The KEXEC_CMDLINE hook function only supports the pcr conditional. Make
this clear at policy load so that IMA policy authors don't assume that
other conditionals are supported.
Since KEXEC_CMDLINE's inception, ima_match_rules() has always returned
true on any loaded KEXEC_CMDLINE rule without any consideration for
other conditionals present in the rule. Make it clear that pcr is the
only supported KEXEC_CMDLINE conditional by returning an error during
policy load.
An example of why this is a problem can be explained with the following
rule:
dont_measure func=KEXEC_CMDLINE obj_type=foo_t
An IMA policy author would have assumed that rule is valid because the
parser accepted it but the result was that measurements for all
KEXEC_CMDLINE operations would be disabled.
Fixes: b0935123a183 ("IMA: Define a new hook to measure the kexec boot command line arguments")
Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Reviewed-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
---
* v3
- Adjust for the indentation change introduced in patch #4
- Added Lakshmi's Reviewed-by
* v2
- Added Mimi's Reviewed-by
security/integrity/ima/ima_policy.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 40c28f1a6a5a..1c64bd6f1728 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -343,6 +343,17 @@ static int ima_lsm_update_rule(struct ima_rule_entry *entry)
return 0;
}
+static bool ima_rule_contains_lsm_cond(struct ima_rule_entry *entry)
+{
+ int i;
+
+ for (i = 0; i < MAX_LSM_RULES; i++)
+ if (entry->lsm[i].args_p)
+ return true;
+
+ return false;
+}
+
/*
* The LSM policy can be reloaded, leaving the IMA LSM based rules referring
* to the old, stale LSM policy. Update the IMA LSM based rules to reflect
@@ -998,6 +1009,16 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
/* Validation of these hook functions is in ima_parse_rule() */
break;
case KEXEC_CMDLINE:
+ if (entry->action & ~(MEASURE | DONT_MEASURE))
+ return false;
+
+ if (entry->flags & ~(IMA_FUNC | IMA_PCR))
+ return false;
+
+ if (ima_rule_contains_lsm_cond(entry))
+ return false;
+
+ break;
case KEY_CHECK:
if (entry->action & ~(MEASURE | DONT_MEASURE))
return false;
--
2.25.1
