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Use setusercontext(3) where available #334

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merged 2 commits into from
Jan 17, 2024
Merged

Use setusercontext(3) where available #334

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c8597ae
Add code to use setusercontext
madpilot78 Dec 23, 2023
948f1f9
Tell configure to check for setusercontext
madpilot78 Dec 23, 2023
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2 changes: 1 addition & 1 deletion configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ AC_CHECK_HEADERS(security/pam_appl.h, [], AC_MSG_ERROR(PAM not found))

AC_CHECK_HEADERS(gcrypt.h, [], AC_MSG_ERROR(libgcrypt not found))

AC_CHECK_FUNCS(setresgid setresuid clearenv __getgroups_chk)
AC_CHECK_FUNCS(setresgid setresuid setusercontext clearenv __getgroups_chk)

PKG_CHECK_MODULES(LIGHTDM, [
glib-2.0 >= 2.44
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36 changes: 34 additions & 2 deletions src/session-child.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,9 @@
#include <utmp.h>
#include <utmpx.h>
#include <sys/mman.h>
#if HAVE_SETUSERCONTEXT
#include <login_cap.h>
#endif

#if HAVE_LIBAUDIT
#include <libaudit.h>
Expand Down Expand Up @@ -637,6 +640,29 @@ session_child_run (int argc, char **argv)
if (setsid () < 0)
_exit (errno);

#if HAVE_SETUSERCONTEXT
/* Setup user context
* Reset the current environment to what is in the PAM context,
* then setusercontext will add to it as necessary as there is no
* option for setusercontext to add to a PAM context.
*/
extern char **environ;
environ = pam_getenvlist (pam_handle);
struct passwd* pwd = getpwnam (username);
if (pwd) {
if (setusercontext (NULL, pwd, pwd->pw_uid, LOGIN_SETALL) < 0) {
int _errno = errno;
fprintf(stderr, "setusercontext for \"%s\" (%d) failed: %s\n",
username, user_get_uid (user), strerror (errno));
_exit (_errno);
}
endpwent();
} else {
fprintf (stderr, "getpwname for \"%s\" failed: %s\n",
username, strerror (errno));
_exit (ENOENT);
}
#else
/* Change to this user */
if (getuid () == 0)
{
Expand All @@ -646,7 +672,7 @@ session_child_run (int argc, char **argv)
if (setuid (uid) != 0)
_exit (errno);
}

#endif
/* Change working directory */
/* NOTE: This must be done after the permissions are changed because NFS filesystems can
* be setup so the local root user accesses the NFS files as 'nobody'. If the home directories
Expand All @@ -668,7 +694,13 @@ session_child_run (int argc, char **argv)
signal (SIGPIPE, SIG_DFL);

/* Run the command */
execve (command_argv[0], command_argv, pam_getenvlist (pam_handle));
execve (command_argv[0], command_argv,
#if HAVE_SETUSERCONTEXT
environ
#else
pam_getenvlist (pam_handle)
#endif
);
_exit (EXIT_FAILURE);
}

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