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-rw-r--r--tools/testing/selftests/safesetid/safesetid-test.c542
1 files changed, 542 insertions, 0 deletions
diff --git a/tools/testing/selftests/safesetid/safesetid-test.c b/tools/testing/selftests/safesetid/safesetid-test.c
new file mode 100644
index 000000000..eb9bf0aee
--- /dev/null
+++ b/tools/testing/selftests/safesetid/safesetid-test.c
@@ -0,0 +1,542 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <errno.h>
+#include <pwd.h>
+#include <grp.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/capability.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#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_UGID 0
+#define RESTRICTED_PARENT_UGID 1
+#define ALLOWED_CHILD1_UGID 2
+#define ALLOWED_CHILD2_UGID 3
+#define NO_POLICY_UGID 4
+
+#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, ...)
+{
+ va_list ap;
+ va_start(ap, fmt);
+ vfprintf(stderr, fmt, ap);
+ va_end(ap);
+ exit(EXIT_FAILURE);
+}
+
+static bool vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
+{
+ char buf[4096];
+ int fd;
+ ssize_t written;
+ int buf_len;
+
+ buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
+ if (buf_len < 0) {
+ printf("vsnprintf failed: %s\n",
+ strerror(errno));
+ return false;
+ }
+ if (buf_len >= sizeof(buf)) {
+ printf("vsnprintf output truncated\n");
+ return false;
+ }
+
+ fd = open(filename, O_WRONLY);
+ if (fd < 0) {
+ if ((errno == ENOENT) && enoent_ok)
+ return true;
+ return false;
+ }
+ written = write(fd, buf, buf_len);
+ if (written != buf_len) {
+ if (written >= 0) {
+ printf("short write to %s\n", filename);
+ return false;
+ } else {
+ printf("write to %s failed: %s\n",
+ filename, strerror(errno));
+ return false;
+ }
+ }
+ if (close(fd) != 0) {
+ printf("close of %s failed: %s\n",
+ filename, strerror(errno));
+ return false;
+ }
+ return true;
+}
+
+static bool write_file(char *filename, char *fmt, ...)
+{
+ va_list ap;
+ bool ret;
+
+ va_start(ap, fmt);
+ ret = vmaybe_write_file(false, filename, fmt, ap);
+ va_end(ap);
+
+ return ret;
+}
+
+static void ensure_user_exists(uid_t uid)
+{
+ struct passwd p;
+
+ FILE *fd;
+ char name_str[10];
+
+ if (getpwuid(uid) == NULL) {
+ memset(&p,0x00,sizeof(p));
+ fd=fopen("/etc/passwd","a");
+ if (fd == NULL)
+ die("couldn't open file\n");
+ if (fseek(fd, 0, SEEK_END))
+ die("couldn't fseek\n");
+ snprintf(name_str, 10, "user %d", uid);
+ p.pw_name=name_str;
+ p.pw_uid=uid;
+ p.pw_gid=uid;
+ p.pw_gecos="Test account";
+ p.pw_dir="/dev/null";
+ p.pw_shell="/bin/false";
+ int value = putpwent(&p,fd);
+ if (value != 0)
+ die("putpwent failed\n");
+ if (fclose(fd))
+ die("fclose failed\n");
+ }
+}
+
+static void ensure_group_exists(gid_t gid)
+{
+ struct group g;
+
+ FILE *fd;
+ char name_str[10];
+
+ if (getgrgid(gid) == NULL) {
+ memset(&g,0x00,sizeof(g));
+ fd=fopen("/etc/group","a");
+ if (fd == NULL)
+ die("couldn't open group file\n");
+ if (fseek(fd, 0, SEEK_END))
+ die("couldn't fseek group file\n");
+ snprintf(name_str, 10, "group %d", gid);
+ g.gr_name=name_str;
+ g.gr_gid=gid;
+ g.gr_passwd=NULL;
+ g.gr_mem=NULL;
+ int value = putgrent(&g,fd);
+ if (value != 0)
+ die("putgrent failed\n");
+ if (fclose(fd))
+ die("fclose failed\n");
+ }
+}
+
+static void ensure_securityfs_mounted(void)
+{
+ int fd = open(add_uid_whitelist_policy_file, O_WRONLY);
+ if (fd < 0) {
+ if (errno == ENOENT) {
+ // Need to mount securityfs
+ if (mount("securityfs", "/sys/kernel/security",
+ "securityfs", 0, NULL) < 0)
+ die("mounting securityfs failed\n");
+ } else {
+ die("couldn't find securityfs for unknown reason\n");
+ }
+ } else {
+ if (close(fd) != 0) {
+ die("close of %s failed: %s\n",
+ add_uid_whitelist_policy_file, strerror(errno));
+ }
+ }
+}
+
+static void write_uid_policies()
+{
+ static char *policy_str = UGID_POLICY_STRING;
+ ssize_t written;
+ int fd;
+
+ fd = open(add_uid_whitelist_policy_file, O_WRONLY);
+ if (fd < 0)
+ 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_uid_whitelist_policy_file);
+ } else {
+ die("write to %s failed: %s\n",
+ add_uid_whitelist_policy_file, strerror(errno));
+ }
+ }
+ if (close(fd) != 0) {
+ die("close of %s failed: %s\n",
+ add_uid_whitelist_policy_file, strerror(errno));
+ }
+}
+
+static void write_gid_policies()
+{
+ static char *policy_str = UGID_POLICY_STRING;
+ ssize_t written;
+ int fd;
+
+ fd = open(add_gid_whitelist_policy_file, O_WRONLY);
+ if (fd < 0)
+ die("can't open add_gid_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_gid_whitelist_policy_file);
+ } else {
+ die("write to %s failed: %s\n",
+ add_gid_whitelist_policy_file, strerror(errno));
+ }
+ }
+ if (close(fd) != 0) {
+ die("close of %s failed: %s\n",
+ add_gid_whitelist_policy_file, strerror(errno));
+ }
+}
+
+
+static bool test_userns(bool expect_success)
+{
+ uid_t uid;
+ char map_file_name[32];
+ size_t sz = sizeof(map_file_name);
+ pid_t cpid;
+ bool success;
+
+ uid = getuid();
+
+ int clone_flags = CLONE_NEWUSER;
+ cpid = syscall(SYS_clone, clone_flags, NULL);
+ if (cpid == -1) {
+ printf("clone failed");
+ return false;
+ }
+
+ if (cpid == 0) { /* Code executed by child */
+ // Give parent 1 second to write map file
+ sleep(1);
+ exit(EXIT_SUCCESS);
+ } else { /* Code executed by parent */
+ if(snprintf(map_file_name, sz, "/proc/%d/uid_map", cpid) < 0) {
+ printf("preparing file name string failed");
+ return false;
+ }
+ success = write_file(map_file_name, "0 %d 1", uid);
+ return success == expect_success;
+ }
+
+ printf("should not reach here");
+ return false;
+}
+
+static void test_setuid(uid_t child_uid, bool expect_success)
+{
+ pid_t cpid, w;
+ int wstatus;
+
+ cpid = fork();
+ if (cpid == -1) {
+ die("fork\n");
+ }
+
+ if (cpid == 0) { /* Code executed by child */
+ if (setuid(child_uid) < 0)
+ exit(EXIT_FAILURE);
+ if (getuid() == child_uid)
+ exit(EXIT_SUCCESS);
+ else
+ exit(EXIT_FAILURE);
+ } else { /* Code executed by parent */
+ do {
+ w = waitpid(cpid, &wstatus, WUNTRACED | WCONTINUED);
+ if (w == -1) {
+ die("waitpid\n");
+ }
+
+ if (WIFEXITED(wstatus)) {
+ if (WEXITSTATUS(wstatus) == EXIT_SUCCESS) {
+ if (expect_success) {
+ return;
+ } else {
+ die("unexpected success\n");
+ }
+ } else {
+ if (expect_success) {
+ die("unexpected failure\n");
+ } else {
+ return;
+ }
+ }
+ } else if (WIFSIGNALED(wstatus)) {
+ if (WTERMSIG(wstatus) == 9) {
+ if (expect_success)
+ die("killed unexpectedly\n");
+ else
+ return;
+ } else {
+ die("unexpected signal: %d\n", wstatus);
+ }
+ } else {
+ die("unexpected status: %d\n", wstatus);
+ }
+ } while (!WIFEXITED(wstatus) && !WIFSIGNALED(wstatus));
+ }
+
+ die("should not reach here\n");
+}
+
+static void test_setgid(gid_t child_gid, bool expect_success)
+{
+ pid_t cpid, w;
+ int wstatus;
+
+ cpid = fork();
+ if (cpid == -1) {
+ die("fork\n");
+ }
+
+ if (cpid == 0) { /* Code executed by child */
+ if (setgid(child_gid) < 0)
+ exit(EXIT_FAILURE);
+ if (getgid() == child_gid)
+ exit(EXIT_SUCCESS);
+ else
+ exit(EXIT_FAILURE);
+ } else { /* Code executed by parent */
+ do {
+ w = waitpid(cpid, &wstatus, WUNTRACED | WCONTINUED);
+ if (w == -1) {
+ die("waitpid\n");
+ }
+
+ if (WIFEXITED(wstatus)) {
+ if (WEXITSTATUS(wstatus) == EXIT_SUCCESS) {
+ if (expect_success) {
+ return;
+ } else {
+ die("unexpected success\n");
+ }
+ } else {
+ if (expect_success) {
+ die("unexpected failure\n");
+ } else {
+ return;
+ }
+ }
+ } else if (WIFSIGNALED(wstatus)) {
+ if (WTERMSIG(wstatus) == 9) {
+ if (expect_success)
+ die("killed unexpectedly\n");
+ else
+ return;
+ } else {
+ die("unexpected signal: %d\n", wstatus);
+ }
+ } else {
+ die("unexpected status: %d\n", wstatus);
+ }
+ } while (!WIFEXITED(wstatus) && !WIFSIGNALED(wstatus));
+ }
+
+ die("should not reach here\n");
+}
+
+static void test_setgroups(gid_t* child_groups, size_t len, bool expect_success)
+{
+ pid_t cpid, w;
+ int wstatus;
+ gid_t groupset[len];
+ int i, j;
+
+ cpid = fork();
+ if (cpid == -1) {
+ die("fork\n");
+ }
+
+ if (cpid == 0) { /* Code executed by child */
+ if (setgroups(len, child_groups) != 0)
+ exit(EXIT_FAILURE);
+ if (getgroups(len, groupset) != len)
+ exit(EXIT_FAILURE);
+ for (i = 0; i < len; i++) {
+ for (j = 0; j < len; j++) {
+ if (child_groups[i] == groupset[j])
+ break;
+ if (j == len - 1)
+ exit(EXIT_FAILURE);
+ }
+ }
+ exit(EXIT_SUCCESS);
+ } else { /* Code executed by parent */
+ do {
+ w = waitpid(cpid, &wstatus, WUNTRACED | WCONTINUED);
+ if (w == -1) {
+ die("waitpid\n");
+ }
+
+ if (WIFEXITED(wstatus)) {
+ if (WEXITSTATUS(wstatus) == EXIT_SUCCESS) {
+ if (expect_success) {
+ return;
+ } else {
+ die("unexpected success\n");
+ }
+ } else {
+ if (expect_success) {
+ die("unexpected failure\n");
+ } else {
+ return;
+ }
+ }
+ } else if (WIFSIGNALED(wstatus)) {
+ if (WTERMSIG(wstatus) == 9) {
+ if (expect_success)
+ die("killed unexpectedly\n");
+ else
+ return;
+ } else {
+ die("unexpected signal: %d\n", wstatus);
+ }
+ } else {
+ die("unexpected status: %d\n", wstatus);
+ }
+ } while (!WIFEXITED(wstatus) && !WIFSIGNALED(wstatus));
+ }
+
+ die("should not reach here\n");
+}
+
+
+static void ensure_users_exist(void)
+{
+ 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 ensure_groups_exist(void)
+{
+ ensure_group_exists(ROOT_UGID);
+ ensure_group_exists(RESTRICTED_PARENT_UGID);
+ ensure_group_exists(ALLOWED_CHILD1_UGID);
+ ensure_group_exists(ALLOWED_CHILD2_UGID);
+ ensure_group_exists(NO_POLICY_UGID);
+}
+
+static void drop_caps(bool setid_retained)
+{
+ cap_value_t cap_values[] = {CAP_SETUID, CAP_SETGID};
+ cap_t caps;
+
+ caps = cap_get_proc();
+ if (setid_retained)
+ cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
+ else
+ cap_clear(caps);
+ cap_set_proc(caps);
+ cap_free(caps);
+}
+
+int main(int argc, char **argv)
+{
+ ensure_groups_exist();
+ ensure_users_exist();
+ ensure_securityfs_mounted();
+ write_uid_policies();
+ write_gid_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 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");
+ }
+
+ // 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_UGID, false);
+ test_setuid(ALLOWED_CHILD1_UGID, true);
+ test_setuid(ALLOWED_CHILD2_UGID, true);
+ test_setuid(NO_POLICY_UGID, false);
+
+ test_setgid(ROOT_UGID, false);
+ test_setgid(ALLOWED_CHILD1_UGID, true);
+ test_setgid(ALLOWED_CHILD2_UGID, true);
+ test_setgid(NO_POLICY_UGID, false);
+
+ gid_t allowed_supp_groups[2] = {ALLOWED_CHILD1_UGID, ALLOWED_CHILD2_UGID};
+ gid_t disallowed_supp_groups[2] = {ROOT_UGID, NO_POLICY_UGID};
+ test_setgroups(allowed_supp_groups, 2, true);
+ test_setgroups(disallowed_supp_groups, 2, false);
+
+ if (!test_userns(false)) {
+ die("test_userns worked when it should fail\n");
+ }
+
+ // Now take away all caps
+ drop_caps(false);
+ test_setuid(2, false);
+ test_setuid(3, false);
+ test_setuid(4, false);
+ test_setgid(2, false);
+ test_setgid(3, false);
+ test_setgid(4, false);
+
+ // 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;
+}
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