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telnetd: properly close fds in child

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-06-09 23:01:24 +02:00
parent 9d617c44d2
commit a4bcbd0e04
2 changed files with 95 additions and 64 deletions
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2
networking/httpd.c
View File

@ -718,7 +718,7 @@ static void parse_conf(const char *path, int flag)
/* form "/path/file" */
sprintf(cur->before_colon, "/%s%.*s",
path,
after_colon - buf - 1, /* includes "/", but not ":" */
(int) (after_colon - buf - 1), /* includes "/", but not ":" */
buf);
/* canonicalize it */
p = bb_simplify_abs_path_inplace(cur->before_colon);

157
networking/telnetd.c
View File

@ -11,14 +11,14 @@
*
* 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 <dzo@simtreas.ru> 2001
* Set process group corrections, initial busybox port
* Set process group corrections, initial busybox port
*/
#define DEBUG 0
@ -40,10 +40,10 @@ struct tsession {
/* two circular buffers */
/*char *buf1, *buf2;*/
/*#define TS_BUF1 ts->buf1*/
/*#define TS_BUF2 TS_BUF2*/
#define TS_BUF1 ((unsigned char*)(ts + 1))
#define TS_BUF2 (((unsigned 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;
};
@ -54,10 +54,17 @@ enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 };
/* Globals */
static int maxfd;
static struct tsession *sessions;
static const char *loginpath = "/bin/login";
static const char *issuefile = "/etc/issue.net";
struct globals {
struct tsession *sessions;
const char *loginpath;
const char *issuefile;
int maxfd;
};
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
G.loginpath = "/bin/login"; \
G.issuefile = "/etc/issue.net"; \
} while (0)
/*
@ -81,7 +88,7 @@ static const char *issuefile = "/etc/issue.net";
static unsigned char *
remove_iacs(struct tsession *ts, int *pnum_totty)
{
unsigned char *ptr0 = 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);
@ -199,9 +206,17 @@ static size_t iac_safe_write(int fd, const char *buf, size_t count)
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 */
OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
};
static struct tsession *
make_new_session(
IF_FEATURE_TELNETD_STANDALONE(int sock)
IF_FEATURE_TELNETD_STANDALONE(int master_fd, int sock)
IF_NOT_FEATURE_TELNETD_STANDALONE(void)
) {
const char *login_argv[2];
@ -215,8 +230,8 @@ make_new_session(
/* Got a new connection, set up a tty. */
fd = xgetpty(tty_name);
if (fd > maxfd)
maxfd = fd;
if (fd > G.maxfd)
G.maxfd = fd;
ts->ptyfd = fd;
ndelay_on(fd);
#if ENABLE_FEATURE_TELNETD_STANDALONE
@ -229,8 +244,8 @@ make_new_session(
ndelay_on(sock);
}
ts->sockfd_write = sock;
if (sock > maxfd)
maxfd = sock;
if (sock > G.maxfd)
G.maxfd = sock;
#else
/* SO_KEEPALIVE by popular demand */
setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
@ -254,7 +269,7 @@ make_new_session(
};
/* This confuses iac_safe_write(), it will try to duplicate
* each IAC... */
//memcpy(TS_BUF2, iacs_to_send, sizeof(iacs_to_send));
//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...) */
@ -288,13 +303,35 @@ 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. */
/* NB: setsid() disconnects from any previous ctty's. Therefore
* we must open child's side of the tty AFTER setsid! */
close(0);
#if ENABLE_FEATURE_TELNETD_STANDALONE
if (sock != 0) /* if we did not close 0 already */
#endif
close(0);
xopen(tty_name, O_RDWR); /* becomes our ctty */
xdup2(0, 1);
xdup2(0, 2);
@ -316,40 +353,32 @@ make_new_session(
* 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(issuefile, tty_name);
print_login_issue(G.issuefile, tty_name);
/* Exec shell / login / whatever */
login_argv[0] = loginpath;
login_argv[0] = G.loginpath;
login_argv[1] = NULL;
/* exec busybox applet (if PREFER_APPLETS=y), if that fails,
* exec external program */
BB_EXECVP(loginpath, (char **)login_argv);
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", loginpath);*/
_exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", G.loginpath);*/
}
/* 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 */
OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
};
#if ENABLE_FEATURE_TELNETD_STANDALONE
static void
free_session(struct tsession *ts)
{
struct tsession *t = sessions;
struct tsession *t = G.sessions;
if (option_mask32 & OPT_INETD)
exit(EXIT_SUCCESS);
/* Unlink this telnet session from the session list */
if (t == ts)
sessions = ts->next;
G.sessions = ts->next;
else {
while (t->next != ts)
t = t->next;
@ -371,17 +400,17 @@ free_session(struct tsession *ts)
free(ts);
/* Scan all sessions and find new maxfd */
maxfd = 0;
ts = sessions;
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 (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 (maxfd < ts->sockfd_write)
maxfd = ts->sockfd_write;
if (G.maxfd < ts->sockfd_write)
G.maxfd = ts->sockfd_write;
#endif
ts = ts->next;
}
@ -404,7 +433,7 @@ static void handle_sigchld(int sig UNUSED_PARAM)
pid = wait_any_nohang(NULL);
if (pid <= 0)
break;
ts = sessions;
ts = G.sessions;
while (ts) {
if (ts->shell_pid == pid) {
ts->shell_pid = -1;
@ -435,10 +464,12 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
portnbr = 23,
};
#endif
INIT_G();
/* 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"),
&issuefile, &loginpath
&G.issuefile, &G.loginpath
IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr));
if (!IS_INETD /*&& !re_execed*/) {
/* inform that we start in standalone mode?
@ -460,21 +491,21 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
portnbr = xatou16(opt_portnbr);
);
/* Used to check access(loginpath, X_OK) here. Pointless.
/* Used to check access(G.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);
if (!sessions) /* pty opening or vfork problem, exit */
G.sessions = make_new_session(-1, 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);
}
#else
sessions = make_new_session();
if (!sessions) /* pty opening or vfork problem, exit */
G.sessions = make_new_session();
if (!G.sessions) /* pty opening or vfork problem, exit */
return 1; /* make_new_session prints error message */
#endif
@ -512,7 +543,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
* 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) {
struct tsession *next = ts->next; /* in case we free ts. */
if (ts->shell_pid == -1) {
@ -535,11 +566,11 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
/* 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 > maxfd)
maxfd = master_fd;
if (master_fd > G.maxfd)
G.maxfd = master_fd;
}
count = select(maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, NULL);
if (count < 0)
goto again; /* EINTR or ENOMEM */
@ -553,10 +584,10 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
if (fd < 0)
goto again;
/* Create a new session and link it into our active list */
new_ts = make_new_session(fd);
new_ts = make_new_session(master_fd, fd);
if (new_ts) {
new_ts->next = sessions;
sessions = new_ts;
new_ts->next = G.sessions;
G.sessions = new_ts;
} else {
close(fd);
}
@ -564,7 +595,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
#endif
/* Then check for data tunneling. */
ts = sessions;
ts = G.sessions;
while (ts) { /* For all sessions... */
struct tsession *next = ts->next; /* in case we free ts. */
@ -588,7 +619,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
/* Write to socket from buffer 2. */
count = MIN(BUFSIZE - ts->wridx2, ts->size2);
count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2 + ts->wridx2), count);
count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count);
if (count < 0) {
if (errno == EAGAIN)
goto skip2;
@ -618,14 +649,14 @@ 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. */
count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
count = safe_read(ts->sockfd_read, TS_BUF1 + ts->rdidx1, count);
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->rdidx1 + count - 1]) {
if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) {
--count;
}
ts->size1 += count;
@ -637,7 +668,7 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
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->rdidx2, count);
count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
if (count <= 0) {
if (count < 0 && errno == EAGAIN)
goto skip4;