kernel/git - git - PowerEL Git System

Author	SHA1	Message	Date
Brandon Williams	a768a02265	transport: add from_user parameter to is_transport_allowed Add a from_user parameter to is_transport_allowed() to allow http to be able to distinguish between protocol restrictions for redirects versus initial requests. CURLOPT_REDIR_PROTOCOLS can now be set differently from CURLOPT_PROTOCOLS to disallow use of protocols with the "user" policy in redirects. This change allows callers to query if a transport protocol is allowed, given that the caller knows that the protocol is coming from the user (1) or not from the user (0) such as redirects in libcurl. If unknown a -1 should be provided which falls back to reading `GIT_PROTOCOL_FROM_USER` to determine if the protocol came from the user. Signed-off-by: Brandon Williams <bmwill@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	8 years ago
Jeff King	6628eb41db	http: always update the base URL for redirects If a malicious server redirects the initial ref advertisement, it may be able to leak sha1s from other, unrelated servers that the client has access to. For example, imagine that Alice is a git user, she has access to a private repository on a server hosted by Bob, and Mallory runs a malicious server and wants to find out about Bob's private repository. Mallory asks Alice to clone an unrelated repository from her over HTTP. When Alice's client contacts Mallory's server for the initial ref advertisement, the server issues an HTTP redirect for Bob's server. Alice contacts Bob's server and gets the ref advertisement for the private repository. If there is anything to fetch, she then follows up by asking the server for one or more sha1 objects. But who is the server? If it is still Mallory's server, then Alice will leak the existence of those sha1s to her. Since commit `c93c92f30` (http: update base URLs when we see redirects, 2013-09-28), the client usually rewrites the base URL such that all further requests will go to Bob's server. But this is done by textually matching the URL. If we were originally looking for "http://mallory/repo.git/info/refs", and we got pointed at "http://bob/other.git/info/refs", then we know that the right root is "http://bob/other.git". If the redirect appears to change more than just the root, we punt and continue to use the original server. E.g., imagine the redirect adds a URL component that Bob's server will ignore, like "http://bob/other.git/info/refs?dummy=1". We can solve this by aborting in this case rather than silently continuing to use Mallory's server. In addition to protecting from sha1 leakage, it's arguably safer and more sane to refuse a confusing redirect like that in general. For example, part of the motivation in `c93c92f30` is avoiding accidentally sending credentials over clear http, just to get a response that says "try again over https". So even in a non-malicious case, we'd prefer to err on the side of caution. The downside is that it's possible this will break a legitimate but complicated server-side redirection scheme. The setup given in the newly added test does work, but it's convoluted enough that we don't need to care about it. A more plausible case would be a server which redirects a request for "info/refs?service=git-upload-pack" to just "info/refs" (because it does not do smart HTTP, and for some reason really dislikes query parameters). Right now we would transparently downgrade to dumb-http, but with this patch, we'd complain (and the user would have to set GIT_SMART_HTTP=0 to fetch). Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	8 years ago
Blake Burkhart	b258116462	http: limit redirection depth By default, libcurl will follow circular http redirects forever. Let's put a cap on this so that somebody who can trigger an automated fetch of an arbitrary repository (e.g., for CI) cannot convince git to loop infinitely. The value chosen is 20, which is the same default that Firefox uses. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	10 years ago
Blake Burkhart	f4113cac0c	http: limit redirection to protocol-whitelist Previously, libcurl would follow redirection to any protocol it was compiled for support with. This is desirable to allow redirection from HTTP to HTTPS. However, it would even successfully allow redirection from HTTP to SFTP, a protocol that git does not otherwise support at all. Furthermore git's new protocol-whitelisting could be bypassed by following a redirect within the remote helper, as it was only enforced at transport selection time. This patch limits redirects within libcurl to HTTP, HTTPS, FTP and FTPS. If there is a protocol-whitelist present, this list is limited to those also allowed by the whitelist. As redirection happens from within libcurl, it is impossible for an HTTP redirect to a protocol implemented within another remote helper. When the curl version git was compiled with is too old to support restrictions on protocol redirection, we warn the user if GIT_ALLOW_PROTOCOL restrictions were requested. This is a little inaccurate, as even without that variable in the environment, we would still restrict SFTP, etc, and we do not warn in that case. But anything else means we would literally warn every time git accesses an http remote. This commit includes a test, but it is not as robust as we would hope. It redirects an http request to ftp, and checks that curl complained about the protocol, which means that we are relying on curl's specific error message to know what happened. Ideally we would redirect to a working ftp server and confirm that we can clone without protocol restrictions, and not with them. But we do not have a portable way of providing an ftp server, nor any other protocol that curl supports (https is the closest, but we would have to deal with certificates). [jk: added test and version warning] Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	10 years ago
Jeff King	a5adaced2e	transport: add a protocol-whitelist environment variable If we are cloning an untrusted remote repository into a sandbox, we may also want to fetch remote submodules in order to get the complete view as intended by the other side. However, that opens us up to attacks where a malicious user gets us to clone something they would not otherwise have access to (this is not necessarily a problem by itself, but we may then act on the cloned contents in a way that exposes them to the attacker). Ideally such a setup would sandbox git entirely away from high-value items, but this is not always practical or easy to set up (e.g., OS network controls may block multiple protocols, and we would want to enable some but not others). We can help this case by providing a way to restrict particular protocols. We use a whitelist in the environment. This is more annoying to set up than a blacklist, but defaults to safety if the set of protocols git supports grows). If no whitelist is specified, we continue to default to allowing all protocols (this is an "unsafe" default, but since the minority of users will want this sandboxing effect, it is the only sensible one). A note on the tests: ideally these would all be in a single test file, but the git-daemon and httpd test infrastructure is an all-or-nothing proposition rather than a test-by-test prerequisite. By putting them all together, we would be unable to test the file-local code on machines without apache. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	10 years ago