335 lines
6.9 KiB
C
Executable File
335 lines
6.9 KiB
C
Executable File
/*
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* tftp.c - a simple, read-only tftp server for qemu
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*
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* Copyright (c) 2004 Magnus Damm <damm@opensource.se>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <slirp.h>
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struct tftp_session {
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int in_use;
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char filename[TFTP_FILENAME_MAX];
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struct in_addr client_ip;
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u_int16_t client_port;
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int timestamp;
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};
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struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];
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const char *tftp_prefix;
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static void tftp_session_update(struct tftp_session *spt)
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{
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spt->timestamp = curtime;
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spt->in_use = 1;
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}
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static void tftp_session_terminate(struct tftp_session *spt)
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{
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spt->in_use = 0;
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}
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static int tftp_session_allocate(struct tftp_t *tp)
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{
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struct tftp_session *spt;
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int k;
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for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
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spt = &tftp_sessions[k];
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if (!spt->in_use)
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goto found;
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/* sessions time out after 5 inactive seconds */
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if ((int)(curtime - spt->timestamp) > 5000)
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goto found;
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}
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return -1;
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found:
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memset(spt, 0, sizeof(*spt));
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memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
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spt->client_port = tp->udp.uh_sport;
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tftp_session_update(spt);
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return k;
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}
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static int tftp_session_find(struct tftp_t *tp)
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{
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struct tftp_session *spt;
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int k;
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for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
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spt = &tftp_sessions[k];
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if (spt->in_use) {
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if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
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if (spt->client_port == tp->udp.uh_sport) {
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return k;
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}
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}
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}
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}
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return -1;
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}
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static int tftp_read_data(struct tftp_session *spt, u_int16_t block_nr,
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u_int8_t *buf, int len)
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{
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int fd;
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int bytes_read = 0;
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fd = open(spt->filename, O_RDONLY | O_BINARY);
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if (fd < 0) {
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return -1;
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}
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if (len) {
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lseek(fd, block_nr * 512, SEEK_SET);
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bytes_read = read(fd, buf, len);
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}
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close(fd);
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return bytes_read;
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}
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static int tftp_send_error(struct tftp_session *spt,
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u_int16_t errorcode, const char *msg,
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struct tftp_t *recv_tp)
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{
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struct sockaddr_in saddr, daddr;
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struct mbuf *m;
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struct tftp_t *tp;
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int nobytes;
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m = m_get();
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if (!m) {
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return -1;
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}
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memset(m->m_data, 0, m->m_size);
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m->m_data += if_maxlinkhdr;
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tp = (void *)m->m_data;
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m->m_data += sizeof(struct udpiphdr);
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tp->tp_op = htons(TFTP_ERROR);
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tp->x.tp_error.tp_error_code = htons(errorcode);
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strncpy((char *)tp->x.tp_error.tp_msg, msg, sizeof(tp->x.tp_error.tp_msg));
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tp->x.tp_error.tp_msg[sizeof(tp->x.tp_error.tp_msg)-1] = 0;
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saddr.sin_addr = recv_tp->ip.ip_dst;
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saddr.sin_port = recv_tp->udp.uh_dport;
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daddr.sin_addr = spt->client_ip;
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daddr.sin_port = spt->client_port;
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nobytes = 2;
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m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
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sizeof(struct ip) - sizeof(struct udphdr);
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udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
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tftp_session_terminate(spt);
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return 0;
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}
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static int tftp_send_data(struct tftp_session *spt,
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u_int16_t block_nr,
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struct tftp_t *recv_tp)
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{
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struct sockaddr_in saddr, daddr;
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struct mbuf *m;
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struct tftp_t *tp;
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int nobytes;
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if (block_nr < 1) {
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return -1;
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}
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m = m_get();
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if (!m) {
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return -1;
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}
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memset(m->m_data, 0, m->m_size);
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m->m_data += if_maxlinkhdr;
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tp = (void *)m->m_data;
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m->m_data += sizeof(struct udpiphdr);
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tp->tp_op = htons(TFTP_DATA);
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tp->x.tp_data.tp_block_nr = htons(block_nr);
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saddr.sin_addr = recv_tp->ip.ip_dst;
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saddr.sin_port = recv_tp->udp.uh_dport;
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daddr.sin_addr = spt->client_ip;
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daddr.sin_port = spt->client_port;
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nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
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if (nobytes < 0) {
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m_free(m);
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/* send "file not found" error back */
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tftp_send_error(spt, 1, "File not found", tp);
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return -1;
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}
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m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
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sizeof(struct ip) - sizeof(struct udphdr);
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udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
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if (nobytes == 512) {
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tftp_session_update(spt);
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}
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else {
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tftp_session_terminate(spt);
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}
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return 0;
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}
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static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
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{
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struct tftp_session *spt;
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int s, k, n;
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u_int8_t *src, *dst;
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s = tftp_session_allocate(tp);
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if (s < 0) {
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return;
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}
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spt = &tftp_sessions[s];
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src = tp->x.tp_buf;
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dst = (u_int8_t *)spt->filename;
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n = pktlen - ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
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/* get name */
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for (k = 0; k < n; k++) {
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if (k < TFTP_FILENAME_MAX) {
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dst[k] = src[k];
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}
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else {
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return;
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}
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if (src[k] == '\0') {
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break;
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}
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}
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if (k >= n) {
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return;
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}
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k++;
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/* check mode */
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if ((n - k) < 6) {
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return;
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}
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if (memcmp(&src[k], "octet\0", 6) != 0) {
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tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
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return;
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}
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/* do sanity checks on the filename */
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if ((spt->filename[0] != '/')
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|| (spt->filename[strlen(spt->filename) - 1] == '/')
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|| strstr(spt->filename, "/../")) {
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tftp_send_error(spt, 2, "Access violation", tp);
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return;
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}
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/* only allow exported prefixes */
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if (!tftp_prefix
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|| (strncmp(spt->filename, tftp_prefix, strlen(tftp_prefix)) != 0)) {
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tftp_send_error(spt, 2, "Access violation", tp);
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return;
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}
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/* check if the file exists */
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if (tftp_read_data(spt, 0, (u_int8_t *)spt->filename, 0) < 0) {
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tftp_send_error(spt, 1, "File not found", tp);
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return;
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}
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tftp_send_data(spt, 1, tp);
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}
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static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
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{
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int s;
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s = tftp_session_find(tp);
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if (s < 0) {
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return;
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}
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if (tftp_send_data(&tftp_sessions[s],
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ntohs(tp->x.tp_data.tp_block_nr) + 1,
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tp) < 0) {
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return;
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}
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}
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void tftp_input(struct mbuf *m)
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{
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struct tftp_t *tp = (struct tftp_t *)m->m_data;
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switch(ntohs(tp->tp_op)) {
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case TFTP_RRQ:
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tftp_handle_rrq(tp, m->m_len);
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break;
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case TFTP_ACK:
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tftp_handle_ack(tp, m->m_len);
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break;
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}
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}
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