src/server.c

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