Add native lib src files and android binaries

[cmonfortep]

Task/Issue URL: https://app.asana.com/0/0/1204068537088006/f

Description

Adds native library src code to repository.
Include android libsodium builds.

Structure will be:

• root
• root/native_lib/<sync_crypto_src>
• root/native_lib/third-party/

Steps to test this PR

Feature 1

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[ayoy]

LGTM!

[cmonfortep]

@ayoy just removed the unuse method. good catch

[MarkIngramUK]

x and y should have parenthesis in the preprocessor definition, to prevent incorrect evaluation order when certain operators are used.

e.g.

min(3 | 4, 1 | 2);

Will be evaluated in the following order:

(3 | (4 < 1) | 2) ? (3 | 4) : (1 : 2)

Resulting in a return value of 7, when the correct answer is 3. See the example here:
https://godbolt.org/z/cvq34PbEh

https://en.cppreference.com/w/c/language/operator_precedence

[brindy]

@MarkIngramUK thanks for the comment, do you fancy opening a PR for this?

[MarkIngramUK]

Forgive my question, I'm not familiar with libsodium, but, are these hash salts? If they are, is there any security concern about having the raw string values embedded in the binary?

[brindy]

I'm not sure what the best practice is tbh. But, if this was externalised then each consumer would have to pass in the same context as a parameter. All consumers will be open source (eventually) so I don't see any particularly added value in externalising. I will ping Stefan to validate.

[stefanorri]

These are not hash salts but the "context" which is a string describing what the key is going to be used for. It doesn't have to be secret, just unique for each key derived from the primary key.

[MarkIngramUK]

Thanks for the clarification @stefanorri !