On Tue, 2020-02-04 at 13:37 +0000, Roberto Sassu wrote: > > -----Original Message----- > > From: linux-integrity-owner@xxxxxxxxxxxxxxx [mailto:linux-integrity- > > owner@xxxxxxxxxxxxxxx] On Behalf Of Mimi Zohar > > Sent: Thursday, January 30, 2020 5:23 PM > > To: linux-integrity@xxxxxxxxxxxxxxx > > Cc: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>; James Bottomley > > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>; linux- > > kernel@xxxxxxxxxxxxxxx; Mimi Zohar <zohar@xxxxxxxxxxxxx> > > Subject: [PATCH v3 2/2] ima: support calculating the boot_aggregate based > > on different TPM banks > > > > Calculating the boot_aggregate attempts to read the TPM SHA1 bank, > > assuming it is always enabled. With TPM 2.0 hash agility, TPM chips > > could support multiple TPM PCR banks, allowing firmware to configure and > > enable different banks. > > > > Instead of hard coding the TPM 2.0 bank hash algorithm used for calculating > > the boot-aggregate, use the same hash algorithm for reading the TPM PCRs > > as > > for calculating the boot aggregate digest. Preference is given to the > > configured IMA default hash algorithm. > > > > For TPM 1.2 SHA1 is the only supported hash algorithm. > > > > Reported-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx> > > Suggested-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> > > --- > > security/integrity/ima/ima_crypto.c | 45 > > ++++++++++++++++++++++++++++++++++++- > > 1 file changed, 44 insertions(+), 1 deletion(-) > > > > diff --git a/security/integrity/ima/ima_crypto.c > > b/security/integrity/ima/ima_crypto.c > > index 7967a6904851..a020aaefdea8 100644 > > --- a/security/integrity/ima/ima_crypto.c > > +++ b/security/integrity/ima/ima_crypto.c > > @@ -656,13 +656,34 @@ static void __init ima_pcrread(u32 idx, struct > > tpm_digest *d) > > pr_err("Error Communicating to TPM chip\n"); > > } > > > > +static enum hash_algo get_hash_algo(const char *algname) > > +{ > > + int i; > > + > > + for (i = 0; i < HASH_ALGO__LAST; i++) { > > + if (strcmp(algname, hash_algo_name[i]) == 0) > > + break; > > + } > > + > > + return i; > > +} > > + > > /* > > - * Calculate the boot aggregate hash > > + * The boot_aggregate is a cumulative hash over TPM registers 0 - 7. With > > + * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but > > with > > + * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks, > > + * allowing firmware to configure and enable different banks. > > + * > > + * Knowing which TPM bank is read to calculate the boot_aggregate digest > > + * needs to be conveyed to a verifier. For this reason, use the same > > + * hash algorithm for reading the TPM PCRs as for calculating the boot > > + * aggregate digest as stored in the measurement list. > > */ > > static int __init ima_calc_boot_aggregate_tfm(char *digest, > > struct crypto_shash *tfm) > > { > > struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} }; > > + enum hash_algo crypto_id; > > int rc; > > u32 i; > > SHASH_DESC_ON_STACK(shash, tfm); > > @@ -673,6 +694,28 @@ static int __init ima_calc_boot_aggregate_tfm(char > > *digest, > > if (rc != 0) > > return rc; > > > > + crypto_id = get_hash_algo(crypto_shash_alg_name(tfm)); > > + if (crypto_id == HASH_ALGO__LAST) { > > + pr_devel("unknown hash algorithm (%s), failing to read > > PCRs.\n", > > + crypto_shash_alg_name(tfm)); > > + return 0; > > + } > > + > > + for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) { > > + if (ima_tpm_chip->allocated_banks[i].crypto_id == > > crypto_id) { > > + d.alg_id = ima_tpm_chip->allocated_banks[i].alg_id; > > + break; > > + } > > + } > > + if (i == ima_tpm_chip->nr_allocated_banks) { > > + pr_devel("TPM %s bank not allocated, failing to read > > PCRs.\n", > > + crypto_shash_alg_name(tfm)); > > + return 0; > > + } > > + > > + pr_devel("calculating the boot-aggregregate based on TPM > > bank: %04x\n", > > + d.alg_id); > > + > > /* cumulative sha1 over tpm registers 0-7 */ > > for (i = TPM_PCR0; i < TPM_PCR8; i++) { > > ima_pcrread(i, &d); > > The third argument of crypto_shash_update() should be > crypto_shash_digestsize(tfm). Thanks! At this point we know the hash algorithm, so we could use hash_digest_size[]. Mimi
