Adds InvalidRegex TaintConfiguration Error type (#743)

Summary:
**Pre-submission checklist**
- [x] I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running `pip install -r requirements-dev.txt && pre-commit install`
- [x] `pre-commit run`

Adds new error type that can handle Re2 compilation failed exceptions. Previously, when a regex compilation failed, the exception wasn't caught and the program terminated abnormally.

Catch the exception, and throw a custom TaintConfiguration Error to expose the underlying reason why the compilation failed and exit in a more user-friendly fashion.

Pull Request resolved: #743

Test Plan:
- taint.config used:
```json
{
  "sources": [
    {
      "name": "CustomUserControlled",
      "comment": "use to annotate user input"
    }
  ],
  "implicit_sources": {
     "literal_strings": [
       {
         "regexp": "\\d{1Z,3}(\\.\\d{1,3}+",
         "kind": "CustomUserControlled",
         "description": "String that looks like an IP address."
       }
     ]
  },
  "sinks": [
    {
      "name": "CodeExecution",
      "comment": "use to annotate execution of python code"
    }
  ],

  "features": [],

  "rules": [
    {
      "name": "Possible RCE:",
      "code": 5001,
      "sources": [ "CustomUserControlled" ],
      "sinks": [ "CodeExecution" ],
      "message_format": "User specified data may reach a code execution sink"
    }
  ]
}
```

Before:
<img width="990" alt="before" src="https://github.com/facebook/pyre-check/assets/8947010/2d98a7e3-7650-439b-84e5-e300f758bb47">

After:
<img width="990" alt="after" src="https://github.com/facebook/pyre-check/assets/8947010/5aa82960-eae0-4681-b7e8-949079448042">

Fixes part of: MLH-Fellowship#82
Signed-off-by: Abishek V Ashok <abishekvashok@gmail.com>

- `make test`

Reviewed By: saputkin

Differential Revision: D47589737

Pulled By: arthaud

fbshipit-source-id: eb173e8f20f0aec080abc62ea5c3c2ab21d442e5

source/interprocedural_analyses/taint/taintConfiguration.ml

@@ -740,6 +740,10 @@ module Error = struct
     | SinkDuplicate of string
     | TransformDuplicate of string
     | FeatureDuplicate of string
+    | InvalidRegex of {
+        regex: string;
+        reason: string;
+      }
   [@@deriving equal, compare]
 
   type t = {
@@ -824,6 +828,8 @@ module Error = struct
     | SinkDuplicate name -> Format.fprintf formatter "Duplicate entry for sink: `%s`" name
     | TransformDuplicate name -> Format.fprintf formatter "Duplicate entry for transform: `%s`" name
     | FeatureDuplicate name -> Format.fprintf formatter "Duplicate entry for feature: `%s`" name
+    | InvalidRegex { regex; reason } ->
+        Format.fprintf formatter "Invalid regex `%s`: `%s`" regex reason
 
 
   let code = function
@@ -847,6 +853,7 @@ module Error = struct
     | FeatureDuplicate _ -> 18
     | UnsupportedTransform _ -> 19
     | TransformDuplicate _ -> 20
+    | InvalidRegex _ -> 21
 
 
   let show_kind = Format.asprintf "%a" pp_kind
@@ -1325,6 +1332,17 @@ let from_json_list source_json_list =
           ~init:CombinedSourceRules.empty
           ~f:(parse_string_combine_rule ~path ~allowed_sources)
   in
+  let parse_regex ~path ~location pattern =
+    try Result.Ok (Re2.create_exn pattern) with
+    | Re2.Exceptions.Regex_compile_failed error ->
+        Result.Error
+          [
+            Error.create_with_location
+              ~path
+              ~location
+              ~kind:(Error.InvalidRegex { regex = pattern; reason = error });
+          ]
+  in
   let parse_implicit_sinks ~allowed_sinks (path, json) =
     match JsonAst.Json.Util.member "implicit_sinks" json with
     | { JsonAst.Node.value = `Null; _ } -> Result.Ok empty_implicit_sinks
@@ -1352,8 +1370,9 @@ let from_json_list source_json_list =
             parse_sink_reference ~path ~allowed_sinks sink
             |> Result.map_error ~f:(fun error -> [error])
             >>= fun sink_kind ->
-            json_string_member ~path "regexp" json
-            >>| fun pattern -> { sink_kind; pattern = Re2.create_exn pattern })
+            json_string_member_with_location ~path "regexp" json
+            >>= fun (raw_pattern, location) ->
+            parse_regex ~path ~location raw_pattern >>| fun pattern -> { sink_kind; pattern })
           literal_strings
         |> Result.combine_errors
         |> Result.map_error ~f:List.concat
@@ -1379,8 +1398,9 @@ let from_json_list source_json_list =
             parse_source_reference ~path ~allowed_sources source
             |> Result.map_error ~f:(fun error -> [error])
             >>= fun source_kind ->
-            json_string_member ~path "regexp" json
-            >>| fun pattern -> { source_kind; pattern = Re2.create_exn pattern })
+            json_string_member_with_location ~path "regexp" json
+            >>= fun (raw_pattern, location) ->
+            parse_regex ~path ~location raw_pattern >>| fun pattern -> { source_kind; pattern })
           literal_strings
         |> Result.combine_errors
         |> Result.map_error ~f:List.concat

source/interprocedural_analyses/taint/taintConfiguration.mli

@@ -156,6 +156,10 @@ module Error : sig
     | SinkDuplicate of string
     | TransformDuplicate of string
     | FeatureDuplicate of string
+    | InvalidRegex of {
+        regex: string;
+        reason: string;
+      }
   [@@deriving equal, show]
 
   type t = {