Multi-realm KDC null deref [CVE-2013-1418]

If a KDC serves multiple realms, certain requests can cause
setup_server_realm() to dereference a null pointer, crashing the KDC.

CVSSv2: AV:N/AC:M/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C

A related but more minor vulnerability requires authentication to
exploit, and is only present if a third-party KDC database module can
dereference a null pointer under certain conditions.

(back ported from commit 5d2d9a1abe46a2c1a8614d4672d08d9d30a5f8bf)

ticket: 7757 (new)
version_fixed: 1.10.7
status: resolved
finish_realms()
{
    int i;

    for (i = 0; i < kdc_numrealms; i++) {
        finish_realm(kdc_realmlist[i]);
        kdc_realmlist[i] = 0;
    }
    kdc_numrealms = 0;
}

finish_realms()
{
    int i;

    for (i = 0; i < kdc_numrealms; i++) {
        finish_realm(kdc_realmlist[i]);
        kdc_realmlist[i] = 0;
    }
    kdc_numrealms = 0;
}
