linux-kernel - [PATCH v3 5/5] tpm: ensure that output of PCR read contains the correct digest size

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20181030154711.2782-6-roberto.sassu@huawei.com>
Date:   Tue, 30 Oct 2018 16:47:11 +0100
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <jarkko.sakkinen@...ux.intel.com>, <zohar@...ux.ibm.com>
CC:     <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <silviu.vlasceanu@...wei.com>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v3 5/5] tpm: ensure that output of PCR read contains the correct digest size

This patch ensures that the digest size returned by the TPM during a PCR
read matches the size of the algorithm passed as argument to
tpm2_pcr_read(). The check is performed after information about the PCR
banks has been retrieved.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 drivers/char/tpm/tpm2-cmd.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 8e821e7b4674..477dcc30fc53 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -187,15 +187,28 @@ struct tpm2_pcr_read_out {
 int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx,
 		  struct tpm_digest *digest_struct, u16 *digest_size_ptr)
 {
+	int i;
 	int rc;
 	struct tpm_buf buf;
 	struct tpm2_pcr_read_out *out;
 	u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0};
 	u16 digest_size;
+	u16 expected_digest_size = 0;
 
 	if (pcr_idx >= TPM2_PLATFORM_PCR)
 		return -EINVAL;
 
+	if (!digest_size_ptr) {
+		for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
+		     chip->active_banks[i].alg_id != digest_struct->alg_id; i++)
+			;
+
+		if (i == ARRAY_SIZE(chip->active_banks))
+			return -EINVAL;
+
+		expected_digest_size = chip->active_banks[i].digest_size;
+	}
+
 	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
 	if (rc)
 		return rc;
@@ -215,7 +228,8 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx,
 
 	out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
 	digest_size = be16_to_cpu(out->digest_size);
-	if (digest_size > sizeof(digest_struct->digest)) {
+	if ((digest_size_ptr && digest_size > sizeof(digest_struct->digest)) ||
+	    (!digest_size_ptr && digest_size != expected_digest_size)) {
 		rc = -EINVAL;
 		goto out;
 	}
-- 
2.17.1