linux-kernel - [PATCH v3 3/4] ima: limit secure boot feedback scope for appraise

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Date:   Fri,  4 Sep 2020 22:20:20 -0300
From:   Bruno Meneguele <bmeneg@...hat.com>
To:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     zohar@...ux.ibm.com, Bruno Meneguele <bmeneg@...hat.com>
Subject: [PATCH v3 3/4] ima: limit secure boot feedback scope for appraise

Only prompt the unknown/invalid appraisal option if secureboot is enabled and
if the current appraisal state is different from the original one.

Signed-off-by: Bruno Meneguele <bmeneg@...hat.com>
---
Changelog:
v3:
- fix sb_state conditional (Mimi)
v2: 
- update commit message (Mimi)
- work with a temporary var instead of directly with ima_appraise (Mimi)

 security/integrity/ima/ima_appraise.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 2193b51c2743..4f028f6e8f8d 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -19,22 +19,29 @@
 static int __init default_appraise_setup(char *str)
 {
 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
-	if (arch_ima_get_secureboot()) {
-		pr_info("Secure boot enabled: ignoring ima_appraise=%s boot parameter option",
-			str);
-		return 1;
-	}
+	bool sb_state = arch_ima_get_secureboot();
+	int appraisal_state = ima_appraise;
 
 	if (strncmp(str, "off", 3) == 0)
-		ima_appraise = 0;
+		appraisal_state = 0;
 	else if (strncmp(str, "log", 3) == 0)
-		ima_appraise = IMA_APPRAISE_LOG;
+		appraisal_state = IMA_APPRAISE_LOG;
 	else if (strncmp(str, "fix", 3) == 0)
-		ima_appraise = IMA_APPRAISE_FIX;
+		appraisal_state = IMA_APPRAISE_FIX;
 	else if (strncmp(str, "enforce", 7) == 0)
-		ima_appraise = IMA_APPRAISE_ENFORCE;
+		appraisal_state = IMA_APPRAISE_ENFORCE;
 	else
 		pr_err("invalid \"%s\" appraise option", str);
+
+	/* If appraisal state was changed, but secure boot is enabled,
+	 * keep its default */
+	if (sb_state) {
+		if (!(appraisal_state & IMA_APPRAISE_ENFORCE))
+			pr_info("Secure boot enabled: ignoring ima_appraise=%s option",
+				str);
+	} else {
+		ima_appraise = appraisal_state;
+	}
 #endif
 	return 1;
 }
-- 
2.26.2