Use threadsafe wrapper for getpwnam/getgrnam

[ncopa]

Even if rlm_unix is marked as RLM_TYPE_THREAD_UNSAFE, it runs in a
separate thread than the main thread. Both main thread and rlm_unix
uses thread unsafe getpwnam/getgrnam which causes segfault when under
stress.

We create a thread safe wrapper for those that uses TLS.

This fixes #767

[ncopa]

Thanks for fixing the issue, but you have introduced a new by using a fixed sized buffer. You should really check for ERANGE and increase the buffer if needed.

I have had similar issue before but at that time the lower limit was in uclibc and busybox. And yes, I got surprised that people actually have that big groups in /etc/group and don't in ldap/sql whatever. Since then we have moved to musl libc so I suspect it is just a question of time before someone hits the 1024 char roof.

I'd prefer fix things properly while at it.

[alandekok]

ncopa wrote:

Thanks for fixing the issue, but you have introduced a new by using a
fixed sized buffer. You should really check for ERANGE and increase the
buffer if needed.

Hmm... OK.

I have had similar issue http://bugs.alpinelinux.org/issues/733 before
but at that time the lower limit was in uclibc and busybox. And yes, I
got surprised that people actually have that big groups in /etc/group
and don't in ldap/sql whatever. Since then we have moved to musl libc so
I suspect it is just a question of time before someone hits the 1024
char roof.

I'd prefer fix things properly while at it.

That's reasonable.

Alan DeKok.