From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6127ECAAA1 for ; Fri, 16 Sep 2022 17:05:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229894AbiIPRFx (ORCPT ); Fri, 16 Sep 2022 13:05:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33674 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229877AbiIPRFv (ORCPT ); Fri, 16 Sep 2022 13:05:51 -0400 Received: from smtp-8fa8.mail.infomaniak.ch (smtp-8fa8.mail.infomaniak.ch [83.166.143.168]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2EA04C639 for ; Fri, 16 Sep 2022 10:05:48 -0700 (PDT) Received: from smtp-2-0000.mail.infomaniak.ch (unknown [10.5.36.107]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4MTgSV4MfVzMqk2Q; Fri, 16 Sep 2022 19:05:46 +0200 (CEST) Received: from ns3096276.ip-94-23-54.eu (unknown [23.97.221.149]) by smtp-2-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4MTgST49NYzMpnPl; Fri, 16 Sep 2022 19:05:45 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1663347946; bh=+g0WDxlRJBZqGQK4ZL+TW4WEBNF/nErdboJ3nvBELGY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=m44kfvGmE3IpvKSHpkAIMcc2nangJCH6DfQ68vokAkL0W4HN1uD1soZMmWGJIskON rFgQmx9flRniJExTWLyD0EpS8cO4AIl1ZMaIgtmE+EaesJtcCWXfKnbC7xMSpaK9Jo I0642VCJklQbzwFMXl2S1WuQ3llExL3UwnQGO374= Message-ID: <3f3b7798-c3e1-e257-5094-0033e7605062@digikod.net> Date: Fri, 16 Sep 2022 19:05:44 +0200 MIME-Version: 1.0 User-Agent: Subject: Re: [PATCH v6 3/5] selftests/landlock: Selftests for file truncation support Content-Language: en-US To: =?UTF-8?Q?G=c3=bcnther_Noack?= , linux-security-module@vger.kernel.org Cc: James Morris , Paul Moore , "Serge E . Hallyn" , linux-fsdevel@vger.kernel.org, Konstantin Meskhidze References: <20220908195805.128252-1-gnoack3000@gmail.com> <20220908195805.128252-4-gnoack3000@gmail.com> From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= In-Reply-To: <20220908195805.128252-4-gnoack3000@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: I'd like to have tests similar to base_test.c:ruleset_fd_transfer to check ftruncate with different kind of file descriptors and not-sandboxed processes. That would require some code refactoring to reuse the FD passing code. On 08/09/2022 21:58, Günther Noack wrote: > These tests exercise the following truncation operations: > > * truncate() (truncate by path) > * ftruncate() (truncate by file descriptor) > * open with the O_TRUNC flag > * special case: creat(), which is open with O_CREAT|O_WRONLY|O_TRUNC. > > in the following scenarios: > > * Files with read, write and truncate rights. > * Files with read and truncate rights. > * Files with the truncate right. > * Files without the truncate right. > > In particular, the following scenarios are enforced with the test: > > * open() with O_TRUNC requires the truncate right, if it truncates a file. > open() already checks security_path_truncate() in this case, > and it required no additional check in the Landlock LSM's file_open hook. > * creat() requires the truncate right > when called with an existing filename. > * creat() does *not* require the truncate right > when it's creating a new file. > * ftruncate() requires that the file was opened by a thread that had > the truncate right for the file at the time of open(). (The rights > are carried along with the opened file.) > > Signed-off-by: Günther Noack > --- > tools/testing/selftests/landlock/fs_test.c | 280 +++++++++++++++++++++ > 1 file changed, 280 insertions(+) > > diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c > index 87b28d14a1aa..ddc8c7e57e86 100644 > --- a/tools/testing/selftests/landlock/fs_test.c > +++ b/tools/testing/selftests/landlock/fs_test.c > @@ -58,6 +58,7 @@ static const char file1_s2d3[] = TMP_DIR "/s2d1/s2d2/s2d3/f1"; > static const char file2_s2d3[] = TMP_DIR "/s2d1/s2d2/s2d3/f2"; > > static const char dir_s3d1[] = TMP_DIR "/s3d1"; > +static const char file1_s3d1[] = TMP_DIR "/s3d1/f1"; > /* dir_s3d2 is a mount point. */ > static const char dir_s3d2[] = TMP_DIR "/s3d1/s3d2"; > static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3"; > @@ -83,6 +84,7 @@ static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3"; > * │   ├── f1 > * │   └── f2 > * └── s3d1 > + *    ├── f1 > * └── s3d2 > * └── s3d3 > */ > @@ -208,6 +210,7 @@ static void create_layout1(struct __test_metadata *const _metadata) > create_file(_metadata, file1_s2d3); > create_file(_metadata, file2_s2d3); > > + create_file(_metadata, file1_s3d1); > create_directory(_metadata, dir_s3d2); > set_cap(_metadata, CAP_SYS_ADMIN); > ASSERT_EQ(0, mount("tmp", dir_s3d2, "tmpfs", 0, "size=4m,mode=700")); > @@ -230,6 +233,7 @@ static void remove_layout1(struct __test_metadata *const _metadata) > EXPECT_EQ(0, remove_path(file1_s2d2)); > EXPECT_EQ(0, remove_path(file1_s2d1)); > > + EXPECT_EQ(0, remove_path(file1_s3d1)); > EXPECT_EQ(0, remove_path(dir_s3d3)); > set_cap(_metadata, CAP_SYS_ADMIN); > umount(dir_s3d2); > @@ -3158,6 +3162,282 @@ TEST_F_FORK(layout1, proc_pipe) > ASSERT_EQ(0, close(pipe_fds[1])); > } > > +/* Invokes truncate(2) and returns its errno or 0. */ > +static int test_truncate(const char *const path) > +{ > + if (truncate(path, 10) < 0) > + return errno; > + return 0; > +} > + > +/* > + * Invokes creat(2) and returns its errno or 0. > + * Closes the opened file descriptor on success. > + */ > +static int test_creat(const char *const path) > +{ > + int fd = creat(path, 0600); > + > + if (fd < 0) > + return errno; > + > + /* > + * Mixing error codes from close(2) and creat(2) should not lead to any > + * (access type) confusion for this test. > + */ > + if (close(fd) < 0) > + return errno; > + return 0; > +} > + > +/* > + * Exercises file truncation when it's not restricted, > + * as it was the case before LANDLOCK_ACCESS_FS_TRUNCATE existed. > + */ > +TEST_F_FORK(layout1, truncate_unhandled) > +{ > + const char *const file_r = file1_s1d1; > + const char *const file_w = file2_s1d1; > + const char *const file_none = file1_s1d2; > + const struct rule rules[] = { > + { > + .path = file_r, > + .access = LANDLOCK_ACCESS_FS_READ_FILE, > + }, > + { > + .path = file_w, > + .access = LANDLOCK_ACCESS_FS_WRITE_FILE, > + }, > + /* Implicitly: No rights for file_none. */ > + {}, > + }; > + > + const __u64 handled = LANDLOCK_ACCESS_FS_READ_FILE | > + LANDLOCK_ACCESS_FS_WRITE_FILE; > + int ruleset_fd; > + > + /* Enable Landlock. */ > + ruleset_fd = create_ruleset(_metadata, handled, rules); > + > + ASSERT_LE(0, ruleset_fd); > + enforce_ruleset(_metadata, ruleset_fd); > + ASSERT_EQ(0, close(ruleset_fd)); > + > + /* > + * Checks read right: truncate and open with O_TRUNC work, unless the > + * file is attempted to be opened for writing. > + */ > + EXPECT_EQ(0, test_truncate(file_r)); > + EXPECT_EQ(0, test_open(file_r, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_r, O_WRONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_creat(file_r)); > + > + /* > + * Checks write right: truncate and open with O_TRUNC work, unless the > + * file is attempted to be opened for reading. > + */ > + EXPECT_EQ(0, test_truncate(file_w)); > + EXPECT_EQ(EACCES, test_open(file_w, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(0, test_open(file_w, O_WRONLY | O_TRUNC)); > + EXPECT_EQ(0, test_creat(file_w)); > + > + /* > + * Checks "no rights" case: truncate works but all open attempts fail, > + * including creat. > + */ > + EXPECT_EQ(0, test_truncate(file_none)); > + EXPECT_EQ(EACCES, test_open(file_none, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_none, O_WRONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_creat(file_none)); > +} > + > +TEST_F_FORK(layout1, truncate) > +{ > + const char *const file_rwt = file1_s1d1; > + const char *const file_rw = file2_s1d1; > + const char *const file_rt = file1_s1d2; > + const char *const file_t = file2_s1d2; > + const char *const file_none = file1_s1d3; > + const char *const dir_t = dir_s2d1; > + const char *const file_in_dir_t = file1_s2d1; > + const char *const dir_w = dir_s3d1; > + const char *const file_in_dir_w = file1_s3d1; > + int file_rwt_fd, file_rw_fd; These variables are unused now. > + const struct rule rules[] = { > + { > + .path = file_rwt, > + .access = LANDLOCK_ACCESS_FS_READ_FILE | > + LANDLOCK_ACCESS_FS_WRITE_FILE | > + LANDLOCK_ACCESS_FS_TRUNCATE, > + }, > + { > + .path = file_rw, > + .access = LANDLOCK_ACCESS_FS_READ_FILE | > + LANDLOCK_ACCESS_FS_WRITE_FILE, > + }, > + { > + .path = file_rt, > + .access = LANDLOCK_ACCESS_FS_READ_FILE | > + LANDLOCK_ACCESS_FS_TRUNCATE, > + }, > + { > + .path = file_t, > + .access = LANDLOCK_ACCESS_FS_TRUNCATE, > + }, > + /* Implicitly: No access rights for file_none. */ > + { > + .path = dir_t, > + .access = LANDLOCK_ACCESS_FS_TRUNCATE, > + }, > + { > + .path = dir_w, > + .access = LANDLOCK_ACCESS_FS_WRITE_FILE, > + }, > + {}, > + }; > + const __u64 handled = LANDLOCK_ACCESS_FS_READ_FILE | > + LANDLOCK_ACCESS_FS_WRITE_FILE | > + LANDLOCK_ACCESS_FS_TRUNCATE; > + int ruleset_fd; > + > + /* Enable Landlock. */ > + ruleset_fd = create_ruleset(_metadata, handled, rules); > + > + ASSERT_LE(0, ruleset_fd); > + enforce_ruleset(_metadata, ruleset_fd); > + ASSERT_EQ(0, close(ruleset_fd)); > + > + /* Checks read, write and truncate rights: truncation works. */ > + EXPECT_EQ(0, test_truncate(file_rwt)); > + EXPECT_EQ(0, test_open(file_rwt, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(0, test_open(file_rwt, O_WRONLY | O_TRUNC)); > + > + /* Checks read and write rights: no truncate variant works. */ > + EXPECT_EQ(EACCES, test_truncate(file_rw)); > + EXPECT_EQ(EACCES, test_open(file_rw, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_rw, O_WRONLY | O_TRUNC)); > + > + /* > + * Checks read and truncate rights: truncation works. > + * > + * Note: Files can get truncated using open() even with O_RDONLY. > + */ > + EXPECT_EQ(0, test_truncate(file_rt)); > + EXPECT_EQ(0, test_open(file_rt, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_rt, O_WRONLY | O_TRUNC)); > + > + /* Checks truncate right: truncate works, but can't open file. */ > + EXPECT_EQ(0, test_truncate(file_t)); > + EXPECT_EQ(EACCES, test_open(file_t, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_t, O_WRONLY | O_TRUNC)); > + > + /* Checks "no rights" case: No form of truncation works. */ > + EXPECT_EQ(EACCES, test_truncate(file_none)); > + EXPECT_EQ(EACCES, test_open(file_none, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_none, O_WRONLY | O_TRUNC)); > + > + /* > + * Checks truncate right on directory: truncate works on contained > + * files. > + */ > + EXPECT_EQ(0, test_truncate(file_in_dir_t)); > + EXPECT_EQ(EACCES, test_open(file_in_dir_t, O_RDONLY | O_TRUNC)); > + EXPECT_EQ(EACCES, test_open(file_in_dir_t, O_WRONLY | O_TRUNC)); > + > + /* > + * Checks creat in dir_w: This requires the truncate right when > + * overwriting an existing file, but does not require it when the file > + * is new. > + */ > + EXPECT_EQ(EACCES, test_creat(file_in_dir_w)); > + > + ASSERT_EQ(0, unlink(file_in_dir_w)); > + EXPECT_EQ(0, test_creat(file_in_dir_w)); > +} > + > +static void landlock_single_path(struct __test_metadata *const _metadata, > + const char *const path, __u64 handled, > + __u64 permitted) > +{ > + const struct rule rules[] = { > + { > + .path = path, > + .access = permitted, > + }, > + {}, > + }; > + int ruleset_fd = create_ruleset(_metadata, handled, rules); > + > + ASSERT_LE(0, ruleset_fd); > + > + enforce_ruleset(_metadata, ruleset_fd); > + > + ASSERT_EQ(0, close(ruleset_fd)); > +} > + > +/* Invokes ftruncate(2) and returns its errno or 0. */ > +static int test_ftruncate(int fd) > +{ > + if (ftruncate(fd, 10) < 0) > + return errno; > + return 0; > +} > + > +TEST_F_FORK(layout1, ftruncate) Great! > +{ > + /* > + * This test opens a new file descriptor at different stages of > + * Landlock restriction: > + * > + * without restriction: ftruncate works > + * something else but truncate restricted: ftruncate works > + * truncate restricted and permitted: ftruncate works > + * truncate restricted and not permitted: ftruncate fails > + * > + * Whether this works or not is expected to depend on the time when the > + * FD was opened, not to depend on the time when ftruncate() was > + * called. > + */ > + const char *const path = file1_s1d1; > + int fd0, fd1, fd2, fd3; You can rename them fd_layer0, fd_layer1… > + > + fd0 = open(path, O_WRONLY); > + EXPECT_EQ(0, test_ftruncate(fd0)); > + > + landlock_single_path(_metadata, path, > + LANDLOCK_ACCESS_FS_READ_FILE | > + LANDLOCK_ACCESS_FS_WRITE_FILE, > + LANDLOCK_ACCESS_FS_WRITE_FILE); I'd prefer to follow the current way to write rule layers: write all struct rule at first and then call each enforcement steps. It is a bit more verbose but easier to understand errors. The list of test_ftruncate checks are straightforward to follow. > + > + fd1 = open(path, O_WRONLY); > + EXPECT_EQ(0, test_ftruncate(fd0)); > + EXPECT_EQ(0, test_ftruncate(fd1)); > + > + landlock_single_path(_metadata, path, LANDLOCK_ACCESS_FS_TRUNCATE, > + LANDLOCK_ACCESS_FS_TRUNCATE); > + > + fd2 = open(path, O_WRONLY); > + EXPECT_EQ(0, test_ftruncate(fd0)); > + EXPECT_EQ(0, test_ftruncate(fd1)); > + EXPECT_EQ(0, test_ftruncate(fd2)); > + > + landlock_single_path(_metadata, path, > + LANDLOCK_ACCESS_FS_TRUNCATE | > + LANDLOCK_ACCESS_FS_WRITE_FILE, > + LANDLOCK_ACCESS_FS_WRITE_FILE); > + > + fd3 = open(path, O_WRONLY); > + EXPECT_EQ(0, test_ftruncate(fd0)); > + EXPECT_EQ(0, test_ftruncate(fd1)); > + EXPECT_EQ(0, test_ftruncate(fd2)); > + EXPECT_EQ(EACCES, test_ftruncate(fd3)); > + > + ASSERT_EQ(0, close(fd0)); > + ASSERT_EQ(0, close(fd1)); > + ASSERT_EQ(0, close(fd2)); > + ASSERT_EQ(0, close(fd3)); > +} > + > /* clang-format off */ > FIXTURE(layout1_bind) {}; > /* clang-format on */