diff options
Diffstat (limited to 'security/landlock/fs.c')
| -rw-r--r-- | security/landlock/fs.c | 265 |
1 files changed, 256 insertions, 9 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 0171f7eb6e..3e43e68a63 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -7,6 +7,7 @@ * Copyright © 2021-2022 Microsoft Corporation */ +#include <kunit/test.h> #include <linux/atomic.h> #include <linux/bitops.h> #include <linux/bits.h> @@ -247,15 +248,18 @@ get_handled_fs_accesses(const struct landlock_ruleset *const domain) LANDLOCK_ACCESS_FS_INITIALLY_DENIED; } -static const struct landlock_ruleset *get_current_fs_domain(void) +static const struct landlock_ruleset * +get_fs_domain(const struct landlock_ruleset *const domain) { - const struct landlock_ruleset *const dom = - landlock_get_current_domain(); - - if (!dom || !get_raw_handled_fs_accesses(dom)) + if (!domain || !get_raw_handled_fs_accesses(domain)) return NULL; - return dom; + return domain; +} + +static const struct landlock_ruleset *get_current_fs_domain(void) +{ + return get_fs_domain(landlock_get_current_domain()); } /* @@ -311,6 +315,119 @@ static bool no_more_access( return true; } +#define NMA_TRUE(...) KUNIT_EXPECT_TRUE(test, no_more_access(__VA_ARGS__)) +#define NMA_FALSE(...) KUNIT_EXPECT_FALSE(test, no_more_access(__VA_ARGS__)) + +#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST + +static void test_no_more_access(struct kunit *const test) +{ + const layer_mask_t rx0[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(0), + [BIT_INDEX(LANDLOCK_ACCESS_FS_READ_FILE)] = BIT_ULL(0), + }; + const layer_mask_t mx0[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(0), + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_REG)] = BIT_ULL(0), + }; + const layer_mask_t x0[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(0), + }; + const layer_mask_t x1[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(1), + }; + const layer_mask_t x01[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(0) | + BIT_ULL(1), + }; + const layer_mask_t allows_all[LANDLOCK_NUM_ACCESS_FS] = {}; + + /* Checks without restriction. */ + NMA_TRUE(&x0, &allows_all, false, &allows_all, NULL, false); + NMA_TRUE(&allows_all, &x0, false, &allows_all, NULL, false); + NMA_FALSE(&x0, &x0, false, &allows_all, NULL, false); + + /* + * Checks that we can only refer a file if no more access could be + * inherited. + */ + NMA_TRUE(&x0, &x0, false, &rx0, NULL, false); + NMA_TRUE(&rx0, &rx0, false, &rx0, NULL, false); + NMA_FALSE(&rx0, &rx0, false, &x0, NULL, false); + NMA_FALSE(&rx0, &rx0, false, &x1, NULL, false); + + /* Checks allowed referring with different nested domains. */ + NMA_TRUE(&x0, &x1, false, &x0, NULL, false); + NMA_TRUE(&x1, &x0, false, &x0, NULL, false); + NMA_TRUE(&x0, &x01, false, &x0, NULL, false); + NMA_TRUE(&x0, &x01, false, &rx0, NULL, false); + NMA_TRUE(&x01, &x0, false, &x0, NULL, false); + NMA_TRUE(&x01, &x0, false, &rx0, NULL, false); + NMA_FALSE(&x01, &x01, false, &x0, NULL, false); + + /* Checks that file access rights are also enforced for a directory. */ + NMA_FALSE(&rx0, &rx0, true, &x0, NULL, false); + + /* Checks that directory access rights don't impact file referring... */ + NMA_TRUE(&mx0, &mx0, false, &x0, NULL, false); + /* ...but only directory referring. */ + NMA_FALSE(&mx0, &mx0, true, &x0, NULL, false); + + /* Checks directory exchange. */ + NMA_TRUE(&mx0, &mx0, true, &mx0, &mx0, true); + NMA_TRUE(&mx0, &mx0, true, &mx0, &x0, true); + NMA_FALSE(&mx0, &mx0, true, &x0, &mx0, true); + NMA_FALSE(&mx0, &mx0, true, &x0, &x0, true); + NMA_FALSE(&mx0, &mx0, true, &x1, &x1, true); + + /* Checks file exchange with directory access rights... */ + NMA_TRUE(&mx0, &mx0, false, &mx0, &mx0, false); + NMA_TRUE(&mx0, &mx0, false, &mx0, &x0, false); + NMA_TRUE(&mx0, &mx0, false, &x0, &mx0, false); + NMA_TRUE(&mx0, &mx0, false, &x0, &x0, false); + /* ...and with file access rights. */ + NMA_TRUE(&rx0, &rx0, false, &rx0, &rx0, false); + NMA_TRUE(&rx0, &rx0, false, &rx0, &x0, false); + NMA_FALSE(&rx0, &rx0, false, &x0, &rx0, false); + NMA_FALSE(&rx0, &rx0, false, &x0, &x0, false); + NMA_FALSE(&rx0, &rx0, false, &x1, &x1, false); + + /* + * Allowing the following requests should not be a security risk + * because domain 0 denies execute access, and domain 1 is always + * nested with domain 0. However, adding an exception for this case + * would mean to check all nested domains to make sure none can get + * more privileges (e.g. processes only sandboxed by domain 0). + * Moreover, this behavior (i.e. composition of N domains) could then + * be inconsistent compared to domain 1's ruleset alone (e.g. it might + * be denied to link/rename with domain 1's ruleset, whereas it would + * be allowed if nested on top of domain 0). Another drawback would be + * to create a cover channel that could enable sandboxed processes to + * infer most of the filesystem restrictions from their domain. To + * make it simple, efficient, safe, and more consistent, this case is + * always denied. + */ + NMA_FALSE(&x1, &x1, false, &x0, NULL, false); + NMA_FALSE(&x1, &x1, false, &rx0, NULL, false); + NMA_FALSE(&x1, &x1, true, &x0, NULL, false); + NMA_FALSE(&x1, &x1, true, &rx0, NULL, false); + + /* Checks the same case of exclusive domains with a file... */ + NMA_TRUE(&x1, &x1, false, &x01, NULL, false); + NMA_FALSE(&x1, &x1, false, &x01, &x0, false); + NMA_FALSE(&x1, &x1, false, &x01, &x01, false); + NMA_FALSE(&x1, &x1, false, &x0, &x0, false); + /* ...and with a directory. */ + NMA_FALSE(&x1, &x1, false, &x0, &x0, true); + NMA_FALSE(&x1, &x1, true, &x0, &x0, false); + NMA_FALSE(&x1, &x1, true, &x0, &x0, true); +} + +#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */ + +#undef NMA_TRUE +#undef NMA_FALSE + /* * Removes @layer_masks accesses that are not requested. * @@ -331,6 +448,57 @@ scope_to_request(const access_mask_t access_request, return !memchr_inv(layer_masks, 0, sizeof(*layer_masks)); } +#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST + +static void test_scope_to_request_with_exec_none(struct kunit *const test) +{ + /* Allows everything. */ + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; + + /* Checks and scopes with execute. */ + KUNIT_EXPECT_TRUE(test, scope_to_request(LANDLOCK_ACCESS_FS_EXECUTE, + &layer_masks)); + KUNIT_EXPECT_EQ(test, 0, + layer_masks[BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)]); + KUNIT_EXPECT_EQ(test, 0, + layer_masks[BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)]); +} + +static void test_scope_to_request_with_exec_some(struct kunit *const test) +{ + /* Denies execute and write. */ + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(0), + [BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)] = BIT_ULL(1), + }; + + /* Checks and scopes with execute. */ + KUNIT_EXPECT_FALSE(test, scope_to_request(LANDLOCK_ACCESS_FS_EXECUTE, + &layer_masks)); + KUNIT_EXPECT_EQ(test, BIT_ULL(0), + layer_masks[BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)]); + KUNIT_EXPECT_EQ(test, 0, + layer_masks[BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)]); +} + +static void test_scope_to_request_without_access(struct kunit *const test) +{ + /* Denies execute and write. */ + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT_ULL(0), + [BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)] = BIT_ULL(1), + }; + + /* Checks and scopes without access request. */ + KUNIT_EXPECT_TRUE(test, scope_to_request(0, &layer_masks)); + KUNIT_EXPECT_EQ(test, 0, + layer_masks[BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)]); + KUNIT_EXPECT_EQ(test, 0, + layer_masks[BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)]); +} + +#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */ + /* * Returns true if there is at least one access right different than * LANDLOCK_ACCESS_FS_REFER. @@ -354,6 +522,51 @@ is_eacces(const layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS], return false; } +#define IE_TRUE(...) KUNIT_EXPECT_TRUE(test, is_eacces(__VA_ARGS__)) +#define IE_FALSE(...) KUNIT_EXPECT_FALSE(test, is_eacces(__VA_ARGS__)) + +#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST + +static void test_is_eacces_with_none(struct kunit *const test) +{ + const layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; + + IE_FALSE(&layer_masks, 0); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_REFER); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_EXECUTE); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_WRITE_FILE); +} + +static void test_is_eacces_with_refer(struct kunit *const test) +{ + const layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_REFER)] = BIT_ULL(0), + }; + + IE_FALSE(&layer_masks, 0); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_REFER); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_EXECUTE); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_WRITE_FILE); +} + +static void test_is_eacces_with_write(struct kunit *const test) +{ + const layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)] = BIT_ULL(0), + }; + + IE_FALSE(&layer_masks, 0); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_REFER); + IE_FALSE(&layer_masks, LANDLOCK_ACCESS_FS_EXECUTE); + + IE_TRUE(&layer_masks, LANDLOCK_ACCESS_FS_WRITE_FILE); +} + +#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */ + +#undef IE_TRUE +#undef IE_FALSE + /** * is_access_to_paths_allowed - Check accesses for requests with a common path * @@ -737,6 +950,7 @@ static int current_check_refer_path(struct dentry *const old_dentry, bool allow_parent1, allow_parent2; access_mask_t access_request_parent1, access_request_parent2; struct path mnt_dir; + struct dentry *old_parent; layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {}, layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {}; @@ -784,9 +998,17 @@ static int current_check_refer_path(struct dentry *const old_dentry, mnt_dir.mnt = new_dir->mnt; mnt_dir.dentry = new_dir->mnt->mnt_root; + /* + * old_dentry may be the root of the common mount point and + * !IS_ROOT(old_dentry) at the same time (e.g. with open_tree() and + * OPEN_TREE_CLONE). We do not need to call dget(old_parent) because + * we keep a reference to old_dentry. + */ + old_parent = (old_dentry == mnt_dir.dentry) ? old_dentry : + old_dentry->d_parent; + /* new_dir->dentry is equal to new_dentry->d_parent */ - allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, - old_dentry->d_parent, + allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, old_parent, &layer_masks_parent1); allow_parent2 = collect_domain_accesses( dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2); @@ -1124,7 +1346,8 @@ 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 = get_current_fs_domain(); + const struct landlock_ruleset *const dom = + get_fs_domain(landlock_cred(file->f_cred)->domain); if (!dom) return 0; @@ -1225,3 +1448,27 @@ __init void landlock_add_fs_hooks(void) security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks), &landlock_lsmid); } + +#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST + +/* clang-format off */ +static struct kunit_case test_cases[] = { + KUNIT_CASE(test_no_more_access), + KUNIT_CASE(test_scope_to_request_with_exec_none), + KUNIT_CASE(test_scope_to_request_with_exec_some), + KUNIT_CASE(test_scope_to_request_without_access), + KUNIT_CASE(test_is_eacces_with_none), + KUNIT_CASE(test_is_eacces_with_refer), + KUNIT_CASE(test_is_eacces_with_write), + {} +}; +/* clang-format on */ + +static struct kunit_suite test_suite = { + .name = "landlock_fs", + .test_cases = test_cases, +}; + +kunit_test_suite(test_suite); + +#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */ |