src/server.c

   1 /* server.c --- Handle KDC sessions.
   2  * Copyright (C) 2002, 2003, 2004, 2006, 2007  Simon Josefsson
   3  *
   4  * This file is part of Shishi.
   5  *
   6  * Shishi is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * Shishi is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with Shishi; if not, see http://www.gnu.org/licenses or write
  18  * to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
  19  * Floor, Boston, MA 02110-1301, USA
  20  *
  21  */
  22
  23 /* Note: only use syslog to report errors in this file. */
  24
  25 /* Get Shishid stuff. */
  26 #include "kdc.h"
  27
  28 /* Accept new TCP connection in a new listenspec entry. */
  29 static void
  30 kdc_accept (struct listenspec *ls)
  31 {
  32   struct listenspec *newls;
  33
  34   newls = xzalloc (sizeof (*newls));
  35   newls->next = ls->next;
  36   ls->next = newls;
  37
  38   newls->bufpos = 0;
  39   newls->type = ls->type;
  40   newls->addrlen = sizeof (newls->addr);
  41   newls->sockfd = accept (ls->sockfd, &newls->addr, &newls->addrlen);
  42   newls->sin = (struct sockaddr_in *) &newls->addr;
  43   asprintf (&newls->str, "%s peer %s", ls->str,
  44             inet_ntoa (newls->sin->sin_addr));
  45
  46   syslog (LOG_DEBUG, "Accepted socket %d from socket %d as %s",
  47           newls->sockfd, ls->sockfd, newls->str);
  48 }
  49
  50 /* Destroy listenspec element and return pointer to element before the
  51    removed element, or NULL if the first element was removed (or the
  52    destroyed list element wasn't in the list). */
  53 static struct listenspec *
  54 kdc_close (struct listenspec *ls)
  55 {
  56   struct listenspec *tmp;
  57   int rc;
  58
  59   syslog (LOG_INFO, "Closing %s socket %d", ls->str, ls->sockfd);
  60
  61 #ifdef USE_STARTTLS
  62   if (ls->usetls)
  63     {
  64       do
  65         rc = gnutls_bye (ls->session, GNUTLS_SHUT_RDWR);
  66       while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED);
  67
  68       if (rc != GNUTLS_E_SUCCESS)
  69         syslog (LOG_ERR, "TLS terminate failed to %s on socket %d (%d): %s",
  70                 ls->str, ls->sockfd, rc, gnutls_strerror (rc));
  71
  72       gnutls_deinit (ls->session);
  73     }
  74 #endif
  75
  76   if (ls->sockfd)
  77     {
  78       rc = close (ls->sockfd);
  79       if (rc != 0)
  80         syslog (LOG_ERR, "Close failed to %s on socket %d (%d): %s",
  81                 ls->str, ls->sockfd, rc, strerror (rc));
  82     }
  83
  84   if (ls->str)
  85     free (ls->str);
  86
  87   for (tmp = listenspec; tmp && tmp->next != ls; tmp = tmp->next)
  88     ;
  89   if (tmp)
  90     tmp->next = ls->next;
  91
  92   free (ls);
  93
  94   return tmp;
  95 }
  96
  97 /* Send string to peer, via UDP/TCP/TLS, reporting any errors. */
  98 void
  99 kdc_send1 (struct listenspec *ls)
 100 {
 101   ssize_t sent_bytes;
 102
 103   do
 104 #ifdef USE_STARTTLS
 105     if (ls->usetls)
 106       sent_bytes = gnutls_record_send (ls->session, ls->buf, ls->bufpos);
 107     else
 108 #endif
 109       sent_bytes = sendto (ls->sockfd, ls->buf, ls->bufpos,
 110                            0, &ls->addr, ls->addrlen);
 111   while (sent_bytes == -1 && errno == EAGAIN);
 112
 113   if (sent_bytes < 0)
 114     syslog (LOG_ERR, "Error writing %d bytes to %s on socket %d: %s",
 115             ls->bufpos, ls->str, ls->sockfd, strerror (errno));
 116   else if ((size_t) sent_bytes > ls->bufpos)
 117     syslog (LOG_ERR, "Overlong write (%d > %d) to %s on socket %d",
 118             sent_bytes, ls->bufpos, ls->str, ls->sockfd);
 119   else if ((size_t) sent_bytes < ls->bufpos)
 120     syslog (LOG_ERR, "Short write (%d < %d) to %s on socket %d",
 121             sent_bytes, ls->bufpos, ls->str, ls->sockfd);
 122 }
 123
 124 /* Format response and send it to peer, via UDP/TCP/TLS, reporting any
 125    errors. */
 126 static void
 127 kdc_send (struct listenspec *ls)
 128 {
 129   if (ls->type == SOCK_DGRAM)
 130     syslog (LOG_DEBUG, "Sending %d bytes to %s socket %d via UDP",
 131             ls->bufpos, ls->str, ls->sockfd);
 132   else
 133     {
 134       syslog (LOG_DEBUG, "Sending %d bytes to %s socket %d via %s",
 135               ls->bufpos, ls->str, ls->sockfd, ls->usetls ? "TLS" : "TCP");
 136
 137       if (ls->bufpos + 4 >= sizeof (ls->buf))
 138         ls->bufpos = sizeof (ls->buf) - 4;
 139
 140       memmove (ls->buf + 4, ls->buf, ls->bufpos);
 141       ls->buf[0] = (ls->bufpos >> 24) & 0xFF;
 142       ls->buf[1] = (ls->bufpos >> 16) & 0xFF;
 143       ls->buf[2] = (ls->bufpos >> 8) & 0xFF;
 144       ls->buf[3] = ls->bufpos & 0xFF;
 145       ls->bufpos += 4;
 146     }
 147
 148   kdc_send1 (ls);
 149
 150   ls->bufpos = 0;
 151 }
 152
 153 #ifndef USE_STARTTLS
 154 /* Dummy function to replace starttls.c functionality. */
 155 int
 156 kdc_extension (struct listenspec *ls)
 157 {
 158   return 0;
 159 }
 160 #endif
 161
 162 /* Read data from peer, reporting any errors. */
 163 static int
 164 kdc_read (struct listenspec *ls)
 165 {
 166   ssize_t read_bytes;
 167
 168   ls->addrlen = sizeof (ls->addr);
 169 #ifdef USE_STARTTLS
 170   if (ls->usetls)
 171     read_bytes = gnutls_record_recv (ls->session,
 172                                      ls->buf + ls->bufpos,
 173                                      sizeof (ls->buf) - ls->bufpos);
 174   else
 175 #endif
 176     read_bytes = recvfrom (ls->sockfd, ls->buf + ls->bufpos,
 177                            sizeof (ls->buf) - ls->bufpos, 0,
 178                            &ls->addr, &ls->addrlen);
 179   if (read_bytes < 0)
 180     {
 181 #ifdef USE_STARTTLS
 182       if (ls->usetls)
 183         syslog (LOG_ERR, "Corrupt TLS data from %s on socket %d (%d): %s",
 184                 ls->str, ls->sockfd, read_bytes,
 185                 gnutls_strerror (read_bytes));
 186       else
 187 #endif
 188         syslog (LOG_ERR, "Error reading from %s on socket %d (%d): %s",
 189                 ls->str, ls->sockfd, read_bytes, strerror (read_bytes));
 190       return -1;
 191     }
 192
 193   if (read_bytes == 0 && ls->type == SOCK_STREAM)
 194     {
 195       syslog (LOG_DEBUG, "Peer %s disconnected on socket %d\n",
 196               ls->str, ls->sockfd);
 197       return -1;
 198     }
 199
 200   ls->bufpos += read_bytes;
 201
 202   syslog (LOG_DEBUG, "Has %d bytes from %s on socket %d\n",
 203           ls->bufpos, ls->str, ls->sockfd);
 204
 205   return 0;
 206 }
 207
 208 #define C2I(buf) ((buf[3] & 0xFF) |             \
 209                   ((buf[2] & 0xFF) << 8) |      \
 210                   ((buf[1] & 0xFF) << 16) |     \
 211                   ((buf[0] & 0xFF) << 24))
 212
 213 /* Have we read an entire request? */
 214 static int
 215 kdc_ready (struct listenspec *ls)
 216 {
 217   int waitfor = ls->bufpos >= 4 ? C2I (ls->buf) : 4;
 218
 219   syslog (LOG_DEBUG, "Got %d bytes of %d bytes from %s on socket %d\n",
 220           ls->bufpos, waitfor + 4, ls->str, ls->sockfd);
 221
 222   if (ls->type == SOCK_DGRAM && ls->bufpos > 0)
 223     return 1;
 224   else if (ls->bufpos > 4 && waitfor + 4 == ls->bufpos)
 225     return 1;
 226
 227   return 0;
 228 }
 229
 230 /* Process a request and store reply in same buffer. */
 231 static void
 232 kdc_process (struct listenspec *ls)
 233 {
 234   char *p;
 235   ssize_t plen;
 236
 237   syslog (LOG_DEBUG, "Processing %d from %s on socket %d",
 238           ls->bufpos, ls->str, ls->sockfd);
 239
 240   if (ls->type == SOCK_DGRAM)
 241     plen = process (ls->buf, ls->bufpos, &p);
 242   else
 243     plen = process (ls->buf + 4, ls->bufpos - 4, &p);
 244
 245   if (plen <= 0)
 246     {
 247       syslog (LOG_ERR, "Processing request failed for %s on socket %d (%d)",
 248               ls->str, ls->sockfd, plen);
 249       memcpy (ls->buf, fatal_krberror, fatal_krberror_len);
 250       ls->bufpos = fatal_krberror_len;
 251     }
 252   else
 253     {
 254       memcpy (ls->buf, p, plen);
 255       ls->bufpos = plen;
 256       free (p);
 257     }
 258
 259   syslog (LOG_DEBUG, "Have %d bytes for %s on socket %d",
 260           ls->bufpos, ls->str, ls->sockfd);
 261 }
 262
 263 int quit = 0;
 264
 265 static void
 266 ctrlc (int signum)
 267 {
 268   quit = 1;
 269 }
 270
 271 #define MAX(a,b) ((a) > (b) ? (a) : (b))
 272
 273 /* Main KDC logic, loop around select and call kdc_accept, kdc_read,
 274    kdc_extension, kdc_process and kdc_send.  This return when the
 275    SIGINT or SIGTERM signals are received. */
 276 void
 277 kdc_loop (void)
 278 {
 279   struct listenspec *ls;
 280   fd_set readfds;
 281   int maxfd = 0;
 282   int rc;
 283
 284   signal (SIGINT, ctrlc);
 285   signal (SIGTERM, ctrlc);
 286
 287 #ifdef USE_STARTTLS
 288   syslog (LOG_DEBUG, "Starting (GNUTLS `%s')", gnutls_check_version (NULL));
 289 #else
 290   syslog (LOG_DEBUG, "Starting (no TLS)");
 291 #endif
 292
 293   while (!quit)
 294     {
 295       do
 296         {
 297           FD_ZERO (&readfds);
 298           maxfd = 0;
 299           for (ls = listenspec; ls; ls = ls->next)
 300             {
 301               if (ls->sockfd > 0)
 302                 {
 303                   maxfd = MAX (maxfd, ls->sockfd + 1);
 304                   if (!arg.quiet_flag)
 305                     syslog (LOG_DEBUG, "Listening on %s socket %d\n",
 306                             ls->str, ls->sockfd);
 307                   FD_SET (ls->sockfd, &readfds);
 308                 }
 309             }
 310         }
 311       while ((rc = select (maxfd, &readfds, NULL, NULL, NULL)) == 0);
 312
 313       if (rc < 0)
 314         {
 315           if (errno != EINTR)
 316             syslog (LOG_ERR, "Error listening on sockets (%d): %s",
 317                     rc, strerror (errno));
 318           continue;
 319         }
 320
 321       for (ls = listenspec; ls; ls = ls->next)
 322         if (ls->sockfd > 0 && FD_ISSET (ls->sockfd, &readfds))
 323           {
 324             if (ls->type == SOCK_STREAM && ls->listening)
 325               kdc_accept (ls);
 326             else if (kdc_read (ls) < 0)
 327               ls = kdc_close (ls);
 328             else if (kdc_extension (ls) < 0)
 329               ls = kdc_close (ls);
 330             else if (kdc_ready (ls))
 331               {
 332                 kdc_process (ls);
 333                 kdc_send (ls);
 334               }
 335           }
 336     }
 337
 338   syslog (LOG_DEBUG, "Shutting down");
 339 }