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add xmpp page

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Joey Hess 2012-10-24 20:05:45 -04:00
parent 9aa9cb5bcf
commit 75ad5b062a
4 changed files with 74 additions and 28 deletions
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2
doc/design/assistant.mdwn
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@ -11,7 +11,7 @@ and use cases to add. Feel free to chip in with comments! --[[Joey]]
We are, approximately, here:
* Month 4 "cloud": [[!traillink cloud]] [[!traillink transfer_control]]
* Month 4 "cloud": [[!traillink cloud]] [[!traillink xmpp]] [[!traillink transfer_control]]
* Month 5 user-driven features (see [[polls]])
* Months 6-7 "9k bonus round": [[!traillink Android]] [[!traillink partial_content]] [[!traillink leftovers]]
* Months 8-11: more user-driven features and polishing (see remaining TODO items in all pages above)

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doc/design/assistant/cloud.mdwn
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@ -30,7 +30,7 @@ been a change to Alice's git repo. Then he needs to pull from Alice's git repo,
or some other repo in the cloud she pushed to. Once both steps are done,
the assistant will transfer the file from the cloud to Bob.
* dvcs-autosync uses jabber; all repos need to have the same jabber account
* dvcs-autosync uses xmppp; all repos need to have the same xmpp account
configured, and send self-messages. An alternative would be to have
different accounts that join a channel or message each other. Still needs
account configuration.
@ -44,32 +44,7 @@ the assistant will transfer the file from the cloud to Bob.
* pubsubhubbub does not seem like an option; its hubs want to pull down
a feed over http.
### jabber TODO
* test with big servers, eg google chat
* Prevent idle disconnection. Probably means sending or receiving pings,
but would prefer to avoid eg pinging every 60 seconds as some clients do.
* Make the git-annex clients invisible, so a user can use their regular
account without always seeming to be present when git-annex is logged in.
See <http://xmpp.org/extensions/xep-0126.html>
### jabber security
Any data git-annex sends over this XMPP will be visible to the XMPP
account's buddies, to the XMPP server, and quite likely to other interested
parties. So it's important to consider the security exposure of using it.
If git-annex sends only a single bit notification, this lets attackers know
when the user is active and changing files. Although the assistant's other
syncing activities can somewhat mask this.
As soon as git-annex does anything unlike any other client, an attacker can
see how many clients are connected for a user, and fingerprint the ones
running git-annex, and determine how many clients are running git-annex.
If git-annex sent the UUID of the remote it pushed to, this would let
attackers determine how many different remotes are being used,
and map some of the connections between clients and remotes.
See [[xmpp]] for design of git-annex's use of xmpp for notifications.
## storing git repos in the cloud

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doc/design/assistant/pairing.mdwn
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@ -81,3 +81,4 @@ is escaped before going to the browser.
It should be possible for third parties to tell when pairing is done,
but it's actually rather hard since they don't necessarily share the secret.
* Pairing over XMPP.

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doc/design/assistant/xmpp.mdwn Normal file
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@ -0,0 +1,70 @@
The git-annex assistant uses XMPP to communicate between peers that
cannot directly talk to one-another. A typical scenario is two users
who share a repository, that is stored in the [[cloud]].
### TODO
* test with big servers, eg google chat
* Prevent idle disconnection. Probably means sending or receiving pings,
but would prefer to avoid eg pinging every 60 seconds as some clients do.
* Make the git-annex clients invisible, so a user can use their regular
account without always seeming to be present when git-annex is logged in.
See <http://xmpp.org/extensions/xep-0126.html>
* webapp configuration
* After pulling from a remote, may need to scan for transfers, which
could involve other remotes (ie, S3). Since the remote client is not able to
talk to us directly, it won't be able to upload any new files to us.
Need a fast way to find new files, and get them transferring. The expensive
transfer scan may be needed to get fully in sync, but is too expensive to
run every time this happens.
## design goals
1. Avoid user-visible messages. dvcs-autosync uses XMPP similarly, but
sends user-visible messages. Avoiding user-visible messages lets
the user configure git-annex to use his existing XMPP account
(eg, Google Talk).
2. Send notifications to buddies. dvcs-autosync sends only self-messages,
but that requires every node have the same XMPP account configured.
git-annex should support that mode, but it should also send notifications
to a user's buddies. (This will also allow for using XMPP for pairing
in the future.)
3. Don't make account appear active. Just because git-annex is being an XMPP
client, it doesn't mean that it wants to get chat messages, or make the
user appear active when he's not using his chat program.
## protocol
To avoid relying on XMPP extensions, git-annex communicates
using presence messages. These always mark it as extended away.
To this, it adds its own tag as [extended content](http://xmpp.org/rfcs/rfc6121.html#presence-extended).
The xml namespace is "git-annex" (not an URL because I hate wasting bandwidth).
To indicate it's pushed changes to a git repo, a client uses:
<git-annex xmlns='git-annex' push="uuid" />
The push attribute can be repeated when the push was sent to multiple repos.
### security
Data git-annex sends over XMPP will be visible to the XMPP
account's buddies, to the XMPP server, and quite likely to other interested
parties. So it's important to consider the security exposure of using it.
Even if git-annex sends only a single bit notification, this lets attackers
know when the user is active and changing files. Although the assistant's other
syncing activities can somewhat mask this.
As soon as git-annex does anything unlike any other client, an attacker can
see how many clients are connected for a user, and fingerprint the ones
running git-annex, and determine how many clients are running git-annex.
If git-annex sent the UUID of the remote it pushed to, this would let
attackers determine how many different remotes are being used,
and map some of the connections between clients and remotes.
An attacker could replay push notification messages, reusing UUIDs it's
observed. This would make clients pull repeatedly, perhaps as a DOS.