text: /*
   * tftp.c - a simple, read-only tftp server for qemu
   *
   * Copyright (c) 2004 Magnus Damm <damm@opensource.se>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  #include <slirp.h>
  #include "qemu-common.h"
  
  static inline int tftp_session_in_use(struct tftp_session *spt)
  {
      return (spt->slirp != NULL);
  }
  
  static inline void tftp_session_update(struct tftp_session *spt)
  {
      spt->timestamp = curtime;
  }
  
  static void tftp_session_terminate(struct tftp_session *spt)
  {
      g_free(spt->filename);
      spt->slirp = NULL;
  }
  
  static int tftp_session_allocate(Slirp *slirp, struct tftp_t *tp)
  {
    struct tftp_session *spt;
    int k;
  
    for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
      spt = &slirp->tftp_sessions[k];
  
      if (!tftp_session_in_use(spt))
          goto found;
  
      /* sessions time out after 5 inactive seconds */
      if ((int)(curtime - spt->timestamp) > 5000) {
          g_free(spt->filename);
          goto found;
      }
    }
  
    return -1;
  
   found:
    memset(spt, 0, sizeof(*spt));
    memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
    spt->client_port = tp->udp.uh_sport;
    spt->slirp = slirp;
  
    tftp_session_update(spt);
  
    return k;
  }
  
  static int tftp_session_find(Slirp *slirp, struct tftp_t *tp)
  {
    struct tftp_session *spt;
    int k;
  
    for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
      spt = &slirp->tftp_sessions[k];
  
      if (tftp_session_in_use(spt)) {
        if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
  	if (spt->client_port == tp->udp.uh_sport) {
  	  return k;
  	}
        }
      }
    }
  
    return -1;
  }
  
  static int tftp_read_data(struct tftp_session *spt, uint16_t block_nr,
                            uint8_t *buf, int len)
  {
    int fd;
    int bytes_read = 0;
  
    fd = open(spt->filename, O_RDONLY | O_BINARY);
  
    if (fd < 0) {
      return -1;
    }
  
    if (len) {
      lseek(fd, block_nr * 512, SEEK_SET);
  
      bytes_read = read(fd, buf, len);
    }
  
    close(fd);
  
    return bytes_read;
  }
  
  static int tftp_send_oack(struct tftp_session *spt,
                            const char *key, uint32_t value,
                            struct tftp_t *recv_tp)
  {
      struct sockaddr_in saddr, daddr;
      struct mbuf *m;
      struct tftp_t *tp;
      int n = 0;
  
      m = m_get(spt->slirp);
  
      if (!m)
  	return -1;
  
      memset(m->m_data, 0, m->m_size);
  
      m->m_data += IF_MAXLINKHDR;
      tp = (void *)m->m_data;
      m->m_data += sizeof(struct udpiphdr);
  
      tp->tp_op = htons(TFTP_OACK);
      n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
                    key) + 1;
      n += snprintf(tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
                    value) + 1;
  
      saddr.sin_addr = recv_tp->ip.ip_dst;
      saddr.sin_port = recv_tp->udp.uh_dport;
  
      daddr.sin_addr = spt->client_ip;
      daddr.sin_port = spt->client_port;
  
      m->m_len = sizeof(struct tftp_t) - 514 + n -
          sizeof(struct ip) - sizeof(struct udphdr);
      udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
  
      return 0;
  }
  
  static void tftp_send_error(struct tftp_session *spt,
                              uint16_t errorcode, const char *msg,
                              struct tftp_t *recv_tp)
  {
    struct sockaddr_in saddr, daddr;
    struct mbuf *m;
    struct tftp_t *tp;
  
    m = m_get(spt->slirp);
  
    if (!m) {
      goto out;
    }
  
    memset(m->m_data, 0, m->m_size);
  
    m->m_data += IF_MAXLINKHDR;
    tp = (void *)m->m_data;
    m->m_data += sizeof(struct udpiphdr);
  
    tp->tp_op = htons(TFTP_ERROR);
    tp->x.tp_error.tp_error_code = htons(errorcode);
    pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
  
    saddr.sin_addr = recv_tp->ip.ip_dst;
    saddr.sin_port = recv_tp->udp.uh_dport;
  
    daddr.sin_addr = spt->client_ip;
    daddr.sin_port = spt->client_port;
  
    m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
          sizeof(struct ip) - sizeof(struct udphdr);
  
    udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
  
  out:
    tftp_session_terminate(spt);
  }
  
  static int tftp_send_data(struct tftp_session *spt,
                            uint16_t block_nr,
  			  struct tftp_t *recv_tp)
  {
    struct sockaddr_in saddr, daddr;
    struct mbuf *m;
    struct tftp_t *tp;
    int nobytes;
  
    if (block_nr < 1) {
      return -1;
    }
  
    m = m_get(spt->slirp);
  
    if (!m) {
      return -1;
    }
  
    memset(m->m_data, 0, m->m_size);
  
    m->m_data += IF_MAXLINKHDR;
    tp = (void *)m->m_data;
    m->m_data += sizeof(struct udpiphdr);
  
    tp->tp_op = htons(TFTP_DATA);
    tp->x.tp_data.tp_block_nr = htons(block_nr);
  
    saddr.sin_addr = recv_tp->ip.ip_dst;
    saddr.sin_port = recv_tp->udp.uh_dport;
  
    daddr.sin_addr = spt->client_ip;
    daddr.sin_port = spt->client_port;
  
    nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
  
    if (nobytes < 0) {
      m_free(m);
  
      /* send "file not found" error back */
  
      tftp_send_error(spt, 1, "File not found", tp);
  
      return -1;
    }
  
    m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
          sizeof(struct ip) - sizeof(struct udphdr);
  
    udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
  
    if (nobytes == 512) {
      tftp_session_update(spt);
    }
    else {
      tftp_session_terminate(spt);
    }
  
    return 0;
  }
  
  static void tftp_handle_rrq(Slirp *slirp, struct tftp_t *tp, int pktlen)
  {
    struct tftp_session *spt;
    int s, k;
    size_t prefix_len;
    char *req_fname;
  
    /* check if a session already exists and if so terminate it */
    s = tftp_session_find(slirp, tp);
    if (s >= 0) {
      tftp_session_terminate(&slirp->tftp_sessions[s]);
    }
  
    s = tftp_session_allocate(slirp, tp);
  
    if (s < 0) {
      return;
    }
  
    spt = &slirp->tftp_sessions[s];
  
    /* unspecifed prefix means service disabled */
    if (!slirp->tftp_prefix) {
        tftp_send_error(spt, 2, "Access violation", tp);
        return;
    }
  
    /* skip header fields */
    k = 0;
    pktlen -= offsetof(struct tftp_t, x.tp_buf);
  
    /* prepend tftp_prefix */
    prefix_len = strlen(slirp->tftp_prefix);
    spt->filename = g_malloc(prefix_len + TFTP_FILENAME_MAX + 2);
    memcpy(spt->filename, slirp->tftp_prefix, prefix_len);
    spt->filename[prefix_len] = '/';
  
    /* get name */
    req_fname = spt->filename + prefix_len + 1;
  
    while (1) {
      if (k >= TFTP_FILENAME_MAX || k >= pktlen) {
        tftp_send_error(spt, 2, "Access violation", tp);
        return;
      }
      req_fname[k] = tp->x.tp_buf[k];
      if (req_fname[k++] == '\0') {
        break;
      }
    }
  
    /* check mode */
    if ((pktlen - k) < 6) {
      tftp_send_error(spt, 2, "Access violation", tp);
      return;
    }
  
    if (strcasecmp(&tp->x.tp_buf[k], "octet") != 0) {
        tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
        return;
    }
  
    k += 6; /* skipping octet */
  
    /* do sanity checks on the filename */
    if (!strncmp(req_fname, "../", 3) ||
        req_fname[strlen(req_fname) - 1] == '/' ||
        strstr(req_fname, "/../")) {
        tftp_send_error(spt, 2, "Access violation", tp);
        return;
    }
  
    /* check if the file exists */
    if (tftp_read_data(spt, 0, NULL, 0) < 0) {
        tftp_send_error(spt, 1, "File not found", tp);
        return;
    }
  
    if (tp->x.tp_buf[pktlen - 1] != 0) {
        tftp_send_error(spt, 2, "Access violation", tp);
        return;
    }
  
    while (k < pktlen) {
        const char *key, *value;
  
        key = &tp->x.tp_buf[k];
        k += strlen(key) + 1;
  
        if (k >= pktlen) {
  	  tftp_send_error(spt, 2, "Access violation", tp);
  	  return;
        }
  
        value = &tp->x.tp_buf[k];
        k += strlen(value) + 1;
  
        if (strcasecmp(key, "tsize") == 0) {
  	  int tsize = atoi(value);
  	  struct stat stat_p;
  
  	  if (tsize == 0) {
  	      if (stat(spt->filename, &stat_p) == 0)
  		  tsize = stat_p.st_size;
  	      else {
  		  tftp_send_error(spt, 1, "File not found", tp);
  		  return;
  	      }
  	  }
  
  	  tftp_send_oack(spt, "tsize", tsize, tp);
  	  return;
        }
    }
  
    tftp_send_data(spt, 1, tp);
  }
  
  static void tftp_handle_ack(Slirp *slirp, struct tftp_t *tp, int pktlen)
  {
    int s;
  
    s = tftp_session_find(slirp, tp);
  
    if (s < 0) {
      return;
    }
  
    if (tftp_send_data(&slirp->tftp_sessions[s],
  		     ntohs(tp->x.tp_data.tp_block_nr) + 1,
  		     tp) < 0) {
      return;
    }
  }
  
  static void tftp_handle_error(Slirp *slirp, struct tftp_t *tp, int pktlen)
  {
    int s;
  
    s = tftp_session_find(slirp, tp);
  
    if (s < 0) {
      return;
    }
  
    tftp_session_terminate(&slirp->tftp_sessions[s]);
  }
  
  void tftp_input(struct mbuf *m)
  {
    struct tftp_t *tp = (struct tftp_t *)m->m_data;
  
    switch(ntohs(tp->tp_op)) {
    case TFTP_RRQ:
      tftp_handle_rrq(m->slirp, tp, m->m_len);
      break;
  
    case TFTP_ACK:
      tftp_handle_ack(m->slirp, tp, m->m_len);
      break;
  
    case TFTP_ERROR:
      tftp_handle_error(m->slirp, tp, m->m_len);
      break;
    }
  }
  