protocols/gossipsub: Add message signing and verification configuration (#1583)

This adds optional message signing and verification to the gossipsub protocol as
per the libp2p specifications.

In addition this commit:

- Removes the LruCache received cache and simply uses the memcache in it's
  place.

- Send subscriptions to all peers

- Prevent invalid messages from being gossiped

- Send grafts when subscriptions are added to the mesh

Co-authored-by: Max Inden <mail@max-inden.de>
Co-authored-by: Rüdiger Klaehn <rklaehn@protonmail.com>
Co-authored-by: Rüdiger Klaehn <rklaehn@gmail.com>

examples/ipfs-private.rs

@@ -35,7 +35,7 @@ use async_std::{io, task};
 use futures::{future, prelude::*};
 use libp2p::{
     core::{either::EitherTransport, transport::upgrade::Version, StreamMuxer},
-    gossipsub::{self, Gossipsub, GossipsubConfigBuilder, GossipsubEvent},
+    gossipsub::{self, Gossipsub, GossipsubConfigBuilder, GossipsubEvent, MessageAuthenticity},
     identify::{Identify, IdentifyEvent},
     identity,
     multiaddr::Protocol,
@@ -178,18 +178,14 @@ fn main() -> Result<(), Box<dyn Error>> {
         ping: Ping,
     }
 
-    impl NetworkBehaviourEventProcess<IdentifyEvent>
-        for MyBehaviour
-    {
+    impl NetworkBehaviourEventProcess<IdentifyEvent> for MyBehaviour {
         // Called when `identify` produces an event.
         fn inject_event(&mut self, event: IdentifyEvent) {
             println!("identify: {:?}", event);
         }
     }
 
-    impl NetworkBehaviourEventProcess<GossipsubEvent>
-        for MyBehaviour
-    {
+    impl NetworkBehaviourEventProcess<GossipsubEvent> for MyBehaviour {
         // Called when `gossipsub` produces an event.
         fn inject_event(&mut self, event: GossipsubEvent) {
             match event {
@@ -204,9 +200,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         }
     }
 
-    impl NetworkBehaviourEventProcess<PingEvent>
-        for MyBehaviour
-    {
+    impl NetworkBehaviourEventProcess<PingEvent> for MyBehaviour {
         // Called when `ping` produces an event.
         fn inject_event(&mut self, event: PingEvent) {
             use ping::handler::{PingFailure, PingSuccess};
@@ -245,11 +239,11 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     // Create a Swarm to manage peers and events
     let mut swarm = {
-        let gossipsub_config = GossipsubConfigBuilder::default()
+        let gossipsub_config = GossipsubConfigBuilder::new()
             .max_transmit_size(262144)
             .build();
         let mut behaviour = MyBehaviour {
-            gossipsub: Gossipsub::new(local_peer_id.clone(), gossipsub_config),
+            gossipsub: Gossipsub::new(MessageAuthenticity::Signed(local_key.clone()), gossipsub_config),
             identify: Identify::new(
                 "/ipfs/0.1.0".into(),
                 "rust-ipfs-example".into(),
@@ -280,12 +274,14 @@ fn main() -> Result<(), Box<dyn Error>> {
     let mut listening = false;
     task::block_on(future::poll_fn(move |cx: &mut Context<'_>| {
         loop {
-            match stdin.try_poll_next_unpin(cx)? {
+            if let Err(e) = match stdin.try_poll_next_unpin(cx)? {
                 Poll::Ready(Some(line)) => {
-                    swarm.gossipsub.publish(&gossipsub_topic, line.as_bytes());
+                    swarm.gossipsub.publish(&gossipsub_topic, line.as_bytes())
                 }
                 Poll::Ready(None) => panic!("Stdin closed"),
                 Poll::Pending => break,
+            } {
+                println!("Publish error: {:?}", e);
             }
         }
         loop {