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GITNAMESPACES(7)		  Git Manual		      GITNAMESPACES(7)

NAME
       gitnamespaces - Git namespaces

SYNOPSIS
       GIT_NAMESPACE=<namespace> git upload-pack
       GIT_NAMESPACE=<namespace> git receive-pack

DESCRIPTION
       Git supports dividing the refs of a single repository into multiple
       namespaces, each	of which has its own branches, tags, and HEAD. Git can
       expose each namespace as	an independent repository to pull from and
       push to,	while sharing the object store,	and exposing all the refs to
       operations such as git-gc(1).

       Storing multiple	repositories as	namespaces of a	single repository
       avoids storing duplicate	copies of the same objects, such as when
       storing multiple	branches of the	same source. The alternates mechanism
       provides	similar	support	for avoiding duplicates, but alternates	do not
       prevent duplication between new objects added to	the repositories
       without ongoing maintenance, while namespaces do.

       To specify a namespace, set the GIT_NAMESPACE environment variable to
       the namespace. For each ref namespace, Git stores the corresponding
       refs in a directory under refs/namespaces/. For example,
       GIT_NAMESPACE=foo will store refs under refs/namespaces/foo/. You can
       also specify namespaces via the --namespace option to git(1).

       Note that namespaces which include a / will expand to a hierarchy of
       namespaces; for example,	GIT_NAMESPACE=foo/bar will store refs under
       refs/namespaces/foo/refs/namespaces/bar/. This makes paths in
       GIT_NAMESPACE behave hierarchically, so that cloning with
       GIT_NAMESPACE=foo/bar produces the same result as cloning with
       GIT_NAMESPACE=foo and cloning from that repo with GIT_NAMESPACE=bar. It
       also avoids ambiguity with strange namespace paths such as
       foo/refs/heads/,	which could otherwise generate directory/file
       conflicts within	the refs directory.

       git-upload-pack(1) and git-receive-pack(1) rewrite the names of refs as
       specified by GIT_NAMESPACE. git-upload-pack and git-receive-pack	will
       ignore all references outside the specified namespace.

       The smart HTTP server, git-http-backend(1), will	pass GIT_NAMESPACE
       through to the backend programs;	see git-http-backend(1)	for sample
       configuration to	expose repository namespaces as	repositories.

       For a simple local test,	you can	use git-remote-ext(1):

	   git clone ext::'git --namespace=foo %s /tmp/prefixed.git'

SECURITY
       The fetch and push protocols are	not designed to	prevent	one side from
       stealing	data from the other repository that was	not intended to	be
       shared. If you have private data	that you need to protect from a
       malicious peer, your best option	is to store it in another repository.
       This applies to both clients and	servers. In particular,	namespaces on
       a server	are not	effective for read access control; you should only
       grant read access to a namespace	to clients that	you would trust	with
       read access to the entire repository.

       The known attack	vectors	are as follows:

	1. The victim sends "have" lines advertising the IDs of	objects	it has
	   that	are not	explicitly intended to be shared but can be used to
	   optimize the	transfer if the	peer also has them. The	attacker
	   chooses an object ID	X to steal and sends a ref to X, but isn't
	   required to send the	content	of X because the victim	already	has
	   it. Now the victim believes that the	attacker has X,	and it sends
	   the content of X back to the	attacker later.	(This attack is	most
	   straightforward for a client	to perform on a	server,	by creating a
	   ref to X in the namespace the client	has access to and then
	   fetching it.	The most likely	way for	a server to perform it on a
	   client is to	"merge"	X into a public	branch and hope	that the user
	   does	additional work	on this	branch and pushes it back to the
	   server without noticing the merge.)

	2. As in #1, the attacker chooses an object ID X to steal. The victim
	   sends an object Y that the attacker already has, and	the attacker
	   falsely claims to have X and	not Y, so the victim sends Y as	a
	   delta against X. The	delta reveals regions of X that	are similar to
	   Y to	the attacker.

Git 2.13.2			  06/24/2017		      GITNAMESPACES(7)

NAME | SYNOPSIS | DESCRIPTION | SECURITY

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