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ima: extend boot_aggregate with kernel measurements 

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@ibm.com>
Reviewed-by: Bruno Meneguele <bmeneg@redhat.com>
Tested-by: Bruno Meneguele <bmeneg@redhat.com>  (TPM 1.2, TPM 2.0)
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Maurizio Drocco 2020-06-23 11:57:32 -04:00 committed by Mimi Zohar
parent 48778464bb
commit 20c59ce010
2 changed files with 15 additions and 2 deletions
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2
security/integrity/ima/ima.h
View File

@ -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

15
security/integrity/ima/ima_crypto.c
View File

@ -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;