From patchwork Tue Oct 22 16:10:05 2024 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: 13845919 X-Patchwork-Delegate: paul@paul-moore.com Received: from smtp-bc0c.mail.infomaniak.ch (smtp-bc0c.mail.infomaniak.ch [45.157.188.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0EC841BC08C for ; Tue, 22 Oct 2024 16:10:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.157.188.12 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729613438; cv=none; b=OhpKNt7L30n9a1pv04yZYsNCycd17avhCV4OsVz0LM28wyOXX4ql0CpWgK+4uYdZx+mJKzQMqBD4360BDVcSYfK3et4gdK1l3KCFDDp3Ffx4BLl09/n+fIaJhERpuV4FA1M23wyerY41RhagR3H2RScxScSejNR5OgOt4BK9Sbc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729613438; c=relaxed/simple; bh=evqKCI7XLqjqg1ZetdfGSXOFu87CpDBLB/lbz10tL08=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=NX5syjjgJzDaO3U1ReIc7nQtEYC4PUAaHwJ8P4Qr/aqLaEuTqXoRewR7i/p6TOcc8KHoQ9TRflQ+ug38COwsCHU7doC9+cns7TndRg2NnJEQRKwylWLaVDJo4Bj0chNQ+2xOuCNF9inGbLVU2ZGooAEFNR+QwdUt3v6HtcnDuVo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=uBcqCdy5; arc=none smtp.client-ip=45.157.188.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="uBcqCdy5" Received: from smtp-3-0000.mail.infomaniak.ch (smtp-3-0000.mail.infomaniak.ch [10.4.36.107]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4XXxwn3xpWzMZY; Tue, 22 Oct 2024 18:10:33 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digikod.net; s=20191114; t=1729613433; bh=8jgIrNHhjmhClA1AewvlMzMfw/fFKOQvBW2YCRdj/JY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uBcqCdy59muhPQMlwf1a85Fqss49SpuhpYIXMYNKUcyDXGp0xLIsjLMl1gjPp6mjN hq5ttPomxokI5v/0bByHuNDTXBNvhtwZL2j6HxakhOjDxj6ObTwfHPc2UT8idFSPPK yDfNechLYrZnrbhdgE+jwyM5fVUFstKLz5bHNy/4= Received: from unknown by smtp-3-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4XXxwm5Rn5znfX; Tue, 22 Oct 2024 18:10:32 +0200 (CEST) From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: Eric Paris , Paul Moore , =?utf-8?q?G=C3=BCnther_Noack?= , "Serge E . Hallyn" Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Ben Scarlato , Casey Schaufler , Charles Zaffery , James Morris , Jann Horn , Jeff Xu , Jorge Lucangeli Obes , Kees Cook , Konstantin Meskhidze , Matt Bobrowski , Mikhail Ivanov , Praveen K Paladugu , Robert Salvet , Shervin Oloumi , Song Liu , Tahera Fahimi , audit@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [RFC PATCH v2 10/14] landlock: Log file-related denials Date: Tue, 22 Oct 2024 18:10:05 +0200 Message-ID: <20241022161009.982584-11-mic@digikod.net> In-Reply-To: <20241022161009.982584-1-mic@digikod.net> References: <20241022161009.982584-1-mic@digikod.net> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Infomaniak-Routing: alpha Add audit support for path_mkdir, path_mknod, path_symlink, path_unlink, path_rmdir, path_truncate, path_link, path_rename, and file_open hooks. Audit record sample for a link action: DENY: domain=4533720568 blockers=fs_refer path="/usr/bin" dev="vda2" ino=351 DOM_INFO: domain=4533720568 parent=0 pid=325 uid=0 exe="/root/sandboxer" comm="sandboxer" DENY: domain=4533720568 blockers=fs_make_reg,fs_refer path="/usr/local" dev="vda2" ino=365 SYSCALL: arch=c000003e syscall=265 success=no exit=-13 ... Cc: Günther Noack Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20241022161009.982584-11-mic@digikod.net --- Changes since v2: * Revamp logging and support the path_link and path_rename hooks. * Add KUnit tests. Changes since v1: * Move audit code to the ptrace patch. --- security/landlock/audit.c | 173 ++++++++++++++++++++++++++++++++++++-- security/landlock/audit.h | 9 ++ security/landlock/fs.c | 64 +++++++++++--- 3 files changed, 229 insertions(+), 17 deletions(-) diff --git a/security/landlock/audit.c b/security/landlock/audit.c index 4cd9407459d2..9c8b6c246884 100644 --- a/security/landlock/audit.c +++ b/security/landlock/audit.c @@ -7,23 +7,55 @@ #include #include +#include #include #include #include +#include #include "audit.h" +#include "common.h" #include "cred.h" #include "domain.h" #include "ruleset.h" -static const char *get_blocker(const enum landlock_request_type type) +static const char *const fs_access_strings[] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = "fs_execute", + [BIT_INDEX(LANDLOCK_ACCESS_FS_WRITE_FILE)] = "fs_write_file", + [BIT_INDEX(LANDLOCK_ACCESS_FS_READ_FILE)] = "fs_read_file", + [BIT_INDEX(LANDLOCK_ACCESS_FS_READ_DIR)] = "fs_read_dir", + [BIT_INDEX(LANDLOCK_ACCESS_FS_REMOVE_DIR)] = "fs_remove_dir", + [BIT_INDEX(LANDLOCK_ACCESS_FS_REMOVE_FILE)] = "fs_remove_file", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_CHAR)] = "fs_make_char", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_DIR)] = "fs_make_dir", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_REG)] = "fs_make_reg", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_SOCK)] = "fs_make_sock", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_FIFO)] = "fs_make_fifo", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_BLOCK)] = "fs_make_block", + [BIT_INDEX(LANDLOCK_ACCESS_FS_MAKE_SYM)] = "fs_make_sym", + [BIT_INDEX(LANDLOCK_ACCESS_FS_REFER)] = "fs_refer", + [BIT_INDEX(LANDLOCK_ACCESS_FS_TRUNCATE)] = "fs_truncate", + [BIT_INDEX(LANDLOCK_ACCESS_FS_IOCTL_DEV)] = "fs_ioctl_dev", +}; +static_assert(ARRAY_SIZE(fs_access_strings) == LANDLOCK_NUM_ACCESS_FS); + +static __attribute_const__ const char * +get_blocker(const enum landlock_request_type type, + const unsigned long access_bit) { switch (type) { case LANDLOCK_REQUEST_PTRACE: + WARN_ON_ONCE(access_bit != -1); return "ptrace"; case LANDLOCK_REQUEST_FS_CHANGE_LAYOUT: + WARN_ON_ONCE(access_bit != -1); return "fs_change_layout"; + + case LANDLOCK_REQUEST_FS_ACCESS: + if (WARN_ON_ONCE(access_bit >= ARRAY_SIZE(fs_access_strings))) + return "unknown"; + return fs_access_strings[access_bit]; } WARN_ON_ONCE(1); @@ -31,9 +63,20 @@ static const char *get_blocker(const enum landlock_request_type type) } static void log_blockers(struct audit_buffer *const ab, - const enum landlock_request_type type) + const enum landlock_request_type type, + const access_mask_t access) { - audit_log_format(ab, "%s", get_blocker(type)); + const unsigned long access_mask = access; + unsigned long access_bit; + size_t i = 0; + + for_each_set_bit(access_bit, &access_mask, BITS_PER_TYPE(access)) { + audit_log_format(ab, "%s%s", (i == 0) ? "" : ",", + get_blocker(type, access_bit)); + i++; + } + if (i == 0) + audit_log_format(ab, "%s", get_blocker(type, -1)); } static void log_node(struct landlock_hierarchy *const node) @@ -121,9 +164,110 @@ static void test_get_hierarchy(struct kunit *const test) #endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */ +static size_t get_denied_layer(const struct landlock_ruleset *const domain, + access_mask_t *const access_request, + const layer_mask_t (*const layer_masks)[], + const size_t layer_masks_size) +{ + const unsigned long access_req = *access_request; + unsigned long access_bit; + access_mask_t missing = 0; + long youngest_layer = -1; + + for_each_set_bit(access_bit, &access_req, layer_masks_size) { + const access_mask_t mask = (*layer_masks)[access_bit]; + long layer; + + if (!mask) + continue; + + /* __fls(1) == 0 */ + layer = __fls(mask); + if (layer > youngest_layer) { + youngest_layer = layer; + missing = BIT(access_bit); + } else if (layer == youngest_layer) { + missing |= BIT(access_bit); + } + } + + *access_request = missing; + if (youngest_layer == -1) + return domain->num_layers - 1; + + return youngest_layer; +} + +#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST + +static void test_get_denied_layer(struct kunit *const test) +{ + const struct landlock_ruleset dom = { + .num_layers = 5, + }; + const layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = { + [BIT_INDEX(LANDLOCK_ACCESS_FS_EXECUTE)] = BIT(0), + [BIT_INDEX(LANDLOCK_ACCESS_FS_READ_FILE)] = BIT(1), + [BIT_INDEX(LANDLOCK_ACCESS_FS_READ_DIR)] = BIT(1) | BIT(0), + [BIT_INDEX(LANDLOCK_ACCESS_FS_REMOVE_DIR)] = BIT(2), + }; + access_mask_t access; + + access = LANDLOCK_ACCESS_FS_EXECUTE; + KUNIT_EXPECT_EQ(test, 0, + get_denied_layer(&dom, &access, &layer_masks, + sizeof(layer_masks))); + KUNIT_EXPECT_EQ(test, access, LANDLOCK_ACCESS_FS_EXECUTE); + + access = LANDLOCK_ACCESS_FS_READ_FILE; + KUNIT_EXPECT_EQ(test, 1, + get_denied_layer(&dom, &access, &layer_masks, + sizeof(layer_masks))); + KUNIT_EXPECT_EQ(test, access, LANDLOCK_ACCESS_FS_READ_FILE); + + access = LANDLOCK_ACCESS_FS_READ_DIR; + KUNIT_EXPECT_EQ(test, 1, + get_denied_layer(&dom, &access, &layer_masks, + sizeof(layer_masks))); + KUNIT_EXPECT_EQ(test, access, LANDLOCK_ACCESS_FS_READ_DIR); + + access = LANDLOCK_ACCESS_FS_READ_FILE | LANDLOCK_ACCESS_FS_READ_DIR; + KUNIT_EXPECT_EQ(test, 1, + get_denied_layer(&dom, &access, &layer_masks, + sizeof(layer_masks))); + KUNIT_EXPECT_EQ(test, access, + LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_READ_DIR); + + access = LANDLOCK_ACCESS_FS_EXECUTE | LANDLOCK_ACCESS_FS_READ_DIR; + KUNIT_EXPECT_EQ(test, 1, + get_denied_layer(&dom, &access, &layer_masks, + sizeof(layer_masks))); + KUNIT_EXPECT_EQ(test, access, LANDLOCK_ACCESS_FS_READ_DIR); + + access = LANDLOCK_ACCESS_FS_WRITE_FILE; + KUNIT_EXPECT_EQ(test, 4, + get_denied_layer(&dom, &access, &layer_masks, + sizeof(layer_masks))); + KUNIT_EXPECT_EQ(test, access, 0); +} + +#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */ + static bool is_valid_request(const struct landlock_request *const request) { - if (WARN_ON_ONCE(!request->layer_plus_one)) + if (WARN_ON_ONCE(!(!!request->layer_plus_one ^ !!request->access))) + return false; + + if (request->access) { + if (WARN_ON_ONCE(!request->layer_masks)) + return false; + } else { + if (WARN_ON_ONCE(request->layer_masks)) + return false; + } + + if (WARN_ON_ONCE(!!request->layer_masks ^ !!request->layer_masks_size)) return false; return true; @@ -140,6 +284,7 @@ void landlock_log_denial(const struct landlock_ruleset *const domain, { struct audit_buffer *ab; struct landlock_hierarchy *youngest_denied; + access_mask_t missing; if (WARN_ON_ONCE(!domain || !domain->hierarchy || !request)) return; @@ -155,9 +300,24 @@ void landlock_log_denial(const struct landlock_ruleset *const domain, if (!ab) return; - youngest_denied = get_hierarchy(domain, request->layer_plus_one - 1); + missing = request->access; + if (missing) { + size_t youngest_layer; + + /* Gets the nearest domain that denies the request. */ + if (request->layer_masks) { + youngest_layer = get_denied_layer( + domain, &missing, request->layer_masks, + request->layer_masks_size); + } + youngest_denied = get_hierarchy(domain, youngest_layer); + } else { + youngest_denied = + get_hierarchy(domain, request->layer_plus_one - 1); + } + audit_log_format(ab, "domain=%llu blockers=", youngest_denied->id); - log_blockers(ab, request->type); + log_blockers(ab, request->type, missing); audit_log_lsm_data(ab, &request->audit); audit_log_end(ab); @@ -204,6 +364,7 @@ void landlock_log_drop_domain(const struct landlock_ruleset *const domain) static struct kunit_case test_cases[] = { /* clang-format off */ KUNIT_CASE(test_get_hierarchy), + KUNIT_CASE(test_get_denied_layer), {} /* clang-format on */ }; diff --git a/security/landlock/audit.h b/security/landlock/audit.h index 6f5ad04b83c2..25fc8333cddc 100644 --- a/security/landlock/audit.h +++ b/security/landlock/audit.h @@ -11,11 +11,13 @@ #include #include +#include "access.h" #include "ruleset.h" enum landlock_request_type { LANDLOCK_REQUEST_PTRACE = 1, LANDLOCK_REQUEST_FS_CHANGE_LAYOUT, + LANDLOCK_REQUEST_FS_ACCESS, }; /* @@ -33,6 +35,13 @@ struct landlock_request { * extra one is useful to detect uninitialized field. */ size_t layer_plus_one; + + /* Required field for configurable access control. */ + access_mask_t access; + + /* Required fields for requests with layer masks. */ + const layer_mask_t (*layer_masks)[]; + size_t layer_masks_size; }; #ifdef CONFIG_AUDIT diff --git a/security/landlock/fs.c b/security/landlock/fs.c index a099167d2347..7f69bed9e095 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -730,6 +730,7 @@ static void test_is_eacces_with_write(struct kunit *const test) * those identified by @access_request_parent1). This matrix can * initially refer to domain layer masks and, when the accesses for the * destination and source are the same, to requested layer masks. + * @log_request_parent1: Audit request to fill if the related access is denied. * @dentry_child1: Dentry to the initial child of the parent1 path. This * pointer must be NULL for non-refer actions (i.e. not link nor rename). * @access_request_parent2: Similar to @access_request_parent1 but for a @@ -738,6 +739,7 @@ static void test_is_eacces_with_write(struct kunit *const test) * the source. Must be set to 0 when using a simple path request. * @layer_masks_parent2: Similar to @layer_masks_parent1 but for a refer * action. This must be NULL otherwise. + * @log_request_parent2: Audit request to fill if the related access is denied. * @dentry_child2: Dentry to the initial child of the parent2 path. This * pointer is only set for RENAME_EXCHANGE actions and must be NULL * otherwise. @@ -757,10 +759,12 @@ static bool is_access_to_paths_allowed( const struct path *const path, const access_mask_t access_request_parent1, layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS], - const struct dentry *const dentry_child1, + struct landlock_request *const log_request_parent1, + struct dentry *const dentry_child1, const access_mask_t access_request_parent2, layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS], - const struct dentry *const dentry_child2) + struct landlock_request *const log_request_parent2, + struct dentry *const dentry_child2) { bool allowed_parent1 = false, allowed_parent2 = false, is_dom_check, child1_is_directory = true, child2_is_directory = true; @@ -907,6 +911,24 @@ static bool is_access_to_paths_allowed( } path_put(&walker_path); + if (!allowed_parent1 && log_request_parent1) { + log_request_parent1->type = LANDLOCK_REQUEST_FS_ACCESS, + log_request_parent1->audit.type = LSM_AUDIT_DATA_PATH, + log_request_parent1->audit.u.path = *path; + log_request_parent1->access = access_request_parent1; + log_request_parent1->layer_masks = layer_masks_parent1; + log_request_parent1->layer_masks_size = + ARRAY_SIZE(*layer_masks_parent1); + } + if (!allowed_parent2 && log_request_parent2) { + log_request_parent2->type = LANDLOCK_REQUEST_FS_ACCESS, + log_request_parent2->audit.type = LSM_AUDIT_DATA_PATH, + log_request_parent2->audit.u.path = *path; + log_request_parent2->access = access_request_parent2; + log_request_parent2->layer_masks = layer_masks_parent2; + log_request_parent2->layer_masks_size = + ARRAY_SIZE(*layer_masks_parent2); + } return allowed_parent1 && allowed_parent2; } @@ -915,6 +937,7 @@ static int current_check_access_path(const struct path *const path, { const struct landlock_ruleset *const dom = get_current_fs_domain(); layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; + struct landlock_request request = {}; if (!dom) return 0; @@ -922,9 +945,10 @@ static int current_check_access_path(const struct path *const path, access_request = landlock_init_layer_masks( dom, access_request, &layer_masks, LANDLOCK_KEY_INODE); if (is_access_to_paths_allowed(dom, path, access_request, &layer_masks, - NULL, 0, NULL, NULL)) + &request, NULL, 0, NULL, NULL, NULL)) return 0; + landlock_log_denial(dom, &request); return -EACCES; } @@ -1093,6 +1117,7 @@ static int current_check_refer_path(struct dentry *const old_dentry, struct dentry *old_parent; layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {}, layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {}; + struct landlock_request request1 = {}, request2 = {}; if (!dom) return 0; @@ -1124,10 +1149,13 @@ static int current_check_refer_path(struct dentry *const old_dentry, access_request_parent1 = landlock_init_layer_masks( dom, access_request_parent1 | access_request_parent2, &layer_masks_parent1, LANDLOCK_KEY_INODE); - if (is_access_to_paths_allowed( - dom, new_dir, access_request_parent1, - &layer_masks_parent1, NULL, 0, NULL, NULL)) + if (is_access_to_paths_allowed(dom, new_dir, + access_request_parent1, + &layer_masks_parent1, &request1, + NULL, 0, NULL, NULL, NULL)) return 0; + + landlock_log_denial(dom, &request1); return -EACCES; } @@ -1162,12 +1190,22 @@ static int current_check_refer_path(struct dentry *const old_dentry, * parent access rights. This will be useful to compare with the * destination parent access rights. */ - if (is_access_to_paths_allowed( - dom, &mnt_dir, access_request_parent1, &layer_masks_parent1, - old_dentry, access_request_parent2, &layer_masks_parent2, - exchange ? new_dentry : NULL)) + if (is_access_to_paths_allowed(dom, &mnt_dir, access_request_parent1, + &layer_masks_parent1, &request1, + old_dentry, access_request_parent2, + &layer_masks_parent2, &request2, + exchange ? new_dentry : NULL)) return 0; + if (request1.access) { + request1.audit.u.path.dentry = old_parent; + landlock_log_denial(dom, &request1); + } + if (request2.access) { + request2.audit.u.path.dentry = new_dir->dentry; + landlock_log_denial(dom, &request2); + } + /* * This prioritizes EACCES over EXDEV for all actions, including * renames with RENAME_EXCHANGE. @@ -1546,6 +1584,7 @@ static int hook_file_open(struct file *const file) optional_access; const struct landlock_ruleset *const dom = landlock_match_ruleset( landlock_cred(file->f_cred)->domain, any_fs); + struct landlock_request request = {}; if (!dom) return 0; @@ -1571,7 +1610,7 @@ static int hook_file_open(struct file *const file) dom, &file->f_path, landlock_init_layer_masks(dom, full_access_request, &layer_masks, LANDLOCK_KEY_INODE), - &layer_masks, NULL, 0, NULL, NULL)) { + &layer_masks, &request, NULL, 0, NULL, NULL, NULL)) { allowed_access = full_access_request; } else { unsigned long access_bit; @@ -1601,6 +1640,9 @@ static int hook_file_open(struct file *const file) if ((open_access_request & allowed_access) == open_access_request) return 0; + /* Sets access to reflect the actual request. */ + request.access = open_access_request; + landlock_log_denial(dom, &request); return -EACCES; }