> -----Original Message----- > From: linux-integrity-owner@xxxxxxxxxxxxxxx [mailto:linux-integrity- > owner@xxxxxxxxxxxxxxx] On Behalf Of Mimi Zohar > Sent: Wednesday, March 18, 2020 10:55 PM > To: Roberto Sassu <roberto.sassu@xxxxxxxxxx>; > James.Bottomley@xxxxxxxxxxxxxxxxxxxxx; > jarkko.sakkinen@xxxxxxxxxxxxxxx > Cc: linux-integrity@xxxxxxxxxxxxxxx; linux-security-module@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; Silviu Vlasceanu > <Silviu.Vlasceanu@xxxxxxxxxx> > Subject: Re: [PATCH v3 7/8] ima: Calculate and extend PCR with digests in > ima_template_entry > > On Wed, 2020-03-18 at 12:42 +0000, Roberto Sassu wrote: > > > -----Original Message----- > > > From: owner-linux-security-module@xxxxxxxxxxxxxxx [mailto:owner- > linux- > > > security-module@xxxxxxxxxxxxxxx] On Behalf Of Mimi Zohar > > > Sent: Tuesday, March 3, 2020 5:04 AM > > > To: Roberto Sassu <roberto.sassu@xxxxxxxxxx>; > > > James.Bottomley@xxxxxxxxxxxxxxxxxxxxx; > > > jarkko.sakkinen@xxxxxxxxxxxxxxx > > > Cc: linux-integrity@xxxxxxxxxxxxxxx; linux-security- > module@xxxxxxxxxxxxxxx; > > > linux-kernel@xxxxxxxxxxxxxxx; Silviu Vlasceanu > > > <Silviu.Vlasceanu@xxxxxxxxxx> > > > Subject: Re: [PATCH v3 7/8] ima: Calculate and extend PCR with digests > in > > > ima_template_entry > > > > > > On Mon, 2020-02-10 at 11:04 +0100, Roberto Sassu wrote: > > > > > > > @@ -219,6 +214,8 @@ int ima_restore_measurement_entry(struct > > > ima_template_entry *entry) > > > > > > > > int __init ima_init_digests(void) > > > > { > > > > + u16 digest_size; > > > > + u16 crypto_id; > > > > int i; > > > > > > > > if (!ima_tpm_chip) > > > > @@ -229,8 +226,17 @@ int __init ima_init_digests(void) > > > > if (!digests) > > > > return -ENOMEM; > > > > > > > > - for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) > > > > + for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) { > > > > digests[i].alg_id = ima_tpm_chip->allocated_banks[i].alg_id; > > > > + digest_size = ima_tpm_chip->allocated_banks[i].digest_size; > > > > + crypto_id = ima_tpm_chip->allocated_banks[i].crypto_id; > > > > + > > > > + /* for unmapped TPM algorithms digest is still a padded > > > SHA1 */ > > > > + if (crypto_id == HASH_ALGO__LAST) > > > > + digest_size = SHA1_DIGEST_SIZE; > > > > + > > > > + memset(digests[i].digest, 0xff, digest_size); > > > > > > Shouldn't the memset here be of the actual digest size even for > > > unmapped TPM algorithms. > > > > This is consistent with ima_calc_field_array_hash(), so that a verifier > > will always pad the SHA1 digest with zeros to obtain the final PCR value. > > > > I can set all bytes if you prefer. > > My concern is with violations. The measurement list will be padded > with 0's, but the value being extended into the TPM will only > partially be 0xFF's. When verifying the measurement list, replacing > all 0x00's with all 0xFF's is simpler. If the TPM algorithm is unknown, the starting point is the SHA1 digest. If there is a violation, this should be the one to be modified. Then, after that, padding is done for all entries in the same way, regardless of whether the entry is a violation or not. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli
