From 879b589210a9a0c9f77d301aaf0ddee20f2c5052 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Wed, 6 Feb 2019 17:24:49 +0100 Subject: tpm: retrieve digest size of unknown algorithms with PCR read Currently, the TPM driver retrieves the digest size from a table mapping TPM algorithms identifiers to identifiers defined by the crypto subsystem. If the algorithm is not defined by the latter, the digest size can be retrieved from the output of the PCR read command. The patch modifies the definition of tpm_pcr_read() and tpm2_pcr_read() to pass the desired hash algorithm and obtain the digest size at TPM startup. Algorithms and corresponding digest sizes are stored in the new structure tpm_bank_info, member of tpm_chip, so that the information can be used by other kernel subsystems. tpm_bank_info contains: the TPM algorithm identifier, necessary to generate the event log as defined by Trusted Computing Group (TCG); the digest size, to pad/truncate a digest calculated with a different algorithm; the crypto subsystem identifier, to calculate the digest of event data. This patch also protects against data corruption that could happen in the bus, by checking that the digest size returned by the TPM during a PCR read matches the size of the algorithm passed to tpm2_pcr_read(). For the initial PCR read, when digest sizes are not yet available, this patch ensures that the amount of data copied from the output returned by the TPM does not exceed the size of the array data are copied to. Signed-off-by: Roberto Sassu Reviewed-by: Jarkko Sakkinen Tested-by: Jarkko Sakkinen Acked-by: Mimi Zohar Signed-off-by: Jarkko Sakkinen --- security/integrity/ima/ima_crypto.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'security') diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c index acf2c7df7145..16a4f45863b1 100644 --- a/security/integrity/ima/ima_crypto.c +++ b/security/integrity/ima/ima_crypto.c @@ -643,12 +643,12 @@ int ima_calc_buffer_hash(const void *buf, loff_t len, return calc_buffer_shash(buf, len, hash); } -static void __init ima_pcrread(u32 idx, u8 *pcr) +static void __init ima_pcrread(u32 idx, struct tpm_digest *d) { if (!ima_tpm_chip) return; - if (tpm_pcr_read(ima_tpm_chip, idx, pcr) != 0) + if (tpm_pcr_read(ima_tpm_chip, idx, d) != 0) pr_err("Error Communicating to TPM chip\n"); } @@ -658,7 +658,7 @@ static void __init ima_pcrread(u32 idx, u8 *pcr) static int __init ima_calc_boot_aggregate_tfm(char *digest, struct crypto_shash *tfm) { - u8 pcr_i[TPM_DIGEST_SIZE]; + struct tpm_digest d = { .alg_id = TPM_ALG_SHA1, .digest = {0} }; int rc; u32 i; SHASH_DESC_ON_STACK(shash, tfm); @@ -672,9 +672,9 @@ static int __init ima_calc_boot_aggregate_tfm(char *digest, /* cumulative sha1 over tpm registers 0-7 */ for (i = TPM_PCR0; i < TPM_PCR8; i++) { - ima_pcrread(i, pcr_i); + ima_pcrread(i, &d); /* now accumulate with current aggregate */ - rc = crypto_shash_update(shash, pcr_i, TPM_DIGEST_SIZE); + rc = crypto_shash_update(shash, d.digest, TPM_DIGEST_SIZE); } if (!rc) crypto_shash_final(shash, digest); -- cgit v1.2.3-58-ga151