffer) != 3) {
312 syslog(LOG_DEBUG, "smarthost authentication:"
313 " AUTH cram-md5 not available: %s", neterr);
314 /* if cram-md5 is not available */
315 free(temp);
316 return (-1);
317 }
318
319 /* skip 3 char status + 1 char space */
320 base64_decode(buffer + 4, temp);
321 hmac_md5((unsigned char *)temp, strlen(temp),
322 (unsigned char *)password, strlen(password), digest);
323 free(temp);
324
325 ascii_digest[32] = 0;
326 for (i = 0; i < 16; i++) {
327 ascii_digest[2*i] = hextab[digest[i] >> 4];
328 ascii_digest[2*i+1] = hextab[digest[i] & 15];
329 }
330
331 /* prepare answer */
332 snprintf(buffer, BUF_SIZE, "%s %s", login, ascii_digest);
333
334 /* encode answer */
335 len = base64_encode(buffer, strlen(buffer), &temp);
336 if (len < 0) {
337 syslog(LOG_ERR, "can not encode auth reply: %m");
338 return (-1);
339 }
340
341 /* send answer */
342 send_remote_command(fd, "%s", temp);
343 free(temp);
344 if (read_remote(fd, 0, NULL) != 2) {
345 syslog(LOG_WARNING, "remote delivery deferred:"
346 " AUTH cram-md5 failed: %s", neterr);
347 return (-2);
348 }
349
350 return (0);
351 }
352