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Initialize MAC context in internal functions for one-shot MAC

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In functions that bypass the API functions and call an internal MAC setup
function directly, make sure to initialize the driver-specific part of the
context. This is a union, and initializing the union to `{0}` only
guarantees that the first member of the union is initialized, not
necessarily the member used by the driver. Most compilers do initialize the
whole union to all-bits-zero, but some don't. With compilers that don't, the
lack of initialization caused failures of the affected operations. This
affected one-shot MAC operations using the built-in implementation.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2025-02-05 19:53:54 +01:00
parent bbec1c1d25
commit 0e4907d4f5
1 changed files with 9 additions and 0 deletions
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9
library/psa_crypto_mac.c
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@ -465,6 +465,15 @@ psa_status_t mbedtls_psa_mac_compute(
{
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
mbedtls_psa_mac_operation_t operation = MBEDTLS_PSA_MAC_OPERATION_INIT;
/* Make sure the whole the operation is zeroed.
* PSA_MAC_OPERATION_INIT does not necessarily do it fully,
* since one field is a union and initializing a union does not
* necessarily initialize all of its members.
* In multipart operations, this is done in the API functions,
* before driver dispatch, since it needs to be done before calling
* the driver entry point. Here, we bypass the multipart API,
* so it's our job. */
memset(&operation, 0, sizeof(operation));
status = psa_mac_setup(&operation,
attributes, key_buffer, key_buffer_size,