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CTR_DRBG: add mbedtls_ctr_drbg_update_ret

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Deprecate mbedtls_ctr_drbg_update (which returns void) in favor of a
new function mbedtls_ctr_drbg_update_ret which reports error. The old
function is not officially marked as deprecated in this branch because
this is a stable maintenance branch.
This commit is contained in:
Gilles Peskine 2018-09-11 16:41:54 +02:00
parent f249e37e86
commit 9ce2972399
3 changed files with 60 additions and 21 deletions
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33
include/mbedtls/ctr_drbg.h
View file

@ -227,14 +227,37 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
* *
* \param ctx The CTR_DRBG context. * \param ctx The CTR_DRBG context.
* \param additional The data to update the state with. * \param additional The data to update the state with.
* \param add_len Length of \p additional data. * \param add_len Length of \p additional in bytes. This must be at
* most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
* *
* \note If \p add_len is greater than #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, * \return \c 0 on success.
* only the first #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used. * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if
* The remaining Bytes are silently discarded. * \p add_len is more than
* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
* \return An error from the underlying AES cipher on failure.
*/
int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional,
size_t add_len );
/**
* \brief This function updates the state of the CTR_DRBG context.
*
* \warning This function cannot report errors. You should use
* mbedtls_ctr_drbg_update_ret() instead.
*
* \note If \p add_len is greater than
* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first
* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
* The remaining Bytes are silently discarded.
*
* \param ctx The CTR_DRBG context.
* \param additional The data to update the state with.
* \param add_len Length of \p additional data.
*/ */
void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx, void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t add_len ); const unsigned char *additional,
size_t add_len );
/** /**
* \brief This function updates a CTR_DRBG instance with additional * \brief This function updates a CTR_DRBG instance with additional

40
library/ctr_drbg.c
View file

@ -303,22 +303,36 @@ exit:
return( ret ); return( ret );
} }
void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx, int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t add_len ) const unsigned char *additional,
size_t add_len )
{ {
unsigned char add_input[MBEDTLS_CTR_DRBG_SEEDLEN]; unsigned char add_input[MBEDTLS_CTR_DRBG_SEEDLEN];
int ret;
if( add_len > 0 ) if( add_len == 0 )
{ return( 0 );
/* MAX_INPUT would be more logical here, but we have to match
* block_cipher_df()'s limits since we can't propagate errors */
if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT;
block_cipher_df( add_input, additional, add_len ); if( ( ret = block_cipher_df( add_input, additional, add_len ) ) != 0 )
ctr_drbg_update_internal( ctx, add_input ); goto exit;
mbedtls_zeroize( add_input, sizeof( add_input ) ); if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 )
} goto exit;
exit:
mbedtls_zeroize( add_input, sizeof( add_input ) );
return( ret );
}
/* Deprecated function, kept for backward compatibility. */
void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional,
size_t add_len )
{
/* MAX_INPUT would be more logical here, but we have to match
* block_cipher_df()'s limits since we can't propagate errors */
if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT;
(void) mbedtls_ctr_drbg_update_ret( ctx, additional, add_len );
} }
int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx, int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
@ -514,7 +528,7 @@ int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char
if( fread( buf, 1, n, f ) != n ) if( fread( buf, 1, n, f ) != n )
ret = MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR; ret = MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR;
else else
mbedtls_ctr_drbg_update( ctx, buf, n ); ret = mbedtls_ctr_drbg_update_ret( ctx, buf, n );
fclose( f ); fclose( f );

8
tests/suites/test_suite_ctr_drbg.function
View file

@ -177,9 +177,11 @@ void ctr_drbg_entropy_usage( )
} }
TEST_ASSERT( last_idx == test_offset_idx ); TEST_ASSERT( last_idx == test_offset_idx );
/* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT) /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT).
* (just make sure it doesn't cause memory corruption) */ * Make sure it's detected as an error and doesn't cause memory
mbedtls_ctr_drbg_update( &ctx, entropy, sizeof( entropy ) ); * corruption. */
TEST_ASSERT( mbedtls_ctr_drbg_update_ret(
&ctx, entropy, sizeof( entropy ) ) != 0 );
/* Now enable PR, so the next few calls should all reseed */ /* Now enable PR, so the next few calls should all reseed */
mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON ); mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );