From patchwork Tue Jul 14 18:16:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 11663325 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 99203722 for ; Tue, 14 Jul 2020 18:17:59 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id D4F192242B for ; Tue, 14 Jul 2020 18:17:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D4F192242B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19316-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 3720 invoked by uid 550); 14 Jul 2020 18:17:09 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 3579 invoked from network); 14 Jul 2020 18:17:08 -0000 From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: linux-kernel@vger.kernel.org Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Aleksa Sarai , Alexei Starovoitov , Al Viro , Andrew Morton , Andy Lutomirski , Christian Brauner , Christian Heimes , Daniel Borkmann , Deven Bowers , Dmitry Vyukov , Eric Biggers , Eric Chiang , Florian Weimer , James Morris , Jan Kara , Jann Horn , Jonathan Corbet , Kees Cook , Lakshmi Ramasubramanian , Matthew Garrett , Matthew Wilcox , Michael Kerrisk , =?utf-8?q?Micka=C3=ABl_Sala=C3=BC?= =?utf-8?q?n?= , Mimi Zohar , =?utf-8?q?Philippe_Tr=C3=A9buchet?= , Scott Shell , Sean Christopherson , Shuah Khan , Steve Dower , Steve Grubb , Tetsuo Handa , Thibaut Sautereau , Vincent Strubel , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v6 6/7] selftest/openat2: Add tests for O_MAYEXEC enforcing Date: Tue, 14 Jul 2020 20:16:37 +0200 Message-Id: <20200714181638.45751-7-mic@digikod.net> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200714181638.45751-1-mic@digikod.net> References: <20200714181638.45751-1-mic@digikod.net> MIME-Version: 1.0 X-Antivirus: Dr.Web (R) for Unix mail servers drweb plugin ver.6.0.2.8 X-Antivirus-Code: 0x100000 Test propagation of noexec mount points or file executability through files open with or without O_MAYEXEC, thanks to the fs.open_mayexec_enforce sysctl. Signed-off-by: Mickaël Salaün Reviewed-by: Thibaut Sautereau Cc: Aleksa Sarai Cc: Al Viro Cc: Kees Cook Cc: Shuah Khan Reviewed-by: Kees Cook --- Changes since v5: * Refactor with FIXTURE_VARIANT, which make the tests much more easy to read and maintain. * Save and restore initial sysctl value (suggested by Kees Cook). * Test with a sysctl value of 0. * Check errno in sysctl_access_write test. * Update tests for the CAP_SYS_ADMIN switch. * Update tests to check -EISDIR (replacing -EACCES). * Replace FIXTURE_DATA() with FIXTURE() (spotted by Kees Cook). * Use global const strings. Changes since v3: * Replace RESOLVE_MAYEXEC with O_MAYEXEC. * Add tests to check that O_MAYEXEC is ignored by open(2) and openat(2). Changes since v2: * Move tests from exec/ to openat2/ . * Replace O_MAYEXEC with RESOLVE_MAYEXEC from openat2(2). * Cleanup tests. Changes since v1: * Move tests from yama/ to exec/ . * Fix _GNU_SOURCE in kselftest_harness.h . * Add a new test sysctl_access_write to check if CAP_MAC_ADMIN is taken into account. * Test directory execution which is always forbidden since commit 73601ea5b7b1 ("fs/open.c: allow opening only regular files during execve()"), and also check that even the root user can not bypass file execution checks. * Make sure delete_workspace() always as enough right to succeed. * Cosmetic cleanup. --- tools/testing/selftests/kselftest_harness.h | 3 + tools/testing/selftests/openat2/Makefile | 3 +- tools/testing/selftests/openat2/config | 1 + tools/testing/selftests/openat2/helpers.h | 1 + .../testing/selftests/openat2/omayexec_test.c | 262 ++++++++++++++++++ 5 files changed, 269 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/openat2/config create mode 100644 tools/testing/selftests/openat2/omayexec_test.c diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h index c9f03ef93338..68a0acd9ea1e 100644 --- a/tools/testing/selftests/kselftest_harness.h +++ b/tools/testing/selftests/kselftest_harness.h @@ -50,7 +50,10 @@ #ifndef __KSELFTEST_HARNESS_H #define __KSELFTEST_HARNESS_H +#ifndef _GNU_SOURCE #define _GNU_SOURCE +#endif + #include #include #include diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile index 4b93b1417b86..cb98bdb4d5b1 100644 --- a/tools/testing/selftests/openat2/Makefile +++ b/tools/testing/selftests/openat2/Makefile @@ -1,7 +1,8 @@ # SPDX-License-Identifier: GPL-2.0-or-later CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test +LDLIBS += -lcap +TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test omayexec_test include ../lib.mk diff --git a/tools/testing/selftests/openat2/config b/tools/testing/selftests/openat2/config new file mode 100644 index 000000000000..dd53c266bf52 --- /dev/null +++ b/tools/testing/selftests/openat2/config @@ -0,0 +1 @@ +CONFIG_SYSCTL=y diff --git a/tools/testing/selftests/openat2/helpers.h b/tools/testing/selftests/openat2/helpers.h index a6ea27344db2..1dcd3e1e2f38 100644 --- a/tools/testing/selftests/openat2/helpers.h +++ b/tools/testing/selftests/openat2/helpers.h @@ -9,6 +9,7 @@ #define _GNU_SOURCE #include +#include #include #include #include "../kselftest.h" diff --git a/tools/testing/selftests/openat2/omayexec_test.c b/tools/testing/selftests/openat2/omayexec_test.c new file mode 100644 index 000000000000..a33f31e59045 --- /dev/null +++ b/tools/testing/selftests/openat2/omayexec_test.c @@ -0,0 +1,262 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Test O_MAYEXEC + * + * Copyright © 2018-2020 ANSSI + * + * Author: Mickaël Salaün + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +#include "helpers.h" +#include "../kselftest_harness.h" + +#ifndef O_MAYEXEC +#define O_MAYEXEC 040000000 +#endif + +static const char sysctl_path[] = "/proc/sys/fs/open_mayexec_enforce"; + +static const char workdir_path[] = "./test-mount"; +static const char file_path[] = "./test-mount/file"; +static const char dir_path[] = "./test-mount/directory"; + +static void ignore_dac(struct __test_metadata *_metadata, int override) +{ + cap_t caps; + const cap_value_t cap_val[2] = { + CAP_DAC_OVERRIDE, + CAP_DAC_READ_SEARCH, + }; + + caps = cap_get_proc(); + ASSERT_NE(NULL, caps); + ASSERT_EQ(0, cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_val, + override ? CAP_SET : CAP_CLEAR)); + ASSERT_EQ(0, cap_set_proc(caps)); + EXPECT_EQ(0, cap_free(caps)); +} + +static void ignore_sys_admin(struct __test_metadata *_metadata, int override) +{ + cap_t caps; + const cap_value_t cap_val[1] = { + CAP_SYS_ADMIN, + }; + + caps = cap_get_proc(); + ASSERT_NE(NULL, caps); + ASSERT_EQ(0, cap_set_flag(caps, CAP_EFFECTIVE, 1, cap_val, + override ? CAP_SET : CAP_CLEAR)); + ASSERT_EQ(0, cap_set_proc(caps)); + EXPECT_EQ(0, cap_free(caps)); +} + +static void test_omx(struct __test_metadata *_metadata, + const char *const path, const int err_code) +{ + struct open_how how = { + .flags = O_RDONLY | O_CLOEXEC, + }; + int fd; + + /* Opens without O_MAYEXEC. */ + fd = sys_openat2(AT_FDCWD, path, &how); + ASSERT_LE(0, fd); + EXPECT_EQ(0, close(fd)); + + how.flags |= O_MAYEXEC; + + /* Checks that O_MAYEXEC is ignored with open(2). */ + fd = open(path, how.flags); + ASSERT_LE(0, fd); + EXPECT_EQ(0, close(fd)); + + /* Checks that O_MAYEXEC is ignored with openat(2). */ + fd = openat(AT_FDCWD, path, how.flags); + ASSERT_LE(0, fd); + EXPECT_EQ(0, close(fd)); + + /* Opens with O_MAYEXEC. */ + fd = sys_openat2(AT_FDCWD, path, &how); + if (!err_code) { + ASSERT_LE(0, fd); + EXPECT_EQ(0, close(fd)); + } else { + ASSERT_EQ(err_code, fd); + } +} + +static void test_omx_dir_file(struct __test_metadata *_metadata, const int err_code) +{ + test_omx(_metadata, dir_path, -EISDIR); + test_omx(_metadata, file_path, err_code); +} + +static void test_dir_file(struct __test_metadata *_metadata, const int err_code) +{ + /* Tests as root. */ + ignore_dac(_metadata, 1); + test_omx_dir_file(_metadata, err_code); + + /* Tests without bypass. */ + ignore_dac(_metadata, 0); + test_omx_dir_file(_metadata, err_code); +} + +static void sysctl_write_char(struct __test_metadata *_metadata, const char value) +{ + int fd; + + fd = open(sysctl_path, O_WRONLY | O_CLOEXEC); + ASSERT_LE(0, fd); + ASSERT_EQ(1, write(fd, &value, 1)); + EXPECT_EQ(0, close(fd)); +} + +static char sysctl_read_char(struct __test_metadata *_metadata) +{ + int fd; + char sysctl_value; + + fd = open(sysctl_path, O_RDONLY | O_CLOEXEC); + ASSERT_LE(0, fd); + ASSERT_EQ(1, read(fd, &sysctl_value, 1)); + EXPECT_EQ(0, close(fd)); + return sysctl_value; +} + +FIXTURE(omayexec) { + char initial_sysctl_value; +}; + +FIXTURE_VARIANT(omayexec) { + const bool mount_exec; + const bool file_exec; + const int sysctl_err_code[3]; +}; + +FIXTURE_VARIANT_ADD(omayexec, mount_exec_file_exec) { + .mount_exec = true, + .file_exec = true, + .sysctl_err_code = {0, 0, 0}, +}; + +FIXTURE_VARIANT_ADD(omayexec, mount_exec_file_noexec) +{ + .mount_exec = true, + .file_exec = false, + .sysctl_err_code = {0, -EACCES, -EACCES}, +}; + +FIXTURE_VARIANT_ADD(omayexec, mount_noexec_file_exec) +{ + .mount_exec = false, + .file_exec = true, + .sysctl_err_code = {-EACCES, 0, -EACCES}, +}; + +FIXTURE_VARIANT_ADD(omayexec, mount_noexec_file_noexec) +{ + .mount_exec = false, + .file_exec = false, + .sysctl_err_code = {-EACCES, -EACCES, -EACCES}, +}; + +FIXTURE_SETUP(omayexec) +{ + int fd; + + /* + * Cleans previous workspace if any error previously happened (don't + * check errors). + */ + umount(workdir_path); + rmdir(workdir_path); + + /* Creates a clean mount point. */ + ASSERT_EQ(0, mkdir(workdir_path, 00700)); + ASSERT_EQ(0, mount("test", workdir_path, "tmpfs", MS_MGC_VAL | + (variant->mount_exec ? 0 : MS_NOEXEC), + "mode=0700,size=4k")); + + /* Creates a test file. */ + fd = open(file_path, O_CREAT | O_RDONLY | O_CLOEXEC, + variant->file_exec ? 00500 : 00400); + ASSERT_LE(0, fd); + EXPECT_EQ(0, close(fd)); + + /* Creates a test directory. */ + ASSERT_EQ(0, mkdir(dir_path, variant->file_exec ? 00500 : 00400)); + + /* Saves initial sysctl value. */ + self->initial_sysctl_value = sysctl_read_char(_metadata); + + /* Prepares for sysctl writes. */ + ignore_sys_admin(_metadata, 1); +} + +FIXTURE_TEARDOWN(omayexec) +{ + /* Restores initial sysctl value. */ + sysctl_write_char(_metadata, self->initial_sysctl_value); + + /* There is no need to unlink file_path nor dir_path. */ + ASSERT_EQ(0, umount(workdir_path)); + ASSERT_EQ(0, rmdir(workdir_path)); +} + +TEST_F(omayexec, sysctl_0) +{ + /* Do not enforce anything. */ + sysctl_write_char(_metadata, '0'); + test_dir_file(_metadata, 0); +} + +TEST_F(omayexec, sysctl_1) +{ + /* Enforces mount exec check. */ + sysctl_write_char(_metadata, '1'); + test_dir_file(_metadata, variant->sysctl_err_code[0]); +} + +TEST_F(omayexec, sysctl_2) +{ + /* Enforces file exec check. */ + sysctl_write_char(_metadata, '2'); + test_dir_file(_metadata, variant->sysctl_err_code[1]); +} + +TEST_F(omayexec, sysctl_3) +{ + /* Enforces mount and file exec check. */ + sysctl_write_char(_metadata, '3'); + test_dir_file(_metadata, variant->sysctl_err_code[2]); +} + +TEST(sysctl_access_write) +{ + int fd; + ssize_t ret; + + ignore_sys_admin(_metadata, 1); + sysctl_write_char(_metadata, '0'); + + ignore_sys_admin(_metadata, 0); + fd = open(sysctl_path, O_WRONLY | O_CLOEXEC); + ASSERT_LE(0, fd); + ret = write(fd, "0", 1); + ASSERT_EQ(-1, ret); + ASSERT_EQ(EPERM, errno); + EXPECT_EQ(0, close(fd)); +} + +TEST_HARNESS_MAIN