tftpd源代码

tftpd源代码，摘自iptuils

/* * Copyright (c) 1983 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright *    notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright *    notice, this list of conditions and the following disclaimer in the *    documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software *    must display the following acknowledgement: *This product includes software developed by the University of *California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors *    may be used to endorse or promote products derived from this software *    without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */#ifndef lintchar copyright[] ="@(#) Copyright (c) 1983 Regents of the University of California.\n\ All rights reserved.\n";#endif /* not lint */#ifndef lint/*static char sccsid[] = "from: @(#)tftpd.c5.13 (Berkeley) 2/26/91";*//*static char rcsid[] = "$Id: tftpd.c,v 1.3 1993/08/01 18:28:53 mycroft Exp $";*/#endif /* not lint *//* * Trivial file transfer protocol server. * * This version includes many modifications by Jim Guyton <guyton@rand-unix> */#include <sys/types.h>#include <sys/ioctl.h>#include <sys/stat.h>#include <unistd.h>#include <signal.h>#include <fcntl.h>#include <sys/socket.h>#include <netinet/in.h>#include <netdb.h>#include <setjmp.h>#include <syslog.h>#include <stdio.h>#include <errno.h>#include <ctype.h>#include <string.h>#include <stdlib.h>#include "tftp.h"#ifndef MSG_CONFIRM#define MSG_CONFIRM 0#warning Please, upgrade kernel, otherwise this tftpd has no advantages.#endif#defineTIMEOUT5intpeer;intrexmtval = TIMEOUT;intmaxtimeout = 5*TIMEOUT;#definePKTSIZESEGSIZE+4charbuf[PKTSIZE];charackbuf[PKTSIZE];union {structsockaddr     sa;structsockaddr_in  sin;structsockaddr_in6 sin6;} from;socklen_tfromlen;#define MAXARG1char*dirs[MAXARG+1];void tftp(struct tftphdr *tp, int size) __attribute__((noreturn));void nak(int error);int validate_access(char *filename, int mode);struct formats;void sendfile(struct formats *pf);void recvfile(struct formats *pf);int main(int ac, char **av){register struct tftphdr *tp;register int n = 0;int on = 1;/* Sanity. If parent forgot to setuid() on us. */if (geteuid() == 0) {setgid(65534);setuid(65534);}ac--; av++;while (ac-- > 0 && n < MAXARG)dirs[n++] = *av++;openlog("tftpd", LOG_PID, LOG_DAEMON);if (ioctl(0, FIONBIO, &on) < 0) {syslog(LOG_ERR, "ioctl(FIONBIO): %m\n");exit(1);}fromlen = sizeof (from);n = recvfrom(0, buf, sizeof (buf), 0,    (struct sockaddr *)&from, &fromlen);if (n < 0) {if (errno != EAGAIN)syslog(LOG_ERR, "recvfrom: %m\n");exit(1);}/* * Now that we have read the message out of the UDP * socket, we fork and exit.  Thus, inetd will go back * to listening to the tftp port, and the next request * to come in will start up a new instance of tftpd. * * We do this so that inetd can run tftpd in "wait" mode. * The problem with tftpd running in "nowait" mode is that * inetd may get one or more successful "selects" on the * tftp port before we do our receive, so more than one * instance of tftpd may be started up.  Worse, if tftpd * break before doing the above "recvfrom", inetd would * spawn endless instances, clogging the system. */{int pid;int i;socklen_t j;for (i = 1; i < 20; i++) {    pid = fork();    if (pid < 0) {sleep(i);/* * flush out to most recently sent request. * * This may drop some request, but those * will be resent by the clients when * they timeout.  The positive effect of * this flush is to (try to) prevent more * than one tftpd being started up to service * a single request from a single client. */j = sizeof from;i = recvfrom(0, buf, sizeof (buf), 0,    (struct sockaddr *)&from, &j);if (i > 0) {n = i;fromlen = j;}    } else {break;    }}if (pid < 0) {syslog(LOG_ERR, "fork: %m\n");exit(1);} else if (pid != 0) {exit(0);}}alarm(0);close(0);close(1);peer = socket(from.sa.sa_family, SOCK_DGRAM, 0);if (peer < 0) {syslog(LOG_ERR, "socket: %m\n");exit(1);}if (connect(peer, (struct sockaddr *)&from, sizeof(from)) < 0) {syslog(LOG_ERR, "connect: %m\n");exit(1);}tp = (struct tftphdr *)buf;tp->th_opcode = ntohs(tp->th_opcode);if (tp->th_opcode == RRQ || tp->th_opcode == WRQ)tftp(tp, n);exit(1);}struct formats {char*f_mode;int(*f_validate)(char *filename, int mode);void(*f_send)(struct formats*);void(*f_recv)(struct formats*);intf_convert;} formats[] = {{ "netascii",validate_access,sendfile,recvfile, 1 },{ "octet",validate_access,sendfile,recvfile, 0 },#ifdef notdef{ "mail",validate_user,sendmail,recvmail, 1 },#endif{ 0 }};/* * Handle initial connection protocol. */void tftp(struct tftphdr *tp, int size){register char *cp;int first = 1, ecode;register struct formats *pf;char *filename, *mode = NULL;filename = cp = tp->th_stuff;again:while (cp < buf + size) {if (*cp == '\0')break;cp++;}if (*cp != '\0') {nak(EBADOP);exit(1);}if (first) {mode = ++cp;first = 0;goto again;}for (cp = mode; *cp; cp++)if (isupper(*cp))*cp = tolower(*cp);for (pf = formats; pf->f_mode; pf++)if (strcmp(pf->f_mode, mode) == 0)break;if (pf->f_mode == 0) {nak(EBADOP);exit(1);}ecode = (*pf->f_validate)(filename, tp->th_opcode);if (ecode) {nak(ecode);exit(1);}if (tp->th_opcode == WRQ)(*pf->f_recv)(pf);else(*pf->f_send)(pf);exit(0);}FILE *file;/* * Validate file access.  Since we * have no uid or gid, for now require * file to exist and be publicly * readable/writable. * If we were invoked with arguments * from inetd then the file must also be * in one of the given directory prefixes. * Note also, full path name must be * given as we have no login directory. */int validate_access(char *filename, int mode){struct stat stbuf;int    fd;char  *cp;char   fnamebuf[1024+512];for (cp = filename; *cp; cp++) {if(*cp == '.' && (cp == filename || strncmp(cp-1, "/../", 4) == 0)) {syslog(LOG_ERR, "bad path %s", filename);return(EACCESS);}}if (*filename == '/')filename++;if (!*dirs) {syslog(LOG_ERR, "no dirs");return EACCESS;}snprintf(fnamebuf, sizeof(fnamebuf)-1, "%s/%s", *dirs, filename);filename = fnamebuf;if (stat(filename, &stbuf) < 0) {syslog(LOG_ERR, "stat %s : %m", filename);return (errno == ENOENT ? ENOTFOUND : EACCESS);}if (mode == RRQ) {if ((stbuf.st_mode&(S_IREAD >> 6)) == 0) {syslog(LOG_ERR, "not readable %s", filename);return (EACCESS);}} else {if ((stbuf.st_mode&(S_IWRITE >> 6)) == 0) {syslog(LOG_ERR, "not writable %s", filename);return (EACCESS);}}fd = open(filename, mode == RRQ ? 0 : 1);if (fd < 0) {syslog(LOG_ERR, "cannot open %s: %m", filename);return (errno + 100);}file = fdopen(fd, (mode == RRQ)? "r":"w");if (file == NULL) {return errno+100;}return (0);}intconfirmed;inttimeout;jmp_buftimeoutbuf;void timer(int signo){confirmed = 0;timeout += rexmtval;if (timeout >= maxtimeout)exit(1);longjmp(timeoutbuf, 1);}/* * Send the requested file. */void sendfile(struct formats *pf){struct tftphdr *dp;register struct tftphdr *ap;    /* ack packet */volatile int block = 1;int size, n;confirmed = 0;signal(SIGALRM, timer);dp = r_init();ap = (struct tftphdr *)ackbuf;do {size = readit(file, &dp, pf->f_convert);if (size < 0) {nak(errno + 100);goto abort;}dp->th_opcode = htons((u_short)DATA);dp->th_block = htons((u_short)block);timeout = 0;(void) setjmp(timeoutbuf);send_data:if (send(peer, dp, size + 4, confirmed) != size + 4) {syslog(LOG_ERR, "tftpd: write: %m\n");goto abort;}confirmed = 0;read_ahead(file, pf->f_convert);for ( ; ; ) {alarm(rexmtval);        /* read the ack */n = recv(peer, ackbuf, sizeof (ackbuf), 0);alarm(0);if (n < 0) {syslog(LOG_ERR, "tftpd: read: %m\n");goto abort;}ap->th_opcode = ntohs((u_short)ap->th_opcode);ap->th_block = ntohs((u_short)ap->th_block);if (ap->th_opcode == ERROR)goto abort;if (ap->th_opcode == ACK) {if (ap->th_block == block) {confirmed = MSG_CONFIRM;break;}/* Re-synchronize with the other side */synchnet(peer);if (ap->th_block == (block -1)) {goto send_data;}}}block++;} while (size == SEGSIZE);abort:(void) fclose(file);}void justquit(int signo){exit(0);}/* * Receive a file. */void recvfile(struct formats *pf){struct tftphdr *dp;register struct tftphdr *ap;    /* ack buffer */volatile int block = 0, n, size;confirmed = 0;signal(SIGALRM, timer);dp = w_init();ap = (struct tftphdr *)ackbuf;do {timeout = 0;ap->th_opcode = htons((u_short)ACK);ap->th_block = htons((u_short)block);block++;(void) setjmp(timeoutbuf);send_ack:if (send(peer, ackbuf, 4, confirmed) != 4) {syslog(LOG_ERR, "tftpd: write: %m\n");goto abort;}confirmed = 0;write_behind(file, pf->f_convert);for ( ; ; ) {alarm(rexmtval);n = recv(peer, dp, PKTSIZE, 0);alarm(0);if (n < 0) {            /* really? */syslog(LOG_ERR, "tftpd: read: %m\n");goto abort;}dp->th_opcode = ntohs((u_short)dp->th_opcode);dp->th_block = ntohs((u_short)dp->th_block);if (dp->th_opcode == ERROR)goto abort;if (dp->th_opcode == DATA) {if (dp->th_block == block) {confirmed = MSG_CONFIRM;break;   /* normal */}/* Re-synchronize with the other side */(void) synchnet(peer);if (dp->th_block == (block-1))goto send_ack;          /* rexmit */}}/*  size = write(file, dp->th_data, n - 4); */size = writeit(file, &dp, n - 4, pf->f_convert);if (size != (n-4)) {                    /* ahem */if (size < 0) nak(errno + 100);else nak(ENOSPACE);goto abort;}} while (size == SEGSIZE);write_behind(file, pf->f_convert);(void) fclose(file);            /* close data file */ap->th_opcode = htons((u_short)ACK);    /* send the "final" ack */ap->th_block = htons((u_short)(block));(void) send(peer, ackbuf, 4, confirmed);signal(SIGALRM, justquit);      /* just quit on timeout */alarm(rexmtval);n = recv(peer, buf, sizeof (buf), 0); /* normally times out and quits */alarm(0);if (n >= 4 &&                   /* if read some data */    dp->th_opcode == DATA &&    /* and got a data block */    block == dp->th_block) {/* then my last ack was lost */(void) send(peer, ackbuf, 4, 0);     /* resend final ack */}abort:return;}struct errmsg {inte_code;char*e_msg;} errmsgs[] = {{ EUNDEF,"Undefined error code" },{ ENOTFOUND,"File not found" },{ EACCESS,"Access violation" },{ ENOSPACE,"Disk full or allocation exceeded" },{ EBADOP,"Illegal TFTP operation" },{ EBADID,"Unknown transfer ID" },{ EEXISTS,"File already exists" },{ ENOUSER,"No such user" },{ -1,0 }};/* * Send a nak packet (error message). * Error code passed in is one of the * standard TFTP codes, or a UNIX errno * offset by 100. */void nak(int error){register struct tftphdr *tp;int length;register struct errmsg *pe;tp = (struct tftphdr *)buf;tp->th_opcode = htons((u_short)ERROR);tp->th_code = htons((u_short)error);for (pe = errmsgs; pe->e_code >= 0; pe++)if (pe->e_code == error)break;if (pe->e_code < 0) {pe->e_msg = strerror(error - 100);tp->th_code = EUNDEF;   /* set 'undef' errorcode */}strcpy(tp->th_msg, pe->e_msg);length = strlen(pe->e_msg);tp->th_msg[length] = '\0';length += 5;if (send(peer, buf, length, 0) != length)syslog(LOG_ERR, "nak: %m\n");}