mirror of
https://github.com/sheumann/hush.git
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telnetd: properly close fds in child
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
parent
9d617c44d2
commit
a4bcbd0e04
@ -718,7 +718,7 @@ static void parse_conf(const char *path, int flag)
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/* form "/path/file" */
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sprintf(cur->before_colon, "/%s%.*s",
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path,
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after_colon - buf - 1, /* includes "/", but not ":" */
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(int) (after_colon - buf - 1), /* includes "/", but not ":" */
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buf);
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/* canonicalize it */
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p = bb_simplify_abs_path_inplace(cur->before_colon);
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@ -11,14 +11,14 @@
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*
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* The telnetd manpage says it all:
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*
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* Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for
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* a client, then creating a login process which has the slave side of the
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* pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
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* master side of the pseudo-terminal, implementing the telnet protocol and
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* passing characters between the remote client and the login process.
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* Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for
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* a client, then creating a login process which has the slave side of the
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* pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
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* master side of the pseudo-terminal, implementing the telnet protocol and
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* passing characters between the remote client and the login process.
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*
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* Vladimir Oleynik <dzo@simtreas.ru> 2001
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* Set process group corrections, initial busybox port
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* Set process group corrections, initial busybox port
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*/
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#define DEBUG 0
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@ -40,10 +40,10 @@ struct tsession {
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/* two circular buffers */
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/*char *buf1, *buf2;*/
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/*#define TS_BUF1 ts->buf1*/
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/*#define TS_BUF2 TS_BUF2*/
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#define TS_BUF1 ((unsigned char*)(ts + 1))
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#define TS_BUF2 (((unsigned char*)(ts + 1)) + BUFSIZE)
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/*#define TS_BUF1(ts) ts->buf1*/
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/*#define TS_BUF2(ts) TS_BUF2(ts)*/
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#define TS_BUF1(ts) ((unsigned char*)(ts + 1))
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#define TS_BUF2(ts) (((unsigned char*)(ts + 1)) + BUFSIZE)
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int rdidx1, wridx1, size1;
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int rdidx2, wridx2, size2;
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};
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@ -54,10 +54,17 @@ enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 };
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/* Globals */
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static int maxfd;
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static struct tsession *sessions;
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static const char *loginpath = "/bin/login";
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static const char *issuefile = "/etc/issue.net";
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struct globals {
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struct tsession *sessions;
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const char *loginpath;
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const char *issuefile;
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int maxfd;
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};
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#define G (*(struct globals*)&bb_common_bufsiz1)
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#define INIT_G() do { \
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G.loginpath = "/bin/login"; \
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G.issuefile = "/etc/issue.net"; \
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} while (0)
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/*
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@ -81,7 +88,7 @@ static const char *issuefile = "/etc/issue.net";
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static unsigned char *
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remove_iacs(struct tsession *ts, int *pnum_totty)
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{
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unsigned char *ptr0 = TS_BUF1 + ts->wridx1;
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unsigned char *ptr0 = TS_BUF1(ts) + ts->wridx1;
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unsigned char *ptr = ptr0;
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unsigned char *totty = ptr;
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unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
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@ -199,9 +206,17 @@ static size_t iac_safe_write(int fd, const char *buf, size_t count)
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return total + rc;
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}
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/* Must match getopt32 string */
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enum {
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OPT_WATCHCHILD = (1 << 2), /* -K */
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OPT_INETD = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */
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OPT_PORT = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p */
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OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
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};
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static struct tsession *
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make_new_session(
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IF_FEATURE_TELNETD_STANDALONE(int sock)
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IF_FEATURE_TELNETD_STANDALONE(int master_fd, int sock)
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IF_NOT_FEATURE_TELNETD_STANDALONE(void)
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) {
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const char *login_argv[2];
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@ -215,8 +230,8 @@ make_new_session(
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/* Got a new connection, set up a tty. */
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fd = xgetpty(tty_name);
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if (fd > maxfd)
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maxfd = fd;
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if (fd > G.maxfd)
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G.maxfd = fd;
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ts->ptyfd = fd;
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ndelay_on(fd);
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#if ENABLE_FEATURE_TELNETD_STANDALONE
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@ -229,8 +244,8 @@ make_new_session(
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ndelay_on(sock);
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}
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ts->sockfd_write = sock;
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if (sock > maxfd)
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maxfd = sock;
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if (sock > G.maxfd)
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G.maxfd = sock;
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#else
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/* SO_KEEPALIVE by popular demand */
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setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
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@ -254,7 +269,7 @@ make_new_session(
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};
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/* This confuses iac_safe_write(), it will try to duplicate
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* each IAC... */
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//memcpy(TS_BUF2, iacs_to_send, sizeof(iacs_to_send));
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//memcpy(TS_BUF2(ts), iacs_to_send, sizeof(iacs_to_send));
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//ts->rdidx2 = sizeof(iacs_to_send);
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//ts->size2 = sizeof(iacs_to_send);
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/* So just stuff it into TCP stream! (no error check...) */
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@ -288,13 +303,35 @@ make_new_session(
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/* Restore default signal handling ASAP */
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bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
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#if ENABLE_FEATURE_TELNETD_STANDALONE
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if (!(option_mask32 & OPT_INETD)) {
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struct tsession *tp = G.sessions;
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while (tp) {
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close(tp->ptyfd);
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close(tp->sockfd_read);
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/* sockfd_write == sockfd_read for standalone telnetd */
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/*close(tp->sockfd_write);*/
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tp = tp->next;
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}
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}
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#endif
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/* Make new session and process group */
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setsid();
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close(fd);
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#if ENABLE_FEATURE_TELNETD_STANDALONE
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if (master_fd >= 0)
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close(master_fd);
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close(sock);
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#endif
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/* Open the child's side of the tty. */
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/* NB: setsid() disconnects from any previous ctty's. Therefore
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* we must open child's side of the tty AFTER setsid! */
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close(0);
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#if ENABLE_FEATURE_TELNETD_STANDALONE
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if (sock != 0) /* if we did not close 0 already */
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#endif
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close(0);
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xopen(tty_name, O_RDWR); /* becomes our ctty */
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xdup2(0, 1);
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xdup2(0, 2);
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@ -316,40 +353,32 @@ make_new_session(
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* issue files, and they may block writing to fd 1,
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* (parent is supposed to read it, but parent waits
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* for vforked child to exec!) */
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print_login_issue(issuefile, tty_name);
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print_login_issue(G.issuefile, tty_name);
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/* Exec shell / login / whatever */
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login_argv[0] = loginpath;
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login_argv[0] = G.loginpath;
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login_argv[1] = NULL;
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/* exec busybox applet (if PREFER_APPLETS=y), if that fails,
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* exec external program */
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BB_EXECVP(loginpath, (char **)login_argv);
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BB_EXECVP(G.loginpath, (char **)login_argv);
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/* _exit is safer with vfork, and we shouldn't send message
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* to remote clients anyway */
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_exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", loginpath);*/
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_exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", G.loginpath);*/
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}
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/* Must match getopt32 string */
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enum {
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OPT_WATCHCHILD = (1 << 2), /* -K */
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OPT_INETD = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */
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OPT_PORT = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p */
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OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
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};
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#if ENABLE_FEATURE_TELNETD_STANDALONE
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static void
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free_session(struct tsession *ts)
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{
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struct tsession *t = sessions;
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struct tsession *t = G.sessions;
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if (option_mask32 & OPT_INETD)
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exit(EXIT_SUCCESS);
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/* Unlink this telnet session from the session list */
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if (t == ts)
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sessions = ts->next;
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G.sessions = ts->next;
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else {
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while (t->next != ts)
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t = t->next;
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@ -371,17 +400,17 @@ free_session(struct tsession *ts)
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free(ts);
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/* Scan all sessions and find new maxfd */
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maxfd = 0;
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ts = sessions;
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G.maxfd = 0;
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ts = G.sessions;
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while (ts) {
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if (maxfd < ts->ptyfd)
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maxfd = ts->ptyfd;
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if (maxfd < ts->sockfd_read)
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maxfd = ts->sockfd_read;
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if (G.maxfd < ts->ptyfd)
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G.maxfd = ts->ptyfd;
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if (G.maxfd < ts->sockfd_read)
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G.maxfd = ts->sockfd_read;
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#if 0
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/* Again, sockfd_write == sockfd_read here */
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if (maxfd < ts->sockfd_write)
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maxfd = ts->sockfd_write;
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if (G.maxfd < ts->sockfd_write)
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G.maxfd = ts->sockfd_write;
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#endif
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ts = ts->next;
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}
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@ -404,7 +433,7 @@ static void handle_sigchld(int sig UNUSED_PARAM)
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pid = wait_any_nohang(NULL);
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if (pid <= 0)
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break;
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ts = sessions;
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ts = G.sessions;
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while (ts) {
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if (ts->shell_pid == pid) {
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ts->shell_pid = -1;
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@ -435,10 +464,12 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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portnbr = 23,
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};
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#endif
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INIT_G();
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/* Even if !STANDALONE, we accept (and ignore) -i, thus people
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* don't need to guess whether it's ok to pass -i to us */
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opt = getopt32(argv, "f:l:Ki" IF_FEATURE_TELNETD_STANDALONE("p:b:F"),
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&issuefile, &loginpath
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&G.issuefile, &G.loginpath
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IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr));
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if (!IS_INETD /*&& !re_execed*/) {
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/* inform that we start in standalone mode?
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@ -460,21 +491,21 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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portnbr = xatou16(opt_portnbr);
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);
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/* Used to check access(loginpath, X_OK) here. Pointless.
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/* Used to check access(G.loginpath, X_OK) here. Pointless.
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* exec will do this for us for free later. */
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#if ENABLE_FEATURE_TELNETD_STANDALONE
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if (IS_INETD) {
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sessions = make_new_session(0);
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if (!sessions) /* pty opening or vfork problem, exit */
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G.sessions = make_new_session(-1, 0);
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if (!G.sessions) /* pty opening or vfork problem, exit */
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return 1; /* make_new_session prints error message */
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} else {
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master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr);
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xlisten(master_fd, 1);
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}
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#else
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sessions = make_new_session();
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if (!sessions) /* pty opening or vfork problem, exit */
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G.sessions = make_new_session();
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if (!G.sessions) /* pty opening or vfork problem, exit */
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return 1; /* make_new_session prints error message */
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#endif
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@ -512,7 +543,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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* ptys if there is room in their session buffers.
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* NB: scalability problem: we recalculate entire bitmap
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* before each select. Can be a problem with 500+ connections. */
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ts = sessions;
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ts = G.sessions;
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while (ts) {
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struct tsession *next = ts->next; /* in case we free ts. */
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if (ts->shell_pid == -1) {
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@ -535,11 +566,11 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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/* This is needed because free_session() does not
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* take master_fd into account when it finds new
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* maxfd among remaining fd's */
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if (master_fd > maxfd)
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maxfd = master_fd;
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if (master_fd > G.maxfd)
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G.maxfd = master_fd;
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}
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count = select(maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
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count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
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if (count < 0)
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goto again; /* EINTR or ENOMEM */
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@ -553,10 +584,10 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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if (fd < 0)
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goto again;
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/* Create a new session and link it into our active list */
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new_ts = make_new_session(fd);
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new_ts = make_new_session(master_fd, fd);
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if (new_ts) {
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new_ts->next = sessions;
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sessions = new_ts;
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new_ts->next = G.sessions;
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G.sessions = new_ts;
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} else {
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close(fd);
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}
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@ -564,7 +595,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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#endif
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/* Then check for data tunneling. */
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ts = sessions;
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ts = G.sessions;
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while (ts) { /* For all sessions... */
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struct tsession *next = ts->next; /* in case we free ts. */
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@ -588,7 +619,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
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/* Write to socket from buffer 2. */
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count = MIN(BUFSIZE - ts->wridx2, ts->size2);
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count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2 + ts->wridx2), count);
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count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count);
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if (count < 0) {
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if (errno == EAGAIN)
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goto skip2;
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@ -618,14 +649,14 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) {
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/* Read from socket to buffer 1. */
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count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
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count = safe_read(ts->sockfd_read, TS_BUF1 + ts->rdidx1, count);
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count = safe_read(ts->sockfd_read, TS_BUF1(ts) + ts->rdidx1, count);
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if (count <= 0) {
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if (count < 0 && errno == EAGAIN)
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goto skip3;
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goto kill_session;
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}
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/* Ignore trailing NUL if it is there */
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if (!TS_BUF1[ts->rdidx1 + count - 1]) {
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if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) {
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--count;
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}
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ts->size1 += count;
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@ -637,7 +668,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
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/* Read from pty to buffer 2. */
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count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
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count = safe_read(ts->ptyfd, TS_BUF2 + ts->rdidx2, count);
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count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
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if (count <= 0) {
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if (count < 0 && errno == EAGAIN)
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goto skip4;
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