[LTP] [PATCH v4] open16: allow restricted O_CREAT of FIFOs and regular files

[Wei Gao]

Signed-off-by: Wei Gao <wegao@suse.com>

This commit adds test cases to verify the security restrictions for opening
FIFOs and regular files in world-writable sticky directories.

Signed-off-by: Wei Gao <wegao@suse.com>
---
 runtest/syscalls                          |   1 +
 testcases/kernel/syscalls/open/.gitignore |   1 +
 testcases/kernel/syscalls/open/open16.c   | 121 ++++++++++++++++++++++
 3 files changed, 123 insertions(+)
 create mode 100644 testcases/kernel/syscalls/open/open16.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 839c23d0a..7a1a64c01 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -974,6 +974,7 @@ open12 open12
 open13 open13
 open14 open14
 open15 open15
+open16 open16
 
 openat01 openat01
 openat02 openat02
diff --git a/testcases/kernel/syscalls/open/.gitignore b/testcases/kernel/syscalls/open/.gitignore
index af5997572..d2cacc02e 100644
--- a/testcases/kernel/syscalls/open/.gitignore
+++ b/testcases/kernel/syscalls/open/.gitignore
@@ -13,3 +13,4 @@
 /open13
 /open14
 /open15
+/open16
diff --git a/testcases/kernel/syscalls/open/open16.c b/testcases/kernel/syscalls/open/open16.c
new file mode 100644
index 000000000..709c5c87f
--- /dev/null
+++ b/testcases/kernel/syscalls/open/open16.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023 Wei Gao <wegao@suse.com>
+ */
+
+/*\
+ * Verify disallows open of FIFOs or regular files not owned by the user in world
+ * writable sticky directories
+ */
+
+#include <pwd.h>
+#include <stdlib.h>
+#include "tst_test.h"
+#include "tst_safe_file_at.h"
+
+#define  FILENAME  "setuid04_testfile"
+#define  DIR "ltp_tmp_check1"
+#define  TEST_FILE "test_file_1"
+#define  TEST_FIFO "test_fifo_1"
+#define  LTP_USR_UID1 1000
+#define  LTP_USR_UID2 1001
+#define  CONCAT(dir, filename) dir "/" filename
+#define  PROTECTED_REGULAR "/proc/sys/fs/protected_regular"
+#define  PROTECTED_FIFOS "/proc/sys/fs/protected_fifos"
+
+static int dir_fd;
+
+static void run(void)
+{
+	SAFE_CHMOD(DIR, 0777 | S_ISVTX);
+	SAFE_FILE_PRINTF(PROTECTED_REGULAR, "%d", 0);
+	SAFE_FILE_PRINTF(PROTECTED_FIFOS, "%d", 0);
+
+	if (!SAFE_FORK()) {
+		SAFE_SETUID(LTP_USR_UID1);
+
+		int fd = TST_EXP_FD(openat(dir_fd, TEST_FILE, O_CREAT | O_RDWR, 0777));
+
+		SAFE_CLOSE(fd);
+
+		SAFE_MKFIFO(CONCAT(DIR, TEST_FIFO), 0777);
+
+		exit(0);
+	}
+
+	tst_reap_children();
+
+	if (!SAFE_FORK()) {
+		SAFE_SETUID(LTP_USR_UID2);
+
+		int fd = TST_EXP_FD(openat(dir_fd, TEST_FILE, O_CREAT | O_RDWR, 0777));
+
+		SAFE_CLOSE(fd);
+
+		fd = TST_EXP_FD(open(CONCAT(DIR, TEST_FIFO), O_RDWR | O_CREAT, 0777));
+		SAFE_CLOSE(fd);
+
+		exit(0);
+	}
+
+	tst_reap_children();
+
+	SAFE_FILE_PRINTF(PROTECTED_REGULAR, "%d", 1);
+	SAFE_FILE_PRINTF(PROTECTED_FIFOS, "%d", 1);
+
+	if (!SAFE_FORK()) {
+		SAFE_SETUID(LTP_USR_UID2);
+		TST_EXP_FAIL(openat(dir_fd, TEST_FILE, O_RDWR | O_CREAT, 0777), EACCES);
+		TST_EXP_FAIL(open(CONCAT(DIR, TEST_FIFO), O_RDWR | O_CREAT, 0777), EACCES);
+
+		exit(0);
+	}
+
+	tst_reap_children();
+
+	SAFE_FILE_PRINTF(PROTECTED_REGULAR, "%d", 2);
+	SAFE_FILE_PRINTF(PROTECTED_FIFOS, "%d", 2);
+	SAFE_CHMOD(DIR, 0020 | S_ISVTX);
+
+	if (!SAFE_FORK()) {
+		SAFE_SETUID(LTP_USR_UID2);
+		TST_EXP_FAIL(openat(dir_fd, TEST_FILE, O_RDWR | O_CREAT, 0777), EACCES);
+		TST_EXP_FAIL(open(CONCAT(DIR, TEST_FIFO), O_RDWR | O_CREAT, 0777), EACCES);
+
+		exit(0);
+	}
+
+	tst_reap_children();
+	SAFE_UNLINK(CONCAT(DIR, TEST_FIFO));
+}
+
+static void setup(void)
+{
+	umask(0);
+	SAFE_MKDIR(DIR, 0777 | S_ISVTX);
+	dir_fd = SAFE_OPEN(DIR, O_DIRECTORY);
+}
+
+static void cleanup(void)
+{
+	if (dir_fd != -1)
+		SAFE_CLOSE(dir_fd);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.needs_root = 1,
+	.test_all = run,
+	.needs_tmpdir = 1,
+	.forks_child = 1,
+	.save_restore = (const struct tst_path_val[]) {
+		{PROTECTED_REGULAR, NULL, TST_SR_TCONF},
+		{PROTECTED_FIFOS, NULL, TST_SR_TCONF},
+		{}
+	},
+	.tags = (const struct tst_tag[]) {
+		{"linux-git", "30aba6656f61ed44cba445a3c0d38b296fa9e8f5"},
+		{}
+	}
+};
-- 
2.35.3