libexec/dma/crypto.c

   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
  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
  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
 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
 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
 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 }