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The "SECURITY" section of the gitnamespaces(7) man page described two ways for a client to steal data from a server that wasn't intended to be shared. Similar attacks can be performed by a server on a client, so adapt the section to cover both directions and add it to the git-fetch(1), git-pull(1), and git-push(1) man pages. Also add references to this section from the documentation of server configuration options that attempt to control data leakage but may not be fully effective. Signed-off-by: Matt McCutchen <matt@mattmccutchen.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
30 lines
1.7 KiB
Text
30 lines
1.7 KiB
Text
SECURITY
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--------
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The fetch and push protocols are not designed to prevent one side from
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stealing data from the other repository that was not intended to be
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shared. If you have private data that you need to protect from a malicious
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peer, your best option is to store it in another repository. This applies
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to both clients and servers. In particular, namespaces on a server are not
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effective for read access control; you should only grant read access to a
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namespace to clients that you would trust with read access to the entire
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repository.
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The known attack vectors are as follows:
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. The victim sends "have" lines advertising the IDs of objects it has that
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are not explicitly intended to be shared but can be used to optimize the
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transfer if the peer also has them. The attacker chooses an object ID X
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to steal and sends a ref to X, but isn't required to send the content of
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X because the victim already has it. Now the victim believes that the
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attacker has X, and it sends the content of X back to the attacker
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later. (This attack is most straightforward for a client to perform on a
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server, by creating a ref to X in the namespace the client has access
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to and then fetching it. The most likely way for a server to perform it
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on a client is to "merge" X into a public branch and hope that the user
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does additional work on this branch and pushes it back to the server
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without noticing the merge.)
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. As in #1, the attacker chooses an object ID X to steal. The victim sends
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an object Y that the attacker already has, and the attacker falsely
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claims to have X and not Y, so the victim sends Y as a delta against X.
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The delta reveals regions of X that are similar to Y to the attacker.
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