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|
open Core
open Yojson.Basic.Util
(* AST types. *)
type expr = Term of term | Every of string option * string * term * query
[@@deriving eq, show]
and literal =
| Exists of expr list * with_modifier option
| Expr of expr * with_modifier option
| Negate of expr * with_modifier option
[@@deriving eq, show]
and query = literal list [@@deriving eq, show]
and term =
| Scalar of scalar
| Var of string
| Ref of reference
| Array of term list
| Object of (object_key * term) list
| Set of term list
| ArrayComprehension of term * query
| ObjectComprehension of (object_key * term) * query
| SetComprehension of term * query
| Call of reference * term list
[@@deriving eq, show]
and scalar = String of string | Number of float | Bool of bool | Null
[@@deriving eq, show]
and reference = ref_target * term list [@@deriving eq, show]
and ref_target =
| Var of string
| Array of term list
| Object of (object_key * term) list
| Set of term list
| ArrayComprehension of term * query
| ObjectComprehension of (object_key * term) * query
| SetComprehension of term * query
| Call of reference * term list
[@@deriving eq, show]
and object_key = Scalar of scalar | Ref of reference | Var of string
[@@deriving eq, show]
and with_modifier = (term * term) list [@@deriving eq, show]
type assign_operator = Assign | Unify [@@deriving eq, show]
type rule_head_lhs = reference [@@deriving eq, show]
type rule_head_rhs =
| Assignment of assign_operator * term
| Function of assign_operator * string list * term
| Set of term
[@@deriving eq, show]
type rule_head = rule_head_lhs * rule_head_rhs [@@deriving eq, show]
type rule = {
default : bool;
head : rule_head;
body : query;
otherwise : rule option;
}
[@@deriving eq, show]
type import = { alias : string option; path : reference } [@@deriving eq, show]
type package = { path : reference; imports : import list; policy : rule list }
[@@deriving eq, show]
(* Additional JSON utility functions. *)
let is_null : Yojson.Basic.t -> bool = function `Null -> true | _ -> false
let to_bool_or_false : Yojson.Basic.t -> bool = function
| `Bool b -> b
| _ -> false
let to_list_or_empty : Yojson.Basic.t -> Yojson.Basic.t list = function
| `Null -> []
| `List xs -> xs
| _ -> failwith "Not a list or null"
let object_key_of_term : term -> object_key = function
| Scalar s -> Scalar s
| Ref r -> Ref r
| Var v -> Var v
| _ -> failwith "failed to convert term to object_key"
(* Code to parse the JSON output of `opa parse`. *)
let rec parse_term (tree : Yojson.Basic.t) : term =
let term_type = tree |> member "type" |> to_string in
match term_type with
| "var" -> Var (tree |> member "value" |> to_string)
| "ref" -> Ref (tree |> member "value" |> to_list |> parse_ref)
| "boolean" -> Scalar (Bool (tree |> member "value" |> to_bool))
| "number" -> Scalar (Number (tree |> member "value" |> to_number))
| "string" -> Scalar (String (tree |> member "value" |> to_string))
| "array" ->
Array (tree |> member "value" |> to_list |> List.map ~f:parse_term)
| "set" -> Set (tree |> member "value" |> to_list |> List.map ~f:parse_term)
| "object" ->
Object
(tree |> member "value" |> to_list
|> List.map ~f:(function
| `List [ x; y ] ->
(x |> parse_term |> object_key_of_term, y |> parse_term)
| _ -> failwith "ill-formed object"))
| "arraycomprehension" ->
ArrayComprehension
( tree |> member "value" |> member "term" |> parse_term,
tree |> member "value" |> member "body" |> to_list
|> List.map ~f:parse_literal )
| "setcomprehension" ->
SetComprehension
( tree |> member "value" |> member "term" |> parse_term,
tree |> member "value" |> member "body" |> to_list
|> List.map ~f:parse_literal )
| "objectcomprehension" ->
ObjectComprehension
( ( tree |> member "value" |> member "key" |> parse_term
|> object_key_of_term,
tree |> member "value" |> member "value" |> parse_term ),
tree |> member "value" |> member "body" |> to_list
|> List.map ~f:parse_literal )
| "call" -> (
match tree |> member "value" |> to_list with
| func :: args ->
Call
( func |> member "value" |> to_list |> parse_ref,
List.map ~f:parse_term args )
| _ -> failwith "ill-formed call")
| _ -> failwith ("unsupported term type " ^ term_type)
and parse_literal tree : literal =
let with_expr = tree |> member "with" in
let with_expr =
match with_expr with
| `Null -> None
| `List xs ->
Some
(List.map xs ~f:(fun x ->
( x |> member "target" |> parse_term,
x |> member "value" |> parse_term )))
| _ ->
failwith
("ill-formed with expression " ^ Yojson.Basic.to_string with_expr)
in
match tree |> member "terms" with
| `List (func :: args) ->
Expr
( Term
(Call
( func |> member "value" |> to_list |> parse_ref,
List.map ~f:parse_term args )),
with_expr )
| `List _ -> failwith "ill-formed call"
| x ->
if not (x |> member "symbols" |> is_null) then
Exists
( x |> member "symbols" |> to_list
|> List.map ~f:(fun x -> Term (parse_term x)),
with_expr )
else if x |> member "domain" |> is_null then
Expr (Term (parse_term x), with_expr)
else
Expr
( Every
( (if x |> member "key" |> is_null then None
else Some (x |> member "key" |> member "value" |> to_string)),
x |> member "value" |> member "value" |> to_string,
x |> member "domain" |> parse_term,
List.map ~f:parse_literal (x |> member "body" |> to_list) ),
with_expr )
and parse_ref_target tree : ref_target =
let term = parse_term tree in
match term with
| Var term -> Var term
| Array term -> Array term
| Object term -> Object term
| Set term -> Set term
| ArrayComprehension (term, y) -> ArrayComprehension (term, y)
| ObjectComprehension (term, y) -> ObjectComprehension (term, y)
| SetComprehension (term, y) -> SetComprehension (term, y)
| Call (term, y) -> Call (term, y)
| _ -> failwith ("unsupported ref_target " ^ show_term term)
and parse_ref tree =
match tree with
| target :: args -> (parse_ref_target target, List.map ~f:parse_term args)
| _ -> failwith "empty reference"
let parse_head tree =
(* Variables are desugared to empty references. *)
let lhs = tree |> member "ref" |> to_list |> parse_ref in
let assign_operator =
if tree |> member "assign" |> to_bool_or_false then Assign else Unify
in
let rhs =
if not (tree |> member "key" |> is_null) then
Set (tree |> member "key" |> parse_term)
else if tree |> member "args" |> to_bool_or_false then
Function
( assign_operator,
tree |> member "args" |> to_list
|> List.map ~f:(fun x -> x |> member "value" |> to_string),
tree |> member "value" |> parse_term )
else Assignment (assign_operator, tree |> member "value" |> parse_term)
in
(lhs, rhs)
let rec parse_rule tree =
{
default = tree |> member "default" |> to_bool_or_false;
head = tree |> member "head" |> parse_head;
body = List.map ~f:parse_literal (tree |> member "body" |> to_list_or_empty);
otherwise =
(match tree |> member "else" with
| `Null -> None
| else_branch -> Some (parse_rule else_branch));
}
let parse_import_path tree =
match tree |> member "type" |> to_string with
| "ref" -> tree |> member "value" |> to_list |> parse_ref
| _ -> failwith "unimplemented"
let parse_import tree =
{
alias = tree |> member "alias" |> to_string_option;
path = tree |> member "path" |> parse_import_path;
}
let parse_package tree = tree |> member "path" |> to_list |> parse_ref
let parse_tree tree =
{
path = tree |> member "package" |> parse_package;
imports =
List.map ~f:parse_import (tree |> member "imports" |> to_list_or_empty);
policy = List.map ~f:parse_rule (tree |> member "rules" |> to_list_or_empty);
}
(* OPA interaction. *)
let invoke ?(stdin = "") ?(env = [||]) cmd =
let ic, oc, ec = UnixLabels.open_process_full cmd ~env in
Out_channel.output_string oc stdin;
Out_channel.close oc;
(In_channel.input_all ic, In_channel.input_all ec)
let ast_of_string policy_code =
let stdout, _ =
invoke "/home/jakob/.local/bin/opa parse -f json /dev/stdin"
~stdin:policy_code ~env:[||]
in
Yojson.Basic.from_string stdout |> parse_tree
|
