X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=networking%2Ftelnetd.c;h=33020f1b416436d6ad1315459704637401ca4a40;hb=3a9365e2732f5df2cdef758bc1f6e5e9da8fbcef;hp=9ce793fb7fa7a4cddcb424fda9cad81416ec533e;hpb=59d7c43dbe502ef7425f6828bb43528c5adfc9a9;p=oweals%2Fbusybox.git diff --git a/networking/telnetd.c b/networking/telnetd.c index 9ce793fb7..33020f1b4 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 @@ -11,40 +11,61 @@ * * 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 */ +//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 #if DEBUG -#define TELCMDS -#define TELOPTS +# define TELCMDS +# define TELOPTS #endif #include -#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; /* two circular buffers */ /*char *buf1, *buf2;*/ -/*#define TS_BUF1 ts->buf1*/ -/*#define TS_BUF2 TS_BUF2*/ -#define TS_BUF1 ((char*)(ts + 1)) -#define TS_BUF2 (((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; }; @@ -55,14 +76,17 @@ enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 }; /* Globals */ -static int maxfd; -static struct tsession *sessions; -#if ENABLE_LOGIN -static const char *loginpath = "/bin/login"; -#else -static const char *loginpath = DEFAULT_SHELL; -#endif -static const char *issuefile = "/etc/issue.net"; +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 { \ + G.loginpath = "/bin/login"; \ + G.issuefile = "/etc/issue.net"; \ +} while (0) /* @@ -71,169 +95,193 @@ static const char *issuefile = "/etc/issue.net"; 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. + 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 + 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. - FIXME - if we mean to send 0xFF to the terminal then it will be escaped, - what is the escape character? We aren't handling that situation here. + CR-LF ->'s CR mapping is also done here, for convenience. - CR-LF ->'s CR mapping is also done here, for convenience + NB: may fail to remove iacs which wrap around buffer! */ -static char * +static unsigned char * remove_iacs(struct tsession *ts, int *pnum_totty) { - unsigned char *ptr0 = (unsigned char *)TS_BUF1 + ts->wridx1; + 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 processed; int num_totty; while (ptr < end) { if (*ptr != IAC) { - int c = *ptr; - *totty++ = *ptr++; - /* We now map \r\n ==> \r for pragmatic reasons. + 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 == '\n' || *ptr == 0) && ptr < end) + if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0')) ptr++; - } else { - /* - * TELOPT_NAWS support! - */ - 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; - } + continue; + } - /* - * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE - */ - else if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) { - 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]; - ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); - ptr += 9; - } else { - /* skip 3-byte IAC non-SB cmd */ + 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; + } + + /* + * TELOPT_NAWS support! + */ + 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; + } + /* + * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE + */ + if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) { + 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]; + ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); + ptr += 9; + continue; + } + /* skip 3-byte IAC non-SB cmd */ #if DEBUG - fprintf(stderr, "Ignoring IAC %s,%s\n", - TELCMD(ptr[1]), TELOPT(ptr[2])); + fprintf(stderr, "Ignoring IAC %s,%s\n", + TELCMD(ptr[1]), TELOPT(ptr[2])); #endif - ptr += 3; - } - } + ptr += 3; } - processed = ptr - ptr0; num_totty = totty - ptr0; - /* the difference between processed and num_to tty - is all the iacs we removed from the stream. - Adjust buf1 accordingly. */ - ts->wridx1 += processed - num_totty; - ts->size1 -= processed - num_totty; *pnum_totty = num_totty; - /* move the chars meant for the terminal towards the end of the - buffer. */ + /* 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); } - -static int -getpty(char *line, int size) +/* + * Converting single IAC into double on output + */ +static size_t iac_safe_write(int fd, const char *buf, size_t count) { - int p; -#if ENABLE_FEATURE_DEVPTS - p = open("/dev/ptmx", O_RDWR); - if (p > 0) { - const char *name; - grantpt(p); - unlockpt(p); - name = ptsname(p); - if (!name) { - bb_perror_msg("ptsname error (is /dev/pts mounted?)"); - return -1; - } - safe_strncpy(line, name, size); - return p; - } -#else - struct stat stb; - int i; - int j; - - strcpy(line, "/dev/ptyXX"); - - for (i = 0; i < 16; i++) { - line[8] = "pqrstuvwxyzabcde"[i]; - line[9] = '0'; - if (stat(line, &stb) < 0) { + 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); + if (rc != 2) + break; + buf++; + total++; + count--; continue; } - for (j = 0; j < 16; j++) { - line[9] = j < 10 ? j + '0' : j - 10 + 'a'; - if (DEBUG) - fprintf(stderr, "Trying to open device: %s\n", line); - p = open(line, O_RDWR | O_NOCTTY); - if (p >= 0) { - line[5] = 't'; - return p; - } - } + /* 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; } -#endif /* FEATURE_DEVPTS */ - return -1; + 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_r, int sock_w) - 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; - char tty_name[32]; + 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 = getpty(tty_name, 32); - if (fd < 0) { - bb_error_msg("can't create pty"); - return NULL; - } - if (fd > maxfd) maxfd = fd; + /* 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(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1)); #if ENABLE_FEATURE_TELNETD_STANDALONE - if (sock_w > maxfd) maxfd = sock_w; - ts->sockfd_write = sock_w; - ndelay_on(sock_w); - if (sock_r > maxfd) maxfd = sock_r; - ts->sockfd_read = sock_r; - ndelay_on(sock_r); + 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_write = 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 @@ -242,68 +290,102 @@ 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 }; - memcpy(TS_BUF2, iacs_to_send, sizeof(iacs_to_send)); - ts->rdidx2 = sizeof(iacs_to_send); - ts->size2 = sizeof(iacs_to_send); + /* This confuses iac_safe_write(), 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(NULL); /* flush all streams */ + fflush_all(); pid = vfork(); /* NOMMU-friendly */ if (pid < 0) { free(ts); close(fd); - /* sock_r and sock_w will be closed by caller */ + /* sock will be closed by caller */ bb_perror_msg("vfork"); return NULL; } if (pid > 0) { /* Parent */ - /*ts->shell_pid = pid;*/ + ts->shell_pid = pid; return ts; } /* Child */ /* Careful - we are after vfork! */ - /* make new session and process group */ + /* 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. */ + /* 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! */ - fd = xopen(tty_name, O_RDWR); /* becomes our ctty */ - dup2(fd, 0); - dup2(fd, 1); - dup2(fd, 2); - while (fd > 2) close(fd--); - 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)). */ + 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(0, TCSANOW, &termbuf); + 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. */ - print_login_issue(issuefile, NULL); + * 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] = loginpath; + login_argv[0] = G.loginpath; login_argv[1] = NULL; - execvp(loginpath, (char **)login_argv); - /* Safer with vfork, and we shouldn't send this to the client anyway */ - _exit(1); /*bb_perror_msg_and_die("execv %s", loginpath);*/ + /* 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 @@ -311,124 +393,172 @@ make_new_session( 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; 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); - wait4(ts->shell_pid, NULL, 0, NULL);*/ + kill(ts->shell_pid, SIGKILL); + waitpid(ts->shell_pid, NULL, 0); +#endif close(ts->ptyfd); close(ts->sockfd_read); - /* error if ts->sockfd_read == ts->sockfd_write. So what? ;) */ - close(ts->sockfd_write); + /* 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 */ - ts = sessions; - maxfd = 0; + 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 (maxfd < ts->sockfd_write) - maxfd = ts->sockfd_write; + 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 */ -/* Never actually called */ -void free_session(struct tsession *ts); +/* 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; +// 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); + break; + } + ts = ts->next; + } + } + + errno = save_errno; +} int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; -int telnetd_main(int argc, char **argv) +int telnetd_main(int argc UNUSED_PARAM, char **argv) { fd_set rdfdset, wrfdset; unsigned opt; - int selret, maxlen, w, r; + int count; 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 - enum { - OPT_INETD = (1 << 2) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */ - OPT_PORT = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p */ - OPT_FOREGROUND = (1 << 5) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */ - }; + INIT_G(); - /* If !STANDALONE, we accept (and ignore) -i, thus people + /* -w NUM, and implies -F. -w and -i don't mix */ + IF_FEATURE_TELNETD_INETD_WAIT(opt_complementary = "wF:w+: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:i" 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 */ + /*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_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; } - //if (opt & 1) // -f - //if (opt & 2) // -l - USE_FEATURE_TELNETD_STANDALONE( - if (opt & OPT_PORT) // -p - portnbr = xatou16(opt_portnbr); - //if (opt & 8) // -b - //if (opt & 0x10) // -F - //if (opt & 0x20) // -i - ); - - /* 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, 1); - 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 { -//vda: inform that we start in standalone mode? - master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr); - xlisten(master_fd, 1); - if (!(opt & OPT_FOREGROUND)) -//vda: NOMMU? - bb_daemonize(DAEMON_CHDIR_ROOT); + 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 */ 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 the movement - of data. + This is how the buffers are used. The arrows indicate data flow. + +-------+ wridx1++ +------+ rdidx1++ +----------+ | | <-------------- | buf1 | <-------------- | | | | size1-- +------+ size1++ | | @@ -447,38 +577,57 @@ int telnetd_main(int argc, char **argv) again: FD_ZERO(&rdfdset); FD_ZERO(&wrfdset); - if (!IS_INETD) { - FD_SET(master_fd, &rdfdset); - /* This is needed because free_session() does not - * take into account master_fd when it finds new - * maxfd among remaining fd's: */ - if (master_fd > maxfd) - maxfd = master_fd; - } /* 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 = sessions; + ts = G.sessions; while (ts) { - 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 = ts->next; + 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; } - selret = select(maxfd + 1, &rdfdset, &wrfdset, NULL, NULL); - if (selret < 0) + { + 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; @@ -486,64 +635,62 @@ int telnetd_main(int argc, 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(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 = 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; - char *ptr; - /* Write to pty from buffer 1. */ + unsigned char *ptr; + /* Write to pty from buffer 1 */ ptr = remove_iacs(ts, &num_totty); - w = safe_write(ts->ptyfd, ptr, num_totty); - if (w < 0) { + count = safe_write(ts->ptyfd, ptr, num_totty); + if (count < 0) { if (errno == EAGAIN) goto skip1; - if (IS_INETD) - return 0; - free_session(ts); - ts = next; - continue; + goto kill_session; } - ts->size1 -= w; - ts->wridx1 += w; + 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. */ - maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2); - w = safe_write(ts->sockfd_write, TS_BUF2 + ts->wridx2, maxlen); - if (w < 0) { + /* 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) { if (errno == EAGAIN) goto skip2; - if (IS_INETD) - return 0; - free_session(ts); - ts = next; - continue; + goto kill_session; } - ts->size2 -= w; - ts->wridx2 += w; + ts->size2 -= count; + ts->wridx2 += count; if (ts->wridx2 >= BUFSIZE) /* actually == BUFSIZE */ ts->wridx2 = 0; } skip2: -#if 0 - /* Not strictly needed, but allows for bigger reads in common case */ + /* 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; @@ -552,51 +699,49 @@ int telnetd_main(int argc, char **argv) ts->rdidx2 = 0; ts->wridx2 = 0; } -#endif + if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) { - /* Read from socket to buffer 1. */ - maxlen = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1); - r = safe_read(ts->sockfd_read, TS_BUF1 + ts->rdidx1, maxlen); - if (r <= 0) { - if (r < 0 && errno == EAGAIN) + /* 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; - if (IS_INETD) - return 0; - free_session(ts); - ts = next; - continue; + goto kill_session; } /* Ignore trailing NUL if it is there */ - if (!TS_BUF1[ts->rdidx1 + r - 1]) { - if (!--r) - goto skip3; + if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) { + --count; } - ts->size1 += r; - ts->rdidx1 += r; + 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. */ - maxlen = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2); - r = safe_read(ts->ptyfd, TS_BUF2 + ts->rdidx2, maxlen); - if (r <= 0) { - if (r < 0 && errno == EAGAIN) + /* 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; - if (IS_INETD) - return 0; - free_session(ts); - ts = next; - continue; + goto kill_session; } - ts->size2 += r; - ts->rdidx2 += r; + 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(ts->shell_pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL); + free_session(ts); + ts = next; } + goto again; }