diff options
| -rw-r--r-- | security/landlock/fs.c | 48 | ||||
| -rw-r--r-- | tools/testing/selftests/landlock/fs_test.c | 155 |
2 files changed, 170 insertions, 33 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index ec5a6247cd3e..a9dbd99d9ee7 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -150,6 +150,16 @@ retry: /* clang-format on */ /* + * All access rights that are denied by default whether they are handled or not + * by a ruleset/layer. This must be ORed with all ruleset->fs_access_masks[] + * entries when we need to get the absolute handled access masks. + */ +/* clang-format off */ +#define ACCESS_INITIALLY_DENIED ( \ + LANDLOCK_ACCESS_FS_REFER) +/* clang-format on */ + +/* * @path: Should have been checked by get_path_from_fd(). */ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, @@ -167,7 +177,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, return -EINVAL; /* Transforms relative access rights to absolute ones. */ - access_rights |= LANDLOCK_MASK_ACCESS_FS & ~ruleset->fs_access_masks[0]; + access_rights |= + LANDLOCK_MASK_ACCESS_FS & + ~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED); object = get_inode_object(d_backing_inode(path->dentry)); if (IS_ERR(object)) return PTR_ERR(object); @@ -277,23 +289,12 @@ static inline bool is_nouser_or_private(const struct dentry *dentry) static inline access_mask_t get_handled_accesses(const struct landlock_ruleset *const domain) { - access_mask_t access_dom = 0; - unsigned long access_bit; - - for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS; - access_bit++) { - size_t layer_level; + access_mask_t access_dom = ACCESS_INITIALLY_DENIED; + size_t layer_level; - for (layer_level = 0; layer_level < domain->num_layers; - layer_level++) { - if (domain->fs_access_masks[layer_level] & - BIT_ULL(access_bit)) { - access_dom |= BIT_ULL(access_bit); - break; - } - } - } - return access_dom; + for (layer_level = 0; layer_level < domain->num_layers; layer_level++) + access_dom |= domain->fs_access_masks[layer_level]; + return access_dom & LANDLOCK_MASK_ACCESS_FS; } static inline access_mask_t @@ -316,8 +317,13 @@ init_layer_masks(const struct landlock_ruleset *const domain, for_each_set_bit(access_bit, &access_req, ARRAY_SIZE(*layer_masks)) { - if (domain->fs_access_masks[layer_level] & - BIT_ULL(access_bit)) { + /* + * Artificially handles all initially denied by default + * access rights. + */ + if (BIT_ULL(access_bit) & + (domain->fs_access_masks[layer_level] | + ACCESS_INITIALLY_DENIED)) { (*layer_masks)[access_bit] |= BIT_ULL(layer_level); handled_accesses |= BIT_ULL(access_bit); @@ -857,10 +863,6 @@ static int current_check_refer_path(struct dentry *const old_dentry, NULL, NULL); } - /* Backward compatibility: no reparenting support. */ - if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER)) - return -EXDEV; - access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER; access_request_parent2 |= LANDLOCK_ACCESS_FS_REFER; diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 21a2ce8fa739..45de42a027c5 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -4,7 +4,7 @@ * * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net> * Copyright © 2020 ANSSI - * Copyright © 2020-2021 Microsoft Corporation + * Copyright © 2020-2022 Microsoft Corporation */ #define _GNU_SOURCE @@ -371,6 +371,13 @@ TEST_F_FORK(layout1, inval) ASSERT_EQ(EINVAL, errno); path_beneath.allowed_access &= ~LANDLOCK_ACCESS_FS_EXECUTE; + /* Tests with denied-by-default access right. */ + path_beneath.allowed_access |= LANDLOCK_ACCESS_FS_REFER; + ASSERT_EQ(-1, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH, + &path_beneath, 0)); + ASSERT_EQ(EINVAL, errno); + path_beneath.allowed_access &= ~LANDLOCK_ACCESS_FS_REFER; + /* Test with unknown (64-bits) value. */ path_beneath.allowed_access |= (1ULL << 60); ASSERT_EQ(-1, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH, @@ -1826,6 +1833,20 @@ TEST_F_FORK(layout1, link) ASSERT_EQ(0, link(file1_s1d3, file2_s1d3)); } +static int test_rename(const char *const oldpath, const char *const newpath) +{ + if (rename(oldpath, newpath)) + return errno; + return 0; +} + +static int test_exchange(const char *const oldpath, const char *const newpath) +{ + if (renameat2(AT_FDCWD, oldpath, AT_FDCWD, newpath, RENAME_EXCHANGE)) + return errno; + return 0; +} + TEST_F_FORK(layout1, rename_file) { const struct rule rules[] = { @@ -1867,10 +1888,10 @@ TEST_F_FORK(layout1, rename_file) * to a different directory (which allows file removal). */ ASSERT_EQ(-1, rename(file1_s2d1, file1_s1d3)); - ASSERT_EQ(EXDEV, errno); + ASSERT_EQ(EACCES, errno); ASSERT_EQ(-1, renameat2(AT_FDCWD, file1_s2d1, AT_FDCWD, file1_s1d3, RENAME_EXCHANGE)); - ASSERT_EQ(EXDEV, errno); + ASSERT_EQ(EACCES, errno); ASSERT_EQ(-1, renameat2(AT_FDCWD, dir_s2d2, AT_FDCWD, file1_s1d3, RENAME_EXCHANGE)); ASSERT_EQ(EXDEV, errno); @@ -1894,7 +1915,7 @@ TEST_F_FORK(layout1, rename_file) ASSERT_EQ(EXDEV, errno); ASSERT_EQ(0, unlink(file1_s1d3)); ASSERT_EQ(-1, rename(file1_s2d1, file1_s1d3)); - ASSERT_EQ(EXDEV, errno); + ASSERT_EQ(EACCES, errno); /* Exchanges and renames files with same parent. */ ASSERT_EQ(0, renameat2(AT_FDCWD, file2_s2d3, AT_FDCWD, file1_s2d3, @@ -2014,6 +2035,115 @@ TEST_F_FORK(layout1, reparent_refer) ASSERT_EQ(0, rename(dir_s1d3, dir_s2d3)); } +/* Checks renames beneath dir_s1d1. */ +static void refer_denied_by_default(struct __test_metadata *const _metadata, + const struct rule layer1[], + const int layer1_err, + const struct rule layer2[]) +{ + int ruleset_fd; + + ASSERT_EQ(0, unlink(file1_s1d2)); + + ruleset_fd = create_ruleset(_metadata, layer1[0].access, layer1); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* + * If the first layer handles LANDLOCK_ACCESS_FS_REFER (according to + * layer1_err), then it allows some different-parent renames and links. + */ + ASSERT_EQ(layer1_err, test_rename(file1_s1d1, file1_s1d2)); + if (layer1_err == 0) + ASSERT_EQ(layer1_err, test_rename(file1_s1d2, file1_s1d1)); + ASSERT_EQ(layer1_err, test_exchange(file2_s1d1, file2_s1d2)); + ASSERT_EQ(layer1_err, test_exchange(file2_s1d2, file2_s1d1)); + + ruleset_fd = create_ruleset(_metadata, layer2[0].access, layer2); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* + * Now, either the first or the second layer does not handle + * LANDLOCK_ACCESS_FS_REFER, which means that any different-parent + * renames and links are denied, thus making the layer handling + * LANDLOCK_ACCESS_FS_REFER null and void. + */ + ASSERT_EQ(EXDEV, test_rename(file1_s1d1, file1_s1d2)); + ASSERT_EQ(EXDEV, test_exchange(file2_s1d1, file2_s1d2)); + ASSERT_EQ(EXDEV, test_exchange(file2_s1d2, file2_s1d1)); +} + +const struct rule layer_dir_s1d1_refer[] = { + { + .path = dir_s1d1, + .access = LANDLOCK_ACCESS_FS_REFER, + }, + {}, +}; + +const struct rule layer_dir_s1d1_execute[] = { + { + /* Matches a parent directory. */ + .path = dir_s1d1, + .access = LANDLOCK_ACCESS_FS_EXECUTE, + }, + {}, +}; + +const struct rule layer_dir_s2d1_execute[] = { + { + /* Does not match a parent directory. */ + .path = dir_s2d1, + .access = LANDLOCK_ACCESS_FS_EXECUTE, + }, + {}, +}; + +/* + * Tests precedence over renames: denied by default for different parent + * directories, *with* a rule matching a parent directory, but not directly + * denying access (with MAKE_REG nor REMOVE). + */ +TEST_F_FORK(layout1, refer_denied_by_default1) +{ + refer_denied_by_default(_metadata, layer_dir_s1d1_refer, 0, + layer_dir_s1d1_execute); +} + +/* + * Same test but this time turning around the ABI version order: the first + * layer does not handle LANDLOCK_ACCESS_FS_REFER. + */ +TEST_F_FORK(layout1, refer_denied_by_default2) +{ + refer_denied_by_default(_metadata, layer_dir_s1d1_execute, EXDEV, + layer_dir_s1d1_refer); +} + +/* + * Tests precedence over renames: denied by default for different parent + * directories, *without* a rule matching a parent directory, but not directly + * denying access (with MAKE_REG nor REMOVE). + */ +TEST_F_FORK(layout1, refer_denied_by_default3) +{ + refer_denied_by_default(_metadata, layer_dir_s1d1_refer, 0, + layer_dir_s2d1_execute); +} + +/* + * Same test but this time turning around the ABI version order: the first + * layer does not handle LANDLOCK_ACCESS_FS_REFER. + */ +TEST_F_FORK(layout1, refer_denied_by_default4) +{ + refer_denied_by_default(_metadata, layer_dir_s2d1_execute, EXDEV, + layer_dir_s1d1_refer); +} + TEST_F_FORK(layout1, reparent_link) { const struct rule layer1[] = { @@ -2336,11 +2466,12 @@ TEST_F_FORK(layout1, reparent_exdev_layers_rename1) ASSERT_EQ(EXDEV, errno); /* - * However, moving the file2_s1d3 file below dir_s2d3 is allowed - * because it cannot inherit MAKE_REG nor MAKE_DIR rights (which are - * dedicated to directories). + * Moving the file2_s1d3 file below dir_s2d3 is denied because the + * second layer does not handle REFER, which is always denied by + * default. */ - ASSERT_EQ(0, rename(file2_s1d3, file1_s2d3)); + ASSERT_EQ(-1, rename(file2_s1d3, file1_s2d3)); + ASSERT_EQ(EXDEV, errno); } TEST_F_FORK(layout1, reparent_exdev_layers_rename2) @@ -2373,8 +2504,12 @@ TEST_F_FORK(layout1, reparent_exdev_layers_rename2) ASSERT_EQ(EACCES, errno); ASSERT_EQ(-1, rename(file1_s1d1, file1_s2d3)); ASSERT_EQ(EXDEV, errno); - /* Modify layout! */ - ASSERT_EQ(0, rename(file2_s1d2, file1_s2d3)); + /* + * Modifying the layout is now denied because the second layer does not + * handle REFER, which is always denied by default. + */ + ASSERT_EQ(-1, rename(file2_s1d2, file1_s2d3)); + ASSERT_EQ(EXDEV, errno); /* Without REFER source, EACCES wins over EXDEV. */ ASSERT_EQ(-1, rename(dir_s1d1, file1_s2d2)); |