ERL-915: wrong spec for pubkey_pbe:pbdkdf2/7

[OTP-Maintainer]

Original reporter: sdl.web@gmail.com
Affected version: OTP-21.3
Fixed in version: OTP-22.1
Component: public_key
Migrated from: https://bugs.erlang.org/browse/ERL-915

---

The spec says first argument is string() but it crashes with badarg when given any thing larger than 255. BTW, is is possible to provide a public API for pbdkdf2?

{code:erlang}
-spec pbdkdf2(string(), iodata(), integer(), integer(), fun(), atom(), integer())
	     -> binary().
%%
%% Description: Implements password based decryption key derive function 2.
%% Exported mainly for testing purposes.
%%--------------------------------------------------------------------
pbdkdf2(Password, Salt, Count, DerivedKeyLen, Prf, PrfHash, PrfOutputLen)->
    NumBlocks = ceiling(DerivedKeyLen / PrfOutputLen),
    NumLastBlockOctets = DerivedKeyLen - (NumBlocks - 1) * PrfOutputLen ,
    blocks(NumBlocks, NumLastBlockOctets, 1, Password, Salt, 
	   Count, Prf, PrfHash, PrfOutputLen, <<>>).
{code}

[OTP-Maintainer]

ingela said:

Without checking, I would say that  it is only a sub type of string() that will actually work for this function. We will look into that. It would be possible to have a public API for password based encryption functions, we have thought of doing it, but it has never been prioritized high enough.
Once you make a function public, it is hard to change, so we like it to be thought through. You are welcome to make a PR if you have a suggestion. 

[OTP-Maintainer]

sdl.web@gmail.com said:

Thanks for looking into this. I can live with pubkey_pbe:pbdkdf2/7 for now until a proper public API is provided.

[OTP-Maintainer]

ingela said:

I think this spec ought to be iodata(), and when making a public
API the API function should perhaps have an ascci_str()  type.

[OTP-Maintainer]

ingela said:

I fixed the spec. However I do not see the API being prioritized real soon, even if it would be nice.

[OTP-Maintainer]

sdl.web@gmail.com said:

Thank you for the fix.