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Fix psa_aead_decrypt to read the tag at the end of the ciphertext

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This commit is contained in:
Gilles Peskine 2018-06-01 19:23:52 +02:00 committed by itayzafrir
parent 36a74b71a0
commit ee652a344c
2 changed files with 60 additions and 28 deletions
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86
library/psa_crypto.c
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@ -1544,6 +1544,14 @@ psa_status_t psa_aead_encrypt( psa_key_slot_t key,
if( nonce_length < 7 || nonce_length > 13 )
return( PSA_ERROR_INVALID_ARGUMENT );
tag_length = 16;
status = psa_aead_unpadded_locate_tag( tag_length,
ciphertext, ciphertext_length,
plaintext_size, plaintext_length,
&tag );
if( status != PSA_SUCCESS )
return( status );
mbedtls_ccm_init( &ccm );
ret = mbedtls_ccm_setkey( &ccm, cipher_id,
slot->data.raw.data, key_bits );
@ -1575,6 +1583,29 @@ psa_status_t psa_aead_encrypt( psa_key_slot_t key,
return( PSA_SUCCESS );
}
/* Locate the tag in a ciphertext buffer containing the encrypted data
* followed by the tag. Return the length of the part preceding the tag in
* *plaintext_length. This is the size of the plaintext in modes where
* the encrypted data has the same size as the plaintext, such as
* CCM and GCM. */
static psa_status_t psa_aead_unpadded_locate_tag( size_t tag_length,
const uint8_t *ciphertext,
size_t ciphertext_length,
size_t plaintext_size,
size_t *plaintext_length,
const uint8_t **p_tag )
{
size_t payload_length;
if( tag_length > ciphertext_length )
return( PSA_ERROR_INVALID_ARGUMENT );
payload_length = ciphertext_length - tag_length;
if( payload_length > plaintext_size )
return( PSA_ERROR_BUFFER_TOO_SMALL );
*p_tag = ciphertext + payload_length;
*plaintext_length = payload_length;
return( PSA_SUCCESS );
}
psa_status_t psa_aead_decrypt( psa_key_slot_t key,
psa_algorithm_t alg,
const uint8_t *nonce,
@ -1592,11 +1623,11 @@ psa_status_t psa_aead_decrypt( psa_key_slot_t key,
key_slot_t *slot;
psa_key_type_t key_type;
size_t key_bits;
unsigned char tag[16];
const uint8_t *tag;
size_t tag_length;
mbedtls_cipher_id_t cipher_id;
if( plaintext_size < ciphertext_length )
return( PSA_ERROR_INVALID_ARGUMENT );
*plaintext_length = 0;
status = psa_get_key_information( key, &key_type, &key_bits );
if( status != PSA_SUCCESS )
@ -1622,6 +1653,14 @@ psa_status_t psa_aead_decrypt( psa_key_slot_t key,
{
mbedtls_gcm_context gcm;
tag_length = 16;
status = psa_aead_unpadded_locate_tag( tag_length,
ciphertext, ciphertext_length,
plaintext_size, plaintext_length,
&tag );
if( status != PSA_SUCCESS )
return( status );
mbedtls_gcm_init( &gcm );
ret = mbedtls_gcm_setkey( &gcm, cipher_id,
slot->data.raw.data, key_bits );
@ -1630,18 +1669,13 @@ psa_status_t psa_aead_decrypt( psa_key_slot_t key,
mbedtls_gcm_free( &gcm );
return( mbedtls_to_psa_error( ret ) );
}
ret = mbedtls_gcm_crypt_and_tag( &gcm, MBEDTLS_GCM_DECRYPT,
ciphertext_length, nonce, nonce_length,
additional_data, additional_data_length,
ciphertext, plaintext,
sizeof( tag ), tag );
if( ret != 0 )
{
mbedtls_gcm_free( &gcm );
mbedtls_zeroize( plaintext, ciphertext_length );
return( mbedtls_to_psa_error( ret ) );
}
ret = mbedtls_gcm_auth_decrypt( &gcm,
*plaintext_length,
nonce, nonce_length,
additional_data, additional_data_length,
tag, tag_length,
ciphertext, plaintext );
mbedtls_gcm_free( &gcm );
}
else if( alg == PSA_ALG_CCM )
@ -1659,17 +1693,11 @@ psa_status_t psa_aead_decrypt( psa_key_slot_t key,
mbedtls_ccm_free( &ccm );
return( mbedtls_to_psa_error( ret ) );
}
ret = mbedtls_ccm_auth_decrypt( &ccm, ciphertext_length,
nonce, nonce_length, additional_data,
additional_data_length, ciphertext,
plaintext, tag, sizeof( tag ) );
if( ret != 0 )
{
mbedtls_ccm_free( &ccm );
mbedtls_zeroize( plaintext, ciphertext_length );
return( mbedtls_to_psa_error( ret ) );
}
ret = mbedtls_ccm_auth_decrypt( &ccm, *plaintext_length,
nonce, nonce_length,
additional_data, additional_data_length,
ciphertext, plaintext,
tag, tag_length );
mbedtls_ccm_free( &ccm );
}
else
@ -1677,8 +1705,12 @@ psa_status_t psa_aead_decrypt( psa_key_slot_t key,
return( PSA_ERROR_INVALID_ARGUMENT );
}
*plaintext_length = ciphertext_length;
return( PSA_SUCCESS );
if( ret != 0 )
{
mbedtls_zeroize( plaintext, *plaintext_length );
*plaintext_length = 0;
}
return( mbedtls_to_psa_error( ret ) );
}

2
tests/suites/test_suite_psa_crypto.function
View File

@ -637,7 +637,7 @@ void aead_encrypt_decrypt( int key_type_arg, char * key_hex,
TEST_ASSERT( psa_aead_decrypt( slot, alg,
nonce, nonce_length,
additional_data, additional_data_length,
output_data, output_length - tag_length, output_data2,
output_data, output_length, output_data2,
output_length, &output_length2 ) == expected_result );