LSM: selftests for Linux Security Module syscalls

Add selftests for the three system calls supporting the LSM
infrastructure. This set of tests is limited by the differences
in access policy enforced by the existing security modules.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Mickaël Salaün <mic@digikod.net>
Tested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Paul Moore <paul@paul-moore.com>

MAINTAINERS

@@ -19513,6 +19513,7 @@ W:	http://kernsec.org/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git
 F:	include/uapi/linux/lsm.h
 F:	security/
+F:	tools/testing/selftests/lsm/
 X:	security/selinux/
 
 SELINUX SECURITY MODULE

tools/testing/selftests/Makefile

@@ -43,6 +43,7 @@ TARGETS += landlock
 TARGETS += lib
 TARGETS += livepatch
 TARGETS += lkdtm
+TARGETS += lsm
 TARGETS += membarrier
 TARGETS += memfd
 TARGETS += memory-hotplug

tools/testing/selftests/lsm/.gitignore

+/*_test

tools/testing/selftests/lsm/Makefile

+# SPDX-License-Identifier: GPL-2.0
+#
+# First run: make -C ../../../.. headers_install
+
+CFLAGS += -Wall -O2 $(KHDR_INCLUDES)
+LOCAL_HDRS += common.h
+
+TEST_GEN_PROGS := lsm_get_self_attr_test lsm_list_modules_test \
+		  lsm_set_self_attr_test
+
+include ../lib.mk
+
+$(OUTPUT)/lsm_get_self_attr_test: lsm_get_self_attr_test.c common.c
+$(OUTPUT)/lsm_set_self_attr_test: lsm_set_self_attr_test.c common.c
+$(OUTPUT)/lsm_list_modules_test: lsm_list_modules_test.c common.c
+
+EXTRA_CLEAN = $(OUTPUT)/common.o

tools/testing/selftests/lsm/common.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ *
+ * Copyright © 2023 Casey Schaufler <casey@schaufler-ca.com>
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "common.h"
+
+#define PROCATTR "/proc/self/attr/"
+
+int read_proc_attr(const char *attr, char *value, size_t size)
+{
+	int fd;
+	int len;
+	char *path;
+
+	len = strlen(PROCATTR) + strlen(attr) + 1;
+	path = calloc(len, 1);
+	if (path == NULL)
+		return -1;
+	sprintf(path, "%s%s", PROCATTR, attr);
+
+	fd = open(path, O_RDONLY);
+	free(path);
+
+	if (fd < 0)
+		return -1;
+	len = read(fd, value, size);
+
+	close(fd);
+
+	/* Ensure value is terminated */
+	if (len <= 0 || len == size)
+		return -1;
+	value[len] = '\0';
+
+	path = strchr(value, '\n');
+	if (path)
+		*path = '\0';
+
+	return 0;
+}
+
+int read_sysfs_lsms(char *lsms, size_t size)
+{
+	FILE *fp;
+	size_t red;
+
+	fp = fopen("/sys/kernel/security/lsm", "r");
+	if (fp == NULL)
+		return -1;
+	red = fread(lsms, 1, size, fp);
+	fclose(fp);
+
+	if (red <= 0 || red == size)
+		return -1;
+	lsms[red] = '\0';
+	return 0;
+}
+
+int attr_lsm_count(void)
+{
+	char *names = calloc(sysconf(_SC_PAGESIZE), 1);
+	int count = 0;
+
+	if (!names)
+		return 0;
+
+	if (read_sysfs_lsms(names, sysconf(_SC_PAGESIZE)))
+		return 0;
+
+	if (strstr(names, "selinux"))
+		count++;
+	if (strstr(names, "smack"))
+		count++;
+	if (strstr(names, "apparmor"))
+		count++;
+
+	return count;
+}

tools/testing/selftests/lsm/common.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Linux Security Module infrastructure tests
+ *
+ * Copyright © 2023 Casey Schaufler <casey@schaufler-ca.com>
+ */
+
+#ifndef lsm_get_self_attr
+static inline int lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
+				    size_t *size, __u32 flags)
+{
+	return syscall(__NR_lsm_get_self_attr, attr, ctx, size, flags);
+}
+#endif
+
+#ifndef lsm_set_self_attr
+static inline int lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
+				    size_t size, __u32 flags)
+{
+	return syscall(__NR_lsm_set_self_attr, attr, ctx, size, flags);
+}
+#endif
+
+#ifndef lsm_list_modules
+static inline int lsm_list_modules(__u64 *ids, size_t *size, __u32 flags)
+{
+	return syscall(__NR_lsm_list_modules, ids, size, flags);
+}
+#endif
+
+extern int read_proc_attr(const char *attr, char *value, size_t size);
+extern int read_sysfs_lsms(char *lsms, size_t size);
+int attr_lsm_count(void);

tools/testing/selftests/lsm/config

+CONFIG_SYSFS=y
+CONFIG_SECURITY=y
+CONFIG_SECURITYFS=y

tools/testing/selftests/lsm/lsm_get_self_attr_test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ * Tests for the lsm_get_self_attr system call
+ *
+ * Copyright © 2022 Casey Schaufler <casey@schaufler-ca.com>
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "../kselftest_harness.h"
+#include "common.h"
+
+static struct lsm_ctx *next_ctx(struct lsm_ctx *ctxp)
+{
+	void *vp;
+
+	vp = (void *)ctxp + sizeof(*ctxp) + ctxp->ctx_len;
+	return (struct lsm_ctx *)vp;
+}
+
+TEST(size_null_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+
+	ASSERT_NE(NULL, ctx);
+	errno = 0;
+	ASSERT_EQ(-1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, NULL, 0));
+	ASSERT_EQ(EINVAL, errno);
+
+	free(ctx);
+}
+
+TEST(ctx_null_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	size_t size = page_size;
+	int rc;
+
+	rc = lsm_get_self_attr(LSM_ATTR_CURRENT, NULL, &size, 0);
+
+	if (attr_lsm_count()) {
+		ASSERT_NE(-1, rc);
+		ASSERT_NE(1, size);
+	} else {
+		ASSERT_EQ(-1, rc);
+	}
+}
+
+TEST(size_too_small_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	size_t size = 1;
+
+	ASSERT_NE(NULL, ctx);
+	errno = 0;
+	ASSERT_EQ(-1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size, 0));
+	if (attr_lsm_count()) {
+		ASSERT_EQ(E2BIG, errno);
+	} else {
+		ASSERT_EQ(EOPNOTSUPP, errno);
+	}
+	ASSERT_NE(1, size);
+
+	free(ctx);
+}
+
+TEST(flags_zero_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	size_t size;
+	int lsmcount;
+	int i;
+
+	ASSERT_NE(NULL, ctx);
+	errno = 0;
+	size = page_size;
+	ASSERT_EQ(-1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size,
+					LSM_FLAG_SINGLE));
+	ASSERT_EQ(EINVAL, errno);
+	ASSERT_EQ(page_size, size);
+
+	lsmcount = syscall(__NR_lsm_list_modules, syscall_lsms, &size, 0);
+	ASSERT_LE(1, lsmcount);
+	ASSERT_NE(NULL, syscall_lsms);
+
+	for (i = 0; i < lsmcount; i++) {
+		errno = 0;
+		size = page_size;
+		ctx->id = syscall_lsms[i];
+
+		if (syscall_lsms[i] == LSM_ID_SELINUX ||
+		    syscall_lsms[i] == LSM_ID_SMACK ||
+		    syscall_lsms[i] == LSM_ID_APPARMOR) {
+			ASSERT_EQ(1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx,
+						       &size, LSM_FLAG_SINGLE));
+		} else {
+			ASSERT_EQ(-1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx,
+							&size,
+							LSM_FLAG_SINGLE));
+		}
+	}
+
+	free(ctx);
+}
+
+TEST(flags_overset_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	size_t size;
+
+	ASSERT_NE(NULL, ctx);
+
+	errno = 0;
+	size = page_size;
+	ASSERT_EQ(-1, lsm_get_self_attr(LSM_ATTR_CURRENT | LSM_ATTR_PREV, ctx,
+					&size, 0));
+	ASSERT_EQ(EOPNOTSUPP, errno);
+
+	errno = 0;
+	size = page_size;
+	ASSERT_EQ(-1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size,
+					LSM_FLAG_SINGLE |
+					(LSM_FLAG_SINGLE << 1)));
+	ASSERT_EQ(EINVAL, errno);
+
+	free(ctx);
+}
+
+TEST(basic_lsm_get_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	size_t size = page_size;
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	struct lsm_ctx *tctx = NULL;
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	char *attr = calloc(page_size, 1);
+	int cnt_current = 0;
+	int cnt_exec = 0;
+	int cnt_fscreate = 0;
+	int cnt_keycreate = 0;
+	int cnt_prev = 0;
+	int cnt_sockcreate = 0;
+	int lsmcount;
+	int count;
+	int i;
+
+	ASSERT_NE(NULL, ctx);
+	ASSERT_NE(NULL, syscall_lsms);
+
+	lsmcount = syscall(__NR_lsm_list_modules, syscall_lsms, &size, 0);
+	ASSERT_LE(1, lsmcount);
+
+	for (i = 0; i < lsmcount; i++) {
+		switch (syscall_lsms[i]) {
+		case LSM_ID_SELINUX:
+			cnt_current++;
+			cnt_exec++;
+			cnt_fscreate++;
+			cnt_keycreate++;
+			cnt_prev++;
+			cnt_sockcreate++;
+			break;
+		case LSM_ID_SMACK:
+			cnt_current++;
+			break;
+		case LSM_ID_APPARMOR:
+			cnt_current++;
+			cnt_exec++;
+			cnt_prev++;
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (cnt_current) {
+		size = page_size;
+		count = lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size, 0);
+		ASSERT_EQ(cnt_current, count);
+		tctx = ctx;
+		ASSERT_EQ(0, read_proc_attr("current", attr, page_size));
+		ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_exec) {
+		size = page_size;
+		count = lsm_get_self_attr(LSM_ATTR_EXEC, ctx, &size, 0);
+		ASSERT_GE(cnt_exec, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("exec", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_fscreate) {
+		size = page_size;
+		count = lsm_get_self_attr(LSM_ATTR_FSCREATE, ctx, &size, 0);
+		ASSERT_GE(cnt_fscreate, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("fscreate", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_keycreate) {
+		size = page_size;
+		count = lsm_get_self_attr(LSM_ATTR_KEYCREATE, ctx, &size, 0);
+		ASSERT_GE(cnt_keycreate, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("keycreate", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+	if (cnt_prev) {
+		size = page_size;
+		count = lsm_get_self_attr(LSM_ATTR_PREV, ctx, &size, 0);
+		ASSERT_GE(cnt_prev, count);
+		if (count > 0) {
+			tctx = ctx;
+			ASSERT_EQ(0, read_proc_attr("prev", attr, page_size));
+			ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+			for (i = 1; i < count; i++) {
+				tctx = next_ctx(tctx);
+				ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+			}
+		}
+	}
+	if (cnt_sockcreate) {
+		size = page_size;
+		count = lsm_get_self_attr(LSM_ATTR_SOCKCREATE, ctx, &size, 0);
+		ASSERT_GE(cnt_sockcreate, count);
+		if (count > 0) {
+			tctx = ctx;
+			if (read_proc_attr("sockcreate", attr, page_size) == 0)
+				ASSERT_EQ(0, strcmp((char *)tctx->ctx, attr));
+		}
+		for (i = 1; i < count; i++) {
+			tctx = next_ctx(tctx);
+			ASSERT_NE(0, strcmp((char *)tctx->ctx, attr));
+		}
+	}
+
+	free(ctx);
+	free(attr);
+	free(syscall_lsms);
+}
+
+TEST_HARNESS_MAIN

tools/testing/selftests/lsm/lsm_list_modules_test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ * Tests for the lsm_list_modules system call
+ *
+ * Copyright © 2022 Casey Schaufler <casey@schaufler-ca.com>
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "../kselftest_harness.h"
+#include "common.h"
+
+TEST(size_null_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__u64 *syscall_lsms = calloc(page_size, 1);
+
+	ASSERT_NE(NULL, syscall_lsms);
+	errno = 0;
+	ASSERT_EQ(-1, lsm_list_modules(syscall_lsms, NULL, 0));
+	ASSERT_EQ(EFAULT, errno);
+
+	free(syscall_lsms);
+}
+
+TEST(ids_null_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	size_t size = page_size;
+
+	errno = 0;
+	ASSERT_EQ(-1, lsm_list_modules(NULL, &size, 0));
+	ASSERT_EQ(EFAULT, errno);
+	ASSERT_NE(1, size);
+}
+
+TEST(size_too_small_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	size_t size = 1;
+
+	ASSERT_NE(NULL, syscall_lsms);
+	errno = 0;
+	ASSERT_EQ(-1, lsm_list_modules(syscall_lsms, &size, 0));
+	ASSERT_EQ(E2BIG, errno);
+	ASSERT_NE(1, size);
+
+	free(syscall_lsms);
+}
+
+TEST(flags_set_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	size_t size = page_size;
+
+	ASSERT_NE(NULL, syscall_lsms);
+	errno = 0;
+	ASSERT_EQ(-1, lsm_list_modules(syscall_lsms, &size, 7));
+	ASSERT_EQ(EINVAL, errno);
+	ASSERT_EQ(page_size, size);
+
+	free(syscall_lsms);
+}
+
+TEST(correct_lsm_list_modules)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	size_t size = page_size;
+	__u64 *syscall_lsms = calloc(page_size, 1);
+	char *sysfs_lsms = calloc(page_size, 1);
+	char *name;
+	char *cp;
+	int count;
+	int i;
+
+	ASSERT_NE(NULL, sysfs_lsms);
+	ASSERT_NE(NULL, syscall_lsms);
+	ASSERT_EQ(0, read_sysfs_lsms(sysfs_lsms, page_size));
+
+	count = lsm_list_modules(syscall_lsms, &size, 0);
+	ASSERT_LE(1, count);
+	cp = sysfs_lsms;
+	for (i = 0; i < count; i++) {
+		switch (syscall_lsms[i]) {
+		case LSM_ID_CAPABILITY:
+			name = "capability";
+			break;
+		case LSM_ID_SELINUX:
+			name = "selinux";
+			break;
+		case LSM_ID_SMACK:
+			name = "smack";
+			break;
+		case LSM_ID_TOMOYO:
+			name = "tomoyo";
+			break;
+		case LSM_ID_IMA:
+			name = "ima";
+			break;
+		case LSM_ID_APPARMOR:
+			name = "apparmor";
+			break;
+		case LSM_ID_YAMA:
+			name = "yama";
+			break;
+		case LSM_ID_LOADPIN:
+			name = "loadpin";
+			break;
+		case LSM_ID_SAFESETID:
+			name = "safesetid";
+			break;
+		case LSM_ID_LOCKDOWN:
+			name = "lockdown";
+			break;
+		case LSM_ID_BPF:
+			name = "bpf";
+			break;
+		case LSM_ID_LANDLOCK:
+			name = "landlock";
+			break;
+		default:
+			name = "INVALID";
+			break;
+		}
+		ASSERT_EQ(0, strncmp(cp, name, strlen(name)));
+		cp += strlen(name) + 1;
+	}
+
+	free(sysfs_lsms);
+	free(syscall_lsms);
+}
+
+TEST_HARNESS_MAIN

tools/testing/selftests/lsm/lsm_set_self_attr_test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux Security Module infrastructure tests
+ * Tests for the lsm_set_self_attr system call
+ *
+ * Copyright © 2022 Casey Schaufler <casey@schaufler-ca.com>
+ */
+
+#define _GNU_SOURCE
+#include <linux/lsm.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "../kselftest_harness.h"
+#include "common.h"
+
+TEST(ctx_null_lsm_set_self_attr)
+{
+	ASSERT_EQ(-1, lsm_set_self_attr(LSM_ATTR_CURRENT, NULL,
+					sizeof(struct lsm_ctx), 0));
+}
+
+TEST(size_too_small_lsm_set_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	size_t size = page_size;
+
+	ASSERT_NE(NULL, ctx);
+	if (attr_lsm_count()) {
+		ASSERT_LE(1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size,
+					       0));
+	}
+	ASSERT_EQ(-1, lsm_set_self_attr(LSM_ATTR_CURRENT, ctx, 1, 0));
+
+	free(ctx);
+}
+
+TEST(flags_zero_lsm_set_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	struct lsm_ctx *ctx = calloc(page_size, 1);
+	size_t size = page_size;
+
+	ASSERT_NE(NULL, ctx);
+	if (attr_lsm_count()) {
+		ASSERT_LE(1, lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size,
+					       0));
+	}
+	ASSERT_EQ(-1, lsm_set_self_attr(LSM_ATTR_CURRENT, ctx, size, 1));
+
+	free(ctx);
+}
+
+TEST(flags_overset_lsm_set_self_attr)
+{
+	const long page_size = sysconf(_SC_PAGESIZE);
+	char *ctx = calloc(page_size, 1);
+	size_t size = page_size;
+	struct lsm_ctx *tctx = (struct lsm_ctx *)ctx;
+
+	ASSERT_NE(NULL, ctx);
+	if (attr_lsm_count()) {
+		ASSERT_LE(1, lsm_get_self_attr(LSM_ATTR_CURRENT, tctx, &size,
+					       0));
+	}
+	ASSERT_EQ(-1, lsm_set_self_attr(LSM_ATTR_CURRENT | LSM_ATTR_PREV, tctx,
+					size, 0));
+
+	free(ctx);
+}
+
+TEST_HARNESS_MAIN