slirp/tftp.c

   1 /*
   2  * tftp.c - a simple, read-only tftp server for qemu
   3  *
   4  * Copyright (c) 2004 Magnus Damm <damm@opensource.se>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu/osdep.h"
  26 #include "slirp.h"
  27 #include "qemu-common.h"
  28
  29 static inline int tftp_session_in_use(struct tftp_session *spt)
  30 {
  31     return (spt->slirp != NULL);
  32 }
  33
  34 static inline void tftp_session_update(struct tftp_session *spt)
  35 {
  36     spt->timestamp = curtime;
  37 }
  38
  39 static void tftp_session_terminate(struct tftp_session *spt)
  40 {
  41     if (spt->fd >= 0) {
  42         close(spt->fd);
  43         spt->fd = -1;
  44     }
  45     g_free(spt->filename);
  46     spt->slirp = NULL;
  47 }
  48
  49 static int tftp_session_allocate(Slirp *slirp, struct sockaddr_storage *srcsas,
  50                                  struct tftp_t *tp)
  51 {
  52   struct tftp_session *spt;
  53   int k;
  54
  55   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  56     spt = &slirp->tftp_sessions[k];
  57
  58     if (!tftp_session_in_use(spt))
  59         goto found;
  60
  61     /* sessions time out after 5 inactive seconds */
  62     if ((int)(curtime - spt->timestamp) > 5000) {
  63         tftp_session_terminate(spt);
  64         goto found;
  65     }
  66   }
  67
  68   return -1;
  69
  70  found:
  71   memset(spt, 0, sizeof(*spt));
  72   memcpy(&spt->client_addr, srcsas, sockaddr_size(srcsas));
  73   spt->fd = -1;
  74   spt->block_size = 512;
  75   spt->client_port = tp->udp.uh_sport;
  76   spt->slirp = slirp;
  77
  78   tftp_session_update(spt);
  79
  80   return k;
  81 }
  82
  83 static int tftp_session_find(Slirp *slirp, struct sockaddr_storage *srcsas,
  84                              struct tftp_t *tp)
  85 {
  86   struct tftp_session *spt;
  87   int k;
  88
  89   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  90     spt = &slirp->tftp_sessions[k];
  91
  92     if (tftp_session_in_use(spt)) {
  93       if (sockaddr_equal(&spt->client_addr, srcsas)) {
  94         if (spt->client_port == tp->udp.uh_sport) {
  95           return k;
  96         }
  97       }
  98     }
  99   }
 100
 101   return -1;
 102 }
 103
 104 static int tftp_read_data(struct tftp_session *spt, uint32_t block_nr,
 105                           uint8_t *buf, int len)
 106 {
 107     int bytes_read = 0;
 108
 109     if (spt->fd < 0) {
 110         spt->fd = open(spt->filename, O_RDONLY | O_BINARY);
 111     }
 112
 113     if (spt->fd < 0) {
 114         return -1;
 115     }
 116
 117     if (len) {
 118         lseek(spt->fd, block_nr * spt->block_size, SEEK_SET);
 119
 120         bytes_read = read(spt->fd, buf, len);
 121     }
 122
 123     return bytes_read;
 124 }
 125
 126 static struct tftp_t *tftp_prep_mbuf_data(struct tftp_session *spt,
 127                                           struct mbuf *m)
 128 {
 129     struct tftp_t *tp;
 130
 131     memset(m->m_data, 0, m->m_size);
 132
 133     m->m_data += IF_MAXLINKHDR;
 134     if (spt->client_addr.ss_family == AF_INET6) {
 135         m->m_data += sizeof(struct ip6);
 136     } else {
 137         m->m_data += sizeof(struct ip);
 138     }
 139     tp = (void *)m->m_data;
 140     m->m_data += sizeof(struct udphdr);
 141
 142     return tp;
 143 }
 144
 145 static void tftp_udp_output(struct tftp_session *spt, struct mbuf *m,
 146                             struct tftp_t *recv_tp)
 147 {
 148     if (spt->client_addr.ss_family == AF_INET6) {
 149         struct sockaddr_in6 sa6, da6;
 150
 151         sa6.sin6_addr = spt->slirp->vhost_addr6;
 152         sa6.sin6_port = recv_tp->udp.uh_dport;
 153         da6.sin6_addr = ((struct sockaddr_in6 *)&spt->client_addr)->sin6_addr;
 154         da6.sin6_port = spt->client_port;
 155
 156         udp6_output(NULL, m, &sa6, &da6);
 157     } else {
 158         struct sockaddr_in sa4, da4;
 159
 160         sa4.sin_addr = spt->slirp->vhost_addr;
 161         sa4.sin_port = recv_tp->udp.uh_dport;
 162         da4.sin_addr = ((struct sockaddr_in *)&spt->client_addr)->sin_addr;
 163         da4.sin_port = spt->client_port;
 164
 165         udp_output(NULL, m, &sa4, &da4, IPTOS_LOWDELAY);
 166     }
 167 }
 168
 169 static int tftp_send_oack(struct tftp_session *spt,
 170                           const char *keys[], uint32_t values[], int nb,
 171                           struct tftp_t *recv_tp)
 172 {
 173     struct mbuf *m;
 174     struct tftp_t *tp;
 175     int i, n = 0;
 176
 177     m = m_get(spt->slirp);
 178
 179     if (!m)
 180         return -1;
 181
 182     tp = tftp_prep_mbuf_data(spt, m);
 183
 184     tp->tp_op = htons(TFTP_OACK);
 185     for (i = 0; i < nb; i++) {
 186         n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
 187                       keys[i]) + 1;
 188         n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
 189                       values[i]) + 1;
 190     }
 191
 192     m->m_len = sizeof(struct tftp_t) - (TFTP_BLOCKSIZE_MAX + 2) + n
 193                - sizeof(struct udphdr);
 194     tftp_udp_output(spt, m, recv_tp);
 195
 196     return 0;
 197 }
 198
 199 static void tftp_send_error(struct tftp_session *spt,
 200                             uint16_t errorcode, const char *msg,
 201                             struct tftp_t *recv_tp)
 202 {
 203   struct mbuf *m;
 204   struct tftp_t *tp;
 205
 206   DEBUG_TFTP("tftp error msg: %s", msg);
 207
 208   m = m_get(spt->slirp);
 209
 210   if (!m) {
 211     goto out;
 212   }
 213
 214   tp = tftp_prep_mbuf_data(spt, m);
 215
 216   tp->tp_op = htons(TFTP_ERROR);
 217   tp->x.tp_error.tp_error_code = htons(errorcode);
 218   slirp_pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
 219
 220   m->m_len = sizeof(struct tftp_t) - (TFTP_BLOCKSIZE_MAX + 2) + 3 + strlen(msg)
 221              - sizeof(struct udphdr);
 222   tftp_udp_output(spt, m, recv_tp);
 223
 224 out:
 225   tftp_session_terminate(spt);
 226 }
 227
 228 static void tftp_send_next_block(struct tftp_session *spt,
 229                                  struct tftp_t *recv_tp)
 230 {
 231   struct mbuf *m;
 232   struct tftp_t *tp;
 233   int nobytes;
 234
 235   m = m_get(spt->slirp);
 236
 237   if (!m) {
 238     return;
 239   }
 240
 241   tp = tftp_prep_mbuf_data(spt, m);
 242
 243   tp->tp_op = htons(TFTP_DATA);
 244   tp->x.tp_data.tp_block_nr = htons((spt->block_nr + 1) & 0xffff);
 245
 246   nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf,
 247                            spt->block_size);
 248
 249   if (nobytes < 0) {
 250     m_free(m);
 251
 252     /* send "file not found" error back */
 253
 254     tftp_send_error(spt, 1, "File not found", tp);
 255
 256     return;
 257   }
 258
 259   m->m_len = sizeof(struct tftp_t) - (TFTP_BLOCKSIZE_MAX - nobytes)
 260              - sizeof(struct udphdr);
 261   tftp_udp_output(spt, m, recv_tp);
 262
 263   if (nobytes == spt->block_size) {
 264     tftp_session_update(spt);
 265   }
 266   else {
 267     tftp_session_terminate(spt);
 268   }
 269
 270   spt->block_nr++;
 271 }
 272
 273 static void tftp_handle_rrq(Slirp *slirp, struct sockaddr_storage *srcsas,
 274                             struct tftp_t *tp, int pktlen)
 275 {
 276   struct tftp_session *spt;
 277   int s, k;
 278   size_t prefix_len;
 279   char *req_fname;
 280   const char *option_name[2];
 281   uint32_t option_value[2];
 282   int nb_options = 0;
 283
 284   /* check if a session already exists and if so terminate it */
 285   s = tftp_session_find(slirp, srcsas, tp);
 286   if (s >= 0) {
 287     tftp_session_terminate(&slirp->tftp_sessions[s]);
 288   }
 289
 290   s = tftp_session_allocate(slirp, srcsas, tp);
 291
 292   if (s < 0) {
 293     return;
 294   }
 295
 296   spt = &slirp->tftp_sessions[s];
 297
 298   /* unspecified prefix means service disabled */
 299   if (!slirp->tftp_prefix) {
 300       tftp_send_error(spt, 2, "Access violation", tp);
 301       return;
 302   }
 303
 304   /* skip header fields */
 305   k = 0;
 306   pktlen -= offsetof(struct tftp_t, x.tp_buf);
 307
 308   /* prepend tftp_prefix */
 309   prefix_len = strlen(slirp->tftp_prefix);
 310   spt->filename = g_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
 311   memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
 312   spt->filename[prefix_len] = '/';
 313
 314   /* get name */
 315   req_fname = spt->filename + prefix_len + 1;
 316
 317   while (1) {
 318     if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
 319       tftp_send_error(spt, 2, "Access violation", tp);
 320       return;
 321     }
 322     req_fname[k] = tp->x.tp_buf[k];
 323     if (req_fname[k++] == '\0') {
 324       break;
 325     }
 326   }
 327
 328   DEBUG_TFTP("tftp rrq file: %s", req_fname);
 329
 330   /* check mode */
 331   if ((pktlen - k) < 6) {
 332     tftp_send_error(spt, 2, "Access violation", tp);
 333     return;
 334   }
 335
 336   if (strcasecmp(&tp->x.tp_buf[k], "octet") != 0) {
 337       tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
 338       return;
 339   }
 340
 341   k += 6; /* skipping octet */
 342
 343   /* do sanity checks on the filename */
 344   if (!strncmp(req_fname, "../", 3) ||
 345       req_fname[strlen(req_fname) - 1] == '/' ||
 346       strstr(req_fname, "/../")) {
 347       tftp_send_error(spt, 2, "Access violation", tp);
 348       return;
 349   }
 350
 351   /* check if the file exists */
 352   if (tftp_read_data(spt, 0, NULL, 0) < 0) {
 353       tftp_send_error(spt, 1, "File not found", tp);
 354       return;
 355   }
 356
 357   if (tp->x.tp_buf[pktlen - 1] != 0) {
 358       tftp_send_error(spt, 2, "Access violation", tp);
 359       return;
 360   }
 361
 362   while (k < pktlen && nb_options < G_N_ELEMENTS(option_name)) {
 363       const char *key, *value;
 364
 365       key = &tp->x.tp_buf[k];
 366       k += strlen(key) + 1;
 367
 368       if (k >= pktlen) {
 369           tftp_send_error(spt, 2, "Access violation", tp);
 370           return;
 371       }
 372
 373       value = &tp->x.tp_buf[k];
 374       k += strlen(value) + 1;
 375
 376       if (strcasecmp(key, "tsize") == 0) {
 377           int tsize = atoi(value);
 378           struct stat stat_p;
 379
 380           if (tsize == 0) {
 381               if (stat(spt->filename, &stat_p) == 0)
 382                   tsize = stat_p.st_size;
 383               else {
 384                   tftp_send_error(spt, 1, "File not found", tp);
 385                   return;
 386               }
 387           }
 388
 389           option_name[nb_options] = "tsize";
 390           option_value[nb_options] = tsize;
 391           nb_options++;
 392       } else if (strcasecmp(key, "blksize") == 0) {
 393           int blksize = atoi(value);
 394
 395           /* Accept blksize up to our maximum size */
 396           if (blksize > 0) {
 397               spt->block_size = MIN(blksize, TFTP_BLOCKSIZE_MAX);
 398               option_name[nb_options] = "blksize";
 399               option_value[nb_options] = spt->block_size;
 400               nb_options++;
 401           }
 402       }
 403   }
 404
 405   if (nb_options > 0) {
 406       assert(nb_options <= G_N_ELEMENTS(option_name));
 407       tftp_send_oack(spt, option_name, option_value, nb_options, tp);
 408       return;
 409   }
 410
 411   spt->block_nr = 0;
 412   tftp_send_next_block(spt, tp);
 413 }
 414
 415 static void tftp_handle_ack(Slirp *slirp, struct sockaddr_storage *srcsas,
 416                             struct tftp_t *tp, int pktlen)
 417 {
 418   int s;
 419
 420   s = tftp_session_find(slirp, srcsas, tp);
 421
 422   if (s < 0) {
 423     return;
 424   }
 425
 426   tftp_send_next_block(&slirp->tftp_sessions[s], tp);
 427 }
 428
 429 static void tftp_handle_error(Slirp *slirp, struct sockaddr_storage *srcsas,
 430                               struct tftp_t *tp, int pktlen)
 431 {
 432   int s;
 433
 434   s = tftp_session_find(slirp, srcsas, tp);
 435
 436   if (s < 0) {
 437     return;
 438   }
 439
 440   tftp_session_terminate(&slirp->tftp_sessions[s]);
 441 }
 442
 443 void tftp_input(struct sockaddr_storage *srcsas, struct mbuf *m)
 444 {
 445   struct tftp_t *tp = (struct tftp_t *)m->m_data;
 446
 447   switch(ntohs(tp->tp_op)) {
 448   case TFTP_RRQ:
 449     tftp_handle_rrq(m->slirp, srcsas, tp, m->m_len);
 450     break;
 451
 452   case TFTP_ACK:
 453     tftp_handle_ack(m->slirp, srcsas, tp, m->m_len);
 454     break;
 455
 456   case TFTP_ERROR:
 457     tftp_handle_error(m->slirp, srcsas, tp, m->m_len);
 458     break;
 459   }
 460 }