Michelson: enforce a maximum stack item type size

src/proto/alpha/constants_repr.ml

@@ -43,6 +43,7 @@ type constants = {
   max_number_of_operations: int list ;
   max_operation_data_length: int ;
   initial_roll_value: Tez_repr.t ;
+  michelson_maximum_type_size: int;
 }
 
 let read_public_key s =
@@ -79,6 +80,7 @@ let default = {
     16 * 1024 ; (* 16kB *)
   initial_roll_value =
     Tez_repr.of_cents_exn 10000_00L ;
+  michelson_maximum_type_size = 1000 ;
 }
 
 let opt (=) def v = if def = v then None else Some v
@@ -136,6 +138,9 @@ let constants_encoding =
        and initial_roll_value =
          opt Tez_repr.(=)
            default.initial_roll_value c.initial_roll_value
+       and michelson_maximum_type_size =
+         opt Compare.Int.(=)
+           default.michelson_maximum_type_size c.michelson_maximum_type_size
        in
        ((( cycle_length,
            voting_period_length,
@@ -149,7 +154,8 @@ let constants_encoding =
            dictator_pubkey),
          (max_number_of_operations,
           max_operation_data_length,
-          initial_roll_value)), ()) )
+          initial_roll_value,
+          michelson_maximum_type_size)), ()) )
     (fun ((( cycle_length,
              voting_period_length,
              time_before_reward,
@@ -162,7 +168,8 @@ let constants_encoding =
              dictator_pubkey),
            (max_number_of_operations,
             max_operation_data_length,
-            initial_roll_value)), ()) ->
+            initial_roll_value,
+            michelson_maximum_type_size)), ()) ->
       { cycle_length =
           unopt default.cycle_length cycle_length ;
         voting_period_length =
@@ -191,6 +198,8 @@ let constants_encoding =
           unopt default.max_operation_data_length max_operation_data_length ;
         initial_roll_value =
           unopt default.initial_roll_value initial_roll_value ;
+        michelson_maximum_type_size =
+          unopt default.michelson_maximum_type_size michelson_maximum_type_size ;
       } )
     Data_encoding.(
       merge_objs
@@ -206,10 +215,11 @@ let constants_encoding =
               (opt "proof_of_work_threshold" int64)
               (opt "bootstrap_keys" (list Ed25519.Public_key.encoding))
               (opt "dictator_pubkey" Ed25519.Public_key.encoding))
-           (obj3
+           (obj4
               (opt "max_number_of_operations" (list uint16))
               (opt "max_number_of_operations" int31)
               (opt "initial_roll_value" Tez_repr.encoding)
+              (opt "michelson_maximum_type_size" uint16)
            ))
         unit)
 

src/proto/alpha/script_ir_translator.ml

@@ -44,6 +44,7 @@ type error += Unexpected_annotation of Script.location
 type error += Invalid_map_body : Script.location * _ stack_ty -> error
 type error += Invalid_map_block_fail of Script.location
 type error += Invalid_iter_body : Script.location * _ stack_ty * _ stack_ty -> error
+type error += Type_too_large : Script.location * int * int -> error
 
 (* Value typing errors *)
 type error += Invalid_constant : Script.location * Script.expr * _ ty -> error
@@ -81,6 +82,58 @@ let default_annot ~default = function
   | None -> default
   | annot -> annot
 
+(* ---- Type size accounting ------------------------------------------------*)
+
+let comparable_type_size : type t. t comparable_ty -> int = function
+  (* No wildcard to force the update when comparable_ty chages. *)
+  | Int_key -> 1
+  | Nat_key -> 1
+  | String_key -> 1
+  | Tez_key -> 1
+  | Bool_key -> 1
+  | Key_hash_key -> 1
+  | Timestamp_key -> 1
+
+let rec type_size : type t. t ty -> int = function
+  | Unit_t -> 1
+  | Int_t -> 1
+  | Nat_t -> 1
+  | Signature_t -> 1
+  | String_t -> 1
+  | Tez_t -> 1
+  | Key_hash_t -> 1
+  | Key_t -> 1
+  | Timestamp_t -> 1
+  | Bool_t -> 1
+  | Pair_t ((l, _), (r, _)) ->
+      1 + type_size l + type_size r
+  | Union_t ((l, _), (r, _)) ->
+      1 + type_size l + type_size r
+  | Lambda_t (arg, ret) ->
+      1 + type_size arg + type_size ret
+  | Option_t t ->
+      1 + type_size t
+  | List_t t ->
+      1 + type_size t
+  | Set_t k ->
+      1 + comparable_type_size k
+  | Map_t (k, v) ->
+      1 + comparable_type_size k + type_size v
+  | Contract_t (arg, ret) ->
+      1 + type_size arg + type_size ret
+
+let rec type_size_of_stack_head
+  : type st. st stack_ty -> up_to:int -> int
+  = fun stack ~up_to ->
+    match stack with
+    | Empty_t -> 0
+    | Item_t (head, tail, _annot) ->
+        if Compare.Int.(up_to > 0) then
+          Compare.Int.max (type_size head)
+            (type_size_of_stack_head tail ~up_to:(up_to - 1))
+        else
+          0
+
 (* ---- Error helpers -------------------------------------------------------*)
 
 let location = function
@@ -1040,7 +1093,18 @@ and parse_instr
     ?type_logger: (int -> Script.expr list -> Script.expr list -> unit) ->
     Script.node -> bef stack_ty -> bef judgement tzresult Lwt.t =
   fun tc_context ctxt ?type_logger script_instr stack_ty ->
-    let return : bef judgement -> bef judgement tzresult Lwt.t = return in
+    let return (judgement : bef judgement) : bef judgement tzresult Lwt.t =
+      match judgement with
+      | Typed { loc; aft } ->
+          (* No instruction builds more than two new stack slots. *)
+          let maximum_type_size = Constants.michelson_maximum_type_size ctxt in
+          let type_size = type_size_of_stack_head aft ~up_to:2 in
+          if Compare.Int.(type_size > maximum_type_size) then
+            fail (Type_too_large (loc, type_size, maximum_type_size))
+          else
+            return judgement
+      | Failed _ ->
+          return judgement in
     let keep_or_rewrite_annot value_annot instr_annot =
       match value_annot, instr_annot with
       | annot, None -> annot
@@ -2329,6 +2393,19 @@ let () =
       | Invalid_iter_body (loc, bef, aft) -> Some (loc, Ex_stack_ty bef, Ex_stack_ty aft)
       | _ -> None)
     (fun (loc, Ex_stack_ty bef, Ex_stack_ty aft) -> Invalid_iter_body (loc, bef, aft)) ;
+  register_error_kind
+    `Permanent
+    ~id:"typeTooLarge"
+    ~title:"Stack item type too large"
+    ~description:"An instruction generated a type larger than the limit."
+    (obj3
+       (req "loc" Script.location_encoding)
+       (req "typeSize" uint16)
+       (req "maximumTypeSize" uint16))
+    (function
+      | Type_too_large (loc, ts, maxts) -> Some (loc, ts, maxts)
+      | _ -> None)
+    (fun (loc, ts, maxts) -> Type_too_large (loc, ts, maxts)) ;
   (* Toplevel errors *)
   register_error_kind
     `Permanent
@@ -2347,7 +2424,6 @@ let () =
       | _ -> None)
     (fun (name, Ex_ty ty,  expr) ->
        Ill_typed_data (name, expr, ty)) ;
-  (* type error += Ill_formed_type of string option * Script.expr *)
   register_error_kind
     `Permanent
     ~id:"illFormedTypeTypeError"

src/proto/alpha/tezos_context.ml

@@ -91,6 +91,9 @@ module Constants = struct
   let max_operation_data_length c =
     let constants = Raw_context.constants c in
     constants.max_operation_data_length
+  let michelson_maximum_type_size c =
+    let constants = Raw_context.constants c in
+    constants.michelson_maximum_type_size
 end
 
 module Delegates_pubkey = Public_key_storage

src/proto/alpha/tezos_context.mli

@@ -280,7 +280,7 @@ module Constants : sig
   val dictator_pubkey: context -> Ed25519.Public_key.t
   val max_number_of_operations: context -> int list
   val max_operation_data_length: context -> int
-
+  val michelson_maximum_type_size: context -> int
 end
 
 (** Global storage for all delegates public keys *)