Fix for vulnerability CVE-2014-9390
This is a security-fix for CVE-2014-9390, which affects users on Windows and Mac OS X but not typical UNIX users.
We used to allow committing a path ".Git/config" with JGit & EGit that is running on a case sensitive filesystem, but an attempt to check out such a path with Git that runs on a case insensitive filesystem would have clobbered ".git/config", which is definitely not what the user would have expected. JGit now prevents you from tracking a path with ".Git" (in any case combination) as a path component.
On Windows, certain path components that are different from ".git" are mapped to ".git", e.g. "git~1/config" is treated as if it were ".git/config". HFS+ has a similar issue, where certain unicode codepoints are ignored, e.g. ".g\u200cit/config" is treated as if it were ".git/config". Pathnames with these potential issues are rejected on the affected systems.
As described in Securing your Git server native git has been enhanced by configuration parameters allowing to configure a git server to check all objects it receives against problematic pathes. A server running e.g. on Linux can be configured to check also for pathes problematic on HFS+ or NTFS. This is also possible for JGit based Git servers. JGit understands the boolean config parameters receive.fsckobjects, fsck.safeForWindows and fsck.safeForMacOS. They match native git's receive.fsckobjects, core.protectNTFS, core.protectHFS.
enable checks when receiving objects
check pathes problematic on NTFS
check pathes problematic on HFS+
Enabling receive.fsckObjects makes JGit check the integrity of objects before a push is accepted, which is a pre-requisite for the other flags. The fsck.safeForMacOS and fsck.safeForWindows flags prevent the Mac OS X and Windows vulnerabilities described above, respectively. Both default to true on their respective systems but will need to be enabled specifically on other platforms. Since clients could be using a different operating system to your server you should enable both on JGit based servers.
A big "thanks!" for bringing this issue to us goes to our friends in the Mercurial land, namely, Matt Mackall and Augie Fackler.