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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 23:24:02 +00:00
parent 016a0d3b6f
commit ba2fda645a
4 changed files with 15 additions and 4 deletions
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10
ChangeLog
View File

@ -1,5 +1,15 @@
mbed TLS ChangeLog (Sorted per branch, date)
= mbed TLS 2.x.x branch released xxxx-xx-xx
Bugfix
* 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 2.1.6 branch released 2016-10-17
Security

4
library/cipher.c
View File

@ -300,9 +300,9 @@ 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 <= mbedtls_cipher_get_block_size( ctx ) ) ||
ilen <= mbedtls_cipher_get_block_size( ctx ) - ctx->unprocessed_len ) ||
( ctx->operation == MBEDTLS_ENCRYPT &&
ilen + ctx->unprocessed_len < mbedtls_cipher_get_block_size( ctx ) ) )
ilen < mbedtls_cipher_get_block_size( ctx ) - 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
View File

@ -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;