On Mon, 26 Sep 2016, Török Edwin wrote:

> /* If we get here, it means we need to seed the PRNG using a "silly"
> approach! */
> do {
> unsigned char randb[64];
> int len = sizeof(randb);
> RAND_bytes(randb, len);
> RAND_add(randb, len, (len >> 1));
> } while(!RAND_status());

I'm not sure this particular loop is as stupid as the comment implies.
RAND_bytes() is supposed to give crypto safe random and according to
https://wiki.openssl.org/index.php/Random_Numbers the function will even init
the random generator itself if it wasn't done before.

> I'd prefer to get an error if (lib)curl cannot seed OpenSSL with enough
> entropy (AFAICT OpenSSL wants at least 256 bits): something is seriously
> wrong if it can't (e.g. running curl in a chroot without mounting /dev), and
> I'd rather want to know about it and fix it, than establish a possibly
> insecure HTTPS connection (the PRNG might be used to generate ephemeral
> keys).
>
> Could there be a flag added to libcurl that would cause it to return an
> error in this case?

Sure. But I'm not sure when that would happen (in a fashion that we can test)
and how you can tell in that function?

-- 
  / daniel.haxx.se

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Received on 2016-09-27