Fix parsing of table size updates

src/decoder.ml

@@ -64,29 +64,39 @@ let header_field table max_size prefix prefix_length =
   (name, value)
 
 let rec header ({table; max_size_limit; max_field_size} as decoder) =
-  let* b = any_uint8 in
-  if b >= 32 && b < 64 then
-    let* max_size = any_int b 5 <* commit in
-    if max_size <= max_size_limit then begin
-      Dynamic_table.change_max_size table max_size;
-      header decoder
-    end else fail "exceeded size limit"
-  else if table.max_size > max_size_limit then
-    fail "exceeded size limit"
-  else if b >= 128 then
-    let* index = any_int b 7 in
-    match get_indexed_field table index with
-    | name, value -> return (Header.make name value)
-    | exception Invalid_index -> fail "invalid index"
-  else if b >= 64 then
-    let* (name, value) = header_field table max_field_size b 6 <* commit in
-    Dynamic_table.add table (name, value) |> ignore;
-    return (Header.make name value)
-  else
-    let* (name, value) = header_field table max_field_size b 4 <* commit in
-    return (Header.make ~never_index:(b >= 16) name value)
+  at_end_of_input >>= function
+  | true -> return None
+  | false ->
+    let* b = any_uint8 in
+    if b >= 32 && b < 64 then
+      let* max_size = any_int b 5 <* commit in
+      if max_size <= max_size_limit then begin
+        Dynamic_table.change_max_size table max_size;
+        header decoder
+      end else fail "exceeded size limit"
+    else if table.max_size > max_size_limit then
+      fail "exceeded size limit"
+    else if b >= 128 then
+      let* index = any_int b 7 <* commit in
+      match get_indexed_field table index with
+      | name, value -> return (Some (Header.make name value))
+      | exception Invalid_index -> fail "invalid index"
+    else if b >= 64 then
+      let* (name, value) = header_field table max_field_size b 6 <* commit in
+      Dynamic_table.add table (name, value) |> ignore;
+      return (Some (Header.make name value))
+    else
+      let* (name, value) = header_field table max_field_size b 4 <* commit in
+      return (Some (Header.make ~never_index:(b >= 16) name value))
 
-let headers t = many (header t) <* end_of_input
+let headers t =
+  fix begin fun m ->
+    header t >>= function
+    | Some h ->
+      let* hs = m in
+      return (h :: hs)
+    | None -> return []
+  end
 
 let change_table_size_limit ({table; _} as decoder) max_size_limit =
   if max_size_limit < 0 then

src/decoder.mli

@@ -9,7 +9,7 @@ val create : ?max_size_limit:int -> ?max_field_size:int -> unit -> t
     field. The default is 4096.
 *)
 
-val header : t -> Header.t Angstrom.t
+val header : t -> Header.t option Angstrom.t
 (** A parser for one header *)
 
 val headers : t -> Header.t list Angstrom.t

test/test.ml

@@ -25,25 +25,28 @@ let rec headers_of_entries = function
   | Size _ :: entries -> headers_of_entries entries
   | [] -> []
 
-let test entries s = [
-  "Encode", `Quick, begin fun () ->
-    let t = Faraday.create 100 in
-    let encoder = Encoder.create () in
-    entries |> List.iter begin function
-    | Header header -> Encoder.encode_header encoder t header
-    | Size size -> Encoder.change_table_size encoder size
-    end;
-    let s' = Faraday.serialize_to_string t in
-    Alcotest.(check encoding) "same encoding" s s'
-  end;
-  "Decode", `Quick, begin fun () ->
-    let decoder = Decoder.create () in
-    Alcotest.(check (result (list header) reject))
-      "same headers"
-      (Angstrom.parse_string (Decoder.headers decoder) s)
-      (Ok (headers_of_entries entries))
-  end;
-]
+let test_encode entries s =
+  ("Encode", `Quick, begin fun () ->
+      let t = Faraday.create 100 in
+      let encoder = Encoder.create () in
+      entries |> List.iter begin function
+      | Header header -> Encoder.encode_header encoder t header
+      | Size size -> Encoder.change_table_size encoder size
+      end;
+      let s' = Faraday.serialize_to_string t in
+      Alcotest.(check encoding) "same encoding" s s'
+    end)
+
+let test_decode entries s =
+  ("Decode", `Quick, begin fun () ->
+      let decoder = Decoder.create () in
+      Alcotest.(check (result (list header) reject))
+        "same headers"
+        (Angstrom.parse_string (Decoder.headers decoder) s)
+        (Ok (headers_of_entries entries))
+    end)
+
+let test entries s = [test_encode entries s; test_decode entries s]
 
 let test_static =
   let entries = [
@@ -126,6 +129,13 @@ let test_eviction =
      \x40\x04ABCD\x03XYZ" in
   test entries s
 
+let test_empty = test [] ""
+
+let test_resize_only = [
+  test_encode [Size 0] "";
+  test_decode [Size 0] "\x20"
+]
+
 let () =
   Alcotest.run "Hpack" [
     "Static Indexing", test_static; (* RFC7541§2.3.1 *)
@@ -135,4 +145,6 @@ let () =
     "Never Index", test_never_index; (* RFC7541§7.1.3 *)
     "Table Size Update", test_size_update; (* RFC7541§4.2 *)
     "Entry Eviction", test_eviction; (* RFC7541§4.4 *)
+    "Empty header list", test_empty;
+    "Empty header list with table size update", test_resize_only;
   ]