[PATCH v2 2/2] ima: Fail rule parsing when asymmetric key measurement isn't supportable

[Tyler Hicks]

Measuring keys is currently only supported for asymmetric keys. In the
future, this might change.

For now, the "func=KEY_CHECK" and "keyrings=" options are only
appropriate when CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is enabled. Make
this clear at policy load so that IMA policy authors don't assume that
these policy language constructs are supported.

Fixes: 2b60c0ecedf8 ("IMA: Read keyrings= option from the IMA policy")
Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
Suggested-by: Nayna Jain <na...@linux.ibm.com>
Signed-off-by: Tyler Hicks <tyhi...@linux.microsoft.com>
Reviewed-by: Lakshmi Ramasubramanian <nra...@linux.microsoft.com>
---
 security/integrity/ima/ima_policy.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c 
b/security/integrity/ima/ima_policy.c
index ea224f00b305..fe1df373c113 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1233,7 +1233,8 @@ static int ima_parse_rule(char *rule, struct 
ima_rule_entry *entry)
                                entry->func = POLICY_CHECK;
                        else if (strcmp(args[0].from, "KEXEC_CMDLINE") == 0)
                                entry->func = KEXEC_CMDLINE;
-                       else if (strcmp(args[0].from, "KEY_CHECK") == 0)
+                       else if (IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) 
&&
+                                strcmp(args[0].from, "KEY_CHECK") == 0)
                                entry->func = KEY_CHECK;
                        else
                                result = -EINVAL;
@@ -1290,7 +1291,8 @@ static int ima_parse_rule(char *rule, struct 
ima_rule_entry *entry)
                case Opt_keyrings:
                        ima_log_string(ab, "keyrings", args[0].from);
 
-                       if (entry->keyrings) {
+                       if (!IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) ||
+                           entry->keyrings) {
                                result = -EINVAL;
                                break;
                        }
-- 
2.25.1