Shell: enforce the context hash of the block header

lib_node_shell/block_validator.ml

@@ -486,8 +486,6 @@ let rec worker_loop bv =
                   end
                 end >>= function
                 | Ok result -> begin
-                    lwt_log_info "validated block %a"
-                      Block_hash.pp_short hash >>= fun () ->
                     Lwt_utils.protect ~canceler:bv.canceler begin fun () ->
                       Distributed_db.commit_block
                         net_db hash header operations result
@@ -495,6 +493,8 @@ let rec worker_loop bv =
                     | None ->
                         assert false (* should not happen *)
                     | Some block ->
+                        lwt_log_info "validated block %a"
+                          Block_hash.pp_short hash >>= fun () ->
                         Protocol_validator.prefetch_and_compile_protocols
                           bv.protocol_validator
                           ?peer ~timeout:bv.protocol_timeout

lib_node_shell/state.ml

@@ -441,6 +441,22 @@ module Block = struct
       read_exn net_state header.shell.predecessor >>= fun block ->
       Lwt.return (Some block)
 
+  type error += Inconsistent_hash of Context_hash.t * Context_hash.t
+
+  let () =
+    Error_monad.register_error_kind
+      `Permanent
+      ~id:"inconsistentContextHash"
+      ~title:"Inconsistent commit hash"
+      ~description:
+        "When commiting the context of a block, the announced context \
+         hash was not the one computed at commit time."
+      Data_encoding.(obj2
+                       (req "wrong_context_hash" Context_hash.encoding)
+                       (req "expected_context_hash" Context_hash.encoding))
+      (function Inconsistent_hash (got, exp) -> Some (got, exp) | _ -> None)
+      (fun (got, exp) -> Inconsistent_hash (got, exp))
+
   let store
       net_state block_header operations
       { Updater.context ; message ; max_operations_ttl ;
@@ -457,6 +473,9 @@ module Block = struct
       else begin
         Context.commit
           ~time:block_header.shell.timestamp ?message context >>= fun commit ->
+        fail_unless
+          (Context_hash.equal block_header.shell.context commit)
+          (Inconsistent_hash (commit, block_header.shell.context)) >>=? fun () ->
         let contents = {
           Store.Block.header = block_header ;
           message ;

lib_node_shell/state.mli

@@ -104,6 +104,8 @@ module Block : sig
   val read_opt: Net.t -> Block_hash.t -> block option Lwt.t
   val read_exn: Net.t -> Block_hash.t -> block Lwt.t
 
+  type error += Inconsistent_hash of Context_hash.t * Context_hash.t
+
   val store:
     Net.t ->
     Block_header.t ->