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When allocating BSD-style ptys, we should not be satisfied with a

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/dev/ptyXX we can open: we must also check that we can open and use
the corresponding /dev/ttyXX, because if it's been left in the wrong
mode then we will look terribly silly when we fork and _then_
discover our pty is unusable.

[originally from svn r5257]
This commit is contained in:
Simon Tatham 2005-02-05 15:33:36 +00:00
parent 0eb1e5df8d
commit fd961b398a
1 changed files with 32 additions and 8 deletions
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38
unix/uxpty.c
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@ -70,7 +70,7 @@
#endif #endif
static Config pty_cfg; static Config pty_cfg;
static int pty_master_fd; static int pty_master_fd, pty_slave_fd;
static void *pty_frontend; static void *pty_frontend;
static char pty_name[FILENAME_MAX]; static char pty_name[FILENAME_MAX];
static int pty_signal_pipe[2]; static int pty_signal_pipe[2];
@ -186,6 +186,14 @@ static void fatal_sig_handler(int signum)
} }
#endif #endif
static int pty_open_slave(void)
{
if (pty_slave_fd < 0)
pty_slave_fd = open(pty_name, O_RDWR);
return pty_slave_fd;
}
static void pty_open_master(void) static void pty_open_master(void)
{ {
#ifdef BSD_PTYS #ifdef BSD_PTYS
@ -201,8 +209,24 @@ static void pty_open_master(void)
pty_master_fd = open(master_name, O_RDWR); pty_master_fd = open(master_name, O_RDWR);
if (pty_master_fd >= 0) { if (pty_master_fd >= 0) {
if (geteuid() == 0 || if (geteuid() == 0 ||
access(master_name, R_OK | W_OK) == 0) access(master_name, R_OK | W_OK) == 0) {
goto got_one; /*
* We must also check at this point that we are
* able to open the slave side of the pty. We
* wouldn't want to allocate the wrong master,
* get all the way down to forking, and _then_
* find we're unable to open the slave.
*/
strcpy(pty_name, master_name);
pty_name[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */
if (pty_open_slave() >= 0 &&
access(pty_name, R_OK | W_OK) == 0)
goto got_one;
if (pty_slave_fd > 0)
close(pty_slave_fd);
pty_slave_fd = -1;
}
close(pty_master_fd); close(pty_master_fd);
} }
} }
@ -212,8 +236,6 @@ static void pty_open_master(void)
exit(1); exit(1);
got_one: got_one:
strcpy(pty_name, master_name);
pty_name[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */
/* We need to chown/chmod the /dev/ttyXX device. */ /* We need to chown/chmod the /dev/ttyXX device. */
gp = getgrnam("tty"); gp = getgrnam("tty");
@ -265,7 +287,7 @@ void pty_pre_init(void)
/* set the child signal handler straight away; it needs to be set /* set the child signal handler straight away; it needs to be set
* before we ever fork. */ * before we ever fork. */
putty_signal(SIGCHLD, sigchld_handler); putty_signal(SIGCHLD, sigchld_handler);
pty_master_fd = -1; pty_master_fd = pty_slave_fd = -1;
if (geteuid() != getuid() || getegid() != getgid()) { if (geteuid() != getuid() || getegid() != getgid()) {
pty_open_master(); pty_open_master();
@ -564,7 +586,7 @@ static const char *pty_init(void *frontend, void **backend_handle, Config *cfg,
* We are the child. * We are the child.
*/ */
slavefd = open(pty_name, O_RDWR); slavefd = pty_open_slave();
if (slavefd < 0) { if (slavefd < 0) {
perror("slave pty: open"); perror("slave pty: open");
_exit(1); _exit(1);
@ -652,6 +674,8 @@ static const char *pty_init(void *frontend, void **backend_handle, Config *cfg,
pty_child_pid = pid; pty_child_pid = pid;
pty_child_dead = FALSE; pty_child_dead = FALSE;
pty_finished = FALSE; pty_finished = FALSE;
if (pty_slave_fd > 0)
close(pty_slave_fd);
} }
if (pipe(pty_signal_pipe) < 0) { if (pipe(pty_signal_pipe) < 0) {