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 <slirp.h>
  26 #include "qemu-common.h"
  27
  28 static inline int tftp_session_in_use(struct tftp_session *spt)
  29 {
  30     return (spt->slirp != NULL);
  31 }
  32
  33 static inline void tftp_session_update(struct tftp_session *spt)
  34 {
  35     spt->timestamp = curtime;
  36 }
  37
  38 static void tftp_session_terminate(struct tftp_session *spt)
  39 {
  40     qemu_free(spt->filename);
  41     spt->slirp = NULL;
  42 }
  43
  44 static int tftp_session_allocate(Slirp *slirp, struct tftp_t *tp)
  45 {
  46   struct tftp_session *spt;
  47   int k;
  48
  49   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  50     spt = &slirp->tftp_sessions[k];
  51
  52     if (!tftp_session_in_use(spt))
  53         goto found;
  54
  55     /* sessions time out after 5 inactive seconds */
  56     if ((int)(curtime - spt->timestamp) > 5000) {
  57         qemu_free(spt->filename);
  58         goto found;
  59     }
  60   }
  61
  62   return -1;
  63
  64  found:
  65   memset(spt, 0, sizeof(*spt));
  66   memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
  67   spt->client_port = tp->udp.uh_sport;
  68   spt->slirp = slirp;
  69
  70   tftp_session_update(spt);
  71
  72   return k;
  73 }
  74
  75 static int tftp_session_find(Slirp *slirp, struct tftp_t *tp)
  76 {
  77   struct tftp_session *spt;
  78   int k;
  79
  80   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  81     spt = &slirp->tftp_sessions[k];
  82
  83     if (tftp_session_in_use(spt)) {
  84       if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
  85         if (spt->client_port == tp->udp.uh_sport) {
  86           return k;
  87         }
  88       }
  89     }
  90   }
  91
  92   return -1;
  93 }
  94
  95 static int tftp_read_data(struct tftp_session *spt, u_int16_t block_nr,
  96                           u_int8_t *buf, int len)
  97 {
  98   int fd;
  99   int bytes_read = 0;
 100
 101   fd = open(spt->filename, O_RDONLY | O_BINARY);
 102
 103   if (fd < 0) {
 104     return -1;
 105   }
 106
 107   if (len) {
 108     lseek(fd, block_nr * 512, SEEK_SET);
 109
 110     bytes_read = read(fd, buf, len);
 111   }
 112
 113   close(fd);
 114
 115   return bytes_read;
 116 }
 117
 118 static int tftp_send_oack(struct tftp_session *spt,
 119                           const char *key, uint32_t value,
 120                           struct tftp_t *recv_tp)
 121 {
 122     struct sockaddr_in saddr, daddr;
 123     struct mbuf *m;
 124     struct tftp_t *tp;
 125     int n = 0;
 126
 127     m = m_get(spt->slirp);
 128
 129     if (!m)
 130         return -1;
 131
 132     memset(m->m_data, 0, m->m_size);
 133
 134     m->m_data += IF_MAXLINKHDR;
 135     tp = (void *)m->m_data;
 136     m->m_data += sizeof(struct udpiphdr);
 137
 138     tp->tp_op = htons(TFTP_OACK);
 139     n += snprintf((char *)tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
 140                   key) + 1;
 141     n += snprintf((char *)tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
 142                   value) + 1;
 143
 144     saddr.sin_addr = recv_tp->ip.ip_dst;
 145     saddr.sin_port = recv_tp->udp.uh_dport;
 146
 147     daddr.sin_addr = spt->client_ip;
 148     daddr.sin_port = spt->client_port;
 149
 150     m->m_len = sizeof(struct tftp_t) - 514 + n -
 151         sizeof(struct ip) - sizeof(struct udphdr);
 152     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 153
 154     return 0;
 155 }
 156
 157 static void tftp_send_error(struct tftp_session *spt,
 158                             u_int16_t errorcode, const char *msg,
 159                             struct tftp_t *recv_tp)
 160 {
 161   struct sockaddr_in saddr, daddr;
 162   struct mbuf *m;
 163   struct tftp_t *tp;
 164
 165   m = m_get(spt->slirp);
 166
 167   if (!m) {
 168     goto out;
 169   }
 170
 171   memset(m->m_data, 0, m->m_size);
 172
 173   m->m_data += IF_MAXLINKHDR;
 174   tp = (void *)m->m_data;
 175   m->m_data += sizeof(struct udpiphdr);
 176
 177   tp->tp_op = htons(TFTP_ERROR);
 178   tp->x.tp_error.tp_error_code = htons(errorcode);
 179   pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
 180
 181   saddr.sin_addr = recv_tp->ip.ip_dst;
 182   saddr.sin_port = recv_tp->udp.uh_dport;
 183
 184   daddr.sin_addr = spt->client_ip;
 185   daddr.sin_port = spt->client_port;
 186
 187   m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
 188         sizeof(struct ip) - sizeof(struct udphdr);
 189
 190   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 191
 192 out:
 193   tftp_session_terminate(spt);
 194 }
 195
 196 static int tftp_send_data(struct tftp_session *spt,
 197                           u_int16_t block_nr,
 198                           struct tftp_t *recv_tp)
 199 {
 200   struct sockaddr_in saddr, daddr;
 201   struct mbuf *m;
 202   struct tftp_t *tp;
 203   int nobytes;
 204
 205   if (block_nr < 1) {
 206     return -1;
 207   }
 208
 209   m = m_get(spt->slirp);
 210
 211   if (!m) {
 212     return -1;
 213   }
 214
 215   memset(m->m_data, 0, m->m_size);
 216
 217   m->m_data += IF_MAXLINKHDR;
 218   tp = (void *)m->m_data;
 219   m->m_data += sizeof(struct udpiphdr);
 220
 221   tp->tp_op = htons(TFTP_DATA);
 222   tp->x.tp_data.tp_block_nr = htons(block_nr);
 223
 224   saddr.sin_addr = recv_tp->ip.ip_dst;
 225   saddr.sin_port = recv_tp->udp.uh_dport;
 226
 227   daddr.sin_addr = spt->client_ip;
 228   daddr.sin_port = spt->client_port;
 229
 230   nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
 231
 232   if (nobytes < 0) {
 233     m_free(m);
 234
 235     /* send "file not found" error back */
 236
 237     tftp_send_error(spt, 1, "File not found", tp);
 238
 239     return -1;
 240   }
 241
 242   m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
 243         sizeof(struct ip) - sizeof(struct udphdr);
 244
 245   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 246
 247   if (nobytes == 512) {
 248     tftp_session_update(spt);
 249   }
 250   else {
 251     tftp_session_terminate(spt);
 252   }
 253
 254   return 0;
 255 }
 256
 257 static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
 258 {
 259   struct tftp_session *spt;
 260   int s, k;
 261   size_t prefix_len;
 262   char *req_fname;
 263
 264   /* check if a session already exists and if so terminate it */
 265   s = tftp_session_find(slirp, tp);
 266   if (s >= 0) {
 267     tftp_session_terminate(&slirp->tftp_sessions[s]);
 268   }
 269
 270   s = tftp_session_allocate(slirp, tp);
 271
 272   if (s < 0) {
 273     return;
 274   }
 275
 276   spt = &slirp->tftp_sessions[s];
 277
 278   /* unspecifed prefix means service disabled */
 279   if (!slirp->tftp_prefix) {
 280       tftp_send_error(spt, 2, "Access violation", tp);
 281       return;
 282   }
 283
 284   /* skip header fields */
 285   k = 0;
 286   pktlen -= ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
 287
 288   /* prepend tftp_prefix */
 289   prefix_len = strlen(slirp->tftp_prefix);
 290   spt->filename = qemu_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
 291   memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
 292   spt->filename[prefix_len] = '/';
 293
 294   /* get name */
 295   req_fname = spt->filename + prefix_len + 1;
 296
 297   while (1) {
 298     if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
 299       tftp_send_error(spt, 2, "Access violation", tp);
 300       return;
 301     }
 302     req_fname[k] = (char)tp->x.tp_buf[k];
 303     if (req_fname[k++] == '\0') {
 304       break;
 305     }
 306   }
 307
 308   /* check mode */
 309   if ((pktlen - k) < 6) {
 310     tftp_send_error(spt, 2, "Access violation", tp);
 311     return;
 312   }
 313
 314   if (memcmp(&tp->x.tp_buf[k], "octet\0", 6) != 0) {
 315       tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
 316       return;
 317   }
 318
 319   k += 6; /* skipping octet */
 320
 321   /* do sanity checks on the filename */
 322   if (!strncmp(req_fname, "../", 3) ||
 323       req_fname[strlen(req_fname) - 1] == '/' ||
 324       strstr(req_fname, "/../")) {
 325       tftp_send_error(spt, 2, "Access violation", tp);
 326       return;
 327   }
 328
 329   /* check if the file exists */
 330   if (tftp_read_data(spt, 0, NULL, 0) < 0) {
 331       tftp_send_error(spt, 1, "File not found", tp);
 332       return;
 333   }
 334
 335   if (tp->x.tp_buf[pktlen - 1] != 0) {
 336       tftp_send_error(spt, 2, "Access violation", tp);
 337       return;
 338   }
 339
 340   while (k < pktlen) {
 341       const char *key, *value;
 342
 343       key = (const char *)&tp->x.tp_buf[k];
 344       k += strlen(key) + 1;
 345
 346       if (k >= pktlen) {
 347           tftp_send_error(spt, 2, "Access violation", tp);
 348           return;
 349       }
 350
 351       value = (const char *)&tp->x.tp_buf[k];
 352       k += strlen(value) + 1;
 353
 354       if (strcmp(key, "tsize") == 0) {
 355           int tsize = atoi(value);
 356           struct stat stat_p;
 357
 358           if (tsize == 0) {
 359               if (stat(spt->filename, &stat_p) == 0)
 360                   tsize = stat_p.st_size;
 361               else {
 362                   tftp_send_error(spt, 1, "File not found", tp);
 363                   return;
 364               }
 365           }
 366
 367           tftp_send_oack(spt, "tsize", tsize, tp);
 368           return;
 369       }
 370   }
 371
 372   tftp_send_data(spt, 1, tp);
 373 }
 374
 375 static void tftp_handle_ack(Slirp *slirp, struct tftp_t *tp, int pktlen)
 376 {
 377   int s;
 378
 379   s = tftp_session_find(slirp, tp);
 380
 381   if (s < 0) {
 382     return;
 383   }
 384
 385   if (tftp_send_data(&slirp->tftp_sessions[s],
 386                      ntohs(tp->x.tp_data.tp_block_nr) + 1,
 387                      tp) < 0) {
 388     return;
 389   }
 390 }
 391
 392 static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
 393 {
 394   int s;
 395
 396   s = tftp_session_find(slirp, tp);
 397
 398   if (s < 0) {
 399     return;
 400   }
 401
 402   tftp_session_terminate(&slirp->tftp_sessions[s]);
 403 }
 404
 405 void tftp_input(struct mbuf *m)
 406 {
 407   struct tftp_t *tp = (struct tftp_t *)m->m_data;
 408
 409   switch(ntohs(tp->tp_op)) {
 410   case TFTP_RRQ:
 411     tftp_handle_rrq(m->slirp, tp, m->m_len);
 412     break;
 413
 414   case TFTP_ACK:
 415     tftp_handle_ack(m->slirp, tp, m->m_len);
 416     break;
 417
 418   case TFTP_ERROR:
 419     tftp_handle_error(m->slirp, tp, m->m_len);
 420     break;
 421   }
 422 }