Re: [PATCH v9 11/11] LSM: selftests for Linux Security Module syscalls

Kees Cook
2023-04-21T20:01:32Z

On Fri, Apr 21, 2023 at 10:42:59AM -0700, Casey Schaufler wrote:
> Add selftests for the three system calls supporting the LSM
> infrastructure.

Yay tests!

With nits below fixed:

Reviewed-by: Kees Cook <keescook@chromium.org>

>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
> tools/testing/selftests/Makefile | 1 +
> tools/testing/selftests/lsm/Makefile | 12 +
> tools/testing/selftests/lsm/config | 2 +
> .../selftests/lsm/lsm_get_self_attr_test.c | 267 ++++++++++++++++++
> .../selftests/lsm/lsm_list_modules_test.c | 149 ++++++++++
> .../selftests/lsm/lsm_set_self_attr_test.c | 70 +++++
> 6 files changed, 501 insertions(+)
> create mode 100644 tools/testing/selftests/lsm/Makefile
> create mode 100644 tools/testing/selftests/lsm/config
> create mode 100644 tools/testing/selftests/lsm/lsm_get_self_attr_test.c
> create mode 100644 tools/testing/selftests/lsm/lsm_list_modules_test.c
> create mode 100644 tools/testing/selftests/lsm/lsm_set_self_attr_test.c
>
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 13a6837a0c6b..b18d133a1141 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -38,6 +38,7 @@ TARGETS += landlock
> TARGETS += lib
> TARGETS += livepatch
> TARGETS += lkdtm
> +TARGETS += lsm
> TARGETS += membarrier
> TARGETS += memfd
> TARGETS += memory-hotplug
> diff --git a/tools/testing/selftests/lsm/Makefile b/tools/testing/selftests/lsm/Makefile
> new file mode 100644
> index 000000000000..f39a75212b78
> --- /dev/null
> +++ b/tools/testing/selftests/lsm/Makefile
> @@ -0,0 +1,12 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# First run: make -C ../../../.. headers_install
> +
> +CFLAGS += -Wall -O2 $(KHDR_INCLUDES)
> +
> +TEST_GEN_PROGS := lsm_get_self_attr_test lsm_list_modules_test \
> + lsm_set_self_attr_test
> +
> +include ../lib.mk
> +
> +$(TEST_GEN_PROGS):
> diff --git a/tools/testing/selftests/lsm/config b/tools/testing/selftests/lsm/config
> new file mode 100644
> index 000000000000..afb887715f64
> --- /dev/null
> +++ b/tools/testing/selftests/lsm/config
> @@ -0,0 +1,2 @@
> +CONFIG_SYSFS=y
> +CONFIG_SECURITY=y
> diff --git a/tools/testing/selftests/lsm/lsm_get_self_attr_test.c b/tools/testing/selftests/lsm/lsm_get_self_attr_test.c
> new file mode 100644
> index 000000000000..71c2b1a8a44e
> --- /dev/null
> +++ b/tools/testing/selftests/lsm/lsm_get_self_attr_test.c
> @@ -0,0 +1,267 @@
> +// 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>
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#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"
> +
> +#define PROCATTR "/proc/self/attr/"
> +
> +static int read_proc_attr(const char *attr, char *value, __kernel_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);
> + if (len <= 0)
> + return -1;
> +fprintf(stderr, "len=%d\n", len);

Accidentally leftover debugging?

> + close(fd);
> +
> + path = strchr(value, '\n');
> + if (path)
> + *path = '\0';
> +
> + return 0;
> +}
> +
> +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);
> + char *ctx = calloc(page_size, 1);
> +
> + ASSERT_NE(NULL, ctx);
> + ASSERT_EQ(-1, syscall(__NR_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);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_NE(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, NULL,
> + &size, 0));
> + ASSERT_NE(1, size);
> +}
> +
> +TEST(size_too_small_lsm_get_self_attr)
> +{
> + const long page_size = sysconf(_SC_PAGESIZE);
> + char *ctx = calloc(page_size, 1);
> + __kernel_size_t size = 1;
> +
> + ASSERT_NE(NULL, ctx);
> + ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
> + &size, 0));
> + ASSERT_EQ(E2BIG, errno);
> + ASSERT_NE(1, size);
> +
> + free(ctx);
> +}
> +
> +TEST(flags_zero_lsm_get_self_attr)
> +{
> + const long page_size = sysconf(_SC_PAGESIZE);
> + char *ctx = calloc(page_size, 1);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_NE(NULL, ctx);

I would explicitly set errno to 0 before syscalls, just to sure.

> + ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
> + &size, 1));
> + ASSERT_EQ(EINVAL, errno);
> + ASSERT_EQ(page_size, size);
> +
> + free(ctx);
> +}
> +
> +TEST(flags_overset_lsm_get_self_attr)
> +{
> + const long page_size = sysconf(_SC_PAGESIZE);
> + char *ctx = calloc(page_size, 1);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_NE(NULL, ctx);

e.g.:
errno = 0;

but repeated for all syscalls below...

> + ASSERT_EQ(-1, syscall(__NR_lsm_get_self_attr,
> + LSM_ATTR_CURRENT | LSM_ATTR_PREV, ctx, &size, 0));
> + ASSERT_EQ(EOPNOTSUPP, errno);
> +
> + free(ctx);
> +}
> +
> +TEST(basic_lsm_get_self_attr)
> +{
> + const long page_size = sysconf(_SC_PAGESIZE);
> + __kernel_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 = syscall(__NR_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 = syscall(__NR_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 = syscall(__NR_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 = syscall(__NR_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 = syscall(__NR_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 = syscall(__NR_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
> diff --git a/tools/testing/selftests/lsm/lsm_list_modules_test.c b/tools/testing/selftests/lsm/lsm_list_modules_test.c
> new file mode 100644
> index 000000000000..3ec814002710
> --- /dev/null
> +++ b/tools/testing/selftests/lsm/lsm_list_modules_test.c
> @@ -0,0 +1,149 @@
> +// 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>
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#define _GNU_SOURCE
> +#include <linux/lsm.h>
> +#include <string.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include "../kselftest_harness.h"
> +
> +static int read_sysfs_lsms(char *lsms, __kernel_size_t size)
> +{
> + FILE *fp;
> +
> + fp = fopen("/sys/kernel/security/lsm", "r");
> + if (fp == NULL)
> + return -1;
> + if (fread(lsms, 1, size, fp) <= 0)
> + return -1;
> + fclose(fp);
> + return 0;
> +}
> +
> +TEST(size_null_lsm_list_modules)
> +{
> + const long page_size = sysconf(_SC_PAGESIZE);
> + char *syscall_lsms = calloc(page_size, 1);
> +
> + ASSERT_NE(NULL, syscall_lsms);
> + ASSERT_EQ(-1, syscall(__NR_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);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_EQ(-1, syscall(__NR_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);
> + char *syscall_lsms = calloc(page_size, 1);
> + __kernel_size_t size = 1;
> +
> + ASSERT_NE(NULL, syscall_lsms);
> + ASSERT_EQ(-1, syscall(__NR_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);
> + char *syscall_lsms = calloc(page_size, 1);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_NE(NULL, syscall_lsms);
> + ASSERT_EQ(-1, syscall(__NR_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);
> + __kernel_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 = syscall(__NR_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
> diff --git a/tools/testing/selftests/lsm/lsm_set_self_attr_test.c b/tools/testing/selftests/lsm/lsm_set_self_attr_test.c
> new file mode 100644
> index 000000000000..ca538a703168
> --- /dev/null
> +++ b/tools/testing/selftests/lsm/lsm_set_self_attr_test.c
> @@ -0,0 +1,70 @@
> +// 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>
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#define _GNU_SOURCE
> +#include <linux/lsm.h>
> +#include <string.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include "../kselftest_harness.h"
> +
> +TEST(ctx_null_lsm_set_self_attr)
> +{
> + ASSERT_EQ(-1, syscall(__NR_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);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_NE(NULL, ctx);
> + ASSERT_GE(1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
> + &size, 0));
> + ASSERT_EQ(-1, syscall(__NR_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);
> + char *ctx = calloc(page_size, 1);
> + __kernel_size_t size = page_size;
> +
> + ASSERT_NE(NULL, ctx);
> + ASSERT_GE(1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, ctx,
> + &size, 0));
> + ASSERT_EQ(-1, syscall(__NR_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);
> + __kernel_size_t size = page_size;
> + struct lsm_ctx *tctx = (struct lsm_ctx *)ctx;
> +
> + ASSERT_NE(NULL, ctx);
> + ASSERT_GE(1, syscall(__NR_lsm_get_self_attr, LSM_ATTR_CURRENT, tctx,
> + &size, 0));
> + ASSERT_EQ(-1, syscall(__NR_lsm_set_self_attr,
> + LSM_ATTR_CURRENT | LSM_ATTR_PREV, tctx, size, 0));
> +
> + free(ctx);
> +}
> +
> +TEST_HARNESS_MAIN
> --
> 2.39.2
>

--
Kees Cook