/usr/lib/firebird/2.5/firebird.msg is in firebird2.5-common 2.5.2.26540.ds4-1~deb7u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/firebird/2.5/../../../share/firebird/2.5/firebird.msg
/usr/lib/firebird/2.5/../../../share/firebird/2.5/firebird.msg