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2019-12-05path: safeguard `.git` against NTFS Alternate Streams AccessesLibravatar Johannes Schindelin1-0/+1
Probably inspired by HFS' resource streams, NTFS supports "Alternate Data Streams": by appending `:<stream-name>` to the file name, information in addition to the file contents can be written and read, information that is copied together with the file (unless copied to a non-NTFS location). These Alternate Data Streams are typically used for things like marking an executable as having just been downloaded from the internet (and hence not necessarily being trustworthy). In addition to a stream name, a stream type can be appended, like so: `:<stream-name>:<stream-type>`. Unless specified, the default stream type is `$DATA` for files and `$INDEX_ALLOCATION` for directories. In other words, `.git::$INDEX_ALLOCATION` is a valid way to reference the `.git` directory! In our work in Git v2.2.1 to protect Git on NTFS drives under `core.protectNTFS`, we focused exclusively on NTFS short names, unaware of the fact that NTFS Alternate Data Streams offer a similar attack vector. Let's fix this. Seeing as it is better to be safe than sorry, we simply disallow paths referring to *any* NTFS Alternate Data Stream of `.git`, not just `::$INDEX_ALLOCATION`. This also simplifies the implementation. This closes CVE-2019-1352. Further reading about NTFS Alternate Data Streams: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/c54dec26-1551-4d3a-a0ea-4fa40f848eb3 Reported-by: Nicolas Joly <Nicolas.Joly@microsoft.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2014-12-17read-cache: optionally disallow NTFS .git variantsLibravatar Johannes Schindelin1-0/+13
The point of disallowing ".git" in the index is that we would never want to accidentally overwrite files in the repository directory. But this means we need to respect the filesystem's idea of when two paths are equal. The prior commit added a helper to make such a comparison for NTFS and FAT32; let's use it in verify_path(). We make this check optional for two reasons: 1. It restricts the set of allowable filenames, which is unnecessary for people who are not on NTFS nor FAT32. In practice this probably doesn't matter, though, as the restricted names are rather obscure and almost certainly would never come up in practice. 2. It has a minor performance penalty for every path we insert into the index. This patch ties the check to the core.protectNTFS config option. Though this is expected to be most useful on Windows, we allow it to be set everywhere, as NTFS may be mounted on other platforms. The variable does default to on for Windows, though. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-12-17read-cache: optionally disallow HFS+ .git variantsLibravatar Jeff King1-4/+20
The point of disallowing ".git" in the index is that we would never want to accidentally overwrite files in the repository directory. But this means we need to respect the filesystem's idea of when two paths are equal. The prior commit added a helper to make such a comparison for HFS+; let's use it in verify_path. We make this check optional for two reasons: 1. It restricts the set of allowable filenames, which is unnecessary for people who are not on HFS+. In practice this probably doesn't matter, though, as the restricted names are rather obscure and almost certainly would never come up in practice. 2. It has a minor performance penalty for every path we insert into the index. This patch ties the check to the core.protectHFS config option. Though this is expected to be most useful on OS X, we allow it to be set everywhere, as HFS+ may be mounted on other platforms. The variable does default to on for OS X, though. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-12-17verify_dotfile(): reject .git case-insensitivelyLibravatar Jeff King1-0/+1
We do not allow ".git" to enter into the index as a path component, because checking out the result to the working tree may causes confusion for subsequent git commands. However, on case-insensitive file systems, ".Git" or ".GIT" is the same. We should catch and prevent those, too. Note that technically we could allow this for repos on case-sensitive filesystems. But there's not much point. It's unlikely that anybody cares, and it creates a repository that is unexpectedly non-portable to other systems. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-12-17read-tree: add tests for confusing paths like ".." and ".git"Libravatar Jeff King1-0/+32
We should prevent nonsense paths from entering the index in the first place, as they can cause confusing results if they are ever checked out into the working tree. We already do so, but we never tested it. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>