buffer: make methods work on Uint8Array instances

Removes the reliance on prototype bound methods internally
so that Uint8Arrays can be set as the bound `this` value when calling
the various Buffer methods. Introduces some additional tamper protection
by removing internal reliance on writable properties.

Fixes: #56577

Author: nbbeeken

doc/api/buffer.md

@@ -415,6 +415,21 @@ function:
 * [`Buffer.from(arrayBuffer[, byteOffset[, length]])`][`Buffer.from(arrayBuf)`]
 * [`Buffer.from(string[, encoding])`][`Buffer.from(string)`]
 
+### Buffer methods are callable with `Uint8Array` instances
+
+All methods on the Buffer prototype are callable with a `Uint8Array` instance.
+
+```js
+const { toString, write } = Buffer.prototype;
+
+const uint8array = new Uint8Array(5);
+
+write.call(uint8array, 'hello', 0, 5, 'utf8'); // 5
+// <Uint8Array 68 65 6c 6c 6f>
+
+toString.call(uint8array, 'utf8'); // 'hello'
+```
+
 ## Buffers and iteration
 
 `Buffer` instances can be iterated over using `for..of` syntax:
@@ -2058,6 +2073,10 @@ console.log(buf.fill('zz', 'hex'));
 
 <!-- YAML
 added: v5.3.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `value` {string|Buffer|Uint8Array|integer} What to search for.
@@ -2949,6 +2968,9 @@ changes:
     pr-url: https://github.com/nodejs/node/pull/18395
     description: Removed `noAssert` and no implicit coercion of the offset
                  and `byteLength` to `uint32` anymore.
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `offset` {integer} Number of bytes to skip before starting to read. Must
@@ -2996,6 +3018,9 @@ changes:
     pr-url: https://github.com/nodejs/node/pull/18395
     description: Removed `noAssert` and no implicit coercion of the offset
                  and `byteLength` to `uint32` anymore.
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `offset` {integer} Number of bytes to skip before starting to read. Must
@@ -3278,6 +3303,9 @@ changes:
     pr-url: https://github.com/nodejs/node/pull/18395
     description: Removed `noAssert` and no implicit coercion of the offset
                  and `byteLength` to `uint32` anymore.
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `offset` {integer} Number of bytes to skip before starting to read. Must
@@ -3328,6 +3356,9 @@ changes:
     pr-url: https://github.com/nodejs/node/pull/18395
     description: Removed `noAssert` and no implicit coercion of the offset
                  and `byteLength` to `uint32` anymore.
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `offset` {integer} Number of bytes to skip before starting to read. Must
@@ -3771,6 +3802,10 @@ console.log(copy);
 
 <!-- YAML
 added: v0.1.90
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `encoding` {string} The character encoding to use. **Default:** `'utf8'`.
@@ -3909,6 +3944,10 @@ for (const value of buf) {
 
 <!-- YAML
 added: v0.1.90
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/56578
+    description: supports Uint8Array as `this` value
 -->
 
 * `string` {string} String to write to `buf`.

lib/buffer.js

@@ -26,6 +26,7 @@ const {
   ArrayBufferIsView,
   ArrayIsArray,
   ArrayPrototypeForEach,
+  FunctionPrototypeCall,
   MathFloor,
   MathMin,
   MathTrunc,
@@ -133,6 +134,23 @@ FastBuffer.prototype.constructor = Buffer;
 Buffer.prototype = FastBuffer.prototype;
 addBufferPrototypeMethods(Buffer.prototype);
 
+const {
+  asciiWrite,
+  latin1Write,
+  utf8Write,
+  asciiSlice,
+  base64Slice,
+  base64urlSlice,
+  latin1Slice,
+  hexSlice,
+  ucs2Slice,
+  utf8Slice,
+  base64Write,
+  base64urlWrite,
+  hexWrite,
+  ucs2Write,
+} = Buffer.prototype;
+
 const constants = ObjectDefineProperties({}, {
   MAX_LENGTH: {
     __proto__: null,
@@ -634,44 +652,44 @@ const encodingOps = {
     encoding: 'utf8',
     encodingVal: encodingsMap.utf8,
     byteLength: byteLengthUtf8,
-    write: (buf, string, offset, len) => buf.utf8Write(string, offset, len),
-    slice: (buf, start, end) => buf.utf8Slice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(utf8Write, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(utf8Slice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfString(buf, val, byteOffset, encodingsMap.utf8, dir),
   },
   ucs2: {
     encoding: 'ucs2',
     encodingVal: encodingsMap.utf16le,
     byteLength: (string) => string.length * 2,
-    write: (buf, string, offset, len) => buf.ucs2Write(string, offset, len),
-    slice: (buf, start, end) => buf.ucs2Slice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(ucs2Write, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(ucs2Slice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfString(buf, val, byteOffset, encodingsMap.utf16le, dir),
   },
   utf16le: {
     encoding: 'utf16le',
     encodingVal: encodingsMap.utf16le,
     byteLength: (string) => string.length * 2,
-    write: (buf, string, offset, len) => buf.ucs2Write(string, offset, len),
-    slice: (buf, start, end) => buf.ucs2Slice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(ucs2Write, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(ucs2Slice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfString(buf, val, byteOffset, encodingsMap.utf16le, dir),
   },
   latin1: {
     encoding: 'latin1',
     encodingVal: encodingsMap.latin1,
     byteLength: (string) => string.length,
-    write: (buf, string, offset, len) => buf.latin1Write(string, offset, len),
-    slice: (buf, start, end) => buf.latin1Slice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(latin1Write, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(latin1Slice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfString(buf, val, byteOffset, encodingsMap.latin1, dir),
   },
   ascii: {
     encoding: 'ascii',
     encodingVal: encodingsMap.ascii,
     byteLength: (string) => string.length,
-    write: (buf, string, offset, len) => buf.asciiWrite(string, offset, len),
-    slice: (buf, start, end) => buf.asciiSlice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(asciiWrite, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(asciiSlice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfBuffer(buf,
                     fromStringFast(val, encodingOps.ascii),
@@ -683,8 +701,8 @@ const encodingOps = {
     encoding: 'base64',
     encodingVal: encodingsMap.base64,
     byteLength: (string) => base64ByteLength(string, string.length),
-    write: (buf, string, offset, len) => buf.base64Write(string, offset, len),
-    slice: (buf, start, end) => buf.base64Slice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(base64Write, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(base64Slice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfBuffer(buf,
                     fromStringFast(val, encodingOps.base64),
@@ -697,8 +715,8 @@ const encodingOps = {
     encodingVal: encodingsMap.base64url,
     byteLength: (string) => base64ByteLength(string, string.length),
     write: (buf, string, offset, len) =>
-      buf.base64urlWrite(string, offset, len),
-    slice: (buf, start, end) => buf.base64urlSlice(start, end),
+      FunctionPrototypeCall(base64urlWrite, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(base64urlSlice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfBuffer(buf,
                     fromStringFast(val, encodingOps.base64url),
@@ -710,8 +728,8 @@ const encodingOps = {
     encoding: 'hex',
     encodingVal: encodingsMap.hex,
     byteLength: (string) => string.length >>> 1,
-    write: (buf, string, offset, len) => buf.hexWrite(string, offset, len),
-    slice: (buf, start, end) => buf.hexSlice(start, end),
+    write: (buf, string, offset, len) => FunctionPrototypeCall(hexWrite, buf, string, offset, len),
+    slice: (buf, start, end) => FunctionPrototypeCall(hexSlice, buf, start, end),
     indexOf: (buf, val, byteOffset, dir) =>
       indexOfBuffer(buf,
                     fromStringFast(val, encodingOps.hex),
@@ -836,7 +854,7 @@ Buffer.prototype.copy =
 // to their upper/lower bounds if the value passed is out of range.
 Buffer.prototype.toString = function toString(encoding, start, end) {
   if (arguments.length === 0) {
-    return this.utf8Slice(0, this.length);
+    return FunctionPrototypeCall(utf8Slice, this, 0, this.length);
   }
 
   const len = this.length;
@@ -857,7 +875,7 @@ Buffer.prototype.toString = function toString(encoding, start, end) {
     return '';
 
   if (encoding === undefined)
-    return this.utf8Slice(start, end);
+    return FunctionPrototypeCall(utf8Slice, this, start, end);
 
   const ops = getEncodingOps(encoding);
   if (ops === undefined)
@@ -888,7 +906,7 @@ Buffer.prototype[customInspectSymbol] = function inspect(recurseTimes, ctx) {
   const actualMax = MathMin(max, this.length);
   const remaining = this.length - max;
   let str = StringPrototypeTrim(RegExpPrototypeSymbolReplace(
-    /(.{2})/g, this.hexSlice(0, actualMax), '$1 '));
+    /(.{2})/g, FunctionPrototypeCall(hexSlice, this, 0, actualMax), '$1 '));
   if (remaining > 0)
     str += ` ... ${remaining} more byte${remaining > 1 ? 's' : ''}`;
   // Inspect special properties as well, if possible.
@@ -1027,7 +1045,7 @@ Buffer.prototype.lastIndexOf = function lastIndexOf(val, byteOffset, encoding) {
 };
 
 Buffer.prototype.includes = function includes(val, byteOffset, encoding) {
-  return this.indexOf(val, byteOffset, encoding) !== -1;
+  return bidirectionalIndexOf(this, val, byteOffset, encoding, true) !== -1;
 };
 
 // Usage:
@@ -1112,7 +1130,7 @@ function _fill(buf, value, offset, end, encoding) {
 Buffer.prototype.write = function write(string, offset, length, encoding) {
   // Buffer#write(string);
   if (offset === undefined) {
-    return this.utf8Write(string, 0, this.length);
+    return FunctionPrototypeCall(utf8Write, this, string, 0, this.length);
   }
   // Buffer#write(string, encoding)
   if (length === undefined && typeof offset === 'string') {
@@ -1139,9 +1157,9 @@ Buffer.prototype.write = function write(string, offset, length, encoding) {
   }
 
   if (!encoding || encoding === 'utf8')
-    return this.utf8Write(string, offset, length);
+    return FunctionPrototypeCall(utf8Write, this, string, offset, length);
   if (encoding === 'ascii')
-    return this.asciiWrite(string, offset, length);
+    return FunctionPrototypeCall(asciiWrite, this, string, offset, length);
 
   const ops = getEncodingOps(encoding);
   if (ops === undefined)

lib/internal/buffer.js

@@ -4,6 +4,7 @@ const {
   BigInt,
   Float32Array,
   Float64Array,
+  FunctionPrototypeCall,
   MathFloor,
   Number,
   Uint8Array,
@@ -184,11 +185,11 @@ function readUIntLE(offset, byteLength) {
   if (byteLength === 3)
     return readUInt24LE(this, offset);
   if (byteLength === 4)
-    return this.readUInt32LE(offset);
+    return FunctionPrototypeCall(readUInt32LE, this, offset);
   if (byteLength === 2)
-    return this.readUInt16LE(offset);
+    return FunctionPrototypeCall(readUInt16LE, this, offset);
   if (byteLength === 1)
-    return this.readUInt8(offset);
+    return FunctionPrototypeCall(readUInt8, this, offset);
 
   boundsError(byteLength, 6, 'byteLength');
 }
@@ -273,11 +274,11 @@ function readUIntBE(offset, byteLength) {
   if (byteLength === 3)
     return readUInt24BE(this, offset);
   if (byteLength === 4)
-    return this.readUInt32BE(offset);
+    return FunctionPrototypeCall(readUInt32BE, this, offset);
   if (byteLength === 2)
-    return this.readUInt16BE(offset);
+    return FunctionPrototypeCall(readUInt16BE, this, offset);
   if (byteLength === 1)
-    return this.readUInt8(offset);
+    return FunctionPrototypeCall(readUInt8, this, offset);
 
   boundsError(byteLength, 6, 'byteLength');
 }
@@ -353,11 +354,11 @@ function readIntLE(offset, byteLength) {
   if (byteLength === 3)
     return readInt24LE(this, offset);
   if (byteLength === 4)
-    return this.readInt32LE(offset);
+    return FunctionPrototypeCall(readInt32LE, this, offset);
   if (byteLength === 2)
-    return this.readInt16LE(offset);
+    return FunctionPrototypeCall(readInt16LE, this, offset);
   if (byteLength === 1)
-    return this.readInt8(offset);
+    return FunctionPrototypeCall(readInt8, this, offset);
 
   boundsError(byteLength, 6, 'byteLength');
 }
@@ -445,11 +446,11 @@ function readIntBE(offset, byteLength) {
   if (byteLength === 3)
     return readInt24BE(this, offset);
   if (byteLength === 4)
-    return this.readInt32BE(offset);
+    return FunctionPrototypeCall(readInt32BE, this, offset);
   if (byteLength === 2)
-    return this.readInt16BE(offset);
+    return FunctionPrototypeCall(readInt16BE, this, offset);
   if (byteLength === 1)
-    return this.readInt8(offset);
+    return FunctionPrototypeCall(readInt8, this, offset);
 
   boundsError(byteLength, 6, 'byteLength');
 }

test/fixtures/permission/fs-traversal.js

@@ -98,11 +98,6 @@ const uint8ArrayTraversalPath = new TextEncoder().encode(traversalPath);
     return w.apply(this, [traversalPath, ...args]);
   })(Buffer.prototype.utf8Write);
 
-  // Sanity check (remove if the internals of Buffer.from change):
-  // The custom implementation of utf8Write should cause Buffer.from() to encode
-  // traversalPath instead of the sanitized output of resolve().
-  assert.strictEqual(Buffer.from(resolve(traversalPathWithExtraChars)).toString(), traversalPath);
-
   assert.throws(() => {
     fs.readFileSync(traversalPathWithExtraBytes);
   }, common.expectsError({
@@ -125,4 +120,4 @@ const uint8ArrayTraversalPath = new TextEncoder().encode(traversalPath);
   assert.ok(!process.permission.has('fs.write', traversalPath));
   assert.ok(!process.permission.has('fs.read', traversalFolderPath));
   assert.ok(!process.permission.has('fs.write', traversalFolderPath));
-}
+}