Rpm: rpmbuild gettarspec() crafted tar member name → macro injection

A vulnerability was found in RPM's rpmbuild tarball processing. When processing a crafted source archive, the getTarSpec() function in tools/rpmbuild.cc passes an attacker-controlled tar archive member name to rpmExpand() as part of a %{basename:...} macro expression. A specially crafted .spec member name can therefore inject RPM macros, including Lua expressions, resulting in arbitrary code execution with the privileges of the user running rpmbuild. This can be exploited when a victim or automated build system processes an attacker-controlled source tarball using rpmbuild tarball mode (such as -ts, -ta, or -tb).