implement direct and indirect eval

rewriter/src/lib.rs

@@ -2,8 +2,8 @@ pub mod rewrite;
 
 use std::{panic, str::FromStr};
 
-use js_sys::Function;
-use rewrite::{rewrite, EncodeFn};
+use js_sys::{Function, Object, Reflect};
+use rewrite::{rewrite, Config, EncodeFn};
 use url::Url;
 use wasm_bindgen::prelude::*;
 
@@ -30,42 +30,58 @@ fn create_encode_function(encode: Function) -> EncodeFn {
 }
 
 #[wasm_bindgen]
-pub fn rewrite_js(
-    js: &str,
-    url: &str,
-    prefix: String,
-    encode: Function,
-    wrapfn: String,
-    importfn: String,
-) -> Vec<u8> {
+pub fn rewrite_js(js: &str, url: &str, config: Object) -> Vec<u8> {
     rewrite(
         js,
         Url::from_str(url).unwrap(),
-        prefix,
-        create_encode_function(encode),
-        wrapfn,
-        importfn,
+        Config {
+            prefix: Reflect::get(&config, &"prefix".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+            encode: create_encode_function(Reflect::get(&config, &"encode".into()).unwrap().into()),
+            wrapfn: Reflect::get(&config, &"wrapfn".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+            importfn: Reflect::get(&config, &"importfn".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+            rewritefn: Reflect::get(&config, &"rewritefn".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+        },
     )
 }
 
 #[wasm_bindgen]
-pub fn rewrite_js_from_arraybuffer(
-    js: &[u8],
-    url: &str,
-    prefix: String,
-    encode: Function,
-    wrapfn: String,
-    importfn: String,
-) -> Vec<u8> {
+pub fn rewrite_js_from_arraybuffer(js: &[u8], url: &str, config: Object) -> Vec<u8> {
     // we know that this is a valid utf-8 string
     let js = unsafe { std::str::from_utf8_unchecked(js) };
 
     rewrite(
         js,
         Url::from_str(url).unwrap(),
-        prefix,
-        create_encode_function(encode),
-        wrapfn,
-        importfn,
+        Config {
+            prefix: Reflect::get(&config, &"prefix".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+            encode: create_encode_function(Reflect::get(&config, &"encode".into()).unwrap().into()),
+            wrapfn: Reflect::get(&config, &"wrapfn".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+            importfn: Reflect::get(&config, &"importfn".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+            rewritefn: Reflect::get(&config, &"rewritefn".into())
+                .unwrap()
+                .as_string()
+                .unwrap(),
+        },
     )
 }

rewriter/src/main.rs

@@ -11,6 +11,8 @@ pub mod rewrite;
 use rewrite::rewrite;
 use url::Url;
 
+use crate::rewrite::Config;
+
 // Instruction:
 // create a `test.js`,
 // run `cargo run -p oxc_parser --example visitor`
@@ -112,10 +114,13 @@ fn main() -> std::io::Result<()> {
             rewrite(
                 &source_text,
                 Url::from_str("https://google.com/glorngle/si.js").unwrap(),
-                "/scrammedjet/".to_string(),
-                Box::new(encode_string),
-                "$wrap".to_string(),
-                "$import".to_string(),
+                Config {
+                    prefix: "/scrammedjet/".to_string(),
+                    encode: Box::new(encode_string),
+                    wrapfn: "$wrap".to_string(),
+                    importfn: "$import".to_string(),
+                    rewritefn: "$rewrite".to_string(),
+                }
             )
             .as_slice()
         )

rewriter/src/rewrite.rs

@@ -30,18 +30,24 @@ pub type EncodeFn = Box<dyn Fn(String) -> String>;
 struct Rewriter {
     jschanges: Vec<JsChange>,
     base: Url,
-    prefix: String,
-    wrapfn: String,
-    importfn: String,
-    encode: EncodeFn,
+    config: Config,
 }
+
+pub struct Config {
+    pub prefix: String,
+    pub wrapfn: String,
+    pub importfn: String,
+    pub rewritefn: String,
+    pub encode: EncodeFn,
+}
+
 impl Rewriter {
     fn rewrite_url(&mut self, url: String) -> String {
         let url = self.base.join(&url).unwrap();
 
-        let urlencoded = (self.encode)(url.to_string());
+        let urlencoded = (self.config.encode)(url.to_string());
 
-        format!("\"{}{}\"", self.prefix, urlencoded)
+        format!("\"{}{}\"", self.config.prefix, urlencoded)
     }
 }
 
@@ -57,24 +63,49 @@ impl<'a> Visit<'a> for Rewriter {
         if UNSAFE_GLOBALS.contains(&it.name.to_string().as_str()) {
             self.jschanges.push(JsChange::GenericChange {
                 span: it.span,
-                text: format!("({}({}))", self.wrapfn, it.name),
+                text: format!("({}({}))", self.config.wrapfn, it.name),
             });
         }
     }
     fn visit_this_expression(&mut self, it: &oxc_ast::ast::ThisExpression) {
         self.jschanges.push(JsChange::GenericChange {
             span: it.span,
-            text: format!("({}(this))", self.wrapfn),
+            text: format!("({}(this))", self.config.wrapfn),
         });
     }
 
     fn visit_debugger_statement(&mut self, it: &oxc_ast::ast::DebuggerStatement) {
+        // delete debugger statements entirely. some sites will spam debugger as an anti-debugging measure, and we don't want that!
         self.jschanges.push(JsChange::GenericChange {
             span: it.span,
             text: "".to_string(),
         });
     }
 
+    // we can't overwrite window.eval in the normal way because that would make everything an
+    // indirect eval, which could break things. we handle that edge case here
+    fn visit_call_expression(&mut self, it: &oxc_ast::ast::CallExpression<'a>) {
+        if let Expression::Identifier(s) = &it.callee {
+            // if it's optional that actually makes it an indirect eval which is handled separately
+            if s.name == "eval" && !it.optional {
+                self.jschanges.push(JsChange::GenericChange {
+                    span: Span::new(s.span.start, s.span.end + 1),
+                    text: format!("eval({}(", self.config.rewritefn),
+                });
+                self.jschanges.push(JsChange::GenericChange {
+                    span: Span::new(it.span.end, it.span.end),
+                    text: ")".to_string(),
+                });
+
+                // then we walk the arguments, but not the callee, since we want it to resolve to
+                // the real eval
+                walk::walk_arguments(self, &it.arguments);
+                return;
+            }
+        }
+        walk::walk_call_expression(self, it);
+    }
+
     fn visit_import_declaration(&mut self, it: &oxc_ast::ast::ImportDeclaration<'a>) {
         let name = it.source.value.to_string();
         let text = self.rewrite_url(name);
@@ -87,7 +118,7 @@ impl<'a> Visit<'a> for Rewriter {
     fn visit_import_expression(&mut self, it: &oxc_ast::ast::ImportExpression<'a>) {
         self.jschanges.push(JsChange::GenericChange {
             span: Span::new(it.span.start, it.span.start + 6),
-            text: format!("({}(\"{}\"))", self.importfn, self.base),
+            text: format!("({}(\"{}\"))", self.config.importfn, self.base),
         });
         walk::walk_import_expression(self, it);
     }
@@ -122,7 +153,7 @@ impl<'a> Visit<'a> for Rewriter {
                         if UNSAFE_GLOBALS.contains(&s.name.to_string().as_str()) && p.shorthand {
                             self.jschanges.push(JsChange::GenericChange {
                                 span: s.span,
-                                text: format!("{}: ({}({}))", s.name, self.wrapfn, s.name),
+                                text: format!("{}: ({}({}))", s.name, self.config.wrapfn, s.name),
                             });
                             return;
                         }
@@ -238,7 +269,7 @@ fn expression_span(e: &Expression) -> Span {
 }
 
 // js MUST not be able to get a reference to any of these because sbx
-const UNSAFE_GLOBALS: [&str; 8] = [
+const UNSAFE_GLOBALS: [&str; 9] = [
     "window",
     "self",
     "globalThis",
@@ -247,16 +278,10 @@ const UNSAFE_GLOBALS: [&str; 8] = [
     "top",
     "location",
     "document",
+    "eval",
 ];
 
-pub fn rewrite(
-    js: &str,
-    url: Url,
-    prefix: String,
-    encode: EncodeFn,
-    wrapfn: String,
-    importfn: String,
-) -> Vec<u8> {
+pub fn rewrite(js: &str, url: Url, config: Config) -> Vec<u8> {
     let allocator = Allocator::default();
     let source_type = SourceType::default();
     let ret = Parser::new(&allocator, js, source_type).parse();
@@ -274,10 +299,7 @@ pub fn rewrite(
     let mut ast_pass = Rewriter {
         jschanges: Vec::new(),
         base: url,
-        prefix,
-        encode,
-        wrapfn,
-        importfn,
+        config,
     };
 
     ast_pass.visit_program(&program);

src/client/index.ts

@@ -8,10 +8,6 @@ export const issw = "ServiceWorkerGlobalScope" in self;
 export const isdedicated = "DedicatedWorkerGlobalScope" in self;
 export const isshared = "SharedWorkerGlobalScope" in self;
 
-export const wrapfn = "$scramjet$wrap";
-export const trysetfn = "$scramjet$tryset";
-export const importfn = "$scramjet$import";
-
 dbg.log("scrammin");
 // if it already exists, that means the handlers have probably already been setup by the parent document
 if (!(ScramjetClient.SCRAMJET in self)) {

src/client/shared.ts

@@ -10,3 +10,5 @@ export const {
 		rewriteWorkers,
 	},
 } = self.$scramjet.shared;
+
+export const config = self.$scramjet.config;

src/client/shared/eval.ts

@@ -1,24 +1,47 @@
 import { ScramjetClient, ProxyCtx } from "../client";
-import { rewriteJs } from "../shared";
+import { config, rewriteJs } from "../shared";
 
 function rewriteFunction(ctx: ProxyCtx) {
-    for (const i in ctx.args) {
-        ctx.args[i] = rewriteJs(ctx.args[i]);
-    }
+	for (const i in ctx.args) {
+		ctx.args[i] = rewriteJs(ctx.args[i]);
+	}
 
-    ctx.return(ctx.fn(...ctx.args));
+	ctx.return(ctx.fn(...ctx.args));
 }
 
 export default function (client: ScramjetClient, self: Self) {
-    client.Proxy("Function", {
-        apply(ctx) {
-            rewriteFunction(ctx);
-        },
+	client.Proxy("Function", {
+		apply(ctx) {
+			rewriteFunction(ctx);
+		},
 
-        construct(ctx) {
-            rewriteFunction(ctx);
-        },
-    });
+		construct(ctx) {
+			rewriteFunction(ctx);
+		},
+	});
 
-    Function.prototype.constructor = Function;
+	Function.prototype.constructor = Function;
+
+	// used for proxying *direct eval*
+	// eval("...") -> eval($scramjet$rewrite("..."))
+	Object.defineProperty(self, config.rewritefn, {
+		value: function (js: any) {
+			if (typeof js !== "string") return js;
+
+			const rewritten = rewriteJs(js, client.url);
+
+			return rewritten;
+		},
+		writable: false,
+		configurable: false,
+	});
+}
+
+export function indirectEval(this: ScramjetClient, js: any) {
+	// > If the argument of eval() is not a string, eval() returns the argument unchanged
+	if (typeof js !== "string") return js;
+
+	const indirection = this.global.eval;
+
+	return indirection(rewriteJs(js, this.url) as string);
 }

src/client/shared/import.ts

@@ -1,8 +1,7 @@
-import { encodeUrl } from "../shared";
-import { importfn } from "../";
+import { config, encodeUrl } from "../shared";
 
 export default function (client, self) {
-	self[importfn] = function (base) {
+	self[config.importfn] = function (base) {
 		return function (url) {
 			const resolved = new URL(url, base).href;
 

src/client/shared/wrap.ts

@@ -1,11 +1,12 @@
-import { iswindow, isworker, trysetfn, wrapfn } from "..";
+import { iswindow, isworker } from "..";
 import { ScramjetClient } from "../client";
+import { config } from "../shared";
 
 export default function (client: ScramjetClient, self: typeof globalThis) {
 	// the main magic of the proxy. all attempts to access any "banned objects" will be redirected here, and instead served a proxy object
 	// this contrasts from how other proxies will leave the root object alone and instead attempt to catch every member access
 	// this presents some issues (see element.ts), but makes us a good bit faster at runtime!
-	Object.defineProperty(self, wrapfn, {
+	Object.defineProperty(self, config.wrapfn, {
 		value: function (identifier: any, args: any) {
 			if (args && typeof args === "object" && args.length === 0)
 				for (const arg of args) {
@@ -58,7 +59,7 @@ export default function (client: ScramjetClient, self: typeof globalThis) {
 	// ((t)=>$scramjet$tryset(location,"+=",t)||location+=t)(...);
 	// it has to be a discrete function because there's always the possibility that "location" is a local variable
 	// we have to use an IIFE to avoid duplicating side-effects in the getter
-	Object.defineProperty(self, trysetfn, {
+	Object.defineProperty(self, config.trysetfn, {
 		value: function (lhs: any, op: string, rhs: any) {
 			if (lhs instanceof Location) {
 				// @ts-ignore

src/client/window.ts

@@ -1,6 +1,7 @@
 import { encodeUrl } from "../shared/rewriters/url";
 import { ScramjetClient } from "./client";
-import { wrapfn } from ".";
+import { indirectEval } from "./shared/eval";
+import { config } from "./shared";
 
 export function createWindowProxy(
 	client: ScramjetClient,
@@ -9,16 +10,17 @@ export function createWindowProxy(
 	return new Proxy(self, {
 		get(target, prop) {
 			const propIsString = typeof prop === "string";
-			if (propIsString && prop === "location") {
-				return client.locationProxy;
-			} else if (
+			if (prop === "location") return client.locationProxy;
+
+			if (
 				propIsString &&
 				["window", "top", "self", "globalThis", "parent"].includes(prop)
-			) {
-				return self[wrapfn](self[prop]);
-			} else if (propIsString && prop === "$scramjet") {
-				return;
-			}
+			)
+				return self[config.wrapfn](self[prop]);
+
+			if (prop === "$scramjet") return;
+
+			if (prop === "eval") return indirectEval.bind(client);
 
 			const value = Reflect.get(target, prop);
 

src/scramjet.config.ts

@@ -5,6 +5,10 @@ if (!self.$scramjet) {
 self.$scramjet.config = {
 	prefix: "/scramjet/",
 	codec: self.$scramjet.codecs.plain,
+	wrapfn: "$scramjet$wrap",
+	trysetfn: "$scramjet$tryset",
+	importfn: "$scramjet$import",
+	rewritefn: "$scramjet$rewrite",
 	config: "/scram/scramjet.config.js",
 	shared: "/scram/scramjet.shared.js",
 	worker: "/scram/scramjet.worker.js",

src/shared/rewriters/js.ts

@@ -24,25 +24,21 @@ export function rewriteJs(js: string | ArrayBuffer, origin?: URL) {
 	if ("window" in globalThis) origin ??= new URL(decodeUrl(location.href));
 
 	const before = performance.now();
+	const cfg = {
+		prefix: self.$scramjet.config.prefix,
+		codec: self.$scramjet.config.codec.encode,
+		wrapfn: self.$scramjet.config.wrapfn,
+		trysetfn: self.$scramjet.config.trysetfn,
+		importfn: self.$scramjet.config.importfn,
+		rewritefn: self.$scramjet.config.rewritefn,
+	};
 	if (typeof js === "string") {
-		js = new TextDecoder().decode(
-			rewrite_js(
-				js,
-				origin.toString(),
-				self.$scramjet.config.prefix,
-				self.$scramjet.config.codec.encode as any,
-				"$scramjet$wrap",
-				"$scramjet$import"
-			)
-		);
+		js = new TextDecoder().decode(rewrite_js(js, origin.toString(), cfg));
 	} else {
 		js = rewrite_js_from_arraybuffer(
 			new Uint8Array(js),
 			origin.toString(),
-			self.$scramjet.config.prefix,
-			self.$scramjet.config.codec.encode as any,
-			"$scramjet$wrap",
-			"$scramjet$import"
+			cfg
 		);
 	}
 	const after = performance.now();

src/types.d.ts

@@ -34,6 +34,10 @@ declare global {
 			config: {
 				prefix: string;
 				codec: Codec;
+				wrapfn: string;
+				trysetfn: string;
+				importfn: string;
+				rewritefn: string;
 				config: string;
 				shared: string;
 				worker: string;