Encryption, Signing and OTA is there any how-to?

meddie

if i understood it correctly, i have to use the securitypersonalization.ino on the gw. For the first time i upload this code

/**
 * @def LOCK_CONFIGURATION
 * @brief Uncomment this to enable locking the configuration zone.
 *
 * It is still possible to change the key, and this also enable random key generation.
 * @warning BE AWARE THAT THIS PREVENTS ANY FUTURE CONFIGURATION CHANGE TO THE CHIP
 */
#define LOCK_CONFIGURATION

/**
 * @def LOCK_DATA
 * @brief Uncomment this to enable locking the data zone.
 *
 * It is not required to lock data, key cannot be retrieved anyway, but by locking
 * data, it can be guaranteed that nobody even with physical access to the chip,
 * will be able to change the key.
 * @warning BE AWARE THAT THIS PREVENTS THE KEY TO BE CHANGED
 */
//#define LOCK_DATA

/**
 * @def SKIP_KEY_STORAGE
 * @brief Uncomment this to skip key storage (typically once key has been written once)
 */
#define SKIP_KEY_STORAGE

/**
 * @def USER_KEY
 * @brief Uncomment this to skip key generation and use @ref user_key_data as key instead.
 */
//#define USER_KEY

/**
 * @def SKIP_UART_CONFIRMATION
 * @brief Uncomment this for boards that lack UART
 *
 * @b Important<br> No confirmation will be required for locking any zones with this configuration!
 * Also, key generation is not permitted in this mode as there is no way of presenting the generated key.
 */
//#define SKIP_UART_CONFIRMATION

/**
 * @def USE_SOFT_SIGNING
 * @brief Uncomment this to store data to EEPROM instead of ATSHA204A
 */
//#define USE_SOFT_SIGNING

/**
 * @def STORE_SOFT_KEY
 * @brief Uncomment this to store soft HMAC key to EEPROM
 */
//#define STORE_SOFT_KEY

/**
 * @def USER_SOFT_KEY
 * @brief Uncomment this to skip soft HMAC key generation and use @ref user_soft_key_data as HMAC key instead.
 */
//#define USER_SOFT_KEY

/**
 * @def STORE_SOFT_SERIAL
 * @brief Uncomment this to store soft serial to EEPROM
 */
//#define STORE_SOFT_SERIAL

/**
 * @def USER_SOFT_SERIAL
 * @brief Uncomment this to skip soft serial generation and use @ref user_soft_serial as serial instead.
 */
//#define USER_SOFT_SERIAL

/**
 * @def STORE_AES_KEY
 * @brief Uncomment this to store AES key to EEPROM
 */
//#define STORE_AES_KEY

/**
 * @def USER_AES_KEY
 * @brief Uncomment this to skip AES key generation and use @ref user_aes_key as key instead.
 */
//#define USER_AES_KEY

When its uploaded on first run i will get the AES and HMAC Key, which i have to notice and safe securely.

Then i have to upload the sketch again with this code:

/**
 * @def LOCK_CONFIGURATION
 * @brief Uncomment this to enable locking the configuration zone.
 *
 * It is still possible to change the key, and this also enable random key generation.
 * @warning BE AWARE THAT THIS PREVENTS ANY FUTURE CONFIGURATION CHANGE TO THE CHIP
 */
#define LOCK_CONFIGURATION

/**
 * @def LOCK_DATA
 * @brief Uncomment this to enable locking the data zone.
 *
 * It is not required to lock data, key cannot be retrieved anyway, but by locking
 * data, it can be guaranteed that nobody even with physical access to the chip,
 * will be able to change the key.
 * @warning BE AWARE THAT THIS PREVENTS THE KEY TO BE CHANGED
 */
//#define LOCK_DATA

/**
 * @def SKIP_KEY_STORAGE
 * @brief Uncomment this to skip key storage (typically once key has been written once)
 */
//#define SKIP_KEY_STORAGE

/**
 * @def USER_KEY
 * @brief Uncomment this to skip key generation and use @ref user_key_data as key instead.
 */
#define USER_KEY

/**
 * @def SKIP_UART_CONFIRMATION
 * @brief Uncomment this for boards that lack UART
 *
 * @b Important<br> No confirmation will be required for locking any zones with this configuration!
 * Also, key generation is not permitted in this mode as there is no way of presenting the generated key.
 */
#define SKIP_UART_CONFIRMATION

/**
 * @def USE_SOFT_SIGNING
 * @brief Uncomment this to store data to EEPROM instead of ATSHA204A
 */
//#define USE_SOFT_SIGNING

/**
 * @def STORE_SOFT_KEY
 * @brief Uncomment this to store soft HMAC key to EEPROM
 */
//#define STORE_SOFT_KEY

/**
 * @def USER_SOFT_KEY
 * @brief Uncomment this to skip soft HMAC key generation and use @ref user_soft_key_data as HMAC key instead.
 */
//#define USER_SOFT_KEY

/**
 * @def STORE_SOFT_SERIAL
 * @brief Uncomment this to store soft serial to EEPROM
 */
//#define STORE_SOFT_SERIAL

/**
 * @def USER_SOFT_SERIAL
 * @brief Uncomment this to skip soft serial generation and use @ref user_soft_serial as serial instead.
 */
//#define USER_SOFT_SERIAL

/**
 * @def STORE_AES_KEY
 * @brief Uncomment this to store AES key to EEPROM
 */
#define STORE_AES_KEY

/**
 * @def USER_AES_KEY
 * @brief Uncomment this to skip AES key generation and use @ref user_aes_key as key instead.
 */
//#define USER_AES_KEY

#if defined(SKIP_UART_CONFIRMATION) && !defined(USER_KEY)
#error You have to define USER_KEY for boards that does not have UART
#endif

#ifdef USER_KEY
/** @brief The user-defined HMAC key to use for personalization */
#define MY_HMAC_KEY 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
/** @brief The data to store in key slot 0 */
const uint8_t user_key_data[32] = {MY_HMAC_KEY};
#endif

#ifdef USER_SOFT_KEY
/** @brief The user-defined soft HMAC key to use for EEPROM personalization */
#define MY_SOFT_HMAC_KEY 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
/** @brief The data to store as soft HMAC key in EEPROM */
const uint8_t user_soft_key_data[32] = {MY_SOFT_HMAC_KEY};
#endif

#ifdef USER_SOFT_SERIAL
/** @brief The user-defined soft serial to use for EEPROM personalization */
#define MY_SOFT_SERIAL 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
/** @brief The data to store as soft serial in EEPROM */
const uint8_t user_soft_serial[9] = {MY_SOFT_SERIAL};
#endif

#ifdef USER_AES_KEY
/** @brief The user-defined AES key to use for EEPROM personalization */
#define MY_AES_KEY 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
/** @brief The data to store as AES key in EEPROM */
const uint8_t user_aes_key[16] = {MY_AES_KEY};
#endif

in the second code i have to place the Keys which i got on first run.

after this i can upload the normally gateway sketch

is that correct?
thank you very much

LastSamurai

@meddie said in Encryption, Signing and OTA is there any how-to?:

if i understood it correctly, i have to use the securitypersonalization.ino on the gw. For the first time i upload this code
When its uploaded on first run i will get the AES and HMAC Key, which i have to notice and safe securely.

Then i have to upload the sketch again with this code:
in the second code i have to place the Keys which i got on first run.
after this i can upload the normally gateway sketch

is that correct?
thank you very much

As far as I understand it you can generate and safe the keys in one run (not 100% sure about that) on the gateway. Afterwards you install the normal gateway sketch.
And you also have to use the personalizer sketch on every node to add the HMAC/AES keys.

This is really a topic where we need an easier step-by-step tutorial imho. Perhaps once I find the time for it I'll experiment some more and write such a guide myself (will take some time though).

MLs

@meddie

Hello, I have also begun to look at the hardware lock with ATSHA204.

When you generate the key, you do so with SecurityPersonalizer.ino

https://forum.mysensors.org/topic/6019/sensebender-gateway-and-atsha204

//Mattias

Anticimex

If you feel this page is inadequate as the description for how to use signing, I am all ears for getting suggestions on how to improve it.

MLs

@Anticimex

Personally, I think it is I who do not understand really. and then is afraid to start by destroying the hardware

//Mattias

LastSamurai

@Anticimex said in Encryption, Signing and OTA is there any how-to?:

If you feel this page is inadequate as the description for how to use signing, I am all ears for getting suggestions on how to improve it.

Its a great read but a little too much on the theoretical side for me. I think we should add some practical and complete example. Something like:

get the gw and use this xyz sketch to generate the keys
copy the keys
save the keys with this xyz sketch
flash the normal gateway sketch

then take a node

burn the keys to it
add your xyz sketch with these parts to enable whitelisting, ....

Something like that so that you can point any "noob" at this and tell him to do like that.

Anticimex

@LastSamurai well, if you read far enough you get exactly that. At least as how I view things, but as I am the designer, I might find things obvious which are not. But I really have tried to add specific use case examples and how to configure them.

LastSamurai

@Anticimex Overall I like your text (and your work!) but I can only tell you what I found to be missing when I read this:
the step by step tutorial (like a short summary of your text) containing versions of the personalizer sketch doing configured to do exactly whats needed in that step. Your examples only cover the the last part of my list (the node configuration)!

Anticimex

@LastSamurai I see. Well, I intentionally left the personalizer to be highly customizable since users have varying requirements, but I can add flags to it which preconfigure some typical usecases if that would help?

Anticimex

I hope to be able to file a pull request with updates to the personalizer this or next week. @LastSamurai @MLs @meddie i would really appreciate if you tested and reviewed the change so that you (and others) no longer are deterred from using signing due to its complexity. I will update the pull request until you feel confident in the procedure. I will post a link here when I have something to show for.

LastSamurai

@Anticimex said in Encryption, Signing and OTA is there any how-to?:

@LastSamurai I see. Well, I intentionally left the personalizer to be highly customizable since users have varying requirements, but I can add flags to it which preconfigure some typical usecases if that would help?

That would actually be great! Some flags that automatically set up for:

create everything at the gw and save it
node: takes the provided HMAC (and aes) and saves it, generates new node id

and perhaps some others would really help me (and others I hope). I gladly test your new changes, just keep me updated!

PS We could also add a section to your text describing that you need well working radios (+ caps) because of the longer message sizes. Signing doesn't work for all nodes for me due to that and when I started working with it I thought this to be a problem with signing.

Anticimex

@LastSamurai node IDs is not a signing thing so the personalizer will not touch that.
And regarding working radios, the "real" documentation feature a troubleshooting section where that topic is covered. Doxygen that is. Link is available through the readme on the library on github. I will see if I can incorporate that somehow on the main site. Unfortunately there is no automatic link between the generate docs which are the most recent, and the article on the main site.

LastSamurai

I meant the serial number (forgot that name and it is like a node id, right?). The one thats needed for e.g. whitelisting.

The documentation mentions somewhere that signing might cause errors if the radios aren't working at a 100%? Haven't seen that but that might be important to avoid people being "afraid" of using signing.

Anticimex

Both serial and node id is used for whitelisting.
However, only serial is generated by the personalizer (and only for software signing, atsha204a has a fixed serial).
This is the full documentation with troubleshooting section: https://ci.mysensors.org/job/Verifiers/job/MySensors/branch/development/Doxygen_HTML/group__MySigninggrp.html

MLs

@Anticimex

Ofcourse

//Mattias

Anticimex

While I am working on the personalizer simplifications, perhaps you could have a look at https://www.mysensors.org/about/signing#how-to-use-this where there are (and have been all along) an explicit list of flags to enable/disable for "master" and "slave" devices. I believe this is what you were looking for @LastSamurai ?

LastSamurai

@Anticimex Oh, right that looks very helpful! Some shortcuts for these would be great anyways :)

Anticimex

@LastSamurai I agree, and I will rename a a few concepts as well.

Anticimex

I am inclined to stick to the concept as documented instead of having "node" and "gateway" concepts as we discussed. I will still simplify the procedure.
The reason for this is that I believe it is simpler to have this procedure:

Configure personalizer to generate keys
Reconfigure personalizer to retain and store generated keys

as opposed to

Configure personalizer for "gateway" (to generate and store keys)
Configure personalizer for "node" (to store retained keys)

The reason I think the first and original design is simpler is because it allows you to execute the personalizer once with one setting to obtain keys, then reconfigure the personalizer once and execute the same personalizer on ALL devices. That minimizes the risk of having misalignment in the personalized security data between the nodes. What I will do is to provide two "top-level" definitions which takes care of every setting except the setting of the retained autogenerated keys and the use of ATSHA204A or software signing. The personalizer does output the auto generated keys in a very copy+paste friendly manner so it is not difficult to set these.
The only thing which need to be different between nodes/gateways is the serial (if soft signing is used) so that will always be randomly generated (unless one specifically reconfigure the personalizer to use a specific serial).

Thoughts on this? I am still open for input as it is you that are the users :)
EDIT: I will have four "top-level" flags, so you select ATSHA or soft variant at the top level.

LastSamurai

@Anticimex That sounds really nice to me. I would also (if thats possible without breaking something in the code) move these new flags and the settings for the HMAC (and everything else that needs to be inserted) to the top of the sketch, so that if you stay with the "default" settings you don't need to scroll down. Just for easy of use and for beginners.

Great timing from you btw: I am in the process of switching the controller anyways and will redo some of my nodes too. Now I can incorporate signing (and perhaps encryption) too.

Encryption, Signing and OTA is there any how-to?

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