problem to adding AES encription to secure DFU SDK15.0

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Fri, 28 Dec 2018 10:49:18 GMT

Hi!

I decided. All works. Should crypt by stream chiper. Because nordic DFU use block by 244 bytes.

Hung, please, insert by Nordic team native encryption in the DFU. Really, it is necessary action. All people want to use encryption update via DFU. Same history was in the SDK13, now in the SDK15 I need again use encryption.

Think about it pls.

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Thu, 27 Dec 2018 05:06:36 GMT

Didn't it work for you in SDK v13 ? I can see the CRCs are different after the first write command. We are only limited staff during the holiday so I can't try and test myself but I don't see any reason why we couldn't debug and find why the CRC is different, shouldn't it be very simple to put a break point and see why CRC is calculated differently ? It must start from either the size of the input data or the input data (the write packet) it self ?

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Fri, 21 Dec 2018 09:36:02 GMT

without AES:

devzone.nordicsemi.com/.../wo_5F00_aes2.log

with AES:

devzone.nordicsemi.com/.../aes2.log

Why second data is

az on_data_obj_write_request crc32_compute_*p_req->write.p_data = 0x00000009

? are different.

My oppinion is: I try to decrypt 244 bytes by AES block crypt. One data block DFU is 244 bytes. Therefore, I cant divide 244 to 16 without remainder of the division. For this reason I have changed different data p_req->write.p_data

Is it possible?

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Fri, 21 Dec 2018 08:48:14 GMT

uno momento...

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Fri, 21 Dec 2018 08:46:29 GMT

Hi Mikhail,

Could you printout value of firmware_image_crc ? not the address of it. It's normal to have different address when you modified the code.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Fri, 21 Dec 2018 08:25:01 GMT

seems,

&s_dfu_settings.progress.firmware_image_crc

antother due to adding some code. And address of

&s_dfu_settings.progress.firmware_image_crc

some moved. It is my opinion.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Fri, 21 Dec 2018 08:11:23 GMT

just added AES block or comment:

without AES block:

devzone.nordicsemi.com/.../7485.wo_5F00_aes.log

with AES:

devzone.nordicsemi.com/.../0131.aes.log

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Fri, 21 Dec 2018 06:45:22 GMT

You don't need to resume, just check the input of the CRC calculation function, to see if the input data are the same in both case or not ?

Most likely they are not the same.
The CRC calculation function is very simple. The input is the previous CRC (make sure this one is the same in both cases) and the 244 byte data of new write command. If these 2 are matches the result CRC should be the same.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Thu, 20 Dec 2018 10:37:28 GMT

I can't resume this situation. I see that first CRC in both cases are CRC = 0xA5BE0D95, the second CRC are different.

We should try to understad why

for (int i = 0; i < p_req->write.len; i+=16)
{
AES128_ECB_decrypt (p_req->write.p_data + i, key, p_req->write.p_data + i);
}

this code leads to different CRC. I cant understand it.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Thu, 20 Dec 2018 07:35:00 GMT

Ok, I'll check it. But your say that replace in that part of code CRC -absolutly normal? Or you have any another idea where it does to do best?

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Thu, 20 Dec 2018 03:30:22 GMT

It's pretty strange. Could you print out more info before the CRC calculation (like previous CRC, some data on the write packet )? You can think of adding a counter and set a breakpoint when it count to 3 and step into the code to see why it's different CRCs ? If it's the same data and same previous CRC, the result CRC should be the same.

I think we are getting close to the root cause of the issue.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Wed, 19 Dec 2018 13:24:07 GMT

I try again load with same program encrypted. But in the bootloader I use AES encryption and do not use it.

below two logs.

with AES:

devzone.nordicsemi.com/.../aes.log

WO AES:

devzone.nordicsemi.com/.../wo_5F00_aes.log

I see that first two

az on_data_obj_write_request CRC = 0xA5BE0D95

az on_data_obj_write_request CRC = 0x65491F3A

are same

third CRC is different. Why?

I just take CRC from air and log it. After that I call AES enc function and write in to flash.

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Wed, 19 Dec 2018 11:13:53 GMT

I am trying to have a quick comparison between the wo_enc.log and the log you just sent, and I can see right at the first write command , the CRC already different (0x65491F3A vs 0xE5314F14) could you step in to the code and check why ?
I assume the wo_enc.log and the log you just sent using the same encrypted firmware and the crc calculated on the undecrypted data, so they should be the same.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Wed, 19 Dec 2018 09:26:16 GMT

Yes. 0x39000 written first time and percentage goes from 1 to 3%. When again percentage restarts from 1%, in the log we see again attempt write from 0x39000 ... Therefore- normal behavior.

devzone.nordicsemi.com/.../3757.uint32_5F00_t-crc32_5F00_compute_5F00_encrypted-_3D00_-crc32_5F00_compute.log

log file with AES encryption.

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Wed, 19 Dec 2018 09:17:15 GMT

You are saying the 0x39000 being written twice ?

Could you send the log of the test when you do CRC calculation before decrypting ? The .log file, not the screenshot.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Tue, 18 Dec 2018 10:46:58 GMT

After compare log from bootloader with AES like above my code printscreen, I have CRC check

0> <debug> nrf_dfu_req_handler: Handle NRF_DFU_OP_CRC_GET (data)

and after that CRC check, booltoader again try to wryte data from addr=0x00039000

But on a screen below, I see

that CRC NRF_DFU_OP_CRC_GET and last CRC NRF_DFU_OP_OBJECT_WRITE is same (CRC = 0xB69DF0F4). But after this check, bootloader again write from addr=0x00039000. Therefore, it understand that CRC not correct.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Tue, 18 Dec 2018 10:38:29 GMT

As I understand, I should try to load encrypted DFU in the bootloader. But bootloader without any AES modifications? Correct?

There is:

devzone.nordicsemi.com/.../wo_5F00_enc.log

As you suggest, percentage fill from 1 to 100% and when all loaded - HASH error.

But when try to insert AES, percentage goes 1,2,3... next- error.

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Tue, 18 Dec 2018 10:33:06 GMT

Hmm, could you try to simply update the encrypted image without modifying anything in the bootloader ? Meaning you will update an encrypted application (of course it won't run) , just to see the CRC report from the bootloader. I assume the CRC on the phone and CRC from bootloader should match.

After that you can compare the log of this success update and the above log you just capture and check why it doesn't match. I think they should be the same if you calculate before you decrypt.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Tue, 18 Dec 2018 09:55:10 GMT

Hi!

I tryed it before:

and result is:

on the smartphone- 1,2,3 %... 1,2,3 %... CRC INCORRECT.

On the RTT debug is:

devzone.nordicsemi.com/.../uint32_5F00_t-crc32_5F00_compute_5F00_encrypted-_3D00_-crc32_5F00_compute.log

Therefore, youre suggest doesn't works.

May be do you have one more idea?

RE: problem to adding AES encription to secure DFU SDK15.0

Hung Bui — Tue, 18 Dec 2018 09:17:07 GMT

Hi Mikhail,

I'm not so sure why it worked for you in SDK v13, but my understanding is that you would need to calculate CRC on undecrypted data and send that CRC back to the DFU controller. The DFU controller in my understanding would not need to know about decrypted data as it only cares about sending the encrypted data correctly.

What about you moving the

s_dfu_settings.progress.firmware_image_crc =
crc32_compute(p_req->write.p_data, p_req->write.len, &s_dfu_settings.progress.firmware_image_crc);

above the call to AES128_ECB_decrypt() ?

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Fri, 14 Dec 2018 14:32:10 GMT

Hi!

In the SDK13 I use same method. I encrypted only .bin file. In the bootloader I just take old CRC and replace it CRC with a compared CRC. All works.

In this SDK15 I want just or replace my CRC with comared CRC or (I can't find this place where can I) insert my decode code:

//                for (int i = 0; i < len; i+=16)
//                {
//                    AES128_ECB_decrypt ((uint8_t *)p_src + i, key, (uint8_t *)p_src + i); 
//                }

Therefore, when data from air were received, first I decrypt it and data will like on non encrypted .bin data. And CRC will compare correct.

But if this method is difficult, possible just replace CRC one to another and compare it between themselves.

where should it be done?

RE: problem to adding AES encription to secure DFU SDK15.0

Vidar Berg — Fri, 14 Dec 2018 13:56:32 GMT

You get invalid CRC because you are calculating the CRC on the decrypted data while the phone compares the CRC agains its encrypted image. If you want to skip CRC validation you need to do it in the phone app, not in the bootloader.

RE: problem to adding AES encription to secure DFU SDK15.0

Mikhail — Thu, 13 Dec 2018 08:55:36 GMT

I tryed topic

https://devzone.nordicsemi.com/f/nordic-q-a/37260/adding-encryption-to-secure-dfu-sdk-v15

and without any success. But I use my AES encryption manualy. And crypt in the DFU only .bin file from this package.

Any help?