linux-kernel - [PATCH] ima: Support euid keyword for buffer measurement

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Date:   Mon, 5 Jul 2021 13:56:50 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <zohar@...ux.ibm.com>
CC:     <tusharsu@...ux.microsoft.com>, <nramas@...ux.microsoft.com>,
        <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH] ima: Support euid keyword for buffer measurement

This patch makes the 'euid' keyword available for buffer measurement rules,
in the same way as for other rules. Currently, there is only support for
the 'uid' keyword.

With this change, buffer measurement (or non-measurement) can depend also
on the process effective UID.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 security/integrity/ima/ima_policy.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index fd5d46e511f1..fdaa030fb04b 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -480,6 +480,16 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
 	if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
 		return false;
 
+	if (rule->flags & IMA_EUID) {
+		if (has_capability_noaudit(current, CAP_SETUID)) {
+			if (!rule->uid_op(cred->euid, rule->uid)
+			    && !rule->uid_op(cred->suid, rule->uid)
+			    && !rule->uid_op(cred->uid, rule->uid))
+				return false;
+		} else if (!rule->uid_op(cred->euid, rule->uid))
+			return false;
+	}
+
 	switch (rule->func) {
 	case KEY_CHECK:
 		if (!rule->keyrings)
@@ -1153,7 +1163,7 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
 		if (entry->action & ~(MEASURE | DONT_MEASURE))
 			return false;
 
-		if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
+		if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_EUID | IMA_PCR |
 				     IMA_LABEL))
 			return false;
 
-- 
2.25.1