Buffer based hook functions, such as KEXEC_CMDLINE and KEY_CHECK, can
only measure. The process_buffer_measurement() function quietly ignores
all actions except measure so make this behavior clear at the time of
policy load.
The parsing of the keyrings conditional had a check to ensure that it
was only specified with measure actions but the check should be on the
hook function and not the keyrings conditional since
"appraise func=KEY_CHECK" is not a valid rule.
Fixes: b0935123a183 ("IMA: Define a new hook to measure the kexec boot command line arguments")
Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>
---
* v3
- Add comments to ima_validate_rule() to separate/explain the types of
validation checks (section for action checks, section for hook
function checks, soon to be a section for combination of options
checks, etc.)
- Removed the "if (entry->flags & IMA_FUNC)" conditional around the
switch statement in ima_validate_rule() which reduced the overall indention
by a tab. This could be removed because entry->func is NONE when the
IMA_FUNC flag is not set. We'll explicitly enforce and then leverage
that property in a later patch when we start validating all hook
functions in ima_validate_rule().
- Add comment explicitly stating that all hook functions except
KEXEC_CMDLINE and KEY_CHECK are still being validated in
ima_parse_rule().
* v2
- No change
security/integrity/ima/ima_policy.c | 40 +++++++++++++++++++++++++++--
1 file changed, 38 insertions(+), 2 deletions(-)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index e458cd47c099..40c28f1a6a5a 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -973,6 +973,43 @@ static void check_template_modsig(const struct ima_template_desc *template)
#undef MSG
}
+static bool ima_validate_rule(struct ima_rule_entry *entry)
+{
+ /* Ensure that the action is set */
+ if (entry->action == UNKNOWN)
+ return false;
+
+ /*
+ * Ensure that the hook function is compatible with the other
+ * components of the rule
+ */
+ switch (entry->func) {
+ case NONE:
+ case FILE_CHECK:
+ case MMAP_CHECK:
+ case BPRM_CHECK:
+ case CREDS_CHECK:
+ case POST_SETATTR:
+ case MODULE_CHECK:
+ case FIRMWARE_CHECK:
+ case KEXEC_KERNEL_CHECK:
+ case KEXEC_INITRAMFS_CHECK:
+ case POLICY_CHECK:
+ /* Validation of these hook functions is in ima_parse_rule() */
+ break;
+ case KEXEC_CMDLINE:
+ case KEY_CHECK:
+ if (entry->action & ~(MEASURE | DONT_MEASURE))
+ return false;
+
+ break;
+ default:
+ return false;
+ }
+
+ return true;
+}
+
static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
{
struct audit_buffer *ab;
@@ -1150,7 +1187,6 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
keyrings_len = strlen(args[0].from) + 1;
if ((entry->keyrings) ||
- (entry->action != MEASURE) ||
(entry->func != KEY_CHECK) ||
(keyrings_len < 2)) {
result = -EINVAL;
@@ -1356,7 +1392,7 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
break;
}
}
- if (!result && (entry->action == UNKNOWN))
+ if (!result && !ima_validate_rule(entry))
result = -EINVAL;
else if (entry->action == APPRAISE)
temp_ima_appraise |= ima_appraise_flag(entry->func);
--
2.25.1
