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ima: Fail rule parsing when buffer hook functions have an invalid action

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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: b0935123a1 ("IMA: Define a new hook to measure the kexec boot command line arguments")
Fixes: 5808611ccc ("IMA: Add KEY_CHECK func to measure keys")
Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Tyler Hicks 2020-07-09 01:19:03 -05:00 committed by Mimi Zohar
parent 2bdd737c56
commit 712183437e
1 changed files with 38 additions and 2 deletions
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40
security/integrity/ima/ima_policy.c
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@ -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);