Shell: early detection of incompatible injected blocks

src/lib_shell/chain_validator.ml

@@ -408,22 +408,35 @@ let child w =
       try Some (List.assoc (State.Chain.id chain_state) (Worker.list table))
       with Not_found -> None
 
-let validate_block w ?(force = false) hash block operations =
+let assert_fitness_increases ?(force = false) w distant_header =
+  let pv = Worker.state w in
+  let chain_state = Distributed_db.chain_state pv.parameters.chain_db in
+  Chain.head chain_state >>= fun local_header ->
+  fail_when
+    (not force &&
+     Fitness.compare
+       distant_header.Block_header.shell.fitness
+       (State.Block.fitness local_header) <= 0)
+    (failure "Fitness too low")
+
+let assert_checkpoint w hash (header: Block_header.t) =
+  let pv = Worker.state w in
+  let chain_state = Distributed_db.chain_state pv.parameters.chain_db in
+  State.Chain.acceptable_block chain_state hash header >>= fun acceptable ->
+  fail_unless acceptable
+    (Validation_errors.Checkpoint_error (hash, None))
+
+let validate_block w ?force hash block operations =
   let nv = Worker.state w in
   assert (Block_hash.equal hash (Block_header.hash block)) ;
-  Chain.head nv.parameters.chain_state >>= fun head ->
+  assert_fitness_increases ?force w block >>=? fun () ->
-  let head = State.Block.header head in
+  assert_checkpoint w hash block >>=? fun () ->
-  if
-    force || Fitness.(head.shell.fitness < block.shell.fitness)
-  then
   Block_validator.validate
     ~canceler:(Worker.canceler w)
     ~notify_new_block:(notify_new_block w)
     nv.parameters.block_validator
     nv.parameters.chain_db
     hash block operations
-  else
-    failwith "Fitness too low"
 
 let bootstrapped w =
   let { bootstrapped_waiter } = Worker.state w in

src/lib_shell/state.ml

@@ -571,6 +571,11 @@ module Chain = struct
       end
     end
 
+  let acceptable_block chain_state hash (header : Block_header.t) =
+    Shared.use chain_state.chain_data begin fun chain_data ->
+      Locked_block.acceptable chain_data hash header
+    end
+
   let destroy state chain =
     lwt_debug "destroy %a" Chain_id.pp (id chain) >>= fun () ->
     Shared.use state.global_data begin fun { global_store ; chains } ->

src/lib_shell/state.mli

@@ -84,6 +84,13 @@ module Chain : sig
     Int32.t * Block_hash.t ->
     unit Lwt.t
 
+  (** Check that a block is compatible with the current checkpoint.
+      This function assumes that the predecessor is known valid. *)
+  val acceptable_block:
+    chain_state ->
+    Block_hash.t -> Block_header.t ->
+    bool Lwt.t
+
 end
 
 (** {2 Block database} *****************************************************)