Backport fixes for CVE 2018-11235 #4659
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We should pretend such submdules do not exist as it can lead to RCE.
If the we decide that the "name" of the submodule (i.e. its path inside `.git/modules/`) is trying to escape that directory or otherwise trick us, we ignore the configuration for that submodule. This leaves us with a half-configured submodule when looking it up by path, but it's the same result as if the configuration really were missing. The name check is potentially more strict than it needs to be, but it lets us re-use the check we're doing for the checkout. The function that encapsulates this logic is ready to be exported but we don't want to do that in a security release so it remains internal for now.
Otherwise we would also admit `..\..\foo\bar` as a valid path and fail to protect Windows users. Ideally we would check for both separators without the need for the copied string, but this'll get us over the RCE.
This lets us check for other kinds of reserved files.
It checks against the 8.3 shortname variants, including the one which includes the checksum as part of its name.
Given a path component it knows what to pass to the filesystem-specific functions so we're protected even from trees which try to use the 8.3 naming rules to get around us matching on the filename exactly. The logic and test strings come from the equivalent git change.
These can't go into the public API yet as we don't want to introduce API or ABI changes in a security release.
These will be used by the checkout code to detect them for the particular filesystem they're on.
We want to reject these as they cause compatibility issues and can lead to git writing to files outside of the repository.
We may take in names from the middle of a string so we want the caller to let us know how long the path component is that we should be checking.
This is so we have it available for the path validity checking. In a later commit we will start rejecting `.gitmodules` files as symlinks.
Any part of the library which asks the question can pass in the mode to have it checked against `.gitmodules` being a symlink. This is particularly relevant for adding entries to the index from the worktree and for checking out files.
When dealing with `core.proectNTFS` and `core.protectHFS` we do check against `.gitmodules` but we still have a failing test as the non-filesystem codepath does not check for it.
We still compare case-insensitively to protect more thoroughly as we don't know what specifics we'll see on the system and it's the behaviour from git.
We might modify caches due to us trying to load the configuration to figure out what kinds of filesystem protections we should have.
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Thanks @pks-t for doing the backport. |
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Backporting @carlosmn's fixes so that we can do an 0.27.1 security release. Thanks @carlosmn and @pks-t for the work.