Note that 13.04 is no longer supported. Upgrading to a supported version is the recommended action. But if a short term solution is needed, it's possible to rebuild the packages from source (sample instructions) with a patch applied, e.g.:
sudo apt-get install build-essential fakeroot dpkg-dev devscripts
apt-get source openssl
sudo apt-get build-dep openssl
# ...apply patch...
dpkg-buildpackage -rfakeroot -uc -b
sudo dpkg -i *.deb
From the Ubuntu changelog page for openssl, find the diff file for quantal, which happens to have the same base version of openssl (1.0.1c). This should apply cleanly against the latest source for raring. If following the instructions from the link above, apply the patch after doing the
dch -i part, choose a sensible version number. Ignore/delete the rejected patch for
debian/changelog, and continue the process.