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 <syslog.h>
  44
  45 #include "dma.h"
  46
  47 static int
  48 init_cert_file(SSL_CTX *ctx, const char *path)
  49 {
  50         int error;
  51
  52         /* Load certificate into ctx */
  53         error = SSL_CTX_use_certificate_chain_file(ctx, path);
  54         if (error < 1) {
  55                 syslog(LOG_ERR, "SSL: Cannot load certificate `%s': %s", path, ssl_errstr());
  56                 return (-1);
  57         }
  58
  59         /* Add private key to ctx */
  60         error = SSL_CTX_use_PrivateKey_file(ctx, path, SSL_FILETYPE_PEM);
  61         if (error < 1) {
  62                 syslog(LOG_ERR, "SSL: Cannot load private key `%s': %s", path, ssl_errstr());
  63                 return (-1);
  64         }
  65
  66         /*
  67          * Check the consistency of a private key with the corresponding
  68          * certificate
  69          */
  70         error = SSL_CTX_check_private_key(ctx);
  71         if (error < 1) {
  72                 syslog(LOG_ERR, "SSL: Cannot check private key: %s", ssl_errstr());
  73                 return (-1);
  74         }
  75
  76         return (0);
  77 }
  78
  79 int
  80 smtp_init_crypto(int fd, int feature)
  81 {
  82         SSL_CTX *ctx = NULL;
  83 #if (OPENSSL_VERSION_NUMBER >= 0x00909000L)
  84         const SSL_METHOD *meth = NULL;
  85 #else
  86         SSL_METHOD *meth = NULL;
  87 #endif
  88         X509 *cert;
  89         int error;
  90
  91         /* XXX clean up on error/close */
  92         /* Init SSL library */
  93         SSL_library_init();
  94         SSL_load_error_strings();
  95
  96         meth = TLSv1_client_method();
  97
  98         ctx = SSL_CTX_new(meth);
  99         if (ctx == NULL) {
 100                 syslog(LOG_WARNING, "remote delivery deferred: SSL init failed: %s", ssl_errstr());
 101                 return (1);
 102         }
 103
 104         /* User supplied a certificate */
 105         if (config.certfile != NULL) {
 106                 error = init_cert_file(ctx, config.certfile);
 107                 if (error) {
 108                         syslog(LOG_WARNING, "remote delivery deferred");
 109                         return (1);
 110                 }
 111         }
 112
 113         /*
 114          * If the user wants STARTTLS, we have to send EHLO here
 115          */
 116         if (((feature & SECURETRANS) != 0) &&
 117              (feature & STARTTLS) != 0) {
 118                 /* TLS init phase, disable SSL_write */
 119                 config.features |= NOSSL;
 120
 121                 send_remote_command(fd, "EHLO %s", hostname());
 122                 if (read_remote(fd, 0, NULL) == 2) {
 123                         send_remote_command(fd, "STARTTLS");
 124                         if (read_remote(fd, 0, NULL) != 2) {
 125                                 if ((feature & TLS_OPP) == 0) {
 126                                         syslog(LOG_ERR, "remote delivery deferred: STARTTLS not available: %s", neterr);
 127                                         return (1);
 128                                 } else {
 129                                         syslog(LOG_INFO, "in opportunistic TLS mode, STARTTLS not available: %s", neterr);
 130                                         return (0);
 131                                 }
 132                         }
 133                 }
 134                 /* End of TLS init phase, enable SSL_write/read */
 135                 config.features &= ~NOSSL;
 136         }
 137
 138         config.ssl = SSL_new(ctx);
 139         if (config.ssl == NULL) {
 140                 syslog(LOG_NOTICE, "remote delivery deferred: SSL struct creation failed: %s",
 141                        ssl_errstr());
 142                 return (1);
 143         }
 144
 145         /* Set ssl to work in client mode */
 146         SSL_set_connect_state(config.ssl);
 147
 148         /* Set fd for SSL in/output */
 149         error = SSL_set_fd(config.ssl, fd);
 150         if (error == 0) {
 151                 syslog(LOG_NOTICE, "remote delivery deferred: SSL set fd failed: %s",
 152                        ssl_errstr());
 153                 return (1);
 154         }
 155
 156         /* Open SSL connection */
 157         error = SSL_connect(config.ssl);
 158         if (error < 0) {
 159                 syslog(LOG_ERR, "remote delivery deferred: SSL handshake failed fatally: %s",
 160                        ssl_errstr());
 161                 return (1);
 162         }
 163
 164         /* Get peer certificate */
 165         cert = SSL_get_peer_certificate(config.ssl);
 166         if (cert == NULL) {
 167                 syslog(LOG_WARNING, "remote delivery deferred: Peer did not provide certificate: %s",
 168                        ssl_errstr());
 169         }
 170         X509_free(cert);
 171
 172         return (0);
 173 }
 174
 175 /*
 176  * hmac_md5() taken out of RFC 2104.  This RFC was written by H. Krawczyk,
 177  * M. Bellare and R. Canetti.
 178  *
 179  * text      pointer to data stream
 180  * text_len  length of data stream
 181  * key       pointer to authentication key
 182  * key_len   length of authentication key
 183  * digest    caller digest to be filled int
 184  */
 185 void
 186 hmac_md5(unsigned char *text, int text_len, unsigned char *key, int key_len,
 187     unsigned char* digest)
 188 {
 189         MD5_CTX context;
 190         unsigned char k_ipad[65];    /* inner padding -
 191                                       * key XORd with ipad
 192                                       */
 193         unsigned char k_opad[65];    /* outer padding -
 194                                       * key XORd with opad
 195                                       */
 196         unsigned char tk[16];
 197         int i;
 198         /* if key is longer than 64 bytes reset it to key=MD5(key) */
 199         if (key_len > 64) {
 200
 201                 MD5_CTX      tctx;
 202
 203                 MD5_Init(&tctx);
 204                 MD5_Update(&tctx, key, key_len);
 205                 MD5_Final(tk, &tctx);
 206
 207                 key = tk;
 208                 key_len = 16;
 209         }
 210
 211         /*
 212          * the HMAC_MD5 transform looks like:
 213          *
 214          * MD5(K XOR opad, MD5(K XOR ipad, text))
 215          *
 216          * where K is an n byte key
 217          * ipad is the byte 0x36 repeated 64 times
 218          *
 219          * opad is the byte 0x5c repeated 64 times
 220          * and text is the data being protected
 221          */
 222
 223         /* start out by storing key in pads */
 224         bzero( k_ipad, sizeof k_ipad);
 225         bzero( k_opad, sizeof k_opad);
 226         bcopy( key, k_ipad, key_len);
 227         bcopy( key, k_opad, key_len);
 228
 229         /* XOR key with ipad and opad values */
 230         for (i=0; i<64; i++) {
 231                 k_ipad[i] ^= 0x36;
 232                 k_opad[i] ^= 0x5c;
 233         }
 234         /*
 235          * perform inner MD5
 236          */
 237         MD5_Init(&context);                   /* init context for 1st
 238                                               * pass */
 239         MD5_Update(&context, k_ipad, 64);     /* start with inner pad */
 240         MD5_Update(&context, text, text_len); /* then text of datagram */
 241         MD5_Final(digest, &context);          /* finish up 1st pass */
 242         /*
 243          * perform outer MD5
 244          */
 245         MD5_Init(&context);                   /* init context for 2nd
 246                                               * pass */
 247         MD5_Update(&context, k_opad, 64);     /* start with outer pad */
 248         MD5_Update(&context, digest, 16);     /* then results of 1st
 249                                               * hash */
 250         MD5_Final(digest, &context);          /* finish up 2nd pass */
 251 }
 252
 253 /*
 254  * CRAM-MD5 authentication
 255  */
 256 int
 257 smtp_auth_md5(int fd, char *login, char *password)
 258 {
 259         unsigned char digest[BUF_SIZE];
 260         char buffer[BUF_SIZE], ascii_digest[33];
 261         char *temp;
 262         int len, i;
 263         static char hextab[] = "0123456789abcdef";
 264
 265         temp = calloc(BUF_SIZE, 1);
 266         memset(buffer, 0, sizeof(buffer));
 267         memset(digest, 0, sizeof(digest));
 268         memset(ascii_digest, 0, sizeof(ascii_digest));
 269
 270         /* Send AUTH command according to RFC 2554 */
 271         send_remote_command(fd, "AUTH CRAM-MD5");
 272         if (read_remote(fd, sizeof(buffer), buffer) != 3) {
 273                 syslog(LOG_DEBUG, "smarthost authentication:"
 274                        " AUTH cram-md5 not available: %s", neterr);
 275                 /* if cram-md5 is not available */
 276                 free(temp);
 277                 return (-1);
 278         }
 279
 280         /* skip 3 char status + 1 char space */
 281         base64_decode(buffer + 4, temp);
 282         hmac_md5((unsigned char *)temp, strlen(temp),
 283                  (unsigned char *)password, strlen(password), digest);
 284         free(temp);
 285
 286         ascii_digest[32] = 0;
 287         for (i = 0; i < 16; i++) {
 288                 ascii_digest[2*i] = hextab[digest[i] >> 4];
 289                 ascii_digest[2*i+1] = hextab[digest[i] & 15];
 290         }
 291
 292         /* prepare answer */
 293         snprintf(buffer, BUF_SIZE, "%s %s", login, ascii_digest);
 294
 295         /* encode answer */
 296         len = base64_encode(buffer, strlen(buffer), &temp);
 297         if (len < 0) {
 298                 syslog(LOG_ERR, "can not encode auth reply: %m");
 299                 return (-1);
 300         }
 301
 302         /* send answer */
 303         send_remote_command(fd, "%s", temp);
 304         free(temp);
 305         if (read_remote(fd, 0, NULL) != 2) {
 306                 syslog(LOG_WARNING, "remote delivery deferred:"
 307                                 " AUTH cram-md5 failed: %s", neterr);
 308                 return (-2);
 309         }
 310
 311         return (0);
 312 }