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>

protocols/gossipsub/src/mcache.rs

@@ -65,34 +65,22 @@ impl MessageCache {
         }
     }
 
-    /// Creates a `MessageCache` with a default message id function.
-    #[allow(dead_code)]
-    pub fn new_default(gossip: usize, history_capacity: usize) -> MessageCache {
-        let default_id = |message: &GossipsubMessage| {
-            // default message id is: source + sequence number
-            let mut source_string = message.source.to_base58();
-            source_string.push_str(&message.sequence_number.to_string());
-            MessageId(source_string)
-        };
-        MessageCache {
-            gossip,
-            msgs: HashMap::default(),
-            history: vec![Vec::new(); history_capacity],
-            msg_id: default_id,
-        }
-    }
-
-    /// Put a message into the memory cache
-    pub fn put(&mut self, msg: GossipsubMessage) {
+    /// Put a message into the memory cache.
+    ///
+    /// Returns the message if it already exists.
+    pub fn put(&mut self, msg: GossipsubMessage) -> Option<GossipsubMessage> {
         let message_id = (self.msg_id)(&msg);
         let cache_entry = CacheEntry {
             mid: message_id.clone(),
             topics: msg.topics.clone(),
         };
 
-        self.msgs.insert(message_id, msg);
-
-        self.history[0].push(cache_entry);
+        let seen_message = self.msgs.insert(message_id, msg);
+        if seen_message.is_none() {
+            // Don't add duplicate entries to the cache.
+            self.history[0].push(cache_entry);
+        }
+        seen_message
     }
 
     /// Get a message with `message_id`
@@ -100,6 +88,14 @@ impl MessageCache {
         self.msgs.get(message_id)
     }
 
+    /// Gets and validates a message with `message_id`.
+    pub fn validate(&mut self, message_id: &MessageId) -> Option<&GossipsubMessage> {
+        self.msgs.get_mut(message_id).map(|message| {
+            message.validated = true;
+            &*message
+        })
+    }
+
     /// Get a list of GossipIds for a given topic
     pub fn get_gossip_ids(&self, topic: &TopicHash) -> Vec<MessageId> {
         self.history[..self.gossip]
@@ -110,7 +106,13 @@ impl MessageCache {
                     .iter()
                     .filter_map(|entry| {
                         if entry.topics.iter().any(|t| t == topic) {
-                            Some(entry.mid.clone())
+                            let mid = &entry.mid;
+                            // Only gossip validated messages
+                            if let Some(true) = self.msgs.get(mid).map(|msg| msg.validated) {
+                                Some(mid.clone())
+                            } else {
+                                None
+                            }
                         } else {
                             None
                         }
@@ -143,30 +145,38 @@ mod tests {
 
     fn gen_testm(x: u64, topics: Vec<TopicHash>) -> GossipsubMessage {
         let u8x: u8 = x as u8;
-        let source = PeerId::random();
+        let source = Some(PeerId::random());
         let data: Vec<u8> = vec![u8x];
-        let sequence_number = x;
+        let sequence_number = Some(x);
 
         let m = GossipsubMessage {
             source,
             data,
             sequence_number,
             topics,
+            signature: None,
+            key: None,
+            validated: true,
         };
         m
     }
 
+    fn new_cache(gossip_size: usize, history: usize) -> MessageCache {
+        let default_id = |message: &GossipsubMessage| {
+            // default message id is: source + sequence number
+            let mut source_string = message.source.as_ref().unwrap().to_base58();
+            source_string.push_str(&message.sequence_number.unwrap().to_string());
+            MessageId::from(source_string)
+        };
+
+        MessageCache::new(gossip_size, history, default_id)
+    }
+
     #[test]
     /// Test that the message cache can be created.
     fn test_new_cache() {
-        let default_id = |message: &GossipsubMessage| {
-            // default message id is: source + sequence number
-            let mut source_string = message.source.to_base58();
-            source_string.push_str(&message.sequence_number.to_string());
-            MessageId(source_string)
-        };
         let x: usize = 3;
-        let mc = MessageCache::new(x, 5, default_id);
+        let mc = new_cache(x, 5);
 
         assert_eq!(mc.gossip, x);
     }
@@ -174,7 +184,7 @@ mod tests {
     #[test]
     /// Test you can put one message and get one.
     fn test_put_get_one() {
-        let mut mc = MessageCache::new_default(10, 15);
+        let mut mc = new_cache(10, 15);
 
         let topic1_hash = Topic::new("topic1".into()).no_hash().clone();
         let topic2_hash = Topic::new("topic2".into()).no_hash().clone();
@@ -200,7 +210,7 @@ mod tests {
     #[test]
     /// Test attempting to 'get' with a wrong id.
     fn test_get_wrong() {
-        let mut mc = MessageCache::new_default(10, 15);
+        let mut mc = new_cache(10, 15);
 
         let topic1_hash = Topic::new("topic1".into()).no_hash().clone();
         let topic2_hash = Topic::new("topic2".into()).no_hash().clone();
@@ -210,7 +220,7 @@ mod tests {
         mc.put(m.clone());
 
         // Try to get an incorrect ID
-        let wrong_id = MessageId(String::from("wrongid"));
+        let wrong_id = MessageId::new(b"wrongid");
         let fetched = mc.get(&wrong_id);
         assert_eq!(fetched.is_none(), true);
     }
@@ -218,10 +228,10 @@ mod tests {
     #[test]
     /// Test attempting to 'get' empty message cache.
     fn test_get_empty() {
-        let mc = MessageCache::new_default(10, 15);
+        let mc = new_cache(10, 15);
 
         // Try to get an incorrect ID
-        let wrong_string = MessageId(String::from("imempty"));
+        let wrong_string = MessageId::new(b"imempty");
         let fetched = mc.get(&wrong_string);
         assert_eq!(fetched.is_none(), true);
     }
@@ -229,7 +239,7 @@ mod tests {
     #[test]
     /// Test adding a message with no topics.
     fn test_no_topic_put() {
-        let mut mc = MessageCache::new_default(3, 5);
+        let mut mc = new_cache(3, 5);
 
         // Build the message
         let m = gen_testm(1, vec![]);
@@ -247,7 +257,7 @@ mod tests {
     #[test]
     /// Test shift mechanism.
     fn test_shift() {
-        let mut mc = MessageCache::new_default(1, 5);
+        let mut mc = new_cache(1, 5);
 
         let topic1_hash = Topic::new("topic1".into()).no_hash().clone();
         let topic2_hash = Topic::new("topic2".into()).no_hash().clone();
@@ -271,7 +281,7 @@ mod tests {
     #[test]
     /// Test Shift with no additions.
     fn test_empty_shift() {
-        let mut mc = MessageCache::new_default(1, 5);
+        let mut mc = new_cache(1, 5);
 
         let topic1_hash = Topic::new("topic1".into()).no_hash().clone();
         let topic2_hash = Topic::new("topic2".into()).no_hash().clone();
@@ -297,7 +307,7 @@ mod tests {
     #[test]
     /// Test shift to see if the last history messages are removed.
     fn test_remove_last_from_shift() {
-        let mut mc = MessageCache::new_default(4, 5);
+        let mut mc = new_cache(4, 5);
 
         let topic1_hash = Topic::new("topic1".into()).no_hash().clone();
         let topic2_hash = Topic::new("topic2".into()).no_hash().clone();