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     if (spt->fd >= 0) {
  41         close(spt->fd);
  42         spt->fd = -1;
  43     }
  44     g_free(spt->filename);
  45     spt->slirp = NULL;
  46 }
  47
  48 static int tftp_session_allocate(Slirp *slirp, struct tftp_t *tp)
  49 {
  50   struct tftp_session *spt;
  51   int k;
  52
  53   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  54     spt = &slirp->tftp_sessions[k];
  55
  56     if (!tftp_session_in_use(spt))
  57         goto found;
  58
  59     /* sessions time out after 5 inactive seconds */
  60     if ((int)(curtime - spt->timestamp) > 5000) {
  61         tftp_session_terminate(spt);
  62         goto found;
  63     }
  64   }
  65
  66   return -1;
  67
  68  found:
  69   memset(spt, 0, sizeof(*spt));
  70   memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
  71   spt->fd = -1;
  72   spt->client_port = tp->udp.uh_sport;
  73   spt->slirp = slirp;
  74
  75   tftp_session_update(spt);
  76
  77   return k;
  78 }
  79
  80 static int tftp_session_find(Slirp *slirp, struct tftp_t *tp)
  81 {
  82   struct tftp_session *spt;
  83   int k;
  84
  85   for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
  86     spt = &slirp->tftp_sessions[k];
  87
  88     if (tftp_session_in_use(spt)) {
  89       if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
  90         if (spt->client_port == tp->udp.uh_sport) {
  91           return k;
  92         }
  93       }
  94     }
  95   }
  96
  97   return -1;
  98 }
  99
 100 static int tftp_read_data(struct tftp_session *spt, uint32_t block_nr,
 101                           uint8_t *buf, int len)
 102 {
 103     int bytes_read = 0;
 104
 105     if (spt->fd < 0) {
 106         spt->fd = open(spt->filename, O_RDONLY | O_BINARY);
 107     }
 108
 109     if (spt->fd < 0) {
 110         return -1;
 111     }
 112
 113     if (len) {
 114         lseek(spt->fd, block_nr * 512, SEEK_SET);
 115
 116         bytes_read = read(spt->fd, buf, len);
 117     }
 118
 119     return bytes_read;
 120 }
 121
 122 static int tftp_send_oack(struct tftp_session *spt,
 123                           const char *key, uint32_t value,
 124                           struct tftp_t *recv_tp)
 125 {
 126     struct sockaddr_in saddr, daddr;
 127     struct mbuf *m;
 128     struct tftp_t *tp;
 129     int n = 0;
 130
 131     m = m_get(spt->slirp);
 132
 133     if (!m)
 134         return -1;
 135
 136     memset(m->m_data, 0, m->m_size);
 137
 138     m->m_data += IF_MAXLINKHDR;
 139     tp = (void *)m->m_data;
 140     m->m_data += sizeof(struct udpiphdr);
 141
 142     tp->tp_op = htons(TFTP_OACK);
 143     n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
 144                   key) + 1;
 145     n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
 146                   value) + 1;
 147
 148     saddr.sin_addr = recv_tp->ip.ip_dst;
 149     saddr.sin_port = recv_tp->udp.uh_dport;
 150
 151     daddr.sin_addr = spt->client_ip;
 152     daddr.sin_port = spt->client_port;
 153
 154     m->m_len = sizeof(struct tftp_t) - 514 + n -
 155         sizeof(struct ip) - sizeof(struct udphdr);
 156     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 157
 158     return 0;
 159 }
 160
 161 static void tftp_send_error(struct tftp_session *spt,
 162                             uint16_t errorcode, const char *msg,
 163                             struct tftp_t *recv_tp)
 164 {
 165   struct sockaddr_in saddr, daddr;
 166   struct mbuf *m;
 167   struct tftp_t *tp;
 168
 169   m = m_get(spt->slirp);
 170
 171   if (!m) {
 172     goto out;
 173   }
 174
 175   memset(m->m_data, 0, m->m_size);
 176
 177   m->m_data += IF_MAXLINKHDR;
 178   tp = (void *)m->m_data;
 179   m->m_data += sizeof(struct udpiphdr);
 180
 181   tp->tp_op = htons(TFTP_ERROR);
 182   tp->x.tp_error.tp_error_code = htons(errorcode);
 183   pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
 184
 185   saddr.sin_addr = recv_tp->ip.ip_dst;
 186   saddr.sin_port = recv_tp->udp.uh_dport;
 187
 188   daddr.sin_addr = spt->client_ip;
 189   daddr.sin_port = spt->client_port;
 190
 191   m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
 192         sizeof(struct ip) - sizeof(struct udphdr);
 193
 194   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 195
 196 out:
 197   tftp_session_terminate(spt);
 198 }
 199
 200 static void tftp_send_next_block(struct tftp_session *spt,
 201                                  struct tftp_t *recv_tp)
 202 {
 203   struct sockaddr_in saddr, daddr;
 204   struct mbuf *m;
 205   struct tftp_t *tp;
 206   int nobytes;
 207
 208   m = m_get(spt->slirp);
 209
 210   if (!m) {
 211     return;
 212   }
 213
 214   memset(m->m_data, 0, m->m_size);
 215
 216   m->m_data += IF_MAXLINKHDR;
 217   tp = (void *)m->m_data;
 218   m->m_data += sizeof(struct udpiphdr);
 219
 220   tp->tp_op = htons(TFTP_DATA);
 221   tp->x.tp_data.tp_block_nr = htons((spt->block_nr + 1) & 0xffff);
 222
 223   saddr.sin_addr = recv_tp->ip.ip_dst;
 224   saddr.sin_port = recv_tp->udp.uh_dport;
 225
 226   daddr.sin_addr = spt->client_ip;
 227   daddr.sin_port = spt->client_port;
 228
 229   nobytes = tftp_read_data(spt, spt->block_nr, tp->x.tp_data.tp_buf, 512);
 230
 231   if (nobytes < 0) {
 232     m_free(m);
 233
 234     /* send "file not found" error back */
 235
 236     tftp_send_error(spt, 1, "File not found", tp);
 237
 238     return;
 239   }
 240
 241   m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
 242         sizeof(struct ip) - sizeof(struct udphdr);
 243
 244   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 245
 246   if (nobytes == 512) {
 247     tftp_session_update(spt);
 248   }
 249   else {
 250     tftp_session_terminate(spt);
 251   }
 252
 253   spt->block_nr++;
 254 }
 255
 256 static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
 257 {
 258   struct tftp_session *spt;
 259   int s, k;
 260   size_t prefix_len;
 261   char *req_fname;
 262
 263   /* check if a session already exists and if so terminate it */
 264   s = tftp_session_find(slirp, tp);
 265   if (s >= 0) {
 266     tftp_session_terminate(&slirp->tftp_sessions[s]);
 267   }
 268
 269   s = tftp_session_allocate(slirp, tp);
 270
 271   if (s < 0) {
 272     return;
 273   }
 274
 275   spt = &slirp->tftp_sessions[s];
 276
 277   /* unspecifed prefix means service disabled */
 278   if (!slirp->tftp_prefix) {
 279       tftp_send_error(spt, 2, "Access violation", tp);
 280       return;
 281   }
 282
 283   /* skip header fields */
 284   k = 0;
 285   pktlen -= offsetof(struct tftp_t, x.tp_buf);
 286
 287   /* prepend tftp_prefix */
 288   prefix_len = strlen(slirp->tftp_prefix);
 289   spt->filename = g_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
 290   memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
 291   spt->filename[prefix_len] = '/';
 292
 293   /* get name */
 294   req_fname = spt->filename + prefix_len + 1;
 295
 296   while (1) {
 297     if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
 298       tftp_send_error(spt, 2, "Access violation", tp);
 299       return;
 300     }
 301     req_fname[k] = tp->x.tp_buf[k];
 302     if (req_fname[k++] == '\0') {
 303       break;
 304     }
 305   }
 306
 307   /* check mode */
 308   if ((pktlen - k) < 6) {
 309     tftp_send_error(spt, 2, "Access violation", tp);
 310     return;
 311   }
 312
 313   if (strcasecmp(&tp->x.tp_buf[k], "octet") != 0) {
 314       tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
 315       return;
 316   }
 317
 318   k += 6; /* skipping octet */
 319
 320   /* do sanity checks on the filename */
 321   if (!strncmp(req_fname, "../", 3) ||
 322       req_fname[strlen(req_fname) - 1] == '/' ||
 323       strstr(req_fname, "/../")) {
 324       tftp_send_error(spt, 2, "Access violation", tp);
 325       return;
 326   }
 327
 328   /* check if the file exists */
 329   if (tftp_read_data(spt, 0, NULL, 0) < 0) {
 330       tftp_send_error(spt, 1, "File not found", tp);
 331       return;
 332   }
 333
 334   if (tp->x.tp_buf[pktlen - 1] != 0) {
 335       tftp_send_error(spt, 2, "Access violation", tp);
 336       return;
 337   }
 338
 339   while (k < pktlen) {
 340       const char *key, *value;
 341
 342       key = &tp->x.tp_buf[k];
 343       k += strlen(key) + 1;
 344
 345       if (k >= pktlen) {
 346           tftp_send_error(spt, 2, "Access violation", tp);
 347           return;
 348       }
 349
 350       value = &tp->x.tp_buf[k];
 351       k += strlen(value) + 1;
 352
 353       if (strcasecmp(key, "tsize") == 0) {
 354           int tsize = atoi(value);
 355           struct stat stat_p;
 356
 357           if (tsize == 0) {
 358               if (stat(spt->filename, &stat_p) == 0)
 359                   tsize = stat_p.st_size;
 360               else {
 361                   tftp_send_error(spt, 1, "File not found", tp);
 362                   return;
 363               }
 364           }
 365
 366           tftp_send_oack(spt, "tsize", tsize, tp);
 367           return;
 368       }
 369   }
 370
 371   spt->block_nr = 0;
 372   tftp_send_next_block(spt, 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   tftp_send_next_block(&slirp->tftp_sessions[s], tp);
 386 }
 387
 388 static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
 389 {
 390   int s;
 391
 392   s = tftp_session_find(slirp, tp);
 393
 394   if (s < 0) {
 395     return;
 396   }
 397
 398   tftp_session_terminate(&slirp->tftp_sessions[s]);
 399 }
 400
 401 void tftp_input(struct mbuf *m)
 402 {
 403   struct tftp_t *tp = (struct tftp_t *)m->m_data;
 404
 405   switch(ntohs(tp->tp_op)) {
 406   case TFTP_RRQ:
 407     tftp_handle_rrq(m->slirp, tp, m->m_len);
 408     break;
 409
 410   case TFTP_ACK:
 411     tftp_handle_ack(m->slirp, tp, m->m_len);
 412     break;
 413
 414   case TFTP_ERROR:
 415     tftp_handle_error(m->slirp, tp, m->m_len);
 416     break;
 417   }
 418 }