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login: use some ideas from util-linux's login.

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O_NONBLOCKing output on login timeout.
fchmod instead of chmod (latter is racy).
is_my_tty() is not needed anymore after race is fixed
(is_my_tty() was racy too anyway...).
This commit is contained in:
Denis Vlasenko 2006-09-08 17:56:52 +00:00
parent bd8f43dbab
commit 2f50aa42c5
1 changed files with 15 additions and 25 deletions
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40
loginutils/login.c
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@ -51,14 +51,22 @@ static inline int check_securetty(void) { return 1; }
#endif #endif
static int is_my_tty(void);
static void get_username_or_die(char *buf, int size_buf); static void get_username_or_die(char *buf, int size_buf);
static void motd(void); static void motd(void);
static void nonblock(int fd)
{
fcntl(fd, F_SETFL, O_NONBLOCK | fcntl(fd, F_GETFL));
}
static void alarm_handler(int sig ATTRIBUTE_UNUSED) static void alarm_handler(int sig ATTRIBUTE_UNUSED)
{ {
fprintf(stderr, "\r\nLogin timed out after %d seconds\r\n", TIMEOUT); /* This is the escape hatch! Poor serial line users and the like
* arrive here when their connection is broken.
* We don't want to block here */
nonblock(1);
nonblock(2);
bb_info_msg("\r\nLogin timed out after %d seconds\r", TIMEOUT);
exit(EXIT_SUCCESS); exit(EXIT_SUCCESS);
} }
@ -218,13 +226,10 @@ auth_failed:
} }
} }
#endif #endif
if (!is_my_tty()) /* Try these, but don't complain if they fail.
syslog(LOG_ERR, "unable to determine TTY name, got %s", full_tty); * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
fchown(0, pw->pw_uid, pw->pw_gid);
/* Try these, but don't complain if they fail fchmod(0, 0600);
* (for example when the root fs is read only) */
chown(full_tty, pw->pw_uid, pw->pw_gid);
chmod(full_tty, 0600);
if (ENABLE_LOGIN_SCRIPTS) { if (ENABLE_LOGIN_SCRIPTS) {
char *script = getenv("LOGIN_PRE_SUID_SCRIPT"); char *script = getenv("LOGIN_PRE_SUID_SCRIPT");
@ -257,7 +262,7 @@ auth_failed:
signal(SIGALRM, SIG_DFL); /* default alarm signal */ signal(SIGALRM, SIG_DFL); /* default alarm signal */
if (pw->pw_uid == 0) if (pw->pw_uid == 0)
syslog(LOG_INFO, "root login %s", fromhost); syslog(LOG_INFO, "root login%s", fromhost);
#ifdef CONFIG_SELINUX #ifdef CONFIG_SELINUX
/* well, a simple setexeccon() here would do the job as well, /* well, a simple setexeccon() here would do the job as well,
* but let's play the game for now */ * but let's play the game for now */
@ -348,21 +353,6 @@ static int check_securetty(void)
#endif #endif
/* returns 1 if true */
static int is_my_tty(void)
{
struct stat by_name, by_fd;
if (stat(full_tty, &by_name) || fstat(0, &by_fd))
return 0;
if (by_name.st_rdev != by_fd.st_rdev)
return 0;
else
return 1;
}
static void motd(void) static void motd(void)
{ {
FILE *fp; FILE *fp;