[Toybox] [New Toy] - Add tftpd
Felix Janda
felix.janda at posteo.de
Sat Oct 26 06:34:21 PDT 2013
Ashwini Sharma wrote:
> Hi Rob, All,
>
> Attached is the TFTPD implementation.
> Add it to hg, if you find it fine.
>
> Let me know for any comments/improvements.
>
> -Ashwini
Thanks for your submission. Some comments sprinkled into the code below.
Felix
> /* tftpd.c - TFTP server.
> *
> * Copyright 2013 Ranjan Kumar <ranjankumar.bth at gmail.com>
> * Copyright 2013 Kyungwan Han <asura321 at gmail.com>
> *
> * No Standard.
>
> USE_TFTPD(NEWTOY(tftpd, "rcu:", TOYFLAG_BIN))
>
> config TFTPD
> bool "tftpd"
> default y
> help
> usage: tftpd [-cr] [-u USER] [DIR]
>
> Transfer file from/to tftp server.
>
> -r Prohibit upload
> -c Allow file creation via upload
> -u Access files as USER
> */
> #define FOR_tftpd
> #include "toys.h"
> #include "toynet.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 |
> * ----------------------------------------
> */
Thanks for the useful comments.
> static char g_buff[TFTPD_BLKSIZE];
> static char g_errpkt[TFTPD_BLKSIZE];
How about using toybuf and toybuf + TFTP_BLKSIZE for this?
> static void bind_and_connect(struct sockaddr *srcaddr,
> struct sockaddr *dstaddr, socklen_t socklen)
> {
> int set = 1;
>
> TT.sfd = xsocket(dstaddr->sa_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, srcaddr, socklen)) perror_exit("bind");
> if (connect(TT.sfd, dstaddr, socklen) < 0)
> perror_exit("can't connect to remote host");
> }
This can be inlined into tftpd_main().
> // 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");
> }
Why does this function not set g_errpkt[3] (the error code)? In some cases
before send_errpkt is called it is set up, in some cases not. In the second
type of case I guess the error code of the previous packet would be used.
Is that intentional?
> // 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)
This is also only used once in tftpd_main() and can be inlined. That would
however require quite some work.
> {
> 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) {
> if (change_identity(TT.pw)) perror_exit("Failed to change identity");
> endgrent();
> }
>
> 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_IN:
> 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_IN;
> 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_IN;
> } 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) {
> switch(rblockno) {
> case TFTPD_ER_NOSUCHFILE: error_msg("File not found"); break;
> case TFTPD_ER_ACCESS: error_msg("Access violation"); break;
> case TFTPD_ER_FULL: error_msg("Disk full or allocation exceeded");
> break;
> case TFTPD_ER_ILLEGALOP: error_msg("Illegal TFTP operation"); break;
> case TFTPD_ER_UNKID: error_msg("Unknown transfer ID"); break;
> case TFTPD_ER_EXISTS: error_msg("File already exists"); break;
> case TFTPD_ER_UNKUSER: error_msg("No such user"); break;
> case TFTPD_ER_NEGOTIATE:
> error_msg("Terminate transfer due to option negotiation"); break;
> default: error_msg("DATA Check failure."); break;
> }
How about
char *message = "DATA Check failure.";
if (rblockno && (rblockno < 9)) message =
((char **){"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"})[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_IN;
> } // end of loop
>
> CLEAN_APP:
> if (CFG_TOYBOX_FREE) {
> free(spkt);
> free(rpkt);
> close(fd);
> }
> }
>
> void tftpd_main(void)
> {
> int recvmsg_len, rbuflen, opcode, blksize = TFTPD_BLKSIZE, tsize = 0;
> struct sockaddr_storage srcaddr, dstaddr;
> static socklen_t socklen = sizeof(struct sockaddr_storage);
Leave out the "static".
> char *buf = g_buff;
>
> TT.pw = NULL;
> memset(&srcaddr, 0, sizeof(srcaddr));
> if (getsockname(STDIN_FILENO, (struct sockaddr*)&srcaddr, &socklen)) {
> toys.exithelp = 1;
> error_exit(NULL);
> }
>
> if (toys.optflags & FLAG_u) {
> struct passwd *pw = getpwnam(TT.user);
> if (!pw) error_exit("unknown user %s", TT.user);
> TT.pw = pw;
> }
> if (*toys.optargs) {
> if (chroot(*toys.optargs))
> perror_exit("can't change root directory to '%s'", *toys.optargs);
> if (chdir("/")) perror_exit("can't change directory to '/'");
> }
>
> recvmsg_len = recvfrom(STDIN_FILENO, g_buff, TFTPD_BLKSIZE, 0,
> (struct sockaddr*)&dstaddr, &socklen);
> bind_and_connect((struct sockaddr*)&srcaddr, (struct sockaddr*)&dstaddr, socklen);
> // Error condition.
> if (recvmsg_len < 4 || recvmsg_len > TFTPD_BLKSIZE
> || g_buff[recvmsg_len-1] != '\0') {
> send_errpkt((struct sockaddr*)&dstaddr, socklen, "packet format error");
> return;
> }
>
> // request is either upload or Download.
> opcode = ntohs(*(uint16_t*)buf);
> 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 >= (g_buff + 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 = g_buff + 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, g_buff + 2, opcode, tsize, blksize);
> if (CFG_TOYBOX_FREE) close(STDIN_FILENO);
> }
1382794461.0
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