AuroraMiddleware/mbedtls
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Fix integer overflows in buffer bound checks

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Fix potential integer overflows in the following functions:
  * mbedtls_md2_update() to be bypassed and cause
  * mbedtls_cipher_update()
  * mbedtls_ctr_drbg_reseed()
This overflows would mainly be exploitable in 32-bit systems and could
cause buffer bound checks to be bypassed.
This commit is contained in:
Andres Amaya Garcia 2017-01-17 23:04:22 +00:00 committed by Andres AG
parent f535662894
commit f7cf56fa45
5 changed files with 16 additions and 4 deletions
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6
ChangeLog
View File

@ -21,6 +21,12 @@ Bugfix
* Fixed multiple buffer overreads in mbedtls_pem_read_buffer() when parsing
the input string in PEM format to extract the different components. Found
by Eyal Itkin.
* Fixed potential arithmetic overflow in mbedtls_ctr_drbg_reseed() that could
cause buffer bound checks to be bypassed. Found by Eyal Itkin.
* Fixed potential arithmetic overflows in mbedtls_cipher_update() that could
cause buffer bound checks to be bypassed. Found by Eyal Itkin.
* Fixed potential arithmetic overflow in mbedtls_md2_update() that could
cause buffer bound checks to be bypassed. Found by Eyal Itkin.
= mbed TLS 2.4.1 branch released 2016-12-13

4
library/cipher.c
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@ -326,9 +326,9 @@ int mbedtls_cipher_update( mbedtls_cipher_context_t *ctx, const unsigned char *i
* If there is not enough data for a full block, cache it.
*/
if( ( ctx->operation == MBEDTLS_DECRYPT &&
ilen + ctx->unprocessed_len <= block_size ) ||
ilen <= block_size - ctx->unprocessed_len ) ||
( ctx->operation == MBEDTLS_ENCRYPT &&
ilen + ctx->unprocessed_len < block_size ) )
ilen < block_size - ctx->unprocessed_len ) )
{
memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
ilen );

3
library/ctr_drbg.c
View File

@ -290,7 +290,8 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
unsigned char seed[MBEDTLS_CTR_DRBG_MAX_SEED_INPUT];
size_t seedlen = 0;
if( ctx->entropy_len + len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
if( ctx->entropy_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ||
len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - ctx->entropy_len )
return( MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
memset( seed, 0, MBEDTLS_CTR_DRBG_MAX_SEED_INPUT );

2
library/md2.c
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@ -158,7 +158,7 @@ void mbedtls_md2_update( mbedtls_md2_context *ctx, const unsigned char *input, s
while( ilen > 0 )
{
if( ctx->left + ilen > 16 )
if( ilen > 16 - ctx->left )
fill = 16 - ctx->left;
else
fill = ilen;

5
tests/suites/test_suite_ctr_drbg.function
View File

@ -39,6 +39,11 @@ void ctr_drbg_special_behaviours( )
TEST_ASSERT( mbedtls_ctr_drbg_reseed( &ctx, additional,
MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + 1 ) ==
MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
mbedtls_ctr_drbg_set_entropy_len( &ctx, ~0 );
TEST_ASSERT( mbedtls_ctr_drbg_reseed( &ctx, additional,
MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ) ==
MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
exit:
mbedtls_ctr_drbg_free( &ctx );
}