> -----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). Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli
