Merge tag 'integrity-v5.8-fix-2' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity

Pull integrity updates from Mimi Zohar:
 "Include PCRs 8 & 9 in per TPM 2.0 bank boot_aggregate calculation.

  Prior to Linux 5.8 the SHA1 "boot_aggregate" value was padded with 0's
  and extended into the other TPM 2.0 banks.

  Included in the Linux 5.8 open window, TPM 2.0 PCR bank specific
  "boot_aggregate" values (PCRs 0  - 7) are calculated and extended into the TPM banks.

  Distro releases are now shipping grub2 with TPM support, which extend
  PCRs 8 & 9. I'd like for PCRs 8 & 9 to be included in the new
  "boot_aggregate" calculations.

  For backwards compatibility, if the hash is SHA1, these new PCRs are
  not included in the boot aggregate"

* tag 'integrity-v5.8-fix-2' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
  ima: extend boot_aggregate with kernel measurements

2 files changed, 15 insertions, 2 deletions

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index df93ac258e01..9d94080bdad8 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 220b14920c37..011c3c76af86 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -823,13 +823,26 @@ 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;