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   int nobytes;
 165
 166   m = m_get(spt->slirp);
 167
 168   if (!m) {
 169     goto out;
 170   }
 171
 172   memset(m->m_data, 0, m->m_size);
 173
 174   m->m_data += IF_MAXLINKHDR;
 175   tp = (void *)m->m_data;
 176   m->m_data += sizeof(struct udpiphdr);
 177
 178   tp->tp_op = htons(TFTP_ERROR);
 179   tp->x.tp_error.tp_error_code = htons(errorcode);
 180   pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
 181
 182   saddr.sin_addr = recv_tp->ip.ip_dst;
 183   saddr.sin_port = recv_tp->udp.uh_dport;
 184
 185   daddr.sin_addr = spt->client_ip;
 186   daddr.sin_port = spt->client_port;
 187
 188   nobytes = 2;
 189
 190   m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
 191         sizeof(struct ip) - sizeof(struct udphdr);
 192
 193   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 194
 195 out:
 196   tftp_session_terminate(spt);
 197 }
 198
 199 static int tftp_send_data(struct tftp_session *spt,
 200                           u_int16_t block_nr,
 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   if (block_nr < 1) {
 209     return -1;
 210   }
 211
 212   m = m_get(spt->slirp);
 213
 214   if (!m) {
 215     return -1;
 216   }
 217
 218   memset(m->m_data, 0, m->m_size);
 219
 220   m->m_data += IF_MAXLINKHDR;
 221   tp = (void *)m->m_data;
 222   m->m_data += sizeof(struct udpiphdr);
 223
 224   tp->tp_op = htons(TFTP_DATA);
 225   tp->x.tp_data.tp_block_nr = htons(block_nr);
 226
 227   saddr.sin_addr = recv_tp->ip.ip_dst;
 228   saddr.sin_port = recv_tp->udp.uh_dport;
 229
 230   daddr.sin_addr = spt->client_ip;
 231   daddr.sin_port = spt->client_port;
 232
 233   nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
 234
 235   if (nobytes < 0) {
 236     m_free(m);
 237
 238     /* send "file not found" error back */
 239
 240     tftp_send_error(spt, 1, "File not found", tp);
 241
 242     return -1;
 243   }
 244
 245   m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
 246         sizeof(struct ip) - sizeof(struct udphdr);
 247
 248   udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
 249
 250   if (nobytes == 512) {
 251     tftp_session_update(spt);
 252   }
 253   else {
 254     tftp_session_terminate(spt);
 255   }
 256
 257   return 0;
 258 }
 259
 260 static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
 261 {
 262   struct tftp_session *spt;
 263   int s, k;
 264   size_t prefix_len;
 265   char *req_fname;
 266
 267   /* check if a session already exists and if so terminate it */
 268   s = tftp_session_find(slirp, tp);
 269   if (s >= 0) {
 270     tftp_session_terminate(&slirp->tftp_sessions[s]);
 271   }
 272
 273   s = tftp_session_allocate(slirp, tp);
 274
 275   if (s < 0) {
 276     return;
 277   }
 278
 279   spt = &slirp->tftp_sessions[s];
 280
 281   /* unspecifed prefix means service disabled */
 282   if (!slirp->tftp_prefix) {
 283       tftp_send_error(spt, 2, "Access violation", tp);
 284       return;
 285   }
 286
 287   /* skip header fields */
 288   k = 0;
 289   pktlen -= ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
 290
 291   /* prepend tftp_prefix */
 292   prefix_len = strlen(slirp->tftp_prefix);
 293   spt->filename = qemu_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
 294   memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
 295   spt->filename[prefix_len] = '/';
 296
 297   /* get name */
 298   req_fname = spt->filename + prefix_len + 1;
 299
 300   while (1) {
 301     if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
 302       tftp_send_error(spt, 2, "Access violation", tp);
 303       return;
 304     }
 305     req_fname[k] = (char)tp->x.tp_buf[k];
 306     if (req_fname[k++] == '\0') {
 307       break;
 308     }
 309   }
 310
 311   /* check mode */
 312   if ((pktlen - k) < 6) {
 313     tftp_send_error(spt, 2, "Access violation", tp);
 314     return;
 315   }
 316
 317   if (memcmp(&tp->x.tp_buf[k], "octet\0", 6) != 0) {
 318       tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
 319       return;
 320   }
 321
 322   k += 6; /* skipping octet */
 323
 324   /* do sanity checks on the filename */
 325   if (!strncmp(req_fname, "../", 3) ||
 326       req_fname[strlen(req_fname) - 1] == '/' ||
 327       strstr(req_fname, "/../")) {
 328       tftp_send_error(spt, 2, "Access violation", tp);
 329       return;
 330   }
 331
 332   /* check if the file exists */
 333   if (tftp_read_data(spt, 0, NULL, 0) < 0) {
 334       tftp_send_error(spt, 1, "File not found", tp);
 335       return;
 336   }
 337
 338   if (tp->x.tp_buf[pktlen - 1] != 0) {
 339       tftp_send_error(spt, 2, "Access violation", tp);
 340       return;
 341   }
 342
 343   while (k < pktlen) {
 344       const char *key, *value;
 345
 346       key = (const char *)&tp->x.tp_buf[k];
 347       k += strlen(key) + 1;
 348
 349       if (k >= pktlen) {
 350           tftp_send_error(spt, 2, "Access violation", tp);
 351           return;
 352       }
 353
 354       value = (const char *)&tp->x.tp_buf[k];
 355       k += strlen(value) + 1;
 356
 357       if (strcmp(key, "tsize") == 0) {
 358           int tsize = atoi(value);
 359           struct stat stat_p;
 360
 361           if (tsize == 0) {
 362               if (stat(spt->filename, &stat_p) == 0)
 363                   tsize = stat_p.st_size;
 364               else {
 365                   tftp_send_error(spt, 1, "File not found", tp);
 366                   return;
 367               }
 368           }
 369
 370           tftp_send_oack(spt, "tsize", tsize, tp);
 371       }
 372   }
 373
 374   tftp_send_data(spt, 1, tp);
 375 }
 376
 377 static void tftp_handle_ack(Slirp *slirp, struct tftp_t *tp, int pktlen)
 378 {
 379   int s;
 380
 381   s = tftp_session_find(slirp, tp);
 382
 383   if (s < 0) {
 384     return;
 385   }
 386
 387   if (tftp_send_data(&slirp->tftp_sessions[s],
 388                      ntohs(tp->x.tp_data.tp_block_nr) + 1,
 389                      tp) < 0) {
 390     return;
 391   }
 392 }
 393
 394 static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
 395 {
 396   int s;
 397
 398   s = tftp_session_find(slirp, tp);
 399
 400   if (s < 0) {
 401     return;
 402   }
 403
 404   tftp_session_terminate(&slirp->tftp_sessions[s]);
 405 }
 406
 407 void tftp_input(struct mbuf *m)
 408 {
 409   struct tftp_t *tp = (struct tftp_t *)m->m_data;
 410
 411   switch(ntohs(tp->tp_op)) {
 412   case TFTP_RRQ:
 413     tftp_handle_rrq(m->slirp, tp, m->m_len);
 414     break;
 415
 416   case TFTP_ACK:
 417     tftp_handle_ack(m->slirp, tp, m->m_len);
 418     break;
 419
 420   case TFTP_ERROR:
 421     tftp_handle_error(m->slirp, tp, m->m_len);
 422     break;
 423   }
 424 }