CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 12:28:09 GMT

I will check that with memory alignement.

The example vectors have been taken from an AES CCM implementation, which according to the specification of CCM* coincides. But is not able to handle encryption without authentication.

The test vectors from IEEE802.15.4-2015 i couln't test see:

devzone.nordicsemi.com/.../cryptocell-cc310-aes-ccm-arbitrary-nonce

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 11:38:48 GMT

OK, I found a bug in the code - you have bad memory alignment!

CRYS_AESCCMStar expect to have 16 byte for Mac_Res. You are not passing that.

So you need to increase your arrays in structures aes_ccms_enc_suite_t and aes_ccms_dec_suite_t:

uint8_t m[20 + 16];

and

uint8_t c[20 + 16];

Once this is done you will observe that your encryption test vector (suit[0]) is broken. Cipher text is not matching expected ciper text.

Test vector suit[1] is fine for encryption and decryption.

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 11:23:16 GMT

Ok,

This is much complex problem. In fact you are NOT checking if first test suit was sucessfully encrypted. And... it was not. I don't know why yet but len_m == 0 when using memory compare function. I am trying to investigate that.

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 10:48:22 GMT

Second test suit is decrypting fine (success++). I am checking first one.

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 10:34:24 GMT

okay understood, meanwhile i came to the same thought 🙂

what is then the reason why decryption fails for suite[0] where tag_len is 0 and cipher text length is 20 which i posted above?

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 10:30:20 GMT

But when len was set to 24 you were passing cipher text length == 24 to crypto library and in addition you were passing tag_len = 4. So 28 bytes in total.

So CRYS_AESCCMStar were using 28 bytes on 24 bytes array. This might cause some memory corruption.

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 10:21:53 GMT

CRYS_FATAL_ERROR is gone

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 10:20:05 GMT

Before going further, please let me know if you still see CRYS_FATAL_ERROR ?

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 10:18:12 GMT

applying your solution works. But I have some follow up question. Cutting the length of the input cyphertext means that we cut off the MAC, is that desired as input vector?

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 10:08:38 GMT

compare fails because inverse transformation seems not delivering the expected plaintext.

which is in fact the reverse input data from the encryption tets set

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 09:59:06 GMT

Please use test vectors from attached file and let me know if you still see CRYS_FATAL_ERROR.

In my case updating second decryption vector in decryption suit helped and I don't see CRYS_FATAL_ERROR any more.

You can leave interation as you have it.devzone.nordicsemi.com/.../01bsp_5F00_cryptoengine.c

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 09:51:10 GMT

suite iteration works fine for me. Your right the memcmp fails because of array size.

using:

if(memcmp(suite[i].c, suite[i].expected_plaintext, (suite[i].len_c - suite[i].len_tag)) == 0)

compares the wished context

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 09:40:55 GMT

Maybe I am wrong but I think you shall update second test suit:
24, /* len_c */ to 20, /* len_c */.

With this modification it is working fine with suite iteration.

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 09:25:45 GMT

Please do test with modification I've proposed and let me know if there is any difference. So all arguments to function cryptoengine_aes_ccms_dec shall be changed from suite[i] to suite[0]

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Fri, 09 Mar 2018 09:22:24 GMT

Hi Jakub Rzeszutko,

Sorry for the inconvinience, when I packed the project i deleted to much files. Thanks also for clarification regarding the intialisation process.

this is the state running the 2nd test set for decrypt, thats is cause why run_aes_ccms_dec_suite fails later

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

Jakub Rzeszutko — Fri, 09 Mar 2018 09:20:14 GMT

Hi,

Problem looks to be in your decryption test suit.

When you will update function run_aes_ccms_dec_suite to not iterate suit:

suit[i] -> suit[0]

Problem will gone.

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

chris-ho — Thu, 08 Mar 2018 13:45:55 GMT

Hi MartinBL,

thanks for taking care about this issue please find attached my project.

Note: I'm using the nrf52840 PrevDK and IAR Workbench Version 8.20.1

devzone.nordicsemi.com/.../nrf52840_5F00_cryptocell.zip

Best regards

Chris

RE: CryptoCell CC310 AES CCM* CRYS_FATAL_ERROR after 2nd decrypt operation

MartinBL — Thu, 08 Mar 2018 10:57:45 GMT

Hi,

We are unable to reproduce this. Can you please zip your project files and upload them?