p2p --link now defaults to setting up a bi-directional link

Both the local and remote git repositories get remotes added
pointing at one-another.

Makes pairing twice as easy!

Security: The new LINK command in the protocol can be sent repeatedly,
but only by a peer who has authenticated with us. So, it's entirely safe to
add a link back to that peer, or to some other peer it knows about.
Anything we receive over such a link, the peer could send us over the
current connection.

There is some risk of being flooded with LINKs, and adding too many
remotes. To guard against that, there's a hard cap on the number of remotes
that can be set up this way. This will only be a problem if setting up
large p2p networks that have exceptional interconnectedness.

A new, dedicated authtoken is created when sending LINK.

This also allows, in theory, using a p2p network like tor, to learn about
links on other networks, like telehash.

This commit was sponsored by Bruno BEAUFILS on Patreon.

1 files changed, 15 insertions, 1 deletions

diff --git a/P2P/Protocol.hs b/P2P/Protocol.hs
index 135409e26..c383fa966 100644
--- a/P2P/Protocol.hs
+++ b/P2P/Protocol.hs
@@ -14,6 +14,7 @@ module P2P.Protocol where
 import qualified Utility.SimpleProtocol as Proto
 import Types.Key
 import Types.UUID
+import P2P.Address
 import Utility.AuthToken
 import Utility.Applicative
 import Utility.PartialPrelude
@@ -49,6 +50,7 @@ data Message
 	= AUTH UUID AuthToken -- uuid of the peer that is authenticating
 	| AUTH_SUCCESS UUID -- uuid of the remote peer
 	| AUTH_FAILURE
+	| LINK P2PAddressAuth -- sending an address that the peer may link to
 	| CONNECT Service
 	| CONNECTDONE ExitCode
 	| NOTIFYCHANGE
@@ -69,8 +71,9 @@ data Message
 
 instance Proto.Sendable Message where
 	formatMessage (AUTH uuid authtoken) = ["AUTH", Proto.serialize uuid, Proto.serialize authtoken]
-	formatMessage (AUTH_SUCCESS uuid) = ["AUTH-SUCCESS",  Proto.serialize uuid]
+	formatMessage (AUTH_SUCCESS uuid) = ["AUTH-SUCCESS", Proto.serialize uuid]
 	formatMessage AUTH_FAILURE = ["AUTH-FAILURE"]
+	formatMessage (LINK addr) = ["LINK", Proto.serialize addr]
 	formatMessage (CONNECT service) = ["CONNECT", Proto.serialize service]
 	formatMessage (CONNECTDONE exitcode) = ["CONNECTDONE", Proto.serialize exitcode]
 	formatMessage NOTIFYCHANGE = ["NOTIFYCHANGE"]
@@ -92,6 +95,7 @@ instance Proto.Receivable Message where
 	parseCommand "AUTH" = Proto.parse2 AUTH
 	parseCommand "AUTH-SUCCESS" = Proto.parse1 AUTH_SUCCESS
 	parseCommand "AUTH-FAILURE" = Proto.parse0 AUTH_FAILURE
+	parseCommand "LINK" = Proto.parse1 LINK
 	parseCommand "CONNECT" = Proto.parse1 CONNECT
 	parseCommand "CONNECTDONE" = Proto.parse1 CONNECTDONE
 	parseCommand "NOTIFYCHANGE" = Proto.parse0 NOTIFYCHANGE
@@ -236,6 +240,8 @@ data LocalF c
 	-- with False.
 	| WaitRefChange (ChangedRefs -> c)
 	-- ^ Waits for one or more git refs to change and returns them.
+	| AddLinkToPeer P2PAddressAuth (Bool -> c)
+	-- ^ Adds a link to a peer using the provided address.
 	deriving (Functor)
 
 type Local = Free LocalF
@@ -255,6 +261,11 @@ auth myuuid t = do
 			net $ sendMessage (ERROR "auth failed")
 			return Nothing
 
+link :: P2PAddressAuth -> Proto Bool
+link addr = do
+	net $ sendMessage (LINK addr)
+	checkSuccess
+
 checkPresent :: Key -> Proto Bool
 checkPresent key = do
 	net $ sendMessage (CHECKPRESENT key)
@@ -354,6 +365,9 @@ serveAuth myuuid = serverLoop handler
 serveAuthed :: UUID -> Proto ()
 serveAuthed myuuid = void $ serverLoop handler
   where
+	handler (LINK addr) = do
+		sendSuccess =<< local (addLinkToPeer addr)
+		return ServerContinue
 	handler (LOCKCONTENT key) = do
 		local $ tryLockContent key $ \locked -> do
 			sendSuccess locked