system(3) should ignore SIGINT and SIGQUIT until the shell exits.

This got broken when system.c was converted from signal(3) to sigaction(2).
Also add SIGINT and SIGQUIT to the set of blocked signals and unblock
them in the parent after the signal handlers are installed.
Based on a diff from Leon Fischer.  OK deraadt@

1 files changed, 17 insertions, 4 deletions

diff --git a/lib/libc/stdlib/system.c b/lib/libc/stdlib/system.c
index fe718276b92..28f01a9c5dd 100644
--- a/lib/libc/stdlib/system.c
+++ b/lib/libc/stdlib/system.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: system.c,v 1.12 2016/03/13 18:34:21 guenther Exp $ */
+/*	$OpenBSD: system.c,v 1.13 2022/05/21 00:53:53 millert Exp $ */
 /*
  * Copyright (c) 1988 The Regents of the University of California.
  * All rights reserved.
@@ -33,6 +33,7 @@
 #include <errno.h>
 #include <signal.h>
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 #include <paths.h>
 
@@ -40,7 +41,7 @@ int
 system(const char *command)
 {
 	pid_t pid, cpid;
-	struct sigaction intsave, quitsave;
+	struct sigaction intsave, quitsave, sa;
 	sigset_t mask, omask;
 	int pstat;
 	char *argp[] = {"sh", "-c", NULL, NULL};
@@ -52,6 +53,8 @@ system(const char *command)
 
 	sigemptyset(&mask);
 	sigaddset(&mask, SIGCHLD);
+	sigaddset(&mask, SIGINT);
+	sigaddset(&mask, SIGQUIT);
 	sigprocmask(SIG_BLOCK, &mask, &omask);
 	switch (cpid = vfork()) {
 	case -1:			/* error */
@@ -63,11 +66,21 @@ system(const char *command)
 		_exit(127);
 	}
 
-	sigaction(SIGINT, NULL, &intsave);
-	sigaction(SIGQUIT, NULL, &quitsave);
+	/* Ignore SIGINT and SIGQUIT while waiting for command to complete. */
+	memset(&sa, 0, sizeof(sa));
+	sigemptyset(&sa.sa_mask);
+	sa.sa_handler = SIG_IGN;
+	sigaction(SIGINT, &sa, &intsave);
+	sigaction(SIGQUIT, &sa, &quitsave);
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGINT);
+	sigaddset(&mask, SIGQUIT);
+	sigprocmask(SIG_UNBLOCK, &mask, NULL);
+
 	do {
 		pid = waitpid(cpid, &pstat, 0);
 	} while (pid == -1 && errno == EINTR);
+
 	sigprocmask(SIG_SETMASK, &omask, NULL);
 	sigaction(SIGINT, &intsave, NULL);
 	sigaction(SIGQUIT, &quitsave, NULL);