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 #include "qemu/cutils.h"
  29
  30 static inline int tftp_session_in_use(struct tftp_session *spt)
  31 {
  32     return (spt->slirp != NULL);
  33 }
  34
  35 static inline void tftp_session_update(struct tftp_session *spt)
  36 {
  37     spt->timestamp = curtime;
  38 }
  39
  40 static void tftp_session_terminate(struct tftp_session *spt)
  41 {
  42     if (spt->fd >= 0) {
  43         close(spt->fd);
  44         spt->fd = -1;
  45     }
  46     g_free(spt->filename);
  47     spt->slirp = NULL;
  48 }
  49
  50 static int tftp_session_allocate(Slirp *slirp, struct sockaddr_storage *srcsas,
  51                                  struct tftp_t *tp)
  52 {
  53   struct tftp_session *spt;
  54   int k;
  55
  56   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  57     spt = &slirp->tftp_sessions[k];
  58
  59     if (!tftp_session_in_use(spt))
  60         goto found;
  61
  62     /* sessions time out after 5 inactive seconds */
  63     if ((int)(curtime - spt->timestamp) > 5000) {
  64         tftp_session_terminate(spt);
  65         goto found;
  66     }
  67   }
  68
  69   return -1;
  70
  71  found:
  72   memset(spt, 0, sizeof(*spt));
  73   spt->client_addr = *srcsas;
  74   spt->fd = -1;
  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 * 512, 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) - 514 + n - sizeof(struct udphdr);
 193     tftp_udp_output(spt, m, recv_tp);
 194
 195     return 0;
 196 }
 197
 198 static void tftp_send_error(struct tftp_session *spt,
 199                             uint16_t errorcode, const char *msg,
 200                             struct tftp_t *recv_tp)
 201 {
 202   struct mbuf *m;
 203   struct tftp_t *tp;
 204
 205   m = m_get(spt->slirp);
 206
 207   if (!m) {
 208     goto out;
 209   }
 210
 211   tp = tftp_prep_mbuf_data(spt, m);
 212
 213   tp->tp_op = htons(TFTP_ERROR);
 214   tp->x.tp_error.tp_error_code = htons(errorcode);
 215   pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
 216
 217   m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg)
 218              - sizeof(struct udphdr);
 219   tftp_udp_output(spt, m, recv_tp);
 220
 221 out:
 222   tftp_session_terminate(spt);
 223 }
 224
 225 static void tftp_send_next_block(struct tftp_session *spt,
 226                                  struct tftp_t *recv_tp)
 227 {
 228   struct mbuf *m;
 229   struct tftp_t *tp;
 230   int nobytes;
 231
 232   m = m_get(spt->slirp);
 233
 234   if (!m) {
 235     return;
 236   }
 237
 238   tp = tftp_prep_mbuf_data(spt, m);
 239
 240   tp->tp_op = htons(TFTP_DATA);
 241   tp->x.tp_data.tp_block_nr = htons((spt->block_nr + 1) & 0xffff);
 242
 243   nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf, 512);
 244
 245   if (nobytes < 0) {
 246     m_free(m);
 247
 248     /* send "file not found" error back */
 249
 250     tftp_send_error(spt, 1, "File not found", tp);
 251
 252     return;
 253   }
 254
 255   m->m_len = sizeof(struct tftp_t) - (512 - nobytes) - sizeof(struct udphdr);
 256   tftp_udp_output(spt, m, recv_tp);
 257
 258   if (nobytes == 512) {
 259     tftp_session_update(spt);
 260   }
 261   else {
 262     tftp_session_terminate(spt);
 263   }
 264
 265   spt->block_nr++;
 266 }
 267
 268 static void tftp_handle_rrq(Slirp *slirp, struct sockaddr_storage *srcsas,
 269                             struct tftp_t *tp, int pktlen)
 270 {
 271   struct tftp_session *spt;
 272   int s, k;
 273   size_t prefix_len;
 274   char *req_fname;
 275   const char *option_name[2];
 276   uint32_t option_value[2];
 277   int nb_options = 0;
 278
 279   /* check if a session already exists and if so terminate it */
 280   s = tftp_session_find(slirp, srcsas, tp);
 281   if (s >= 0) {
 282     tftp_session_terminate(&slirp->tftp_sessions[s]);
 283   }
 284
 285   s = tftp_session_allocate(slirp, srcsas, tp);
 286
 287   if (s < 0) {
 288     return;
 289   }
 290
 291   spt = &slirp->tftp_sessions[s];
 292
 293   /* unspecified prefix means service disabled */
 294   if (!slirp->tftp_prefix) {
 295       tftp_send_error(spt, 2, "Access violation", tp);
 296       return;
 297   }
 298
 299   /* skip header fields */
 300   k = 0;
 301   pktlen -= offsetof(struct tftp_t, x.tp_buf);
 302
 303   /* prepend tftp_prefix */
 304   prefix_len = strlen(slirp->tftp_prefix);
 305   spt->filename = g_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
 306   memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
 307   spt->filename[prefix_len] = '/';
 308
 309   /* get name */
 310   req_fname = spt->filename + prefix_len + 1;
 311
 312   while (1) {
 313     if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
 314       tftp_send_error(spt, 2, "Access violation", tp);
 315       return;
 316     }
 317     req_fname[k] = tp->x.tp_buf[k];
 318     if (req_fname[k++] == '\0') {
 319       break;
 320     }
 321   }
 322
 323   /* check mode */
 324   if ((pktlen - k) < 6) {
 325     tftp_send_error(spt, 2, "Access violation", tp);
 326     return;
 327   }
 328
 329   if (strcasecmp(&tp->x.tp_buf[k], "octet") != 0) {
 330       tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
 331       return;
 332   }
 333
 334   k += 6; /* skipping octet */
 335
 336   /* do sanity checks on the filename */
 337   if (!strncmp(req_fname, "../", 3) ||
 338       req_fname[strlen(req_fname) - 1] == '/' ||
 339       strstr(req_fname, "/../")) {
 340       tftp_send_error(spt, 2, "Access violation", tp);
 341       return;
 342   }
 343
 344   /* check if the file exists */
 345   if (tftp_read_data(spt, 0, NULL, 0) < 0) {
 346       tftp_send_error(spt, 1, "File not found", tp);
 347       return;
 348   }
 349
 350   if (tp->x.tp_buf[pktlen - 1] != 0) {
 351       tftp_send_error(spt, 2, "Access violation", tp);
 352       return;
 353   }
 354
 355   while (k < pktlen && nb_options < ARRAY_SIZE(option_name)) {
 356       const char *key, *value;
 357
 358       key = &tp->x.tp_buf[k];
 359       k += strlen(key) + 1;
 360
 361       if (k >= pktlen) {
 362           tftp_send_error(spt, 2, "Access violation", tp);
 363           return;
 364       }
 365
 366       value = &tp->x.tp_buf[k];
 367       k += strlen(value) + 1;
 368
 369       if (strcasecmp(key, "tsize") == 0) {
 370           int tsize = atoi(value);
 371           struct stat stat_p;
 372
 373           if (tsize == 0) {
 374               if (stat(spt->filename, &stat_p) == 0)
 375                   tsize = stat_p.st_size;
 376               else {
 377                   tftp_send_error(spt, 1, "File not found", tp);
 378                   return;
 379               }
 380           }
 381
 382           option_name[nb_options] = "tsize";
 383           option_value[nb_options] = tsize;
 384           nb_options++;
 385       } else if (strcasecmp(key, "blksize") == 0) {
 386           int blksize = atoi(value);
 387
 388           /* If blksize option is bigger than what we will
 389            * emit, accept the option with our packet size.
 390            * Otherwise, simply do as we didn't see the option.
 391            */
 392           if (blksize >= 512) {
 393               option_name[nb_options] = "blksize";
 394               option_value[nb_options] = 512;
 395               nb_options++;
 396           }
 397       }
 398   }
 399
 400   if (nb_options > 0) {
 401       assert(nb_options <= ARRAY_SIZE(option_name));
 402       tftp_send_oack(spt, option_name, option_value, nb_options, tp);
 403       return;
 404   }
 405
 406   spt->block_nr = 0;
 407   tftp_send_next_block(spt, tp);
 408 }
 409
 410 static void tftp_handle_ack(Slirp *slirp, struct sockaddr_storage *srcsas,
 411                             struct tftp_t *tp, int pktlen)
 412 {
 413   int s;
 414
 415   s = tftp_session_find(slirp, srcsas, tp);
 416
 417   if (s < 0) {
 418     return;
 419   }
 420
 421   tftp_send_next_block(&slirp->tftp_sessions[s], tp);
 422 }
 423
 424 static void tftp_handle_error(Slirp *slirp, struct sockaddr_storage *srcsas,
 425                               struct tftp_t *tp, int pktlen)
 426 {
 427   int s;
 428
 429   s = tftp_session_find(slirp, srcsas, tp);
 430
 431   if (s < 0) {
 432     return;
 433   }
 434
 435   tftp_session_terminate(&slirp->tftp_sessions[s]);
 436 }
 437
 438 void tftp_input(struct sockaddr_storage *srcsas, struct mbuf *m)
 439 {
 440   struct tftp_t *tp = (struct tftp_t *)m->m_data;
 441
 442   switch(ntohs(tp->tp_op)) {
 443   case TFTP_RRQ:
 444     tftp_handle_rrq(m->slirp, srcsas, tp, m->m_len);
 445     break;
 446
 447   case TFTP_ACK:
 448     tftp_handle_ack(m->slirp, srcsas, tp, m->m_len);
 449     break;
 450
 451   case TFTP_ERROR:
 452     tftp_handle_error(m->slirp, srcsas, tp, m->m_len);
 453     break;
 454   }
 455 }