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Fix NULL+0 undefined behavior in ECB encryption and decryption

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psa_cipher_encrypt() and psa_cipher_decrypt() sometimes add a zero offset to
a null pointer when the cipher does not use an IV. This is undefined
behavior, although it works as naively expected on most platforms. This
can cause a crash under modern Asan (depending on compiler optimizations).

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
2022-10-22 19:57:16 +02:00
parent ef7f4e47b1
commit bc0ff75455
4 changed files with 15 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
ChangeLog.d/psa-ecb-ub.txt Normal file
View File

@@ -0,0 +1,3 @@
Bugfix
* Fix undefined behavior (typically harmless in practice) in PSA ECB
encryption and decryption.

3
library/psa_crypto.c
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@@ -3467,7 +3467,8 @@ psa_status_t psa_cipher_encrypt( mbedtls_svc_key_id_t key,
status = psa_driver_wrapper_cipher_encrypt(
&attributes, slot->key.data, slot->key.bytes,
alg, local_iv, default_iv_length, input, input_length,
output + default_iv_length, output_size - default_iv_length,
( output == NULL ? NULL : output + default_iv_length ),
output_size - default_iv_length,
output_length );
exit:

11
library/psa_crypto_cipher.c
View File

@@ -517,7 +517,8 @@ psa_status_t mbedtls_psa_cipher_encrypt(
goto exit;
status = mbedtls_psa_cipher_finish( &operation,
output + update_output_length,
( output == NULL ? NULL :
output + update_output_length ),
output_size - update_output_length,
&finish_output_length );
if( status != PSA_SUCCESS )
@@ -563,7 +564,9 @@ psa_status_t mbedtls_psa_cipher_decrypt(
goto exit;
}
status = mbedtls_psa_cipher_update( &operation, input + operation.iv_length,
status = mbedtls_psa_cipher_update( &operation,
( input == NULL ? NULL :
input + operation.iv_length ),
input_length - operation.iv_length,
output, output_size, &olength );
if( status != PSA_SUCCESS )
@@ -571,7 +574,9 @@ psa_status_t mbedtls_psa_cipher_decrypt(
accumulated_length = olength;
status = mbedtls_psa_cipher_finish( &operation, output + accumulated_length,
status = mbedtls_psa_cipher_finish( &operation,
( output == NULL ? NULL :
output + accumulated_length ),
output_size - accumulated_length,
&olength );
if( status != PSA_SUCCESS )

4
tests/suites/test_suite_psa_crypto.function
View File

@@ -3962,7 +3962,7 @@ void cipher_alg_without_iv( int alg_arg, int key_type_arg, data_t *key_data,
TEST_LE_U( length, output_buffer_size );
output_length += length;
PSA_ASSERT( psa_cipher_finish( &operation,
output + output_length,
output == NULL ? NULL : output + output_length,
output_buffer_size - output_length,
&length ) );
output_length += length;
@@ -3980,7 +3980,7 @@ void cipher_alg_without_iv( int alg_arg, int key_type_arg, data_t *key_data,
TEST_LE_U( length, output_buffer_size );
output_length += length;
PSA_ASSERT( psa_cipher_finish( &operation,
output + output_length,
output == NULL ? NULL : output + output_length,
output_buffer_size - output_length,
&length ) );
output_length += length;