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tls13: keys: Avoid input buffer copy

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In mbedtls_ssl_tls13_evolve_secret() avoid
to copy the input buffer into a local buffer
as the copy is avoidable.

This also fixes a potential overflow as the
size of the local buffer was not checked when
copying into it.

With the current calls to mbedtls_ssl_tls13_evolve_secret()
no buffer overflow was expected to happen though.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron 2022-10-05 16:22:59 +02:00
parent 0e7e47147c
commit 831fee68c3
1 changed files with 10 additions and 11 deletions
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21
library/ssl_tls13_keys.c
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@ -38,9 +38,6 @@
#define MBEDTLS_SSL_TLS1_3_LABEL( name, string ) \
.name = string,
#define TLS1_3_EVOLVE_INPUT_SIZE ( PSA_HASH_MAX_SIZE > PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE ) ? \
PSA_HASH_MAX_SIZE : PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE
struct mbedtls_ssl_tls13_labels_struct const mbedtls_ssl_tls13_labels =
{
/* This seems to work in C, despite the string literal being one
@ -334,9 +331,12 @@ int mbedtls_ssl_tls13_evolve_secret(
int ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
psa_status_t abort_status = PSA_ERROR_CORRUPTION_DETECTED;
size_t hlen, ilen;
size_t hlen;
unsigned char tmp_secret[ PSA_MAC_MAX_SIZE ] = { 0 };
unsigned char tmp_input [ TLS1_3_EVOLVE_INPUT_SIZE ] = { 0 };
const unsigned char all_zeroes_input[ MBEDTLS_TLS1_3_MD_MAX_SIZE ] = { 0 };
const unsigned char *l_input = NULL;
size_t l_input_len;
psa_key_derivation_operation_t operation =
PSA_KEY_DERIVATION_OPERATION_INIT;
@ -364,12 +364,13 @@ int mbedtls_ssl_tls13_evolve_secret(
if( input != NULL && input_len != 0 )
{
memcpy( tmp_input, input, input_len );
ilen = input_len;
l_input = input;
l_input_len = input_len;
}
else
{
ilen = hlen;
l_input = all_zeroes_input;
l_input_len = hlen;
}
status = psa_key_derivation_setup( &operation,
@ -388,8 +389,7 @@ int mbedtls_ssl_tls13_evolve_secret(
status = psa_key_derivation_input_bytes( &operation,
PSA_KEY_DERIVATION_INPUT_SECRET,
tmp_input,
ilen );
l_input, l_input_len );
if( status != PSA_SUCCESS )
goto cleanup;
@ -406,7 +406,6 @@ int mbedtls_ssl_tls13_evolve_secret(
status = ( status == PSA_SUCCESS ? abort_status : status );
ret = ( ret == 0 ? psa_ssl_status_to_mbedtls ( status ) : ret );
mbedtls_platform_zeroize( tmp_secret, sizeof(tmp_secret) );
mbedtls_platform_zeroize( tmp_input, sizeof(tmp_input) );
return( ret );
}