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apparmor: Enable tuning of policy paranoid load for embedded systems

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AppArmor by default does an extensive check on loaded policy that
can take quite some time on limited resource systems. Allow
disabling this check for embedded systems where system images are
readonly and have checksumming making the need for the embedded
policy to be fully checked to be redundant.

Note: basic policy checks are still done.

Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
John Johansen 2021-02-03 01:35:12 -08:00
parent d61c57fde8
commit 5bfcbd22ee
3 changed files with 15 additions and 2 deletions
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11
security/apparmor/Kconfig
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@ -94,6 +94,17 @@ config SECURITY_APPARMOR_EXPORT_BINARY
also increases policy load time. This option is required for
checkpoint and restore support, and debugging of loaded policy.
config SECURITY_APPARMOR_PARANOID_LOAD
bool "Perform full verification of loaded policy"
depends on SECURITY_APPARMOR
default y
help
This options allows controlling whether apparmor does a full
verification of loaded policy. This should not be disabled
except for embedded systems where the image is read only,
includes policy, and has some form of integrity check.
Disabling the check will speed up policy loads.
config SECURITY_APPARMOR_KUNIT_TEST
bool "Build KUnit tests for policy_unpack.c" if !KUNIT_ALL_TESTS
depends on KUNIT=y && SECURITY_APPARMOR

2
security/apparmor/lsm.c
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@ -1405,7 +1405,7 @@ module_param_named(path_max, aa_g_path_max, aauint, S_IRUSR);
* DEPRECATED: read only as strict checking of load is always done now
* that none root users (user namespaces) can load policy.
*/
bool aa_g_paranoid_load = true;
bool aa_g_paranoid_load = IS_ENABLED(CONFIG_SECURITY_PARANOID_LOAD);
module_param_named(paranoid_load, aa_g_paranoid_load, aabool, S_IRUGO);
static int param_get_aaintbool(char *buffer, const struct kernel_param *kp);

4
security/apparmor/policy_unpack.c
View File

@ -457,7 +457,9 @@ static struct aa_dfa *unpack_dfa(struct aa_ext *e)
((e->pos - e->start) & 7);
size_t pad = ALIGN(sz, 8) - sz;
int flags = TO_ACCEPT1_FLAG(YYTD_DATA32) |
TO_ACCEPT2_FLAG(YYTD_DATA32) | DFA_FLAG_VERIFY_STATES;
TO_ACCEPT2_FLAG(YYTD_DATA32);
if (aa_g_paranoid_load)
flags |= DFA_FLAG_VERIFY_STATES;
dfa = aa_dfa_unpack(blob + pad, size - pad, flags);
if (IS_ERR(dfa))