/* tftpd.c - TFTP server.
*
* Copyright 2013 Ranjan Kumar <ranjankumar.bth@gmail.com>
* Copyright 2013 Kyungwan Han <asura321@gmail.com>
*
* No Standard.
USE_TFTPD(NEWTOY(tftpd, "rcu:l", TOYFLAG_BIN))
config TFTPD
bool "tftpd"
default n
help
usage: tftpd [-cr] [-u USER] [DIR]
Transfer file from/to tftp server.
-r read only
-c Allow file creation via upload
-u run as USER
-l Log to syslog (inetd mode requires this)
*/
#define FOR_tftpd
#include "toys.h"
GLOBALS(
char *user;
long sfd;
struct passwd *pw;
)
#define TFTPD_BLKSIZE 512 // as per RFC 1350.
// opcodes
#define TFTPD_OP_RRQ 1 // Read Request RFC 1350, RFC 2090
#define TFTPD_OP_WRQ 2 // Write Request RFC 1350
#define TFTPD_OP_DATA 3 // Data chunk RFC 1350
#define TFTPD_OP_ACK 4 // Acknowledgement RFC 1350
#define TFTPD_OP_ERR 5 // Error Message RFC 1350
#define TFTPD_OP_OACK 6 // Option acknowledgment RFC 2347
// Error Codes:
#define TFTPD_ER_NOSUCHFILE 1 // File not found
#define TFTPD_ER_ACCESS 2 // Access violation
#define TFTPD_ER_FULL 3 // Disk full or allocation exceeded
#define TFTPD_ER_ILLEGALOP 4 // Illegal TFTP operation
#define TFTPD_ER_UNKID 5 // Unknown transfer ID
#define TFTPD_ER_EXISTS 6 // File already exists
#define TFTPD_ER_UNKUSER 7 // No such user
#define TFTPD_ER_NEGOTIATE 8 // Terminate transfer due to option negotiation
/* TFTP Packet Formats
* Type Op # Format without header
* 2 bytes string 1 byte string 1 byte
* -----------------------------------------------
* RRQ/ | 01/02 | Filename | 0 | Mode | 0 |
* WRQ -----------------------------------------------
* 2 bytes 2 bytes n bytes
* ---------------------------------
* DATA | 03 | Block # | Data |
* ---------------------------------
* 2 bytes 2 bytes
* -------------------
* ACK | 04 | Block # |
* --------------------
* 2 bytes 2 bytes string 1 byte
* ----------------------------------------
* ERROR | 05 | ErrorCode | ErrMsg | 0 |
* ----------------------------------------
*/
static char *g_errpkt = toybuf + TFTPD_BLKSIZE;
// Create and send error packet.
static void send_errpkt(struct sockaddr *dstaddr,
socklen_t socklen, char *errmsg)
{
error_msg(errmsg);
g_errpkt[1] = TFTPD_OP_ERR;
strcpy(g_errpkt + 4, errmsg);
if (sendto(TT.sfd, g_errpkt, strlen(errmsg)+5, 0, dstaddr, socklen) < 0)
perror_exit("sendto failed");
}
// Used to send / receive packets.
static void do_action(struct sockaddr *srcaddr, struct sockaddr *dstaddr,
socklen_t socklen, char *file, int opcode, int tsize, int blksize)
{
int fd, done = 0, retry_count = 12, timeout = 100, len;
uint16_t blockno = 1, pktopcode, rblockno;
char *ptr, *spkt, *rpkt;
struct pollfd pollfds[1];
spkt = xzalloc(blksize + 4);
rpkt = xzalloc(blksize + 4);
ptr = spkt+2; //point after opcode.
pollfds[0].fd = TT.sfd;
// initialize groups, setgid and setuid
if (TT.pw) xsetuser(TT.pw);
if (opcode == TFTPD_OP_RRQ) fd = open(file, O_RDONLY, 0666);
else fd = open(file, ((toys.optflags & FLAG_c) ?
(O_WRONLY|O_TRUNC|O_CREAT) : (O_WRONLY|O_TRUNC)) , 0666);
if (fd < 0) {
g_errpkt[3] = TFTPD_ER_NOSUCHFILE;
send_errpkt(dstaddr, socklen, "can't open file");
goto CLEAN_APP;
}
// For download -> blockno will be 1.
// 1st ACK will be from dst,which will have blockno-=1
// Create and send ACK packet.
if (blksize != TFTPD_BLKSIZE || tsize) {
pktopcode = TFTPD_OP_OACK;
// add "blksize\000blksize_val\000" in send buffer.
if (blksize != TFTPD_BLKSIZE) {
strcpy(ptr, "blksize");
ptr += strlen("blksize") + 1;
ptr += snprintf(ptr, 6, "%d", blksize) + 1;
}
if (tsize) {// add "tsize\000tsize_val\000" in send buffer.
struct stat sb;
sb.st_size = 0;
fstat(fd, &sb);
strcpy(ptr, "tsize");
ptr += strlen("tsize") + 1;
ptr += sprintf(ptr, "%lu", (unsigned long)sb.st_size)+1;
}
goto SEND_PKT;
}
// upload -> ACK 1st packet with filename, as it has blockno 0.
if (opcode == TFTPD_OP_WRQ) blockno = 0;
// Prepare DATA and/or ACK pkt and send it.
for (;;) {
int poll_ret;
retry_count = 12, timeout = 100, pktopcode = TFTPD_OP_ACK;
ptr = spkt+2;
*((uint16_t*)ptr) = htons(blockno);
blockno++;
ptr += 2;
if (opcode == TFTPD_OP_RRQ) {
pktopcode = TFTPD_OP_DATA;
len = readall(fd, ptr, blksize);
if (len < 0) {
send_errpkt(dstaddr, socklen, "read-error");
break;
}
if (len != blksize) done = 1; //last pkt.
ptr += len;
}
SEND_PKT:
// 1st ACK will be from dst, which will have blockno-=1
*((uint16_t*)spkt) = htons(pktopcode); //append send pkt's opcode.
RETRY_SEND:
if (sendto(TT.sfd, spkt, (ptr - spkt), 0, dstaddr, socklen) <0)
perror_exit("sendto failed");
// if "block size < 512", send ACK and exit.
if ((pktopcode == TFTPD_OP_ACK) && done) break;
POLL_INPUT:
pollfds[0].events = POLLIN;
pollfds[0].fd = TT.sfd;
poll_ret = poll(pollfds, 1, timeout);
if (poll_ret < 0 && (errno == EINTR || errno == ENOMEM)) goto POLL_INPUT;
if (!poll_ret) {
if (!--retry_count) {
error_msg("timeout");
break;
}
timeout += 150;
goto RETRY_SEND;
} else if (poll_ret == 1) {
len = read(pollfds[0].fd, rpkt, blksize + 4);
if (len < 0) {
send_errpkt(dstaddr, socklen, "read-error");
break;
}
if (len < 4) goto POLL_INPUT;
} else {
perror_msg("poll");
break;
}
// Validate receive packet.
pktopcode = ntohs(((uint16_t*)rpkt)[0]);
rblockno = ntohs(((uint16_t*)rpkt)[1]);
if (pktopcode == TFTPD_OP_ERR) {
char *message = "DATA Check failure.";
char *arr[] = {"File not found", "Access violation",
"Disk full or allocation exceeded", "Illegal TFTP operation",
"Unknown transfer ID", "File already exists",
"No such user", "Terminate transfer due to option negotiation"};
if (rblockno && (rblockno < 9)) message = arr[rblockno - 1];
error_msg(message);
break; // Break the for loop.
}
// if download requested by client,
// server will send data pkt and will receive ACK pkt from client.
if ((opcode == TFTPD_OP_RRQ) && (pktopcode == TFTPD_OP_ACK)) {
if (rblockno == (uint16_t) (blockno - 1)) {
if (!done) continue; // Send next chunk of data.
break;
}
}
// server will receive DATA pkt and write the data.
if ((opcode == TFTPD_OP_WRQ) && (pktopcode == TFTPD_OP_DATA)) {
if (rblockno == blockno) {
int nw = writeall(fd, &rpkt[4], len-4);
if (nw != len-4) {
g_errpkt[3] = TFTPD_ER_FULL;
send_errpkt(dstaddr, socklen, "write error");
break;
}
if (nw != blksize) done = 1;
}
continue;
}
goto POLL_INPUT;
} // end of loop
CLEAN_APP:
if (CFG_TOYBOX_FREE) {
free(spkt);
free(rpkt);
close(fd);
}
}
void tftpd_main(void)
{
int fd = 0, recvmsg_len, rbuflen, opcode, blksize = TFTPD_BLKSIZE, tsize = 0, set =1;
struct sockaddr_storage srcaddr, dstaddr;
socklen_t socklen = sizeof(struct sockaddr_storage);
char *buf = toybuf;
memset(&srcaddr, 0, sizeof(srcaddr));
if (getsockname(0, (struct sockaddr *)&srcaddr, &socklen)) help_exit(0);
if (TT.user) TT.pw = xgetpwnam(TT.user);
if (*toys.optargs) xchroot(*toys.optargs);
recvmsg_len = recvfrom(fd, toybuf, blksize, 0, (void *)&dstaddr, &socklen);
TT.sfd = xsocket(dstaddr.ss_family, SOCK_DGRAM, 0);
if (setsockopt(TT.sfd, SOL_SOCKET, SO_REUSEADDR, (const void *)&set,
sizeof(set)) < 0) perror_exit("setsockopt failed");
if (bind(TT.sfd, (void *)&srcaddr, socklen)) perror_exit("bind");
if (connect(TT.sfd, (void *)&dstaddr, socklen) < 0)
perror_exit("can't connect to remote host");
// Error condition.
if (recvmsg_len<4 || recvmsg_len>TFTPD_BLKSIZE || toybuf[recvmsg_len-1]) {
send_errpkt((struct sockaddr*)&dstaddr, socklen, "packet format error");
return;
}
// request is either upload or Download.
opcode = buf[1];
if (((opcode != TFTPD_OP_RRQ) && (opcode != TFTPD_OP_WRQ))
|| ((opcode == TFTPD_OP_WRQ) && (toys.optflags & FLAG_r))) {
send_errpkt((struct sockaddr*)&dstaddr, socklen,
(opcode == TFTPD_OP_WRQ) ? "write error" : "packet format error");
return;
}
buf += 2;
if (*buf == '.' || strstr(buf, "/.")) {
send_errpkt((struct sockaddr*)&dstaddr, socklen, "dot in filename");
return;
}
buf += strlen(buf) + 1; //1 '\0'.
// As per RFC 1350, mode is case in-sensitive.
if (buf >= toybuf+recvmsg_len || strcasecmp(buf, "octet")) {
send_errpkt((struct sockaddr*)&dstaddr, socklen, "packet format error");
return;
}
//RFC2348. e.g. of size type: "ttype1\0ttype1_val\0...ttypeN\0ttypeN_val\0"
buf += strlen(buf) + 1;
rbuflen = toybuf + recvmsg_len - buf;
if (rbuflen) {
int jump = 0, bflag = 0;
for (; rbuflen; rbuflen -= jump, buf += jump) {
if (!bflag && !strcasecmp(buf, "blksize")) { //get blksize
errno = 0;
blksize = strtoul(buf, NULL, 10);
if (errno || blksize > 65564 || blksize < 8) blksize = TFTPD_BLKSIZE;
bflag ^= 1;
} else if (!tsize && !strcasecmp(buf, "tsize")) tsize ^= 1;
jump += strlen(buf) + 1;
}
tsize &= (opcode == TFTPD_OP_RRQ);
}
//do send / receive file.
do_action((struct sockaddr*)&srcaddr, (struct sockaddr*)&dstaddr,
socklen, toybuf + 2, opcode, tsize, blksize);
if (CFG_TOYBOX_FREE) close(STDIN_FILENO);
}