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buffer: prevent string write offset overflow #65043

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15 changes: 12 additions & 3 deletions lib/internal/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -959,30 +959,39 @@ function writeFloatBackwards(val, offset = 0) {

class FastBuffer extends Uint8Array {}

function asciiWrite(buf, string, offset = 0, length = buf.byteLength - offset) {
function asciiWrite(buf, string, offset = 0, length) {
offset = Number(offset);
if (offset < 0 || offset > buf.byteLength) {
throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');
}
if (length === undefined) length = buf.byteLength - offset;
else length = Number(length);
if (length < 0 || length > buf.byteLength - offset) {
throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
}
return asciiWriteStatic(buf, string, offset, length);
}

function latin1Write(buf, string, offset = 0, length = buf.byteLength - offset) {
function latin1Write(buf, string, offset = 0, length) {
offset = Number(offset);
if (offset < 0 || offset > buf.byteLength) {
throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');
}
if (length === undefined) length = buf.byteLength - offset;
else length = Number(length);
if (length < 0 || length > buf.byteLength - offset) {
throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
}
return latin1WriteStatic(buf, string, offset, length);
}

function utf8Write(buf, string, offset = 0, length = buf.byteLength - offset) {
function utf8Write(buf, string, offset = 0, length) {
offset = Number(offset);
if (offset < 0 || offset > buf.byteLength) {
throw new ERR_BUFFER_OUT_OF_BOUNDS('offset');
}
if (length === undefined) length = buf.byteLength - offset;
else length = Number(length);
if (length < 0 || length > buf.byteLength - offset) {
throw new ERR_BUFFER_OUT_OF_BOUNDS('length');
}
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5 changes: 5 additions & 0 deletions src/node_buffer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1727,6 +1727,11 @@ void SlowWriteString(const FunctionCallbackInfo<Value>& args) {
size_t max_length = 0;

THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[2], 0, &offset));
if (offset > ts_obj_length) {
return node::THROW_ERR_BUFFER_OUT_OF_BOUNDS(
env, "\"offset\" is outside of buffer bounds");
}

THROW_AND_RETURN_IF_OOB(
ParseArrayIndex(env, args[3], ts_obj_length - offset, &max_length));

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14 changes: 14 additions & 0 deletions test/parallel/test-buffer-write.js
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Original file line number Diff line number Diff line change
Expand Up @@ -127,3 +127,17 @@ assert.throws(() => {
}, common.expectsError({
code: 'ERR_BUFFER_OUT_OF_BOUNDS',
}));

for (const method of ['asciiWrite', 'latin1Write', 'utf8Write']) {
let calls = 0;
const offset = {
valueOf() {
calls++;
return 2;
},
};
assert.throws(() => Buffer.alloc(1)[method]('ww', offset, 1), common.expectsError({
code: 'ERR_BUFFER_OUT_OF_BOUNDS',
}));
assert.strictEqual(calls, 1);
}
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