From de848d9e9146434817c65d74d1d0313e9d729462 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 14:01:37 +0200 Subject: Adding upstream version 1.4.0. Signed-off-by: Daniel Baumann --- modules/pam_unix/lckpwdf.-c | 142 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 142 insertions(+) create mode 100644 modules/pam_unix/lckpwdf.-c (limited to 'modules/pam_unix/lckpwdf.-c') diff --git a/modules/pam_unix/lckpwdf.-c b/modules/pam_unix/lckpwdf.-c new file mode 100644 index 0000000..7145617 --- /dev/null +++ b/modules/pam_unix/lckpwdf.-c @@ -0,0 +1,142 @@ +/* + * This is a hack, but until libc and glibc both include this function + * by default (libc only includes it if nys is not being used, at the + * moment, and glibc doesn't appear to have it at all) we need to have + * it here, too. :-( + * + * This should not become an official part of PAM. + * + * BEGIN_HACK + */ + +/* + * lckpwdf.c -- prevent simultaneous updates of password files + * + * Before modifying any of the password files, call lckpwdf(). It may block + * for up to 15 seconds trying to get the lock. Return value is 0 on success + * or -1 on failure. When you are done, call ulckpwdf() to release the lock. + * The lock is also released automatically when the process exits. Only one + * process at a time may hold the lock. + * + * These functions are supposed to be conformant with AT&T SVID Issue 3. + * + * Written by Marek Michalkiewicz , + * public domain. + */ + +#include +#include +#ifdef WITH_SELINUX +#include +#endif + +#define LOCKFILE "/etc/.pwd.lock" +#define TIMEOUT 15 + +static int lockfd = -1; + +static int set_close_on_exec(int fd) +{ + int flags = fcntl(fd, F_GETFD, 0); + if (flags == -1) + return -1; + flags |= FD_CLOEXEC; + return fcntl(fd, F_SETFD, flags); +} + +static int do_lock(int fd) +{ + struct flock fl; + + memset(&fl, 0, sizeof fl); + fl.l_type = F_WRLCK; + fl.l_whence = SEEK_SET; + return fcntl(fd, F_SETLKW, &fl); +} + +static void alarm_catch(int sig) +{ +/* does nothing, but fcntl F_SETLKW will fail with EINTR */ +} + +static int lckpwdf(void) +{ + struct sigaction act, oldact; + sigset_t set, oldset; + + if (lockfd != -1) + return -1; + +#ifdef WITH_SELINUX + if(is_selinux_enabled()>0) + { + lockfd = open(LOCKFILE, O_WRONLY); + if(lockfd == -1 && errno == ENOENT) + { + security_context_t create_context; + int rc; + + if(getfilecon("/etc/passwd", &create_context)) + return -1; + rc = setfscreatecon(create_context); + freecon(create_context); + if(rc) + return -1; + lockfd = open(LOCKFILE, O_CREAT | O_WRONLY, 0600); + if(setfscreatecon(NULL)) + return -1; + } + } + else +#endif + lockfd = open(LOCKFILE, O_CREAT | O_WRONLY, 0600); + if (lockfd == -1) + return -1; + if (set_close_on_exec(lockfd) == -1) + goto cleanup_fd; + + memset(&act, 0, sizeof act); + act.sa_handler = alarm_catch; + act.sa_flags = 0; + sigfillset(&act.sa_mask); + if (sigaction(SIGALRM, &act, &oldact) == -1) + goto cleanup_fd; + + sigemptyset(&set); + sigaddset(&set, SIGALRM); + if (sigprocmask(SIG_UNBLOCK, &set, &oldset) == -1) + goto cleanup_sig; + + alarm(TIMEOUT); + if (do_lock(lockfd) == -1) + goto cleanup_alarm; + alarm(0); + sigprocmask(SIG_SETMASK, &oldset, NULL); + sigaction(SIGALRM, &oldact, NULL); + return 0; + + cleanup_alarm: + alarm(0); + sigprocmask(SIG_SETMASK, &oldset, NULL); + cleanup_sig: + sigaction(SIGALRM, &oldact, NULL); + cleanup_fd: + close(lockfd); + lockfd = -1; + return -1; +} + +static int ulckpwdf(void) +{ + unlink(LOCKFILE); + if (lockfd == -1) + return -1; + + if (close(lockfd) == -1) { + lockfd = -1; + return -1; + } + lockfd = -1; + return 0; +} +/* END_HACK */ -- cgit v1.2.3