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SubjectRe: [PATCH v4 6/6] tpm: ensure that the output of PCR read contains the correct digest size
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On 11/8/2018 3:08 PM, Jarkko Sakkinen wrote:
> On Tue, Nov 06, 2018 at 04:01:59PM +0100, Roberto Sassu wrote:
>> This patch protects against data corruption that could happen in the bus,
>> by checking that that the digest size returned by the TPM during a PCR read
>> matches the size of the algorithm passed as argument to tpm2_pcr_read().
>>
>> This check is performed after information about the PCR banks has been
>> retrieved.
>>
>> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
>> ---
>> drivers/char/tpm/tpm2-cmd.c | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
>> index e2d5b84286a7..3b0b5b032901 100644
>> --- a/drivers/char/tpm/tpm2-cmd.c
>> +++ b/drivers/char/tpm/tpm2-cmd.c
>> @@ -187,15 +187,28 @@ struct tpm2_pcr_read_out {
>> int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx,
>> struct tpm_digest *digest_struct, u16 *digest_size_ptr)
>> {
>> + int i;
>> int rc;
>> struct tpm_buf buf;
>> struct tpm2_pcr_read_out *out;
>> u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0};
>> u16 digest_size;
>> + u16 expected_digest_size = 0;
>>
>> if (pcr_idx >= TPM2_PLATFORM_PCR)
>> return -EINVAL;
>>
>> + if (!digest_size_ptr) {
>> + for (i = 0; i < chip->nr_active_banks &&
>> + chip->active_banks[i].alg_id != digest_struct->alg_id; i++)
>> + ;
>
> Not sure if the semicolon should be in its own line.
> `
>> +
>> + if (i == chip->nr_active_banks)
>> + return -EINVAL;
>> +
>> + expected_digest_size = chip->active_banks[i].digest_size;
>> + }
>> +
>> rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
>> if (rc)
>> return rc;
>> @@ -215,7 +228,8 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx,
>>
>> out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
>> digest_size = be16_to_cpu(out->digest_size);
>> - if (digest_size > sizeof(digest_struct->digest)) {
>> + if (digest_size > sizeof(digest_struct->digest) ||
>> + (!digest_size_ptr && digest_size != expected_digest_size)) {
>> rc = -EINVAL;
>> goto out;
>> }
>> --
>> 2.17.1
>>
>
> Please add
>
> Cc: stable@vger.kernel.org.

Should I do the same for the previous patches? This patch cannot be
applied alone.

Roberto


> /Jarkko
>

--
HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Bo PENG, Jian LI, Yanli SHI

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