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Merge pull request #717 from mpg/non-etm-cbc-negative-testing
Add negative tests for non-EtM CBC decryption
This commit is contained in:
Manuel Pégourié-Gonnard
GitHub
commit
ea6a740923
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@ -3452,6 +3452,219 @@ exit:
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}
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/* END_CASE */
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/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_AES_C:MBEDTLS_SSL_PROTO_TLS1_2 */
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void ssl_decrypt_non_etm_cbc( int cipher_type, int hash_id, int trunc_hmac,
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int length_selector )
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{
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/*
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* Test record decryption for CBC without EtM, focused on the verification
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* of padding and MAC.
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*
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* Actually depends on TLS >= 1.0 (SSL 3.0 computes the MAC differently),
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* and either AES, ARIA, Camellia or DES, but since the test framework
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* doesn't support alternation in dependency statements, just depend on
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* TLS 1.2 and AES.
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*
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* The length_selector argument is interpreted as follows:
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* - if it's -1, the plaintext length is 0 and minimal padding is applied
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* - if it's -2, the plaintext length is 0 and maximal padding is applied
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* - otherwise it must be in [0, 255] and is padding_length from RFC 5246:
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* it's the length of the rest of the padding, that is, excluding the
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* byte that encodes the length. The minimal non-zero plaintext length
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* that gives this padding_length is automatically selected.
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*/
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mbedtls_ssl_context ssl; /* ONLY for debugging */
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mbedtls_ssl_transform t0, t1;
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mbedtls_record rec, rec_save;
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unsigned char *buf = NULL, *buf_save = NULL;
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size_t buflen, olen = 0;
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size_t plaintext_len, block_size, i;
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unsigned char padlen; /* excluding the padding_length byte */
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unsigned char add_data[13];
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unsigned char mac[MBEDTLS_MD_MAX_SIZE];
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int exp_ret;
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const unsigned char pad_max_len = 255; /* Per the standard */
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mbedtls_ssl_init( &ssl );
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mbedtls_ssl_transform_init( &t0 );
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mbedtls_ssl_transform_init( &t1 );
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/* Set up transforms with dummy keys */
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TEST_ASSERT( build_transforms( &t0, &t1, cipher_type, hash_id,
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0, trunc_hmac,
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MBEDTLS_SSL_MINOR_VERSION_3,
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0 , 0 ) == 0 );
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/* Determine padding/plaintext length */
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TEST_ASSERT( length_selector >= -2 && length_selector <= 255 );
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block_size = t0.ivlen;
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if( length_selector < 0 )
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{
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plaintext_len = 0;
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/* Minimal padding
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* The +1 is for the padding_length byte, not counted in padlen. */
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padlen = block_size - ( t0.maclen + 1 ) % block_size;
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/* Maximal padding? */
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if( length_selector == -2 )
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padlen += block_size * ( ( pad_max_len - padlen ) / block_size );
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}
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else
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{
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padlen = length_selector;
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/* Minimal non-zero plaintext_length giving desired padding.
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* The +1 is for the padding_length byte, not counted in padlen. */
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plaintext_len = block_size - ( padlen + t0.maclen + 1 ) % block_size;
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}
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/* Prepare a buffer for record data */
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buflen = block_size
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+ plaintext_len
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+ t0.maclen
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+ padlen + 1;
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ASSERT_ALLOC( buf, buflen );
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ASSERT_ALLOC( buf_save, buflen );
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/* Prepare a dummy record header */
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memset( rec.ctr, 0, sizeof( rec.ctr ) );
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rec.type = MBEDTLS_SSL_MSG_APPLICATION_DATA;
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rec.ver[0] = MBEDTLS_SSL_MAJOR_VERSION_3;
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rec.ver[1] = MBEDTLS_SSL_MINOR_VERSION_3;
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#if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
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rec.cid_len = 0;
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#endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
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/* Prepare dummy record content */
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rec.buf = buf;
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rec.buf_len = buflen;
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rec.data_offset = block_size;
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rec.data_len = plaintext_len;
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memset( rec.buf + rec.data_offset, 42, rec.data_len );
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/* Serialized version of record header for MAC purposes */
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memcpy( add_data, rec.ctr, 8 );
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add_data[8] = rec.type;
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add_data[9] = rec.ver[0];
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add_data[10] = rec.ver[1];
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add_data[11] = ( rec.data_len >> 8 ) & 0xff;
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add_data[12] = ( rec.data_len >> 0 ) & 0xff;
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/* Set dummy IV */
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memset( t0.iv_enc, 0x55, t0.ivlen );
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memcpy( rec.buf, t0.iv_enc, t0.ivlen );
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/*
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* Prepare a pre-encryption record (with MAC and padding), and save it.
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*/
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/* MAC with additional data */
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TEST_EQUAL( 0, mbedtls_md_hmac_update( &t0.md_ctx_enc, add_data, 13 ) );
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TEST_EQUAL( 0, mbedtls_md_hmac_update( &t0.md_ctx_enc,
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rec.buf + rec.data_offset,
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rec.data_len ) );
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TEST_EQUAL( 0, mbedtls_md_hmac_finish( &t0.md_ctx_enc, mac ) );
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memcpy( rec.buf + rec.data_offset + rec.data_len, mac, t0.maclen );
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rec.data_len += t0.maclen;
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/* Pad */
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memset( rec.buf + rec.data_offset + rec.data_len, padlen, padlen + 1 );
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rec.data_len += padlen + 1;
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/* Save correct pre-encryption record */
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rec_save = rec;
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rec_save.buf = buf_save;
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memcpy( buf_save, buf, buflen );
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/*
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* Encrypt and decrypt the correct record, expecting success
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*/
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TEST_EQUAL( 0, mbedtls_cipher_crypt( &t0.cipher_ctx_enc,
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t0.iv_enc, t0.ivlen,
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rec.buf + rec.data_offset, rec.data_len,
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rec.buf + rec.data_offset, &olen ) );
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rec.data_offset -= t0.ivlen;
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rec.data_len += t0.ivlen;
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TEST_EQUAL( 0, mbedtls_ssl_decrypt_buf( &ssl, &t1, &rec ) );
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/*
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* Modify each byte of the pre-encryption record before encrypting and
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* decrypting it, expecting failure every time.
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*/
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for( i = block_size; i < buflen; i++ )
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{
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test_set_step( i );
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/* Restore correct pre-encryption record */
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rec = rec_save;
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rec.buf = buf;
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memcpy( buf, buf_save, buflen );
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/* Corrupt one byte of the data (could be plaintext, MAC or padding) */
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rec.buf[i] ^= 0x01;
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/* Encrypt */
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TEST_EQUAL( 0, mbedtls_cipher_crypt( &t0.cipher_ctx_enc,
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t0.iv_enc, t0.ivlen,
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rec.buf + rec.data_offset, rec.data_len,
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rec.buf + rec.data_offset, &olen ) );
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rec.data_offset -= t0.ivlen;
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rec.data_len += t0.ivlen;
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/* Decrypt and expect failure */
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TEST_EQUAL( MBEDTLS_ERR_SSL_INVALID_MAC,
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mbedtls_ssl_decrypt_buf( &ssl, &t1, &rec ) );
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}
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/*
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* Use larger values of the padding bytes - with small buffers, this tests
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* the case where the announced padlen would be larger than the buffer
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* (and before that, than the buffer minus the size of the MAC), to make
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* sure our padding checking code does not perform any out-of-bounds reads
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* in this case. (With larger buffers, ie when the plaintext is long or
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* maximal length padding is used, this is less relevant but still doesn't
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* hurt to test.)
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*
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* (Start the loop with correct padding, just to double-check that record
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* saving did work, and that we're overwriting the correct bytes.)
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*/
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for( i = padlen; i <= pad_max_len; i++ )
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{
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test_set_step( i );
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/* Restore correct pre-encryption record */
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rec = rec_save;
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rec.buf = buf;
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memcpy( buf, buf_save, buflen );
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/* Set padding bytes to new value */
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memset( buf + buflen - padlen - 1, i, padlen + 1 );
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/* Encrypt */
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TEST_EQUAL( 0, mbedtls_cipher_crypt( &t0.cipher_ctx_enc,
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t0.iv_enc, t0.ivlen,
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rec.buf + rec.data_offset, rec.data_len,
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rec.buf + rec.data_offset, &olen ) );
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rec.data_offset -= t0.ivlen;
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rec.data_len += t0.ivlen;
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/* Decrypt and expect failure except the first time */
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exp_ret = ( i == padlen ) ? 0 : MBEDTLS_ERR_SSL_INVALID_MAC;
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TEST_EQUAL( exp_ret, mbedtls_ssl_decrypt_buf( &ssl, &t1, &rec ) );
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}
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exit:
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mbedtls_ssl_free( &ssl );
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mbedtls_ssl_transform_free( &t0 );
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mbedtls_ssl_transform_free( &t1 );
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mbedtls_free( buf );
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mbedtls_free( buf_save );
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}
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/* END_CASE */
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/* BEGIN_CASE */
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void ssl_tls_prf( int type, data_t * secret, data_t * random,
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char *label, data_t *result_hex_str, int exp_ret )
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