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buffer: make methods work on Uint8Array instances
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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: nodejs#56577
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@nbbeeken
nbbeeken committed Jan 13, 2025
1 parent f4fcf0e commit c73de47
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Showing 4 changed files with 1,187 additions and 35 deletions.
15 changes: 15 additions & 0 deletions doc/api/buffer.md
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Original file line number Diff line number Diff line change
Expand Up @@ -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:
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64 changes: 41 additions & 23 deletions lib/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ const {
ArrayBufferIsView,
ArrayIsArray,
ArrayPrototypeForEach,
FunctionPrototypeCall,
MathFloor,
MathMin,
MathTrunc,
Expand Down Expand Up @@ -135,6 +136,23 @@ 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,
Expand Down Expand Up @@ -633,44 +651,44 @@ 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),
Expand All @@ -682,8 +700,8 @@ 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),
Expand All @@ -696,8 +714,8 @@ 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),
Expand All @@ -709,8 +727,8 @@ 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),
Expand Down Expand Up @@ -835,7 +853,7 @@ 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;
Expand All @@ -856,7 +874,7 @@ 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)
Expand Down Expand Up @@ -887,7 +905,7 @@ 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.
Expand Down Expand Up @@ -1026,7 +1044,7 @@ 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) !== -1;
};

// Usage:
Expand Down Expand Up @@ -1111,7 +1129,7 @@ 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') {
Expand All @@ -1138,9 +1156,9 @@ 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)
Expand Down
25 changes: 13 additions & 12 deletions lib/internal/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ const {
BigInt,
Float32Array,
Float64Array,
FunctionPrototypeCall,
MathFloor,
Number,
Uint8Array,
Expand Down Expand Up @@ -177,11 +178,11 @@ 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');
}
Expand Down Expand Up @@ -266,11 +267,11 @@ 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');
}
Expand Down Expand Up @@ -346,11 +347,11 @@ 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');
}
Expand Down Expand Up @@ -438,11 +439,11 @@ 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');
}
Expand Down
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