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RSA: wipe stack buffers

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The RSA private key functions rsa_rsaes_pkcs1_v15_decrypt and
rsa_rsaes_oaep_decrypt put sensitive data (decryption results) on the
stack. Wipe it before returning.

Thanks to Laurent Simon for reporting this issue.
This commit is contained in:
Gilles Peskine 2017-03-23 14:37:37 +01:00 committed by Simon Butcher
parent 98864d5c0b
commit 213aec8688
2 changed files with 41 additions and 8 deletions
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7
ChangeLog
View file

@ -1,5 +1,12 @@
mbed TLS ChangeLog (Sorted per branch, date)
= mbed TLS 1.3.x branch released xxxx-xx-xx
Security
* Wipe stack buffers in RSA private key operations
(rsa_rsaes_pkcs1_v15_decrypt(), rsa_rsaes_oaep_decrypt).
Found by Laurent Simon.
= mbed TLS 1.3.19 branch released 2017-03-08
Security

42
library/rsa.c
View file

@ -56,6 +56,11 @@
#define polarssl_free free
#endif
/* Implementation that should never be optimized out by the compiler */
static void polarssl_zeroize( void *v, size_t n ) {
volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
}
/*
* Initialize an RSA context
*/
@ -720,7 +725,7 @@ int rsa_rsaes_oaep_decrypt( rsa_context *ctx,
: rsa_private( ctx, f_rng, p_rng, input, buf );
if( ret != 0 )
return( ret );
goto cleanup;
/*
* Unmask data and generate lHash
@ -785,15 +790,26 @@ int rsa_rsaes_oaep_decrypt( rsa_context *ctx,
* the different error conditions.
*/
if( bad != 0 )
return( POLARSSL_ERR_RSA_INVALID_PADDING );
{
ret = POLARSSL_ERR_RSA_INVALID_PADDING;
goto cleanup;
}
if( ilen - ( p - buf ) > output_max_len )
return( POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE );
{
ret = POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE;
goto cleanup;
}
*olen = ilen - (p - buf);
memcpy( output, p, *olen );
ret = 0;
return( 0 );
cleanup:
polarssl_zeroize( buf, sizeof( buf ) );
polarssl_zeroize( lhash, sizeof( lhash ) );
return( ret );
}
#endif /* POLARSSL_PKCS1_V21 */
@ -827,7 +843,7 @@ int rsa_rsaes_pkcs1_v15_decrypt( rsa_context *ctx,
: rsa_private( ctx, f_rng, p_rng, input, buf );
if( ret != 0 )
return( ret );
goto cleanup;
p = buf;
bad = 0;
@ -872,15 +888,25 @@ int rsa_rsaes_pkcs1_v15_decrypt( rsa_context *ctx,
bad |= ( pad_count < 8 );
if( bad )
return( POLARSSL_ERR_RSA_INVALID_PADDING );
{
ret = POLARSSL_ERR_RSA_INVALID_PADDING;
goto cleanup;
}
if( ilen - ( p - buf ) > output_max_len )
return( POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE );
{
ret = POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE;
goto cleanup;
}
*olen = ilen - (p - buf);
memcpy( output, p, *olen );
ret = 0;
return( 0 );
cleanup:
polarssl_zeroize( buf, sizeof( buf ) );
return( ret );
}
#endif /* POLARSSL_PKCS1_V15 */