diff options
| -rw-r--r-- | networking/telnetd.c | 90 |
1 files changed, 39 insertions, 51 deletions
diff --git a/networking/telnetd.c b/networking/telnetd.c index 6a8190b..540387f 100644 --- a/networking/telnetd.c +++ b/networking/telnetd.c @@ -32,11 +32,12 @@ #endif #include <arpa/telnet.h> -/* Structure that describes a session */ struct tsession { struct tsession *next; pid_t shell_pid; - int sockfd_read, sockfd_write, ptyfd; + int sockfd_read; + int sockfd_write; + int ptyfd; /* two circular buffers */ /*char *buf1, *buf2;*/ @@ -125,9 +126,9 @@ remove_iacs(struct tsession *ts, int *pnum_totty) * TELOPT_NAWS support! */ if ((ptr+2) >= end) { - /* only the beginning of the IAC is in the + /* Only the beginning of the IAC is in the buffer we were asked to process, we can't - process this char. */ + process this char */ break; } /* @@ -153,13 +154,13 @@ remove_iacs(struct tsession *ts, int *pnum_totty) 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. */ + /* 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 */ + /* Move chars meant for the terminal towards the end of the buffer */ return memmove(ptr - num_totty, ptr0, num_totty); } @@ -216,7 +217,7 @@ enum { static struct tsession * make_new_session( - IF_FEATURE_TELNETD_STANDALONE(int master_fd, int sock) + IF_FEATURE_TELNETD_STANDALONE(int sock) IF_NOT_FEATURE_TELNETD_STANDALONE(void) ) { const char *login_argv[2]; @@ -228,18 +229,20 @@ 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 > G.maxfd) G.maxfd = fd; ts->ptyfd = fd; ndelay_on(fd); + close_on_exec_on(fd); + #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)); + ts->sockfd_read = sock; 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); } @@ -254,6 +257,7 @@ make_new_session( 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 @@ -303,42 +307,20 @@ make_new_session( /* Restore default signal handling ASAP */ bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL); -#if ENABLE_FEATURE_TELNETD_STANDALONE - if (!(option_mask32 & OPT_INETD)) { - struct tsession *tp = G.sessions; - while (tp) { - close(tp->ptyfd); - close(tp->sockfd_read); - /* sockfd_write == sockfd_read for standalone telnetd */ - /*close(tp->sockfd_write);*/ - tp = tp->next; - } - } -#endif - /* Make new session and process group */ setsid(); - close(fd); -#if ENABLE_FEATURE_TELNETD_STANDALONE - if (master_fd >= 0) - close(master_fd); - close(sock); -#endif - /* Open the child's side of the tty. */ + /* 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! */ -#if ENABLE_FEATURE_TELNETD_STANDALONE - if (sock != 0) /* if we did not close 0 already */ -#endif - close(0); + 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 */ - /* 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; @@ -359,7 +341,10 @@ make_new_session( login_argv[0] = G.loginpath; login_argv[1] = NULL; /* exec busybox applet (if PREFER_APPLETS=y), if that fails, - * exec external program */ + * 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 */ @@ -496,12 +481,13 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) #if ENABLE_FEATURE_TELNETD_STANDALONE if (IS_INETD) { - G.sessions = make_new_session(-1, 0); + G.sessions = make_new_session(0); if (!G.sessions) /* pty opening or vfork problem, exit */ return 1; /* make_new_session prints error message */ } else { 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(); @@ -518,8 +504,8 @@ 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++ | | @@ -545,7 +531,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) * 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. */ + struct tsession *next = ts->next; /* in case we free ts */ if (ts->shell_pid == -1) { /* Child died and we detected that */ free_session(ts); @@ -575,7 +561,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) 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; @@ -583,8 +569,10 @@ 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 */ - new_ts = make_new_session(master_fd, fd); + 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; @@ -594,15 +582,15 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) } #endif - /* Then check for data tunneling. */ + /* 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. */ + /* Write to pty from buffer 1 */ ptr = remove_iacs(ts, &num_totty); count = safe_write(ts->ptyfd, ptr, num_totty); if (count < 0) { @@ -617,7 +605,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) } 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) + ts->wridx2), count); if (count < 0) { @@ -647,7 +635,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) } 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) + ts->rdidx1, count); if (count <= 0) { @@ -666,7 +654,7 @@ 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) + ts->rdidx2, count); if (count <= 0) { |