1303 files changed, 32187 insertions, 57138 deletions
diff --git a/networking/telnetd.c b/networking/telnetd.c index d00d87d..f06e958 100644 --- a/networking/telnetd.c +++ b/networking/telnetd.c @@ -20,6 +20,78 @@ * Vladimir Oleynik <dzo@simtreas.ru> 2001 * 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]" @@ -44,6 +116,7 @@ #define DEBUG 0 #include "libbb.h" +#include "common_bufsiz.h" #include <syslog.h> #if DEBUG @@ -59,6 +132,7 @@ struct tsession { int sockfd_read; int sockfd_write; int ptyfd; + smallint buffered_IAC_for_pty; /* two circular buffers */ /*char *buf1, *buf2;*/ @@ -82,114 +156,205 @@ struct globals { const char *issuefile; int maxfd; } FIX_ALIASING; -#define G (*(struct globals*)&bb_common_bufsiz1) +#define G (*(struct globals*)bb_common_bufsiz1) #define INIT_G() do { \ - G.loginpath = "/system/xbin/login"; \ + setup_common_bufsiz(); \ + G.loginpath = "/bin/login"; \ G.issuefile = "/etc/issue.net"; \ } while (0) -/* - 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! +/* 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) + 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. - * See RFC 1123 3.3.1 Telnet End-of-Line Convention. - */ - 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 <cols> <rows> 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 <cols> <rows> 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 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 *IACptr; size_t wr, rc, total; @@ -201,6 +366,7 @@ static size_t iac_safe_write(int fd, const char *buf, size_t count) 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++; @@ -265,7 +431,7 @@ make_new_session( close_on_exec_on(fd); /* SO_KEEPALIVE by popular demand */ - setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1)); + setsockopt_keepalive(sock); #if ENABLE_FEATURE_TELNETD_STANDALONE ts->sockfd_read = sock; ndelay_on(sock); @@ -296,7 +462,7 @@ make_new_session( 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(ts), iacs_to_send, sizeof(iacs_to_send)); //ts->rdidx2 = sizeof(iacs_to_send); @@ -462,15 +628,7 @@ static void handle_sigchld(int sig UNUSED_PARAM) while (ts) { if (ts->shell_pid == pid) { ts->shell_pid = -1; -// man utmp: -// When init(8) finds that a process has exited, it locates its utmp entry -// by ut_pid, sets ut_type to DEAD_PROCESS, and clears ut_user, ut_host -// and ut_time with null bytes. -// [same applies to other processes which maintain utmp entries, like telnetd] -// -// We do not bother actually clearing fields: -// it might be interesting to know who was logged in and from where - update_utmp(pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL); + update_utmp_DEAD_PROCESS(pid); break; } ts = ts->next; @@ -489,8 +647,8 @@ 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 = 0; - int sec_linger = 0; + int master_fd = master_fd; /* for compiler */ + int sec_linger = sec_linger; char *opt_bindaddr = NULL; char *opt_portnbr; #else @@ -502,12 +660,12 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) INIT_G(); /* -w NUM, and implies -F. -w and -i don't mix */ - IF_FEATURE_TELNETD_INETD_WAIT(opt_complementary = "wF:w+:i--w:w--i";) + 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" IF_FEATURE_TELNETD_STANDALONE("p:b:F") - IF_FEATURE_TELNETD_INETD_WAIT("Sw:"), + 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) @@ -655,51 +813,34 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) 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); + 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 */ count = MIN(BUFSIZE - ts->wridx2, ts->size2); - count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + 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 */ @@ -739,7 +880,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) continue; kill_session: if (ts->shell_pid > 0) - update_utmp(ts->shell_pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL); + update_utmp_DEAD_PROCESS(ts->shell_pid); free_session(ts); ts = next; } |