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Zeroize local AES variables before exiting the function

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This issue has been reported by Tuba Yavuz, Farhaan Fowze, Ken (Yihang) Bai,
Grant Hernandez, and Kevin Butler (University of Florida) and
Dave Tian (Purdue University).

In AES encrypt and decrypt some variables were left on the stack. The value
of these variables can be used to recover the last round key. To follow best
practice and to limit the impact of buffer overread vulnerabilities (like
Heartbleed) we need to zeroize them before exiting the function.
This commit is contained in:
Andrzej Kurek 2019-11-12 03:05:51 -05:00
parent ccde952df0
commit 96ae5cd087
1 changed files with 24 additions and 0 deletions
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24
library/aes.c
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@ -918,6 +918,18 @@ int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx,
PUT_UINT32_LE( X2, output, 8 );
PUT_UINT32_LE( X3, output, 12 );
mbedtls_platform_zeroize( &X0, sizeof( X0 ) );
mbedtls_platform_zeroize( &X1, sizeof( X1 ) );
mbedtls_platform_zeroize( &X2, sizeof( X2 ) );
mbedtls_platform_zeroize( &X3, sizeof( X3 ) );
mbedtls_platform_zeroize( &Y0, sizeof( Y0 ) );
mbedtls_platform_zeroize( &Y1, sizeof( Y1 ) );
mbedtls_platform_zeroize( &Y2, sizeof( Y2 ) );
mbedtls_platform_zeroize( &Y3, sizeof( Y3 ) );
mbedtls_platform_zeroize( &RK, sizeof( RK ) );
return( 0 );
}
#endif /* !MBEDTLS_AES_ENCRYPT_ALT */
@ -986,6 +998,18 @@ int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx,
PUT_UINT32_LE( X2, output, 8 );
PUT_UINT32_LE( X3, output, 12 );
mbedtls_platform_zeroize( &X0, sizeof( X0 ) );
mbedtls_platform_zeroize( &X1, sizeof( X1 ) );
mbedtls_platform_zeroize( &X2, sizeof( X2 ) );
mbedtls_platform_zeroize( &X3, sizeof( X3 ) );
mbedtls_platform_zeroize( &Y0, sizeof( Y0 ) );
mbedtls_platform_zeroize( &Y1, sizeof( Y1 ) );
mbedtls_platform_zeroize( &Y2, sizeof( Y2 ) );
mbedtls_platform_zeroize( &Y3, sizeof( Y3 ) );
mbedtls_platform_zeroize( &RK, sizeof( RK ) );
return( 0 );
}
#endif /* !MBEDTLS_AES_DECRYPT_ALT */