linux-kernel - [PATCH v4 5/8] ima: based on policy require signed firmware (sysfs fallback)

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Message-Id: <1527616920-5415-6-git-send-email-zohar@linux.vnet.ibm.com>
Date:   Tue, 29 May 2018 14:01:57 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org, Andres Rodriguez <andresx7@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Luis R . Rodriguez" <mcgrof@...e.com>,
        Matthew Garrett <mjg59@...gle.com>
Subject: [PATCH v4 5/8] ima: based on policy require signed firmware (sysfs fallback)

Luis, is the security_kernel_post_read_file LSM hook in
firmware_loading_store() still needed after this patch?  Should it be
calling security_kernel_load_data() instead?

---

With an IMA policy requiring signed firmware, this patch prevents
the sysfs fallback method of loading firmware.

Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: David Howells <dhowells@...hat.com>
Cc: Matthew Garrett <mjg59@...gle.com>
---
 security/integrity/ima/ima_main.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index a565d46084c2..4a87f78098c8 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -475,8 +475,10 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
 
 	if (!file && read_id == READING_FIRMWARE) {
 		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
-		    (ima_appraise & IMA_APPRAISE_ENFORCE))
+		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+			pr_err("Prevent firmware loading_store.\n");
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
 		return 0;
 	}
 
@@ -520,6 +522,12 @@ int ima_load_data(enum kernel_load_data_id id)
 			pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
 		}
+		break;
+	case LOADING_FIRMWARE:
+		if (ima_appraise & IMA_APPRAISE_FIRMWARE) {
+			pr_err("Prevent firmware sysfs fallback loading.\n");
+			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
 	default:
 		break;
 	}
-- 
2.7.5