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buffer: auto random fill Buffer(num) and new Buffer(num) #11808

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buffer: auto random fill Buffer(num) and new Buffer(num) #11808

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5 changes: 4 additions & 1 deletion lib/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -22,11 +22,14 @@
'use strict';

const binding = process.binding('buffer');
const config = process.binding('config');
const { compare: compare_, compareOffset } = binding;
const { isArrayBuffer, isSharedArrayBuffer, isUint8Array } =
process.binding('util');
const bindingObj = {};
const internalUtil = require('internal/util');
const zeroFillBuffers = !!config.zeroFillBuffers;
const randomFill = zeroFillBuffers ? 0 : Math.floor(Math.random() * 256);
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Why not gather crypto.randomBytes() if crypto is available?

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Because we only need a single byte.

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(and there's no need for it to be cryptographically safe)


class FastBuffer extends Uint8Array {
constructor(arg1, arg2, arg3) {
Expand Down Expand Up @@ -102,7 +105,7 @@ function Buffer(arg, encodingOrOffset, length) {
'If encoding is specified then the first argument must be a string'
);
}
return Buffer.allocUnsafe(arg);
return Buffer.allocUnsafe(arg).fill(randomFill);
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Doing this seems... slow?

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Yep, it is. I went with this approach here because it requires the least amount of code. It is more performant to do a memset in the Allocator inside node.cc, but doing so is a bit more intrusive and introduces a branch that impacts all Allocations (albeit, an extremely minor one).

I maintain that the best thing to do would be to just use calloc and zero-fill instead.

}
return Buffer.from(arg, encodingOrOffset, length);
}
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4 changes: 4 additions & 0 deletions src/node_config.cc
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
#include "node.h"
#include "node_buffer.h"
#include "node_i18n.h"
#include "env.h"
#include "env-inl.h"
Expand Down Expand Up @@ -49,6 +50,9 @@ void InitConfig(Local<Object> target,
if (config_preserve_symlinks)
READONLY_BOOLEAN_PROPERTY("preserveSymlinks");

if (zero_fill_all_buffers)
READONLY_BOOLEAN_PROPERTY("zeroFillBuffers");

if (!config_warning_file.empty()) {
Local<String> name = OneByteString(env->isolate(), "warningFile");
Local<String> value = String::NewFromUtf8(env->isolate(),
Expand Down