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LSM: SafeSetID: selftest cleanup and prepare for GIDs

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Add some notes on how to run the test, update the policy file paths to
reflect recent upstream changes, prepare test for adding GID testing.

Signed-off-by: Micah Morton <mortonm@chromium.org>
This commit is contained in:
Micah Morton 2022-06-15 22:14:14 +00:00
parent 92c005a117
commit b2927170d4
2 changed files with 51 additions and 44 deletions
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2
tools/testing/selftests/safesetid/Makefile
View File

@ -1,5 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
# Makefile for mount selftests.
# Makefile for SafeSetID selftest.
CFLAGS = -Wall -O2
LDLIBS = -lcap

93
tools/testing/selftests/safesetid/safesetid-test.c
View File

@ -16,17 +16,28 @@
#include <stdbool.h>
#include <stdarg.h>
/*
* NOTES about this test:
* - requries libcap-dev to be installed on test system
* - requires securityfs to me mounted at /sys/kernel/security, e.g.:
* mount -n -t securityfs -o nodev,noexec,nosuid securityfs /sys/kernel/security
* - needs CONFIG_SECURITYFS and CONFIG_SAFESETID to be enabled
*/
#ifndef CLONE_NEWUSER
# define CLONE_NEWUSER 0x10000000
#endif
#define ROOT_USER 0
#define RESTRICTED_PARENT 1
#define ALLOWED_CHILD1 2
#define ALLOWED_CHILD2 3
#define NO_POLICY_USER 4
#define ROOT_UGID 0
#define RESTRICTED_PARENT_UGID 1
#define ALLOWED_CHILD1_UGID 2
#define ALLOWED_CHILD2_UGID 3
#define NO_POLICY_UGID 4
char* add_whitelist_policy_file = "/sys/kernel/security/safesetid/add_whitelist_policy";
#define UGID_POLICY_STRING "1:2\n1:3\n2:2\n3:3\n"
char* add_uid_whitelist_policy_file = "/sys/kernel/security/safesetid/uid_allowlist_policy";
char* add_gid_whitelist_policy_file = "/sys/kernel/security/safesetid/gid_allowlist_policy";
static void die(char *fmt, ...)
{
@ -106,7 +117,7 @@ static void ensure_user_exists(uid_t uid)
die("couldn't open file\n");
if (fseek(fd, 0, SEEK_END))
die("couldn't fseek\n");
snprintf(name_str, 10, "%d", uid);
snprintf(name_str, 10, "user %d", uid);
p.pw_name=name_str;
p.pw_uid=uid;
p.pw_gecos="Test account";
@ -122,7 +133,7 @@ static void ensure_user_exists(uid_t uid)
static void ensure_securityfs_mounted(void)
{
int fd = open(add_whitelist_policy_file, O_WRONLY);
int fd = open(add_uid_whitelist_policy_file, O_WRONLY);
if (fd < 0) {
if (errno == ENOENT) {
// Need to mount securityfs
@ -135,36 +146,32 @@ static void ensure_securityfs_mounted(void)
} else {
if (close(fd) != 0) {
die("close of %s failed: %s\n",
add_whitelist_policy_file, strerror(errno));
add_uid_whitelist_policy_file, strerror(errno));
}
}
}
static void write_policies(void)
static void write_uid_policies()
{
static char *policy_str =
"1:2\n"
"1:3\n"
"2:2\n"
"3:3\n";
static char *policy_str = UGID_POLICY_STRING;
ssize_t written;
int fd;
fd = open(add_whitelist_policy_file, O_WRONLY);
fd = open(add_uid_whitelist_policy_file, O_WRONLY);
if (fd < 0)
die("can't open add_whitelist_policy file\n");
die("can't open add_uid_whitelist_policy file\n");
written = write(fd, policy_str, strlen(policy_str));
if (written != strlen(policy_str)) {
if (written >= 0) {
die("short write to %s\n", add_whitelist_policy_file);
die("short write to %s\n", add_uid_whitelist_policy_file);
} else {
die("write to %s failed: %s\n",
add_whitelist_policy_file, strerror(errno));
add_uid_whitelist_policy_file, strerror(errno));
}
}
if (close(fd) != 0) {
die("close of %s failed: %s\n",
add_whitelist_policy_file, strerror(errno));
add_uid_whitelist_policy_file, strerror(errno));
}
}
@ -260,11 +267,11 @@ static void test_setuid(uid_t child_uid, bool expect_success)
static void ensure_users_exist(void)
{
ensure_user_exists(ROOT_USER);
ensure_user_exists(RESTRICTED_PARENT);
ensure_user_exists(ALLOWED_CHILD1);
ensure_user_exists(ALLOWED_CHILD2);
ensure_user_exists(NO_POLICY_USER);
ensure_user_exists(ROOT_UGID);
ensure_user_exists(RESTRICTED_PARENT_UGID);
ensure_user_exists(ALLOWED_CHILD1_UGID);
ensure_user_exists(ALLOWED_CHILD2_UGID);
ensure_user_exists(NO_POLICY_UGID);
}
static void drop_caps(bool setid_retained)
@ -285,39 +292,38 @@ int main(int argc, char **argv)
{
ensure_users_exist();
ensure_securityfs_mounted();
write_policies();
write_uid_policies();
if (prctl(PR_SET_KEEPCAPS, 1L))
die("Error with set keepcaps\n");
// First test to make sure we can write userns mappings from a user
// that doesn't have any restrictions (as long as it has CAP_SETUID);
if (setuid(NO_POLICY_USER) < 0)
die("Error with set uid(%d)\n", NO_POLICY_USER);
if (setgid(NO_POLICY_USER) < 0)
die("Error with set gid(%d)\n", NO_POLICY_USER);
// First test to make sure we can write userns mappings from a non-root
// user that doesn't have any restrictions (as long as it has
// CAP_SETUID);
if (setgid(NO_POLICY_UGID) < 0)
die("Error with set gid(%d)\n", NO_POLICY_UGID);
if (setuid(NO_POLICY_UGID) < 0)
die("Error with set uid(%d)\n", NO_POLICY_UGID);
// Take away all but setid caps
drop_caps(true);
// Need PR_SET_DUMPABLE flag set so we can write /proc/[pid]/uid_map
// from non-root parent process.
if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0))
die("Error with set dumpable\n");
if (!test_userns(true)) {
die("test_userns failed when it should work\n");
}
if (setuid(RESTRICTED_PARENT) < 0)
die("Error with set uid(%d)\n", RESTRICTED_PARENT);
if (setgid(RESTRICTED_PARENT) < 0)
die("Error with set gid(%d)\n", RESTRICTED_PARENT);
// Now switch to a user/group with restrictions
if (setgid(RESTRICTED_PARENT_UGID) < 0)
die("Error with set gid(%d)\n", RESTRICTED_PARENT_UGID);
if (setuid(RESTRICTED_PARENT_UGID) < 0)
die("Error with set uid(%d)\n", RESTRICTED_PARENT_UGID);
test_setuid(ROOT_USER, false);
test_setuid(ALLOWED_CHILD1, true);
test_setuid(ALLOWED_CHILD2, true);
test_setuid(NO_POLICY_USER, false);
test_setuid(ROOT_UGID, false);
test_setuid(ALLOWED_CHILD1_UGID, true);
test_setuid(ALLOWED_CHILD2_UGID, true);
test_setuid(NO_POLICY_UGID, false);
if (!test_userns(false)) {
die("test_userns worked when it should fail\n");
@ -331,5 +337,6 @@ int main(int argc, char **argv)
// NOTE: this test doesn't clean up users that were created in
// /etc/passwd or flush policies that were added to the LSM.
printf("test successful!\n");
return EXIT_SUCCESS;
}