linux-kernel - [PATCH AUTOSEL 5.7 03/30] ima: extend boot

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Date:   Wed,  8 Jul 2020 11:40:49 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Maurizio Drocco <maurizio.drocco@....com>,
        Bruno Meneguele <bmeneg@...hat.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 5.7 03/30] ima: extend boot_aggregate with kernel measurements

From: Maurizio Drocco <maurizio.drocco@....com>

[ Upstream commit 20c59ce010f84300f6c655d32db2610d3433f85c ]

Registers 8-9 are used to store measurements of the kernel and its
command line (e.g., grub2 bootloader with tpm module enabled). IMA
should include them in the boot aggregate. Registers 8-9 should be
only included in non-SHA1 digests to avoid ambiguity.

Signed-off-by: Maurizio Drocco <maurizio.drocco@....com>
Reviewed-by: Bruno Meneguele <bmeneg@...hat.com>
Tested-by: Bruno Meneguele <bmeneg@...hat.com>  (TPM 1.2, TPM 2.0)
Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 security/integrity/ima/ima.h        |  2 +-
 security/integrity/ima/ima_crypto.c | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 495e28bd488e6..844a55225ede0 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -30,7 +30,7 @@
 
 enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_BINARY_NO_FIELD_LEN,
 		     IMA_SHOW_BINARY_OLD_STRING_FMT, IMA_SHOW_ASCII };
-enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
+enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 };
 
 /* digest size for IMA, fits SHA1 or MD5 */
 #define IMA_DIGEST_SIZE		SHA1_DIGEST_SIZE
diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index fb27174806ba4..e0738d1d143d7 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -682,13 +682,26 @@ static int ima_calc_boot_aggregate_tfm(char *digest, u16 alg_id,
 	if (rc != 0)
 		return rc;
 
-	/* cumulative sha1 over tpm registers 0-7 */
+	/* cumulative digest over TPM registers 0-7 */
 	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
 		ima_pcrread(i, &d);
 		/* now accumulate with current aggregate */
 		rc = crypto_shash_update(shash, d.digest,
 					 crypto_shash_digestsize(tfm));
 	}
+	/*
+	 * Extend cumulative digest over TPM registers 8-9, which contain
+	 * measurement for the kernel command line (reg. 8) and image (reg. 9)
+	 * in a typical PCR allocation. Registers 8-9 are only included in
+	 * non-SHA1 boot_aggregate digests to avoid ambiguity.
+	 */
+	if (alg_id != TPM_ALG_SHA1) {
+		for (i = TPM_PCR8; i < TPM_PCR10; i++) {
+			ima_pcrread(i, &d);
+			rc = crypto_shash_update(shash, d.digest,
+						crypto_shash_digestsize(tfm));
+		}
+	}
 	if (!rc)
 		crypto_shash_final(shash, digest);
 	return rc;
-- 
2.25.1