mirror of
https://github.com/sheumann/hush.git
synced 2024-09-08 20:54:39 +00:00
A bit of future-proofing. Some of them can stand just being ignored. function old new delta telnetd_main 1791 1798 +7 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
805 lines
22 KiB
C
805 lines
22 KiB
C
/* vi: set sw=4 ts=4: */
|
|
/*
|
|
* Simple telnet server
|
|
* Bjorn Wesen, Axis Communications AB (bjornw@axis.com)
|
|
*
|
|
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
|
|
*
|
|
* ---------------------------------------------------------------------------
|
|
* (C) Copyright 2000, Axis Communications AB, LUND, SWEDEN
|
|
****************************************************************************
|
|
*
|
|
* 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.
|
|
*
|
|
* Vladimir Oleynik <dzo@simtreas.ru> 2001
|
|
* Set process group corrections, initial busybox port
|
|
*/
|
|
|
|
//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 <syslog.h>
|
|
|
|
#if DEBUG
|
|
# define TELCMDS
|
|
# define TELOPTS
|
|
#endif
|
|
#include <arpa/telnet.h>
|
|
|
|
|
|
struct tsession {
|
|
struct tsession *next;
|
|
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) 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;
|
|
};
|
|
|
|
/* Two buffers are directly after tsession in malloced memory.
|
|
* Make whole thing fit in 4k */
|
|
enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 };
|
|
|
|
|
|
/* Globals */
|
|
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 ssize_t
|
|
safe_write_to_pty_decode_iac(struct tsession *ts)
|
|
{
|
|
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;
|
|
}
|
|
|
|
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;
|
|
|
|
/* 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.
|
|
*/
|
|
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
|
|
*/
|
|
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);
|
|
if (rc <= 0)
|
|
return rc;
|
|
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 (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);
|
|
rc = 7;
|
|
/* trailing IAC SE will be eaten separately, as 2-byte NOP */
|
|
goto update_and_return;
|
|
}
|
|
/* 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(buf[1]), TELOPT(buf[2]));
|
|
#endif
|
|
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;
|
|
}
|
|
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 safe_write_double_iac(int fd, const char *buf, size_t count)
|
|
{
|
|
const char *IACptr;
|
|
size_t wr, rc, total;
|
|
|
|
total = 0;
|
|
while (1) {
|
|
if (count == 0)
|
|
return total;
|
|
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++;
|
|
total++;
|
|
count--;
|
|
continue;
|
|
}
|
|
/* count != 0, *buf != IAC */
|
|
IACptr = memchr(buf, IAC, count);
|
|
wr = count;
|
|
if (IACptr)
|
|
wr = IACptr - buf;
|
|
rc = safe_write(fd, buf, wr);
|
|
if (rc != wr)
|
|
break;
|
|
buf += rc;
|
|
total += rc;
|
|
count -= rc;
|
|
}
|
|
/* here: rc - result of last short write */
|
|
if ((ssize_t)rc < 0) { /* error? */
|
|
if (total == 0)
|
|
return rc;
|
|
rc = 0;
|
|
}
|
|
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(
|
|
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;
|
|
char tty_name[GETPTY_BUFSIZE];
|
|
struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2);
|
|
|
|
/*ts->buf1 = (char *)(ts + 1);*/
|
|
/*ts->buf2 = ts->buf1 + BUFSIZE;*/
|
|
|
|
/* Got a new connection, set up a tty */
|
|
fd = xgetpty(tty_name);
|
|
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;
|
|
ndelay_on(sock);
|
|
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 > G.maxfd)
|
|
G.maxfd = sock;
|
|
#else
|
|
/* 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
|
|
* stuff that requires char-by-char support. */
|
|
{
|
|
static const char iacs_to_send[] ALIGN1 = {
|
|
IAC, DO, TELOPT_ECHO,
|
|
IAC, DO, TELOPT_NAWS,
|
|
/* This requires telnetd.ctrlSQ.patch (incomplete) */
|
|
/*IAC, DO, TELOPT_LFLOW,*/
|
|
IAC, WILL, TELOPT_ECHO,
|
|
IAC, WILL, TELOPT_SGA
|
|
};
|
|
/* 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);
|
|
//ts->size2 = sizeof(iacs_to_send);
|
|
/* 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));
|
|
#else
|
|
safe_write(1, iacs_to_send, sizeof(iacs_to_send));
|
|
#endif
|
|
/*ts->rdidx2 = 0; - xzalloc did it */
|
|
/*ts->size2 = 0;*/
|
|
}
|
|
|
|
fflush_all();
|
|
pid = vfork(); /* NOMMU-friendly */
|
|
if (pid < 0) {
|
|
free(ts);
|
|
close(fd);
|
|
/* sock will be closed by caller */
|
|
bb_perror_msg("vfork");
|
|
return NULL;
|
|
}
|
|
if (pid > 0) {
|
|
/* Parent */
|
|
ts->shell_pid = pid;
|
|
return ts;
|
|
}
|
|
|
|
/* Child */
|
|
/* Careful - we are after vfork! */
|
|
|
|
/* Restore default signal handling ASAP */
|
|
bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
|
|
|
|
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, 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)) */
|
|
tcgetattr(0, &termbuf);
|
|
termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */
|
|
termbuf.c_oflag |= ONLCR | XTABS;
|
|
termbuf.c_iflag |= ICRNL;
|
|
termbuf.c_iflag &= ~IXOFF;
|
|
/*termbuf.c_lflag &= ~ICANON;*/
|
|
tcsetattr_stdin_TCSANOW(&termbuf);
|
|
|
|
/* 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(G.issuefile, tty_name);
|
|
|
|
/* Exec shell / login / whatever */
|
|
login_argv[0] = G.loginpath;
|
|
login_argv[1] = NULL;
|
|
/* exec busybox applet (if PREFER_APPLETS=y), if that fails,
|
|
* 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", G.loginpath);*/
|
|
}
|
|
|
|
#if ENABLE_FEATURE_TELNETD_STANDALONE
|
|
|
|
static void
|
|
free_session(struct tsession *ts)
|
|
{
|
|
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)
|
|
G.sessions = ts->next;
|
|
else {
|
|
while (t->next != ts)
|
|
t = t->next;
|
|
t->next = ts->next;
|
|
}
|
|
|
|
#if 0
|
|
/* It was said that "normal" telnetd just closes ptyfd,
|
|
* doesn't send SIGKILL. When we close ptyfd,
|
|
* kernel sends SIGHUP to processes having slave side opened. */
|
|
kill(ts->shell_pid, SIGKILL);
|
|
waitpid(ts->shell_pid, NULL, 0);
|
|
#endif
|
|
close(ts->ptyfd);
|
|
close(ts->sockfd_read);
|
|
/* We do not need to close(ts->sockfd_write), it's the same
|
|
* as sockfd_read unless we are in inetd mode. But in inetd mode
|
|
* we do not reach this */
|
|
free(ts);
|
|
|
|
/* Scan all sessions and find new maxfd */
|
|
G.maxfd = 0;
|
|
ts = G.sessions;
|
|
while (ts) {
|
|
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 (G.maxfd < ts->sockfd_write)
|
|
G.maxfd = ts->sockfd_write;
|
|
#endif
|
|
ts = ts->next;
|
|
}
|
|
}
|
|
|
|
#else /* !FEATURE_TELNETD_STANDALONE */
|
|
|
|
/* Used in main() only, thus "return 0" actually is exit(EXIT_SUCCESS). */
|
|
#define free_session(ts) return 0
|
|
|
|
#endif
|
|
|
|
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 = 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;
|
|
int telnetd_main(int argc UNUSED_PARAM, char **argv)
|
|
{
|
|
fd_set rdfdset, wrfdset;
|
|
unsigned opt;
|
|
int count;
|
|
struct tsession *ts;
|
|
#if ENABLE_FEATURE_TELNETD_STANDALONE
|
|
#define IS_INETD (opt & OPT_INETD)
|
|
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,
|
|
};
|
|
#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"
|
|
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 */
|
|
/*bb_error_msg("listening for connections");*/
|
|
if (!(opt & OPT_FOREGROUND)) {
|
|
/* DAEMON_CHDIR_ROOT was giving inconsistent
|
|
* behavior with/without -F, -i */
|
|
bb_daemonize_or_rexec(0 /*was DAEMON_CHDIR_ROOT*/, argv);
|
|
}
|
|
}
|
|
/* Redirect log to syslog early, if needed */
|
|
if (IS_INETD || (opt & OPT_SYSLOG) || !(opt & OPT_FOREGROUND)) {
|
|
openlog(applet_name, LOG_PID, LOG_DAEMON);
|
|
logmode = LOGMODE_SYSLOG;
|
|
}
|
|
#if ENABLE_FEATURE_TELNETD_STANDALONE
|
|
if (IS_INETD) {
|
|
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 = 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
|
|
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 */
|
|
signal(SIGPIPE, SIG_IGN);
|
|
|
|
if (opt & OPT_WATCHCHILD)
|
|
signal(SIGCHLD, handle_sigchld);
|
|
else /* prevent dead children from becoming zombies */
|
|
signal(SIGCHLD, SIG_IGN);
|
|
|
|
/*
|
|
This is how the buffers are used. The arrows indicate data flow.
|
|
|
|
+-------+ wridx1++ +------+ rdidx1++ +----------+
|
|
| | <-------------- | buf1 | <-------------- | |
|
|
| | size1-- +------+ size1++ | |
|
|
| pty | | socket |
|
|
| | rdidx2++ +------+ wridx2++ | |
|
|
| | --------------> | buf2 | --------------> | |
|
|
+-------+ size2++ +------+ size2-- +----------+
|
|
|
|
size1: "how many bytes are buffered for pty between rdidx1 and wridx1?"
|
|
size2: "how many bytes are buffered for socket between rdidx2 and wridx2?"
|
|
|
|
Each session has got two buffers. Buffers are circular. If sizeN == 0,
|
|
buffer is empty. If sizeN == BUFSIZE, buffer is full. In both these cases
|
|
rdidxN == wridxN.
|
|
*/
|
|
again:
|
|
FD_ZERO(&rdfdset);
|
|
FD_ZERO(&wrfdset);
|
|
|
|
/* Select on the master socket, all telnet sockets and their
|
|
* 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 = G.sessions;
|
|
while (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);
|
|
} else {
|
|
if (ts->size1 > 0) /* can write to pty */
|
|
FD_SET(ts->ptyfd, &wrfdset);
|
|
if (ts->size1 < BUFSIZE) /* can read from socket */
|
|
FD_SET(ts->sockfd_read, &rdfdset);
|
|
if (ts->size2 > 0) /* can write to socket */
|
|
FD_SET(ts->sockfd_write, &wrfdset);
|
|
if (ts->size2 < BUFSIZE) /* can read from pty */
|
|
FD_SET(ts->ptyfd, &rdfdset);
|
|
}
|
|
ts = next;
|
|
}
|
|
if (!IS_INETD) {
|
|
FD_SET(master_fd, &rdfdset);
|
|
/* 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 > G.maxfd)
|
|
G.maxfd = master_fd;
|
|
}
|
|
|
|
{
|
|
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
|
|
/* Check for and accept new sessions */
|
|
if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) {
|
|
int fd;
|
|
struct tsession *new_ts;
|
|
|
|
fd = accept(master_fd, NULL, NULL);
|
|
if (fd < 0)
|
|
goto again;
|
|
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 = G.sessions;
|
|
G.sessions = new_ts;
|
|
} else {
|
|
close(fd);
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/* Then check for data tunneling */
|
|
ts = G.sessions;
|
|
while (ts) { /* For all sessions... */
|
|
struct tsession *next = ts->next; /* in case we free ts */
|
|
|
|
if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) {
|
|
/* 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;
|
|
}
|
|
}
|
|
skip1:
|
|
if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
|
|
/* Write to socket from buffer 2 */
|
|
count = MIN(BUFSIZE - ts->wridx2, ts->size2);
|
|
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->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:
|
|
|
|
if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) {
|
|
/* Read from socket to buffer 1 */
|
|
count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
|
|
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)[ts->rdidx1 + count - 1]) {
|
|
--count;
|
|
}
|
|
ts->size1 += count;
|
|
ts->rdidx1 += count;
|
|
if (ts->rdidx1 >= BUFSIZE) /* actually == BUFSIZE */
|
|
ts->rdidx1 = 0;
|
|
}
|
|
skip3:
|
|
if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
|
|
/* Read from pty to buffer 2 */
|
|
count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
|
|
count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
|
|
if (count <= 0) {
|
|
if (count < 0 && errno == EAGAIN)
|
|
goto skip4;
|
|
goto kill_session;
|
|
}
|
|
ts->size2 += count;
|
|
ts->rdidx2 += count;
|
|
if (ts->rdidx2 >= BUFSIZE) /* actually == BUFSIZE */
|
|
ts->rdidx2 = 0;
|
|
}
|
|
skip4:
|
|
ts = next;
|
|
continue;
|
|
kill_session:
|
|
if (ts->shell_pid > 0)
|
|
update_utmp_DEAD_PROCESS(ts->shell_pid);
|
|
free_session(ts);
|
|
ts = next;
|
|
}
|
|
|
|
goto again;
|
|
}
|