Wireshark-dev: Re: [Wireshark-dev] Remove our bundled crypto library (in favor of Libgcrypt)?
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From: João Valverde <joao.valverde@xxxxxxxxxxxxxxxxxx>
Date: Sat, 11 Feb 2017 22:14:46 +0000


On 02/11/2017 09:44 PM, Peter Wu wrote:

On Sat, Feb 11, 2017 at 08:54:39PM +0000, João Valverde wrote:
[..]

I think a small abstraction layer above the lower-level crypto routines,
whatever those may be (libgcrypt, nettle, home-grown - yuck), would be a
useful thing to have. It would accomplish two things:

1. Easily change dependencies without having to change dissector code.

2. Disable crypto in a saner way and keep the dependency optional, without
having to use #ifdefs all over the place (just one place in fact). Example:

  int ws_aes_decrypt(...) {
  #ifdef HAVE_AES_DEPENDENCY
     err = aes_decrypt(...);
     if (err == AES_OK) {
     	return WS_CRYPTO_OK;
     } else {
        ...
     }
  #else
     return WS_CRYPTO_DISABLED;
  #endif
  }

Then of course require crypto consumers (dissectors and whatever else) to
handle the WS_CRYPTO_DISABLED case as appropriate.


Disabling is an option if you want to make the crypto library optional,
but the vast majority of the files/functions are hash functions (md5 is
used for example in editcap.c for duplicate detection). Since you need a
crypto library for the hash functions, you get decryption algorithms
like AES for free. (Unless you want to keep the bundled algorithms... I
would rather not).
OK, I'm swayed by those arguments. I was already fine with making it mandatory anyway.