openssh portable and libressl portable cause recursion between arc4random and RAND_bytes

[Hanno Böck]

Hi,

Yesterday I tried to replace the system openssl in a gentoo system with
libressl.

With openssh an interesting issue popped up:
* RAND_bytes in libressl calls arc4random
* arc4random is a compat function both in openssh and libressl
* arc4random from openssh uses RAND_bytes

So what's happening is a recursion. arc4random wants to use RAND_bytes
and RAND_bytes wants to use arc4random. The result is a segfault.
OpenSSH is the latest 6.6.1.

A quick and working solution was to replace the openssh-arc4random with
the one shipped by libressl. One small change is needed: the
libressl-arc4random.c doesn't have the arc4random_stir()-function,
I copied that back from the openssh-arc4random.c.

Works so far, see attached patch.

An alternative would be to check for the availability of arc4random in
libcrypto and use that if available.

cu,
-- 
Hanno Böck
http://hboeck.de/

mail/jabber: hanno at hboeck.de
GPG: BBB51E42
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