X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=networking%2Ftelnetd.c;h=f06e9583e4f8900ece4f388d11f51f3316b98607;hb=179e88bec91cfe58096900dc5509a080ff37b083;hp=f04b32f9e85dfc659689a49ecf5a759441502c21;hpb=9f2f808b0dd531840b906e6dd09550a626c32bf1;p=oweals%2Fbusybox.git diff --git a/networking/telnetd.c b/networking/telnetd.c index f04b32f9e..f06e9583e 100644 --- a/networking/telnetd.c +++ b/networking/telnetd.c @@ -3,7 +3,7 @@ * Simple telnet server * Bjorn Wesen, Axis Communications AB (bjornw@axis.com) * - * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. + * Licensed under GPLv2 or later, see file LICENSE in this source tree. * * --------------------------------------------------------------------------- * (C) Copyright 2000, Axis Communications AB, LUND, SWEDEN @@ -11,39 +11,135 @@ * * The telnetd manpage says it all: * - * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for - * a client, then creating a login process which has the slave side of the - * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the - * master side of the pseudo-terminal, implementing the telnet protocol and - * passing characters between the remote client and the login process. + * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for + * a client, then creating a login process which has the slave side of the + * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the + * master side of the pseudo-terminal, implementing the telnet protocol and + * passing characters between the remote client and the login process. * * Vladimir Oleynik 2001 - * Set process group corrections, initial busybox port + * Set process group corrections, initial busybox port */ +//config:config TELNETD +//config: bool "telnetd" +//config: default y +//config: select FEATURE_SYSLOG +//config: help +//config: A daemon for the TELNET protocol, allowing you to log onto the host +//config: running the daemon. Please keep in mind that the TELNET protocol +//config: sends passwords in plain text. If you can't afford the space for an +//config: SSH daemon and you trust your network, you may say 'y' here. As a +//config: more secure alternative, you should seriously consider installing the +//config: very small Dropbear SSH daemon instead: +//config: http://matt.ucc.asn.au/dropbear/dropbear.html +//config: +//config: Note that for busybox telnetd to work you need several things: +//config: First of all, your kernel needs: +//config: CONFIG_UNIX98_PTYS=y +//config: +//config: Next, you need a /dev/pts directory on your root filesystem: +//config: +//config: $ ls -ld /dev/pts +//config: drwxr-xr-x 2 root root 0 Sep 23 13:21 /dev/pts/ +//config: +//config: Next you need the pseudo terminal master multiplexer /dev/ptmx: +//config: +//config: $ ls -la /dev/ptmx +//config: crw-rw-rw- 1 root tty 5, 2 Sep 23 13:55 /dev/ptmx +//config: +//config: Any /dev/ttyp[0-9]* files you may have can be removed. +//config: Next, you need to mount the devpts filesystem on /dev/pts using: +//config: +//config: mount -t devpts devpts /dev/pts +//config: +//config: You need to be sure that busybox has LOGIN and +//config: FEATURE_SUID enabled. And finally, you should make +//config: certain that Busybox has been installed setuid root: +//config: +//config: chown root.root /bin/busybox +//config: chmod 4755 /bin/busybox +//config: +//config: with all that done, telnetd _should_ work.... +//config: +//config:config FEATURE_TELNETD_STANDALONE +//config: bool "Support standalone telnetd (not inetd only)" +//config: default y +//config: depends on TELNETD +//config: help +//config: Selecting this will make telnetd able to run standalone. +//config: +//config:config FEATURE_TELNETD_INETD_WAIT +//config: bool "Support -w SEC option (inetd wait mode)" +//config: default y +//config: depends on FEATURE_TELNETD_STANDALONE +//config: help +//config: This option allows you to run telnetd in "inet wait" mode. +//config: Example inetd.conf line (note "wait", not usual "nowait"): +//config: +//config: telnet stream tcp wait root /bin/telnetd telnetd -w10 +//config: +//config: In this example, inetd passes _listening_ socket_ as fd 0 +//config: to telnetd when connection appears. +//config: telnetd will wait for connections until all existing +//config: connections are closed, and no new connections +//config: appear during 10 seconds. Then it exits, and inetd continues +//config: to listen for new connections. +//config: +//config: This option is rarely used. "tcp nowait" is much more usual +//config: way of running tcp services, including telnetd. +//config: You most probably want to say N here. + +//applet:IF_TELNETD(APPLET(telnetd, BB_DIR_USR_SBIN, BB_SUID_DROP)) + +//kbuild:lib-$(CONFIG_TELNETD) += telnetd.o + +//usage:#define telnetd_trivial_usage +//usage: "[OPTIONS]" +//usage:#define telnetd_full_usage "\n\n" +//usage: "Handle incoming telnet connections" +//usage: IF_NOT_FEATURE_TELNETD_STANDALONE(" via inetd") "\n" +//usage: "\n -l LOGIN Exec LOGIN on connect" +//usage: "\n -f ISSUE_FILE Display ISSUE_FILE instead of /etc/issue" +//usage: "\n -K Close connection as soon as login exits" +//usage: "\n (normally wait until all programs close slave pty)" +//usage: IF_FEATURE_TELNETD_STANDALONE( +//usage: "\n -p PORT Port to listen on" +//usage: "\n -b ADDR[:PORT] Address to bind to" +//usage: "\n -F Run in foreground" +//usage: "\n -i Inetd mode" +//usage: IF_FEATURE_TELNETD_INETD_WAIT( +//usage: "\n -w SEC Inetd 'wait' mode, linger time SEC" +//usage: "\n -S Log to syslog (implied by -i or without -F and -w)" +//usage: ) +//usage: ) #define DEBUG 0 #include "libbb.h" +#include "common_bufsiz.h" #include #if DEBUG -#define TELCMDS -#define TELOPTS +# define TELCMDS +# define TELOPTS #endif #include -/* Structure that describes a session */ + struct tsession { struct tsession *next; - int sockfd_read, sockfd_write, ptyfd; - int shell_pid; + pid_t shell_pid; + int sockfd_read; + int sockfd_write; + int ptyfd; + smallint buffered_IAC_for_pty; /* two circular buffers */ /*char *buf1, *buf2;*/ -/*#define TS_BUF1 ts->buf1*/ -/*#define TS_BUF2 TS_BUF2*/ -#define TS_BUF1 ((unsigned char*)(ts + 1)) -#define TS_BUF2 (((unsigned char*)(ts + 1)) + BUFSIZE) +/*#define TS_BUF1(ts) ts->buf1*/ +/*#define TS_BUF2(ts) TS_BUF2(ts)*/ +#define TS_BUF1(ts) ((unsigned char*)(ts + 1)) +#define TS_BUF2(ts) (((unsigned char*)(ts + 1)) + BUFSIZE) int rdidx1, wridx1, size1; int rdidx2, wridx2, size2; }; @@ -54,122 +150,223 @@ enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 }; /* Globals */ -static int maxfd; -static struct tsession *sessions; -static const char *loginpath = "/bin/login"; -static const char *issuefile = "/etc/issue.net"; - - -/* - Remove all IAC's from buf1 (received IACs are ignored and must be removed - so as to not be interpreted by the terminal). Make an uninterrupted - string of characters fit for the terminal. Do this by packing - all characters meant for the terminal sequentially towards the end of buf. - - Return a pointer to the beginning of the characters meant for the terminal. - and make *num_totty the number of characters that should be sent to - the terminal. - - Note - If an IAC (3 byte quantity) starts before (bf + len) but extends - past (bf + len) then that IAC will be left unprocessed and *processed - will be less than len. - - CR-LF ->'s CR mapping is also done here, for convenience. - - NB: may fail to remove iacs which wrap around buffer! +struct globals { + struct tsession *sessions; + const char *loginpath; + const char *issuefile; + int maxfd; +} FIX_ALIASING; +#define G (*(struct globals*)bb_common_bufsiz1) +#define INIT_G() do { \ + setup_common_bufsiz(); \ + G.loginpath = "/bin/login"; \ + G.issuefile = "/etc/issue.net"; \ +} while (0) + + +/* Write some buf1 data to pty, processing IACs. + * Update wridx1 and size1. Return < 0 on error. + * Buggy if IAC is present but incomplete: skips them. */ -static unsigned char * -remove_iacs(struct tsession *ts, int *pnum_totty) +static ssize_t +safe_write_to_pty_decode_iac(struct tsession *ts) { - unsigned char *ptr0 = TS_BUF1 + ts->wridx1; - unsigned char *ptr = ptr0; - unsigned char *totty = ptr; - unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1); - int num_totty; - - while (ptr < end) { - if (*ptr != IAC) { - char c = *ptr; - - *totty++ = c; - ptr++; - /* We map \r\n ==> \r for pragmatic reasons. - * Many client implementations send \r\n when - * the user hits the CarriageReturn key. - */ - if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0')) - ptr++; - continue; - } + unsigned wr; + ssize_t rc; + unsigned char *buf; + unsigned char *found; + + buf = TS_BUF1(ts) + ts->wridx1; + wr = MIN(BUFSIZE - ts->wridx1, ts->size1); + /* wr is at least 1 here */ + + if (ts->buffered_IAC_for_pty) { + /* Last time we stopped on a "dangling" IAC byte. + * We removed it from the buffer back then. + * Now pretend it's still there, and jump to IAC processing. + */ + ts->buffered_IAC_for_pty = 0; + wr++; + ts->size1++; + buf--; /* Yes, this can point before the buffer. It's ok */ + ts->wridx1--; + goto handle_iac; + } - if ((ptr+1) >= end) - break; - if (ptr[1] == NOP) { /* Ignore? (putty keepalive, etc.) */ - ptr += 2; - continue; - } - if (ptr[1] == IAC) { /* Literal IAC? (emacs M-DEL) */ - *totty++ = ptr[1]; - ptr += 2; - continue; - } + found = memchr(buf, IAC, wr); + if (found != buf) { + /* There is a "prefix" of non-IAC chars. + * Write only them, and return. + */ + if (found) + wr = found - buf; - /* - * TELOPT_NAWS support! + /* We map \r\n ==> \r for pragmatic reasons: + * many client implementations send \r\n when + * the user hits the CarriageReturn key. + * See RFC 1123 3.3.1 Telnet End-of-Line Convention. */ - if ((ptr+2) >= end) { - /* only the beginning of the IAC is in the - buffer we were asked to process, we can't - process this char. */ - break; + rc = wr; + found = memchr(buf, '\r', wr); + if (found) + rc = found - buf + 1; + rc = safe_write(ts->ptyfd, buf, rc); + if (rc <= 0) + return rc; + if (rc < wr /* don't look past available data */ + && buf[rc-1] == '\r' /* need this: imagine that write was _short_ */ + && (buf[rc] == '\n' || buf[rc] == '\0') + ) { + rc++; } + goto update_and_return; + } + + /* buf starts with IAC char. Process that sequence. + * Example: we get this from our own (bbox) telnet client: + * read(5, "\377\374\1""\377\373\37""\377\372\37\0\262\0@\377\360""\377\375\1""\377\375\3"): + * IAC WONT ECHO, IAC WILL NAWS, IAC SB NAWS IAC SE, IAC DO SGA + * Another example (telnet-0.17 from old-netkit): + * read(4, "\377\375\3""\377\373\30""\377\373\37""\377\373 ""\377\373!""\377\373\"""\377\373'" + * "\377\375\5""\377\373#""\377\374\1""\377\372\37\0\257\0I\377\360""\377\375\1"): + * IAC DO SGA, IAC WILL TTYPE, IAC WILL NAWS, IAC WILL TSPEED, IAC WILL LFLOW, IAC WILL LINEMODE, IAC WILL NEW_ENVIRON, + * IAC DO STATUS, IAC WILL XDISPLOC, IAC WONT ECHO, IAC SB NAWS IAC SE, IAC DO ECHO + */ + if (wr <= 1) { + /* Only the single IAC byte is in the buffer, eat it + * and set a flag "process the rest of the sequence + * next time we are here". + */ + //bb_error_msg("dangling IAC!"); + ts->buffered_IAC_for_pty = 1; + rc = 1; + goto update_and_return; + } + + handle_iac: + /* 2-byte commands (240..250 and 255): + * IAC IAC (255) Literal 255. Supported. + * IAC SE (240) End of subnegotiation. Treated as NOP. + * IAC NOP (241) NOP. Supported. + * IAC BRK (243) Break. Like serial line break. TODO via tcsendbreak()? + * IAC AYT (246) Are you there. Send back evidence that AYT was seen. TODO (send NOP back)? + * These don't look useful: + * IAC DM (242) Data mark. What is this? + * IAC IP (244) Suspend, interrupt or abort the process. (Ancient cousin of ^C). + * IAC AO (245) Abort output. "You can continue running, but do not send me the output". + * IAC EC (247) Erase character. The receiver should delete the last received char. + * IAC EL (248) Erase line. The receiver should delete everything up tp last newline. + * IAC GA (249) Go ahead. For half-duplex lines: "now you talk". + * Implemented only as part of NAWS: + * IAC SB (250) Subnegotiation of an option follows. + */ + if (buf[1] == IAC) { + /* Literal 255 (emacs M-DEL) */ + //bb_error_msg("255!"); + rc = safe_write(ts->ptyfd, &buf[1], 1); /* - * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE + * If we went through buffered_IAC_for_pty==1 path, + * bailing out on error like below messes up the buffer. + * EAGAIN is highly unlikely here, other errors will be + * repeated on next write, let's just skip error check. */ - if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) { +#if 0 + if (rc <= 0) + return rc; +#endif + rc = 2; + goto update_and_return; + } + if (buf[1] >= 240 && buf[1] <= 249) { + /* NOP (241). Ignore (putty keepalive, etc) */ + /* All other 2-byte commands also treated as NOPs here */ + rc = 2; + goto update_and_return; + } + + if (wr <= 2) { +/* BUG: only 2 bytes of the IAC is in the buffer, we just eat them. + * This is not a practical problem since >2 byte IACs are seen only + * in initial negotiation, when buffer is empty + */ + rc = 2; + goto update_and_return; + } + + if (buf[1] == SB) { + if (buf[2] == TELOPT_NAWS) { + /* IAC SB, TELOPT_NAWS, 4-byte, IAC SE */ struct winsize ws; - if ((ptr+8) >= end) - break; /* incomplete, can't process */ - ws.ws_col = (ptr[3] << 8) | ptr[4]; - ws.ws_row = (ptr[5] << 8) | ptr[6]; + if (wr <= 6) { +/* BUG: incomplete, can't process */ + rc = wr; + goto update_and_return; + } + memset(&ws, 0, sizeof(ws)); /* pixel sizes are set to 0 */ + ws.ws_col = (buf[3] << 8) | buf[4]; + ws.ws_row = (buf[5] << 8) | buf[6]; ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); - ptr += 9; - continue; + rc = 7; + /* trailing IAC SE will be eaten separately, as 2-byte NOP */ + goto update_and_return; } - /* skip 3-byte IAC non-SB cmd */ + /* else: other subnegs not supported yet */ + } + + /* Assume it is a 3-byte WILL/WONT/DO/DONT 251..254 command and skip it */ #if DEBUG - fprintf(stderr, "Ignoring IAC %s,%s\n", - TELCMD(ptr[1]), TELOPT(ptr[2])); + fprintf(stderr, "Ignoring IAC %s,%s\n", + TELCMD(buf[1]), TELOPT(buf[2])); #endif - ptr += 3; + rc = 3; + + update_and_return: + ts->wridx1 += rc; + if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */ + ts->wridx1 = 0; + ts->size1 -= rc; + /* + * Hack. We cannot process IACs which wrap around buffer's end. + * Since properly fixing it requires writing bigger code, + * we rely instead on this code making it virtually impossible + * to have wrapped IAC (people don't type at 2k/second). + * It also allows for bigger reads in common case. + */ + if (ts->size1 == 0) { /* very typical */ + //bb_error_msg("zero size1"); + ts->rdidx1 = 0; + ts->wridx1 = 0; + return rc; } - - num_totty = totty - ptr0; - *pnum_totty = num_totty; - /* the difference between ptr and totty is number of iacs - we removed from the stream. Adjust buf1 accordingly. */ - if ((ptr - totty) == 0) /* 99.999% of cases */ - return ptr0; - ts->wridx1 += ptr - totty; - ts->size1 -= ptr - totty; - /* move chars meant for the terminal towards the end of the buffer */ - return memmove(ptr - num_totty, ptr0, num_totty); + wr = ts->wridx1; + if (wr != 0 && wr < ts->rdidx1) { + /* Buffer is not wrapped yet. + * We can easily move it to the beginning. + */ + //bb_error_msg("moved %d", wr); + memmove(TS_BUF1(ts), TS_BUF1(ts) + wr, ts->size1); + ts->rdidx1 -= wr; + ts->wridx1 = 0; + } + return rc; } /* - * Converting single 0xff into double on output + * Converting single IAC into double on output */ -static size_t iac_safe_write(int fd, const char *buf, size_t count) +static size_t safe_write_double_iac(int fd, const char *buf, size_t count) { - const char *oxff; + const char *IACptr; size_t wr, rc, total; total = 0; while (1) { if (count == 0) return total; - if (*buf == (char)0xff) { - rc = safe_write(fd, "\xff\xff", 2); + if (*buf == (char)IAC) { + static const char IACIAC[] ALIGN1 = { IAC, IAC }; + rc = safe_write(fd, IACIAC, 2); +/* BUG: if partial write was only 1 byte long, we end up emitting just one IAC */ if (rc != 2) break; buf++; @@ -177,11 +374,11 @@ static size_t iac_safe_write(int fd, const char *buf, size_t count) count--; continue; } - /* count != 0, *buf != 0xff */ - oxff = memchr(buf, 0xff, count); + /* count != 0, *buf != IAC */ + IACptr = memchr(buf, IAC, count); wr = count; - if (oxff) - wr = oxff - buf; + if (IACptr) + wr = IACptr - buf; rc = safe_write(fd, buf, wr); if (rc != wr) break; @@ -198,11 +395,24 @@ static size_t iac_safe_write(int fd, const char *buf, size_t count) return total + rc; } +/* Must match getopt32 string */ +enum { + OPT_WATCHCHILD = (1 << 2), /* -K */ + OPT_INETD = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */ + OPT_PORT = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p PORT */ + OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */ + OPT_SYSLOG = (1 << 7) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -S */ + OPT_WAIT = (1 << 8) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -w SEC */ +}; + static struct tsession * make_new_session( - USE_FEATURE_TELNETD_STANDALONE(int sock) - SKIP_FEATURE_TELNETD_STANDALONE(void) + IF_FEATURE_TELNETD_STANDALONE(int sock) + IF_NOT_FEATURE_TELNETD_STANDALONE(void) ) { +#if !ENABLE_FEATURE_TELNETD_STANDALONE + enum { sock = 0 }; +#endif const char *login_argv[2]; struct termios termbuf; int fd, pid; @@ -212,32 +422,33 @@ make_new_session( /*ts->buf1 = (char *)(ts + 1);*/ /*ts->buf2 = ts->buf1 + BUFSIZE;*/ - /* Got a new connection, set up a tty. */ + /* Got a new connection, set up a tty */ fd = xgetpty(tty_name); - if (fd > maxfd) - maxfd = fd; + if (fd > G.maxfd) + G.maxfd = fd; ts->ptyfd = fd; ndelay_on(fd); + close_on_exec_on(fd); + + /* SO_KEEPALIVE by popular demand */ + setsockopt_keepalive(sock); #if ENABLE_FEATURE_TELNETD_STANDALONE ts->sockfd_read = sock; - /* SO_KEEPALIVE by popular demand */ - setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1)); ndelay_on(sock); - if (!sock) { /* We are called with fd 0 - we are in inetd mode */ + if (sock == 0) { /* We are called with fd 0 - we are in inetd mode */ sock++; /* so use fd 1 for output */ ndelay_on(sock); } ts->sockfd_write = sock; - if (sock > maxfd) - maxfd = sock; + if (sock > G.maxfd) + G.maxfd = sock; #else - /* SO_KEEPALIVE by popular demand */ - setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1)); /* ts->sockfd_read = 0; - done by xzalloc */ ts->sockfd_write = 1; ndelay_on(0); ndelay_on(1); #endif + /* Make the telnet client understand we will echo characters so it * should not do it locally. We don't tell the client to run linemode, * because we want to handle line editing and tab completion and other @@ -246,22 +457,27 @@ make_new_session( static const char iacs_to_send[] ALIGN1 = { IAC, DO, TELOPT_ECHO, IAC, DO, TELOPT_NAWS, - IAC, DO, TELOPT_LFLOW, + /* This requires telnetd.ctrlSQ.patch (incomplete) */ + /*IAC, DO, TELOPT_LFLOW,*/ IAC, WILL, TELOPT_ECHO, IAC, WILL, TELOPT_SGA }; - /* This confuses iac_safe_write(), it will try to duplicate + /* This confuses safe_write_double_iac(), it will try to duplicate * each IAC... */ - //memcpy(TS_BUF2, iacs_to_send, sizeof(iacs_to_send)); + //memcpy(TS_BUF2(ts), iacs_to_send, sizeof(iacs_to_send)); //ts->rdidx2 = sizeof(iacs_to_send); //ts->size2 = sizeof(iacs_to_send); - /* So just stuff it into TCP buffer! */ + /* So just stuff it into TCP stream! (no error check...) */ +#if ENABLE_FEATURE_TELNETD_STANDALONE safe_write(sock, iacs_to_send, sizeof(iacs_to_send)); - /*ts->rdidx2 = 0; - xzalloc did it! */ +#else + safe_write(1, iacs_to_send, sizeof(iacs_to_send)); +#endif + /*ts->rdidx2 = 0; - xzalloc did it */ /*ts->size2 = 0;*/ } - fflush(NULL); /* flush all streams */ + fflush_all(); pid = vfork(); /* NOMMU-friendly */ if (pid < 0) { free(ts); @@ -279,23 +495,36 @@ make_new_session( /* Child */ /* Careful - we are after vfork! */ - /* make new session and process group */ - setsid(); - - /* Restore default signal handling */ + /* Restore default signal handling ASAP */ bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL); - /* open the child's side of the tty. */ + pid = getpid(); + + if (ENABLE_FEATURE_UTMP) { + len_and_sockaddr *lsa = get_peer_lsa(sock); + char *hostname = NULL; + if (lsa) { + hostname = xmalloc_sockaddr2dotted(&lsa->u.sa); + free(lsa); + } + write_new_utmp(pid, LOGIN_PROCESS, tty_name, /*username:*/ "LOGIN", hostname); + free(hostname); + } + + /* Make new session and process group */ + setsid(); + + /* Open the child's side of the tty */ /* NB: setsid() disconnects from any previous ctty's. Therefore * we must open child's side of the tty AFTER setsid! */ close(0); xopen(tty_name, O_RDWR); /* becomes our ctty */ xdup2(0, 1); xdup2(0, 2); - tcsetpgrp(0, getpid()); /* switch this tty's process group to us */ + tcsetpgrp(0, pid); /* switch this tty's process group to us */ - /* The pseudo-terminal allocated to the client is configured to operate in - * cooked mode, and with XTABS CRMOD enabled (see tty(4)). */ + /* The pseudo-terminal allocated to the client is configured to operate + * in cooked mode, and with XTABS CRMOD enabled (see tty(4)) */ tcgetattr(0, &termbuf); termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */ termbuf.c_oflag |= ONLCR | XTABS; @@ -304,46 +533,42 @@ make_new_session( /*termbuf.c_lflag &= ~ICANON;*/ tcsetattr_stdin_TCSANOW(&termbuf); - /* Uses FILE-based I/O to stdout, but does fflush(stdout), + /* Uses FILE-based I/O to stdout, but does fflush_all(), * so should be safe with vfork. * I fear, though, that some users will have ridiculously big * issue files, and they may block writing to fd 1, * (parent is supposed to read it, but parent waits * for vforked child to exec!) */ - print_login_issue(issuefile, tty_name); + print_login_issue(G.issuefile, tty_name); /* Exec shell / login / whatever */ - login_argv[0] = loginpath; + login_argv[0] = G.loginpath; login_argv[1] = NULL; /* exec busybox applet (if PREFER_APPLETS=y), if that fails, - * exec external program */ - BB_EXECVP(loginpath, (char **)login_argv); + * exec external program. + * NB: sock is either 0 or has CLOEXEC set on it. + * fd has CLOEXEC set on it too. These two fds will be closed here. + */ + BB_EXECVP(G.loginpath, (char **)login_argv); /* _exit is safer with vfork, and we shouldn't send message * to remote clients anyway */ - _exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", loginpath);*/ + _exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", G.loginpath);*/ } -/* Must match getopt32 string */ -enum { - OPT_WATCHCHILD = (1 << 2), /* -K */ - OPT_INETD = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */ - OPT_PORT = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p */ - OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */ -}; - #if ENABLE_FEATURE_TELNETD_STANDALONE static void free_session(struct tsession *ts) { - struct tsession *t = sessions; + struct tsession *t; if (option_mask32 & OPT_INETD) exit(EXIT_SUCCESS); /* Unlink this telnet session from the session list */ + t = G.sessions; if (t == ts) - sessions = ts->next; + G.sessions = ts->next; else { while (t->next != ts) t = t->next; @@ -355,7 +580,7 @@ free_session(struct tsession *ts) * doesn't send SIGKILL. When we close ptyfd, * kernel sends SIGHUP to processes having slave side opened. */ kill(ts->shell_pid, SIGKILL); - wait4(ts->shell_pid, NULL, 0, NULL); + waitpid(ts->shell_pid, NULL, 0); #endif close(ts->ptyfd); close(ts->sockfd_read); @@ -365,17 +590,17 @@ free_session(struct tsession *ts) free(ts); /* Scan all sessions and find new maxfd */ - maxfd = 0; - ts = sessions; + G.maxfd = 0; + ts = G.sessions; while (ts) { - if (maxfd < ts->ptyfd) - maxfd = ts->ptyfd; - if (maxfd < ts->sockfd_read) - maxfd = ts->sockfd_read; + if (G.maxfd < ts->ptyfd) + G.maxfd = ts->ptyfd; + if (G.maxfd < ts->sockfd_read) + G.maxfd = ts->sockfd_read; #if 0 /* Again, sockfd_write == sockfd_read here */ - if (maxfd < ts->sockfd_write) - maxfd = ts->sockfd_write; + if (G.maxfd < ts->sockfd_write) + G.maxfd = ts->sockfd_write; #endif ts = ts->next; } @@ -392,21 +617,25 @@ static void handle_sigchld(int sig UNUSED_PARAM) { pid_t pid; struct tsession *ts; + int save_errno = errno; /* Looping: more than one child may have exited */ while (1) { pid = wait_any_nohang(NULL); if (pid <= 0) break; - ts = sessions; + ts = G.sessions; while (ts) { if (ts->shell_pid == pid) { ts->shell_pid = -1; + update_utmp_DEAD_PROCESS(pid); break; } ts = ts->next; } } + + errno = save_errno; } int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; @@ -418,22 +647,29 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) struct tsession *ts; #if ENABLE_FEATURE_TELNETD_STANDALONE #define IS_INETD (opt & OPT_INETD) - int master_fd = master_fd; /* be happy, gcc */ - unsigned portnbr = 23; + int master_fd = master_fd; /* for compiler */ + int sec_linger = sec_linger; char *opt_bindaddr = NULL; char *opt_portnbr; #else enum { IS_INETD = 1, master_fd = -1, - portnbr = 23, }; #endif + INIT_G(); + + /* -w NUM, and implies -F. -w and -i don't mix */ + IF_FEATURE_TELNETD_INETD_WAIT(opt_complementary = "wF:i--w:w--i";) /* Even if !STANDALONE, we accept (and ignore) -i, thus people * don't need to guess whether it's ok to pass -i to us */ - opt = getopt32(argv, "f:l:Ki" USE_FEATURE_TELNETD_STANDALONE("p:b:F"), - &issuefile, &loginpath - USE_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr)); + opt = getopt32(argv, "f:l:Ki" + IF_FEATURE_TELNETD_STANDALONE("p:b:F") + IF_FEATURE_TELNETD_INETD_WAIT("Sw:+"), + &G.issuefile, &G.loginpath + IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr) + IF_FEATURE_TELNETD_INETD_WAIT(, &sec_linger) + ); if (!IS_INETD /*&& !re_execed*/) { /* inform that we start in standalone mode? * May be useful when people forget to give -i */ @@ -445,31 +681,30 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) } } /* Redirect log to syslog early, if needed */ - if (IS_INETD || !(opt & OPT_FOREGROUND)) { - openlog(applet_name, 0, LOG_USER); + if (IS_INETD || (opt & OPT_SYSLOG) || !(opt & OPT_FOREGROUND)) { + openlog(applet_name, LOG_PID, LOG_DAEMON); logmode = LOGMODE_SYSLOG; } - USE_FEATURE_TELNETD_STANDALONE( - if (opt & OPT_PORT) - portnbr = xatou16(opt_portnbr); - ); - - /* Used to check access(loginpath, X_OK) here. Pointless. - * exec will do this for us for free later. */ - #if ENABLE_FEATURE_TELNETD_STANDALONE if (IS_INETD) { - sessions = make_new_session(0); - if (!sessions) /* pty opening or vfork problem, exit */ - return 1; /* make_new_session prints error message */ + G.sessions = make_new_session(0); + if (!G.sessions) /* pty opening or vfork problem, exit */ + return 1; /* make_new_session printed error message */ } else { - master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr); - xlisten(master_fd, 1); + master_fd = 0; + if (!(opt & OPT_WAIT)) { + unsigned portnbr = 23; + if (opt & OPT_PORT) + portnbr = xatou16(opt_portnbr); + master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr); + xlisten(master_fd, 1); + } + close_on_exec_on(master_fd); } #else - sessions = make_new_session(); - if (!sessions) /* pty opening or vfork problem, exit */ - return 1; /* make_new_session prints error message */ + G.sessions = make_new_session(); + if (!G.sessions) /* pty opening or vfork problem, exit */ + return 1; /* make_new_session printed error message */ #endif /* We don't want to die if just one session is broken */ @@ -481,8 +716,8 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) signal(SIGCHLD, SIG_IGN); /* - This is how the buffers are used. The arrows indicate the movement - of data. + This is how the buffers are used. The arrows indicate data flow. + +-------+ wridx1++ +------+ rdidx1++ +----------+ | | <-------------- | buf1 | <-------------- | | | | size1-- +------+ size1++ | | @@ -506,9 +741,9 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) * ptys if there is room in their session buffers. * NB: scalability problem: we recalculate entire bitmap * before each select. Can be a problem with 500+ connections. */ - ts = sessions; + ts = G.sessions; while (ts) { - struct tsession *next = ts->next; /* in case we free ts. */ + struct tsession *next = ts->next; /* in case we free ts */ if (ts->shell_pid == -1) { /* Child died and we detected that */ free_session(ts); @@ -529,16 +764,29 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) /* This is needed because free_session() does not * take master_fd into account when it finds new * maxfd among remaining fd's */ - if (master_fd > maxfd) - maxfd = master_fd; + if (master_fd > G.maxfd) + G.maxfd = master_fd; } - count = select(maxfd + 1, &rdfdset, &wrfdset, NULL, NULL); + { + struct timeval *tv_ptr = NULL; +#if ENABLE_FEATURE_TELNETD_INETD_WAIT + struct timeval tv; + if ((opt & OPT_WAIT) && !G.sessions) { + tv.tv_sec = sec_linger; + tv.tv_usec = 0; + tv_ptr = &tv; + } +#endif + count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, tv_ptr); + } + if (count == 0) /* "telnetd -w SEC" timed out */ + return 0; if (count < 0) goto again; /* EINTR or ENOMEM */ #if ENABLE_FEATURE_TELNETD_STANDALONE - /* First check for and accept new sessions. */ + /* Check for and accept new sessions */ if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) { int fd; struct tsession *new_ts; @@ -546,80 +794,65 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) fd = accept(master_fd, NULL, NULL); if (fd < 0) goto again; - /* Create a new session and link it into our active list */ + close_on_exec_on(fd); + + /* Create a new session and link it into active list */ new_ts = make_new_session(fd); if (new_ts) { - new_ts->next = sessions; - sessions = new_ts; + new_ts->next = G.sessions; + G.sessions = new_ts; } else { close(fd); } } #endif - /* Then check for data tunneling. */ - ts = sessions; + /* Then check for data tunneling */ + ts = G.sessions; while (ts) { /* For all sessions... */ - struct tsession *next = ts->next; /* in case we free ts. */ + struct tsession *next = ts->next; /* in case we free ts */ if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) { - int num_totty; - unsigned char *ptr; - /* Write to pty from buffer 1. */ - ptr = remove_iacs(ts, &num_totty); - count = safe_write(ts->ptyfd, ptr, num_totty); + /* Write to pty from buffer 1 */ + count = safe_write_to_pty_decode_iac(ts); if (count < 0) { if (errno == EAGAIN) goto skip1; goto kill_session; } - ts->size1 -= count; - ts->wridx1 += count; - if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */ - ts->wridx1 = 0; } skip1: if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) { - /* Write to socket from buffer 2. */ + /* Write to socket from buffer 2 */ count = MIN(BUFSIZE - ts->wridx2, ts->size2); - count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2 + ts->wridx2), count); + count = safe_write_double_iac(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count); if (count < 0) { if (errno == EAGAIN) goto skip2; goto kill_session; } - ts->size2 -= count; ts->wridx2 += count; if (ts->wridx2 >= BUFSIZE) /* actually == BUFSIZE */ ts->wridx2 = 0; + ts->size2 -= count; + if (ts->size2 == 0) { + ts->rdidx2 = 0; + ts->wridx2 = 0; + } } skip2: - /* Should not be needed, but... remove_iacs is actually buggy - * (it cannot process iacs which wrap around buffer's end)! - * Since properly fixing it requires writing bigger code, - * we rely instead on this code making it virtually impossible - * to have wrapped iac (people don't type at 2k/second). - * It also allows for bigger reads in common case. */ - if (ts->size1 == 0) { - ts->rdidx1 = 0; - ts->wridx1 = 0; - } - if (ts->size2 == 0) { - ts->rdidx2 = 0; - ts->wridx2 = 0; - } if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) { - /* Read from socket to buffer 1. */ + /* Read from socket to buffer 1 */ count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1); - count = safe_read(ts->sockfd_read, TS_BUF1 + ts->rdidx1, count); + count = safe_read(ts->sockfd_read, TS_BUF1(ts) + ts->rdidx1, count); if (count <= 0) { if (count < 0 && errno == EAGAIN) goto skip3; goto kill_session; } /* Ignore trailing NUL if it is there */ - if (!TS_BUF1[ts->rdidx1 + count - 1]) { + if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) { --count; } ts->size1 += count; @@ -629,9 +862,9 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) } skip3: if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) { - /* Read from pty to buffer 2. */ + /* Read from pty to buffer 2 */ count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2); - count = safe_read(ts->ptyfd, TS_BUF2 + ts->rdidx2, count); + count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count); if (count <= 0) { if (count < 0 && errno == EAGAIN) goto skip4; @@ -646,6 +879,8 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) ts = next; continue; kill_session: + if (ts->shell_pid > 0) + update_utmp_DEAD_PROCESS(ts->shell_pid); free_session(ts); ts = next; }