linux: Add support for No New Privs flag

This add No New Privs flag for start-stop-daemon and supervise-daemon
by adding --no-new-privs flag. As a result, the user set the No New
Privs flag for the program should run with.
see PR_SET_NO_NEW_PRIVS prctl(2)

man/start-stop-daemon.8

@@ -168,6 +168,8 @@ The format is the same as in cap_iab(3).
 Set the security-bits for the program.
 The numeric value of the security-bits can be found in <sys/secbits.h> header file.
 The format is the same as in strtoul(3).
+.It Fl -no-new-privs
+Set the No New Privs flag for the program. See PR_SET_NO_NEW_PRIVS prctl(2).
 .It Fl w , -wait Ar milliseconds
 Wait
 .Ar milliseconds

man/supervise-daemon.8

@@ -165,6 +165,8 @@ The format is the same as in cap_iab(3).
 Set the security-bits for the program.
 The numeric value of the security-bits can be found in <sys/secbits.h> header file.
 The format is the same as in strtoul(3).
+.It Fl -no-new-privs
+Set the No New Privs flag for the program. See PR_SET_NO_NEW_PRIVS prctl(2).
 .El
 .Sh ENVIRONMENT
 .Va SSD_IONICELEVEL

sh/start-stop-daemon.sh

@@ -55,6 +55,7 @@ ssd_start()
 		${error_logger_arg} \
 		${capabilities+--capabilities} "$capabilities" \
 		${secbits:+--secbits} "$secbits" \
+		${no_new_privs:+--no-new-privs} \
 		${procname:+--name} $procname \
 		${pidfile:+--pidfile} $pidfile \
 		${command_user+--user} $command_user \

sh/supervise-daemon.sh

@@ -38,6 +38,7 @@ supervise_start()
 		${healthcheck_timer:+--healthcheck-timer} $healthcheck_timer \
 		${capabilities+--capabilities} "$capabilities" \
 		${secbits:+--secbits} "$secbits" \
+		${no_new_privs:+--no_new_privs} \
 		${command_user+--user} $command_user \
 		${umask+--umask} $umask \
 		${supervise_daemon_args:-${start_stop_daemon_args}} \

src/rc/start-stop-daemon.c

@@ -31,6 +31,7 @@
 
 #ifdef __linux__
 #include <sys/syscall.h> /* For io priority */
+#include <sys/prctl.h> /* For prctl */
 #endif
 
 #include <ctype.h>
@@ -75,6 +76,7 @@ const char getoptstring[] = "I:KN:PR:Sa:bc:d:e:g:ik:mn:op:s:tu:r:w:x:1:2:3:4:" \
 const struct option longopts[] = {
 	{ "capabilities", 1, NULL, 0x100},
 	{ "secbits",      1, NULL, 0x101},
+	{ "no-new-privs", 0, NULL, 0x102},
 	{ "ionice",       1, NULL, 'I'},
 	{ "stop",         0, NULL, 'K'},
 	{ "nicelevel",    1, NULL, 'N'},
@@ -109,6 +111,7 @@ const struct option longopts[] = {
 const char * const longopts_help[] = {
 	"Set the inheritable, ambient and bounding capabilities",
 	"Set the security-bits for the program",
+	"Set the No New Privs flag for the program",
 	"Set an ionice class:data when starting",
 	"Stop daemon",
 	"Set a nicelevel when starting",
@@ -319,6 +322,9 @@ int main(int argc, char **argv)
 	cap_iab_t cap_iab = NULL;
 	unsigned secbits = 0;
 #endif
+#ifdef PR_SET_NO_NEW_PRIVS
+	bool no_new_privs = false;
+#endif
 
 	applet = basename_c(argv[0]);
 	atexit(cleanup);
@@ -389,6 +395,13 @@ int main(int argc, char **argv)
 #endif
 			break;
 
+		case 0x102:
+#ifdef PR_SET_NO_NEW_PRIVS
+			no_new_privs = true;
+#else
+			eerrorx("The No New Privs flag is only supported by Linux (since 3.5)");
+#endif
+			break;
 
 		case 'I': /* --ionice */
 			if (sscanf(optarg, "%d:%d", &ionicec, &ioniced) == 0)
@@ -915,6 +928,14 @@ int main(int argc, char **argv)
 		}
 #endif
 
+#ifdef PR_SET_NO_NEW_PRIVS
+		if (no_new_privs) {
+			if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
+				eerrorx("Could not set No New Privs flag: %s", strerror(errno));
+		}
+#endif
+
+
 #ifdef TIOCNOTTY
 		ioctl(tty_fd, TIOCNOTTY, 0);
 		close(tty_fd);

src/rc/supervise-daemon.c

@@ -32,6 +32,7 @@
 
 #ifdef __linux__
 #include <sys/syscall.h> /* For io priority */
+#include <sys/prctl.h> /* For prctl */
 #endif
 
 #include <ctype.h>
@@ -79,6 +80,7 @@ const struct option longopts[] = {
 	{ "healthcheck-delay",        1, NULL, 'A'},
 	{ "capabilities", 1, NULL, 0x100},
 	{ "secbits", 1, NULL, 0x101},
+	{ "no-new-privs", 0, NULL, 0x102},
 	{ "respawn-delay",        1, NULL, 'D'},
 	{ "chdir",        1, NULL, 'd'},
 	{ "env",          1, NULL, 'e'},
@@ -106,6 +108,7 @@ const char * const longopts_help[] = {
 	"set a health check timer",
 	"Set the inheritable, ambient and bounding capabilities",
 	"Set the security-bits for the program",
+	"Set the No New Privs flag for the program",
 	"Set a respawn delay",
 	"Change the PWD",
 	"Set an environment string",
@@ -164,6 +167,9 @@ static bool verbose = false;
 static cap_iab_t cap_iab = NULL;
 static unsigned secbits = 0;
 #endif
+#ifdef PR_SET_NO_NEW_PRIVS
+static bool no_new_privs = false;
+#endif
 
 extern char **environ;
 
@@ -437,6 +443,13 @@ static void child_process(char *exec, char **argv)
 	}
 #endif
 
+#ifdef PR_SET_NO_NEW_PRIVS
+	if (no_new_privs) {
+		if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
+			eerrorx("Could not set No New Privs flag: %s", strerror(errno));
+	}
+#endif
+
 	/* remove the controlling tty */
 #ifdef TIOCNOTTY
 	ioctl(tty_fd, TIOCNOTTY, 0);
@@ -854,6 +867,14 @@ int main(int argc, char **argv)
 #endif
 			break;
 
+		case 0x102:
+#ifdef PR_SET_NO_NEW_PRIVS
+			no_new_privs = true;
+#else
+			eerrorx("The No New Privs flag is only supported by Linux (since 3.5)");
+#endif
+			break;
+
 		case 'D':  /* --respawn-delay time */
 			n = sscanf(optarg, "%d", &respawn_delay);
 			if (n	!= 1 || respawn_delay < 1)