Xcode 8.3, to which there recently was a switch, spits out a warning for
the potentially unaligned access to ip6_plen in ip-packet.c, which we
explicitly read via untoh16() hence the access to that pointer is not
actually unaligned. It seems the compiler is not able to determine that
there is no unaligned access even though the function is defined in the
header and marked inline.
This can be useful if the subject DN has to be configured with the
asn1dn: prefix in ipsec.conf (e.g. because the actual encoding can't be
created by strongSwan's string parser/encoder).
This tool shows that it is trivial to re-construct the value memcmp() compares
against by just measuring the time the non-time-constant memcmp() requires to
fail.
It also shows that even when running without any network latencies it gets
very difficult to reconstruct MAC/ICV values, as the time variances due to the
crypto routines are large enough that it gets difficult to measure the time
that memcmp() actually requires after computing the MAC.
However, the faster/time constant an algorithm is, the more likely is a
successful attack. When using AES-NI, it is possible to reconstruct (parts of)
a valid MAC with this tool, for example with AES-GCM.
While this is all theoretical, and way more difficult to exploit with network
jitter, it nonetheless shows that we should replace any use of memcmp/memeq()
with a constant-time alternative in all sensitive places.
While d0d85683 works around a crasher related to the use of libunwind, other
build hangs have been seen in the all test cases. Try to
--disable-unwind-backtraces to see if libunwind is really related to those
and if it fixes these issues.
Ubuntu 12.04 does not seem to provide a sane pkg-config for libiptc or libip4tc.
The monolithic build fails due to missing symbols, so disable it until we have
a newer Ubuntu release.
On Ubuntu 12.04, there seems to be a resource leak related to pthread keys
when initializing glib or related libraries more than once. With our repeated
initialization for libstrongswan tests, we hit the following error:
Lib (gthread-posix.c): Unexpected error from C library during
'pthread_key_create': Resource temporarily unavailable.
The problem is not reproducible on a newer Gnome stack, hence we disable the
glib based soup plugin until we have a more recent Ubuntu on Travis.
Tobias Brunner