The variable GIT_VERSION is always defined, either obtained from Git or
a file that is embedded in tarballs when they are built. Optionally,
that version is declared as VERSION in config.h so it will be used e.g. in
the daemons when they print the version number.
There is a check that should catch missing tags (i.e. if the version number
in AC_INIT() isn't a prefix of the version obtained via Git).
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.
INCLUDES are now deprecated and throw warnings when using automake 1.13.
We now also differentiate AM_CPPFLAGS and AM_CFLAGS, where includes and
defines are passed to AM_CPPFLAGS only.
Tobias Brunner