[PATCH -mm] selftests/capabilities: Add tests for capability evolution

[Andy Lutomirski]

This test focuses on ambient capabilities.  It requires either root
or the ability to create user namespaces.  Some of the test cases
will be skipped for nonroot users.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---

I took taking advantage of the extra week to make my test case work :)

 tools/testing/selftests/capabilities/.gitignore    |   2 +
 tools/testing/selftests/capabilities/Makefile      |  19 +
 tools/testing/selftests/capabilities/test_execve.c | 427 +++++++++++++++++++++
 .../testing/selftests/capabilities/validate_cap.c  |  73 ++++
 4 files changed, 521 insertions(+)
 create mode 100644 tools/testing/selftests/capabilities/.gitignore
 create mode 100644 tools/testing/selftests/capabilities/Makefile
 create mode 100644 tools/testing/selftests/capabilities/test_execve.c
 create mode 100644 tools/testing/selftests/capabilities/validate_cap.c

diff --git a/tools/testing/selftests/capabilities/.gitignore b/tools/testing/selftests/capabilities/.gitignore
new file mode 100644
index 000000000000..b732dd0d4738
--- /dev/null
+++ b/tools/testing/selftests/capabilities/.gitignore
@@ -0,0 +1,2 @@
+test_execve
+validate_cap
diff --git a/tools/testing/selftests/capabilities/Makefile b/tools/testing/selftests/capabilities/Makefile
new file mode 100644
index 000000000000..5b90ed14cccb
--- /dev/null
+++ b/tools/testing/selftests/capabilities/Makefile
@@ -0,0 +1,19 @@
+all:
+
+include ../lib.mk
+
+.PHONY: all clean
+
+TARGETS := validate_cap test_execve
+TEST_PROGS := test_execve
+
+CFLAGS := -O2 -g -std=gnu99 -Wall -lcap-ng
+
+all: $(TARGETS)
+
+clean:
+	$(RM) $(TARGETS)
+
+$(TARGETS): %: %.c
+	$(CC) -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl
+
diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
new file mode 100644
index 000000000000..10a21a958aaf
--- /dev/null
+++ b/tools/testing/selftests/capabilities/test_execve.c
@@ -0,0 +1,427 @@
+#define _GNU_SOURCE
+
+#include <cap-ng.h>
+#include <err.h>
+#include <linux/capability.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <sched.h>
+#include <sys/mount.h>
+#include <limits.h>
+#include <libgen.h>
+#include <malloc.h>
+#include <sys/wait.h>
+#include <sys/prctl.h>
+#include <sys/stat.h>
+
+#ifndef PR_CAP_AMBIENT
+#define PR_CAP_AMBIENT			47
+# define PR_CAP_AMBIENT_IS_SET		1
+# define PR_CAP_AMBIENT_RAISE		2
+# define PR_CAP_AMBIENT_LOWER		3
+# define PR_CAP_AMBIENT_CLEAR_ALL	4
+#endif
+
+static int nerrs;
+
+static void 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) {
+		err(1, "vsnprintf failed");
+	}
+	if (buf_len >= sizeof(buf)) {
+		errx(1, "vsnprintf output truncated");
+	}
+
+	fd = open(filename, O_WRONLY);
+	if (fd < 0) {
+		if ((errno == ENOENT) && enoent_ok)
+			return;
+		err(1, "open of %s failed", filename);
+	}
+	written = write(fd, buf, buf_len);
+	if (written != buf_len) {
+		if (written >= 0) {
+			errx(1, "short write to %s", filename);
+		} else {
+			err(1, "write to %s failed", filename);
+		}
+	}
+	if (close(fd) != 0) {
+		err(1, "close of %s failed", filename);
+	}
+}
+
+static void maybe_write_file(char *filename, char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vmaybe_write_file(true, filename, fmt, ap);
+	va_end(ap);
+}
+
+static void write_file(char *filename, char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vmaybe_write_file(false, filename, fmt, ap);
+	va_end(ap);
+}
+
+static bool create_and_enter_ns(uid_t inner_uid)
+{
+	uid_t outer_uid;
+	gid_t outer_gid;
+	int i;
+	bool have_outer_privilege;
+
+	outer_uid = getuid();
+	outer_gid = getgid();
+
+	/*
+	 * TODO: If we're already root, we could skip creating the userns.
+	 */
+
+	if (unshare(CLONE_NEWNS) == 0) {
+		printf("[NOTE]\tUsing global UIDs for tests\n");
+		if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) != 0)
+			err(1, "PR_SET_KEEPCAPS");
+		if (setresuid(inner_uid, inner_uid, -1) != 0)
+			err(1, "setresuid");
+
+		// Re-enable effective caps
+		capng_get_caps_process();
+		for (i = 0; i < CAP_LAST_CAP; i++)
+			if (capng_have_capability(CAPNG_PERMITTED, i))
+				capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, i);
+		if (capng_apply(CAPNG_SELECT_CAPS) != 0)
+			err(1, "capng_apply");
+
+		have_outer_privilege = true;
+	} else if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == 0) {
+		printf("[NOTE]\tUsing a user namespace for tests\n");
+		maybe_write_file("/proc/self/setgroups", "deny");
+		write_file("/proc/self/uid_map", "%d %d 1", inner_uid, outer_uid);
+		write_file("/proc/self/gid_map", "0 %d 1", outer_gid);
+
+		have_outer_privilege = false;
+	} else {
+		errx(1, "must be root or be able to create a userns");
+	}
+
+	if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL) != 0)
+		err(1, "remount everything private");
+
+	return have_outer_privilege;
+}
+
+static void chdir_to_tmpfs(void)
+{
+	char cwd[PATH_MAX];
+	if (getcwd(cwd, sizeof(cwd)) != cwd)
+		err(1, "getcwd");
+
+	if (mount("private_tmp", ".", "tmpfs", 0, "mode=0777") != 0)
+		err(1, "mount private tmpfs");
+
+	if (chdir(cwd) != 0)
+		err(1, "chdir to private tmpfs");
+
+	if (umount2(".", MNT_DETACH) != 0)
+		err(1, "detach private tmpfs");
+}
+
+static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
+{
+	int from = openat(fromfd, fromname, O_RDONLY);
+	if (from == -1)
+		err(1, "open copy source");
+
+	int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
+
+	while (true) {
+		char buf[4096];
+		ssize_t sz = read(from, buf, sizeof(buf));
+		if (sz == 0)
+			break;
+		if (sz < 0)
+			err(1, "read");
+
+		if (write(to, buf, sz) != sz)
+			err(1, "write");	/* no short writes on tmpfs */
+	}
+
+	close(from);
+	close(to);
+}
+
+static bool fork_wait(void)
+{
+	pid_t child = fork();
+	if (child == 0) {
+		nerrs = 0;
+		return true;
+	} else if (child > 0) {
+		int status;
+		if (waitpid(child, &status, 0) != child ||
+		    !WIFEXITED(status)) {
+			printf("[FAIL]\tChild died\n");
+			nerrs++;
+		} else if (WEXITSTATUS(status) != 0) {
+			printf("[FAIL]\tChild failed\n");
+			nerrs++;
+		} else {
+			printf("[OK]\tChild succeeded\n");
+		}
+
+		return false;
+	} else {
+		err(1, "fork");
+	}
+}
+
+static void exec_other_validate_cap(const char *name,
+				    bool eff, bool perm, bool inh, bool ambient)
+{
+	execl(name, name, (eff ? "1" : "0"),
+	      (perm ? "1" : "0"), (inh ? "1" : "0"), (ambient ? "1" : "0"),
+	      NULL);
+	err(1, "execl");
+}
+
+static void exec_validate_cap(bool eff, bool perm, bool inh, bool ambient)
+{
+	exec_other_validate_cap("./validate_cap", eff, perm, inh, ambient);
+}
+
+static int do_tests(int uid, const char *our_path)
+{
+	bool have_outer_privilege = create_and_enter_ns(uid);
+
+	int ourpath_fd = open(our_path, O_RDONLY | O_DIRECTORY);
+	if (ourpath_fd == -1)
+		err(1, "open '%s'", our_path);
+
+	chdir_to_tmpfs();
+
+	copy_fromat_to(ourpath_fd, "validate_cap", "validate_cap");
+
+	if (have_outer_privilege) {
+		uid_t gid = getegid();
+
+		copy_fromat_to(ourpath_fd, "validate_cap",
+			       "validate_cap_suidroot");
+		if (chown("validate_cap_suidroot", 0, -1) != 0)
+			err(1, "chown");
+		if (chmod("validate_cap_suidroot", S_ISUID | 0700) != 0)
+			err(1, "chmod");
+
+		copy_fromat_to(ourpath_fd, "validate_cap",
+			       "validate_cap_suidnonroot");
+		if (chown("validate_cap_suidnonroot", uid + 1, -1) != 0)
+			err(1, "chown");
+		if (chmod("validate_cap_suidnonroot", S_ISUID | 0700) != 0)
+			err(1, "chmod");
+
+		copy_fromat_to(ourpath_fd, "validate_cap",
+			       "validate_cap_sgidroot");
+		if (chown("validate_cap_sgidroot", -1, 0) != 0)
+			err(1, "chown");
+		if (chmod("validate_cap_sgidroot", S_ISGID | 0710) != 0)
+			err(1, "chmod");
+
+		copy_fromat_to(ourpath_fd, "validate_cap",
+			       "validate_cap_sgidnonroot");
+		if (chown("validate_cap_sgidnonroot", -1, gid + 1) != 0)
+			err(1, "chown");
+		if (chmod("validate_cap_sgidnonroot", S_ISGID | 0710) != 0)
+			err(1, "chmod");
+}
+
+	capng_get_caps_process();
+
+	/* Make sure that i starts out clear */
+	capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
+	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
+		err(1, "capng_apply");
+
+	if (uid == 0) {
+		printf("[RUN]\tRoot => ep\n");
+		if (fork_wait())
+			exec_validate_cap(true, true, false, false);
+	} else {
+		printf("[RUN]\tNon-root => no caps\n");
+		if (fork_wait())
+			exec_validate_cap(false, false, false, false);
+	}
+
+	printf("[OK]\tCheck cap_ambient manipulation rules\n");
+
+	/* We should not be able to add ambient caps yet. */
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != -1 || errno != EPERM) {
+		if (errno == EINVAL)
+			printf("[FAIL]\tPR_CAP_AMBIENT_RAISE isn't supported\n");
+		else
+			printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have failed eith EPERM on a non-inheritable cap\n");
+		return 1;
+	}
+	printf("[OK]\tPR_CAP_AMBIENT_RAISE failed on non-inheritable cap\n");
+
+	capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_RAW);
+	capng_update(CAPNG_DROP, CAPNG_PERMITTED, CAP_NET_RAW);
+	capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, CAP_NET_RAW);
+	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
+		err(1, "capng_apply");
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_RAW, 0, 0, 0) != -1 || errno != EPERM) {
+		printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have failed on a non-permitted cap\n");
+		return 1;
+	}
+	printf("[OK]\tPR_CAP_AMBIENT_RAISE failed on non-permitted cap\n");
+
+	capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
+	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
+		err(1, "capng_apply");
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
+		printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have succeeded\n");
+		return 1;
+	}
+	printf("[OK]\tPR_CAP_AMBIENT_RAISE worked\n");
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 1) {
+		printf("[FAIL]\tPR_CAP_AMBIENT_IS_SET is broken\n");
+		return 1;
+	}
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0, 0) != 0)
+		err(1, "PR_CAP_AMBIENT_CLEAR_ALL");
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
+		printf("[FAIL]\tPR_CAP_AMBIENT_CLEAR_ALL didn't work\n");
+		return 1;
+	}
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0)
+		err(1, "PR_CAP_AMBIENT_RAISE");
+
+	capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
+	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
+		err(1, "capng_apply");
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
+		printf("[FAIL]\tDropping I should have dropped A\n");
+		return 1;
+	}
+
+	printf("[OK]\tBasic manipulation appears to work\n");
+
+	capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
+	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
+		err(1, "capng_apply");
+	if (uid == 0) {
+		printf("[RUN]\tRoot +i => eip\n");
+		if (fork_wait())
+			exec_validate_cap(true, true, true, false);
+	} else {
+		printf("[RUN]\tNon-root +i => i\n");
+		if (fork_wait())
+			exec_validate_cap(false, false, true, false);
+	}
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0)
+		err(1, "PR_CAP_AMBIENT_RAISE");
+
+	printf("[RUN]\tUID %d +ia => eipa\n", uid);
+	if (fork_wait())
+		exec_validate_cap(true, true, true, true);
+
+	/* The remaining tests need real privilege */
+
+	if (!have_outer_privilege) {
+		printf("[SKIP]\tSUID/SGID tests (needs privilege)\n");
+		goto done;
+	}
+
+	if (uid == 0) {
+		printf("[RUN]\tRoot +ia, suidroot => eipa\n");
+		if (fork_wait())
+			exec_other_validate_cap("./validate_cap_suidroot",
+						true, true, true, true);
+
+		printf("[RUN]\tRoot +ia, suidnonroot => ip\n");
+		if (fork_wait())
+			exec_other_validate_cap("./validate_cap_suidnonroot",
+						false, true, true, false);
+
+		printf("[RUN]\tRoot +ia, sgidroot => eipa\n");
+		if (fork_wait())
+			exec_other_validate_cap("./validate_cap_sgidroot",
+						true, true, true, true);
+
+		if (fork_wait()) {
+			printf("[RUN]\tRoot, gid != 0, +ia, sgidroot => eip\n");
+			if (setresgid(1, 1, 1) != 0)
+				err(1, "setresgid");
+			exec_other_validate_cap("./validate_cap_sgidroot",
+						true, true, true, false);
+		}
+
+		printf("[RUN]\tRoot +ia, sgidnonroot => eip\n");
+		if (fork_wait())
+			exec_other_validate_cap("./validate_cap_sgidnonroot",
+						true, true, true, false);
+	} else {
+		printf("[RUN]\tNon-root +ia, sgidnonroot => i\n");
+		exec_other_validate_cap("./validate_cap_sgidnonroot",
+						false, false, true, false);
+
+		if (fork_wait()) {
+			printf("[RUN]\tNon-root +ia, sgidroot => i\n");
+			if (setresgid(1, 1, 1) != 0)
+				err(1, "setresgid");
+			exec_other_validate_cap("./validate_cap_sgidroot",
+						false, false, true, false);
+		}
+	}
+
+done:
+	return nerrs ? 1 : 0;
+}
+
+int main(int argc, char **argv)
+{
+	char *tmp1, *tmp2, *our_path;
+
+	/* Find our path */
+	tmp1 = strdup(argv[0]);
+	if (!tmp1)
+		err(1, "strdup");
+	tmp2 = dirname(tmp1);
+	our_path = strdup(tmp2);
+	if (!our_path)
+		err(1, "strdup");
+	free(tmp1);
+
+	if (fork_wait()) {
+		printf("[RUN]\t+++ Tests with uid == 0 +++\n");
+		return do_tests(0, our_path);
+	}
+
+	if (fork_wait()) {
+		printf("[RUN]\t+++ Tests with uid != 0 +++\n");
+		return do_tests(1, our_path);
+	}
+
+	return nerrs ? 1 : 0;
+}
diff --git a/tools/testing/selftests/capabilities/validate_cap.c b/tools/testing/selftests/capabilities/validate_cap.c
new file mode 100644
index 000000000000..dd3c45f7b23c
--- /dev/null
+++ b/tools/testing/selftests/capabilities/validate_cap.c
@@ -0,0 +1,73 @@
+#include <cap-ng.h>
+#include <err.h>
+#include <linux/capability.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdio.h>
+#include <sys/prctl.h>
+#include <sys/auxv.h>
+
+#ifndef PR_CAP_AMBIENT
+#define PR_CAP_AMBIENT			47
+# define PR_CAP_AMBIENT_IS_SET		1
+# define PR_CAP_AMBIENT_RAISE		2
+# define PR_CAP_AMBIENT_LOWER		3
+# define PR_CAP_AMBIENT_CLEAR_ALL	4
+#endif
+
+#if __GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 19)
+# define HAVE_GETAUXVAL
+#endif
+
+static bool bool_arg(char **argv, int i)
+{
+	if (!strcmp(argv[i], "0"))
+		return false;
+	else if (!strcmp(argv[i], "1"))
+		return true;
+	else
+		errx(1, "wrong argv[%d]", i);
+}
+
+int main(int argc, char **argv)
+{
+	const char *atsec = "";
+
+	/*
+	 * Be careful just in case a setgid or setcapped copy of this
+	 * helper gets out.
+	 */
+
+	if (argc != 5)
+		errx(1, "wrong argc");
+
+#ifdef HAVE_GETAUXVAL
+	if (getauxval(AT_SECURE))
+		atsec = " (AT_SECURE is set)";
+	else
+		atsec = " (AT_SECURE is not set)";
+#endif
+
+	capng_get_caps_process();
+
+	if (capng_have_capability(CAPNG_EFFECTIVE, CAP_NET_BIND_SERVICE) != bool_arg(argv, 1)) {
+		printf("[FAIL]\tWrong effective state%s\n", atsec);
+		return 1;
+	}
+	if (capng_have_capability(CAPNG_PERMITTED, CAP_NET_BIND_SERVICE) != bool_arg(argv, 2)) {
+		printf("[FAIL]\tWrong permitted state%s\n", atsec);
+		return 1;
+	}
+	if (capng_have_capability(CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE) != bool_arg(argv, 3)) {
+		printf("[FAIL]\tWrong inheritable state%s\n", atsec);
+		return 1;
+	}
+
+	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != bool_arg(argv, 4)) {
+		printf("[FAIL]\tWrong ambient state%s\n", atsec);
+		return 1;
+	}
+
+	printf("[OK]\tCapabilities after execve were correct\n");
+	return 0;
+}
-- 
2.4.3

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