diff options
| -rw-r--r-- | include/uapi/linux/landlock.h | 21 | ||||
| -rw-r--r-- | security/landlock/fs.c | 104 | ||||
| -rw-r--r-- | security/landlock/fs.h | 24 | ||||
| -rw-r--r-- | security/landlock/limits.h | 2 | ||||
| -rw-r--r-- | security/landlock/setup.c | 1 | ||||
| -rw-r--r-- | security/landlock/syscalls.c | 2 | ||||
| -rw-r--r-- | security/security.c | 11 | ||||
| -rw-r--r-- | tools/testing/selftests/landlock/base_test.c | 2 | ||||
| -rw-r--r-- | tools/testing/selftests/landlock/fs_test.c | 7 |
9 files changed, 153 insertions, 21 deletions
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 9c4bcc37a455..f3223f964691 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -95,8 +95,19 @@ struct landlock_path_beneath_attr { * A file can only receive these access rights: * * - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file. - * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. + * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that + * you might additionally need the %LANDLOCK_ACCESS_FS_TRUNCATE right in order + * to overwrite files with :manpage:`open(2)` using ``O_TRUNC`` or + * :manpage:`creat(2)`. * - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access. + * - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`, + * :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with + * ``O_TRUNC``. Whether an opened file can be truncated with + * :manpage:`ftruncate(2)` is determined during :manpage:`open(2)`, in the + * same way as read and write permissions are checked during + * :manpage:`open(2)` using %LANDLOCK_ACCESS_FS_READ_FILE and + * %LANDLOCK_ACCESS_FS_WRITE_FILE. This access right is available since the + * third version of the Landlock ABI. * * A directory can receive access rights related to files or directories. The * following access right is applied to the directory itself, and the @@ -139,10 +150,9 @@ struct landlock_path_beneath_attr { * * It is currently not possible to restrict some file-related actions * accessible through these syscall families: :manpage:`chdir(2)`, - * :manpage:`truncate(2)`, :manpage:`stat(2)`, :manpage:`flock(2)`, - * :manpage:`chmod(2)`, :manpage:`chown(2)`, :manpage:`setxattr(2)`, - * :manpage:`utime(2)`, :manpage:`ioctl(2)`, :manpage:`fcntl(2)`, - * :manpage:`access(2)`. + * :manpage:`stat(2)`, :manpage:`flock(2)`, :manpage:`chmod(2)`, + * :manpage:`chown(2)`, :manpage:`setxattr(2)`, :manpage:`utime(2)`, + * :manpage:`ioctl(2)`, :manpage:`fcntl(2)`, :manpage:`access(2)`. * Future Landlock evolutions will enable to restrict them. */ /* clang-format off */ @@ -160,6 +170,7 @@ struct landlock_path_beneath_attr { #define LANDLOCK_ACCESS_FS_MAKE_BLOCK (1ULL << 11) #define LANDLOCK_ACCESS_FS_MAKE_SYM (1ULL << 12) #define LANDLOCK_ACCESS_FS_REFER (1ULL << 13) +#define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 14) /* clang-format on */ #endif /* _UAPI_LINUX_LANDLOCK_H */ diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 87fde50eb550..adcea0fe7e68 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -146,7 +146,8 @@ retry: #define ACCESS_FILE ( \ LANDLOCK_ACCESS_FS_EXECUTE | \ LANDLOCK_ACCESS_FS_WRITE_FILE | \ - LANDLOCK_ACCESS_FS_READ_FILE) + LANDLOCK_ACCESS_FS_READ_FILE | \ + LANDLOCK_ACCESS_FS_TRUNCATE) /* clang-format on */ /* @@ -1154,9 +1155,23 @@ static int hook_path_rmdir(const struct path *const dir, return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR); } +static int hook_path_truncate(const struct path *const path) +{ + return current_check_access_path(path, LANDLOCK_ACCESS_FS_TRUNCATE); +} + /* File hooks */ -static inline access_mask_t get_file_access(const struct file *const file) +/** + * get_required_file_open_access - Get access needed to open a file + * + * @file: File being opened. + * + * Returns the access rights that are required for opening the given file, + * depending on the file type and open mode. + */ +static inline access_mask_t +get_required_file_open_access(const struct file *const file) { access_mask_t access = 0; @@ -1174,19 +1189,95 @@ static inline access_mask_t get_file_access(const struct file *const file) return access; } +static int hook_file_alloc_security(struct file *const file) +{ + /* + * Grants all access rights, even if most of them are not checked later + * on. It is more consistent. + * + * Notably, file descriptors for regular files can also be acquired + * without going through the file_open hook, for example when using + * memfd_create(2). + */ + landlock_file(file)->allowed_access = LANDLOCK_MASK_ACCESS_FS; + return 0; +} + static int hook_file_open(struct file *const file) { + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; + access_mask_t open_access_request, full_access_request, allowed_access; + const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE; const struct landlock_ruleset *const dom = landlock_get_current_domain(); if (!dom) return 0; + /* - * Because a file may be opened with O_PATH, get_file_access() may - * return 0. This case will be handled with a future Landlock + * Because a file may be opened with O_PATH, get_required_file_open_access() + * may return 0. This case will be handled with a future Landlock * evolution. */ - return check_access_path(dom, &file->f_path, get_file_access(file)); + open_access_request = get_required_file_open_access(file); + + /* + * We look up more access than what we immediately need for open(), so + * that we can later authorize operations on opened files. + */ + full_access_request = open_access_request | optional_access; + + if (is_access_to_paths_allowed( + dom, &file->f_path, + init_layer_masks(dom, full_access_request, &layer_masks), + &layer_masks, NULL, 0, NULL, NULL)) { + allowed_access = full_access_request; + } else { + unsigned long access_bit; + const unsigned long access_req = full_access_request; + + /* + * Calculate the actual allowed access rights from layer_masks. + * Add each access right to allowed_access which has not been + * vetoed by any layer. + */ + allowed_access = 0; + for_each_set_bit(access_bit, &access_req, + ARRAY_SIZE(layer_masks)) { + if (!layer_masks[access_bit]) + allowed_access |= BIT_ULL(access_bit); + } + } + + /* + * For operations on already opened files (i.e. ftruncate()), it is the + * access rights at the time of open() which decide whether the + * operation is permitted. Therefore, we record the relevant subset of + * file access rights in the opened struct file. + */ + landlock_file(file)->allowed_access = allowed_access; + + if ((open_access_request & allowed_access) == open_access_request) + return 0; + + return -EACCES; +} + +static int hook_file_truncate(struct file *const file) +{ + /* + * Allows truncation if the truncate right was available at the time of + * opening the file, to get a consistent access check as for read, write + * and execute operations. + * + * Note: For checks done based on the file's Landlock allowed access, we + * enforce them independently of whether the current thread is in a + * Landlock domain, so that open files passed between independent + * processes retain their behaviour. + */ + if (landlock_file(file)->allowed_access & LANDLOCK_ACCESS_FS_TRUNCATE) + return 0; + return -EACCES; } static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { @@ -1206,8 +1297,11 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(path_symlink, hook_path_symlink), LSM_HOOK_INIT(path_unlink, hook_path_unlink), LSM_HOOK_INIT(path_rmdir, hook_path_rmdir), + LSM_HOOK_INIT(path_truncate, hook_path_truncate), + LSM_HOOK_INIT(file_alloc_security, hook_file_alloc_security), LSM_HOOK_INIT(file_open, hook_file_open), + LSM_HOOK_INIT(file_truncate, hook_file_truncate), }; __init void landlock_add_fs_hooks(void) diff --git a/security/landlock/fs.h b/security/landlock/fs.h index 8db7acf9109b..488e4813680a 100644 --- a/security/landlock/fs.h +++ b/security/landlock/fs.h @@ -37,6 +37,24 @@ struct landlock_inode_security { }; /** + * struct landlock_file_security - File security blob + * + * This information is populated when opening a file in hook_file_open, and + * tracks the relevant Landlock access rights that were available at the time + * of opening the file. Other LSM hooks use these rights in order to authorize + * operations on already opened files. + */ +struct landlock_file_security { + /** + * @allowed_access: Access rights that were available at the time of + * opening the file. This is not necessarily the full set of access + * rights available at that time, but it's the necessary subset as + * needed to authorize later operations on the open file. + */ + access_mask_t allowed_access; +}; + +/** * struct landlock_superblock_security - Superblock security blob * * Enable hook_sb_delete() to wait for concurrent calls to release_inode(). @@ -50,6 +68,12 @@ struct landlock_superblock_security { atomic_long_t inode_refs; }; +static inline struct landlock_file_security * +landlock_file(const struct file *const file) +{ + return file->f_security + landlock_blob_sizes.lbs_file; +} + static inline struct landlock_inode_security * landlock_inode(const struct inode *const inode) { diff --git a/security/landlock/limits.h b/security/landlock/limits.h index b54184ab9439..82288f0e9e5e 100644 --- a/security/landlock/limits.h +++ b/security/landlock/limits.h @@ -18,7 +18,7 @@ #define LANDLOCK_MAX_NUM_LAYERS 16 #define LANDLOCK_MAX_NUM_RULES U32_MAX -#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_REFER +#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_TRUNCATE #define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1) #define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS) diff --git a/security/landlock/setup.c b/security/landlock/setup.c index f8e8e980454c..3f196d2ce4f9 100644 --- a/security/landlock/setup.c +++ b/security/landlock/setup.c @@ -19,6 +19,7 @@ bool landlock_initialized __lsm_ro_after_init = false; struct lsm_blob_sizes landlock_blob_sizes __lsm_ro_after_init = { .lbs_cred = sizeof(struct landlock_cred_security), + .lbs_file = sizeof(struct landlock_file_security), .lbs_inode = sizeof(struct landlock_inode_security), .lbs_superblock = sizeof(struct landlock_superblock_security), }; diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index 2ca0ccbd905a..245cc650a4dc 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -129,7 +129,7 @@ static const struct file_operations ruleset_fops = { .write = fop_dummy_write, }; -#define LANDLOCK_ABI_VERSION 2 +#define LANDLOCK_ABI_VERSION 3 /** * sys_landlock_create_ruleset - Create a new ruleset diff --git a/security/security.c b/security/security.c index b55596958d0c..e0fe4ba39eb9 100644 --- a/security/security.c +++ b/security/security.c @@ -185,11 +185,12 @@ static void __init lsm_set_blob_size(int *need, int *lbs) { int offset; - if (*need > 0) { - offset = *lbs; - *lbs += *need; - *need = offset; - } + if (*need <= 0) + return; + + offset = ALIGN(*lbs, sizeof(void *)); + *lbs = offset + *need; + *need = offset; } static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed) diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c index da9290817866..72cdae277b02 100644 --- a/tools/testing/selftests/landlock/base_test.c +++ b/tools/testing/selftests/landlock/base_test.c @@ -75,7 +75,7 @@ TEST(abi_version) const struct landlock_ruleset_attr ruleset_attr = { .handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE, }; - ASSERT_EQ(2, landlock_create_ruleset(NULL, 0, + ASSERT_EQ(3, landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION)); ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0, diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 45de42a027c5..87b28d14a1aa 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -406,9 +406,10 @@ TEST_F_FORK(layout1, inval) #define ACCESS_FILE ( \ LANDLOCK_ACCESS_FS_EXECUTE | \ LANDLOCK_ACCESS_FS_WRITE_FILE | \ - LANDLOCK_ACCESS_FS_READ_FILE) + LANDLOCK_ACCESS_FS_READ_FILE | \ + LANDLOCK_ACCESS_FS_TRUNCATE) -#define ACCESS_LAST LANDLOCK_ACCESS_FS_REFER +#define ACCESS_LAST LANDLOCK_ACCESS_FS_TRUNCATE #define ACCESS_ALL ( \ ACCESS_FILE | \ @@ -422,7 +423,7 @@ TEST_F_FORK(layout1, inval) LANDLOCK_ACCESS_FS_MAKE_FIFO | \ LANDLOCK_ACCESS_FS_MAKE_BLOCK | \ LANDLOCK_ACCESS_FS_MAKE_SYM | \ - ACCESS_LAST) + LANDLOCK_ACCESS_FS_REFER) /* clang-format on */ |