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Merge branch mbedtls-1.3-fix-arithmetic-overflows

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Fix potential integer overflows in the following functions:

 * mbedtls_md2_update()
 * 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:
Simon Butcher 2017-02-01 21:46:47 +00:00
commit 0289920d12
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 1.3.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 1.3.18 branch 2016-10-17
Security

4
library/cipher.c
View File

@ -315,9 +315,9 @@ int cipher_update( cipher_context_t *ctx, const unsigned char *input,
* If there is not enough data for a full block, cache it.
*/
if( ( ctx->operation == POLARSSL_DECRYPT &&
ilen + ctx->unprocessed_len <= cipher_get_block_size( ctx ) ) ||
ilen <= cipher_get_block_size( ctx ) - ctx->unprocessed_len ) ||
( ctx->operation == POLARSSL_ENCRYPT &&
ilen + ctx->unprocessed_len < cipher_get_block_size( ctx ) ) )
ilen < cipher_get_block_size( ctx ) - ctx->unprocessed_len ) )
{
memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
ilen );

3
library/ctr_drbg.c
View File

@ -277,7 +277,8 @@ int ctr_drbg_reseed( ctr_drbg_context *ctx,
unsigned char seed[CTR_DRBG_MAX_SEED_INPUT];
size_t seedlen = 0;
if( ctx->entropy_len + len > CTR_DRBG_MAX_SEED_INPUT )
if( ctx->entropy_len > CTR_DRBG_MAX_SEED_INPUT ||
len > CTR_DRBG_MAX_SEED_INPUT - ctx->entropy_len )
return( POLARSSL_ERR_CTR_DRBG_INPUT_TOO_BIG );
memset( seed, 0, CTR_DRBG_MAX_SEED_INPUT );

2
library/md2.c
View File

@ -155,7 +155,7 @@ void md2_update( md2_context *ctx, const unsigned char *input, size_t ilen )
while( ilen > 0 )
{
if( ctx->left + ilen > 16 )
if( ilen > 16 - ctx->left )
fill = 16 - ctx->left;
else
fill = ilen;