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buffer: fix range checks for slice() #9174

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merged 1 commit into from
Oct 20, 2016
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trevnorris
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Checklist
  • make -j8 test (UNIX), or vcbuild test nosign (Windows) passes
  • tests and/or benchmarks are included
  • commit message follows commit guidelines
Affected core subsystem(s)

buffer

Description of change

Using the black magic of Symbol.toPrimitive the numeric value of
start/end can be changed when Uint32Value() is called once
Buffer::Fill() is entered. Allowing the CHECK() to be bypassed.

The bug report was only for "start", but the same can be done with
"end". Perform checks for both in node::Buffer::Fill() to make sure the
issue can't be triggered, even if process.binding is used directly.

Include tests for each case. Along with a check to make sure the last
time the value is accessed returns -1. This should be enough to make
sure Buffer::Fill() is receiving the correct value. Along with two tests
against process.binding directly.

Fixes: #9149

R=@nodejs/buffer

@trevnorris trevnorris added the buffer Issues and PRs related to the buffer subsystem. label Oct 18, 2016
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@jasnell jasnell left a comment

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LGTM with green CI

@jasnell jasnell added this to the 7.0.0 milestone Oct 18, 2016
const start = {
[Symbol.toPrimitive]() {
// We use this condition to get around the check in lib/buffer.js
if (ctr <= 0) {
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Minor nit: this can be just ctr === 0.

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@trevnorris trevnorris Oct 19, 2016

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no. in case the internals change then cntr may be less than 0. if that's the case then the value needs to be updated. which is why i have the followup check below of

assert.ok(elseWasLast,
          'internal API changed, -1 no longer in correct location');

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mscdex commented Oct 19, 2016

@deian
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deian commented Oct 19, 2016

Here is another test that this fixes that would otherwise have triggered the CHECK:

const buf = new Buffer('w00t');

Object.defineProperty(buf, 'length', {
  value: 1337,
  enumerable: true
});
buf.fill('');

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mscdex commented Oct 19, 2016

+1 to adding more tests!

@jasnell
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jasnell commented Oct 20, 2016

I'd like to get this landed today to be included in the v7.0.0 RC1. Can we add the additional tests in a separate PR?

Using the black magic of Symbol.toPrimitive the numeric value of
start/end can be changed when Uint32Value() is called once
Buffer::Fill() is entered. Allowing the CHECK() to be bypassed.

The bug report was only for "start", but the same can be done with
"end". Perform checks for both in node::Buffer::Fill() to make sure the
issue can't be triggered, even if process.binding is used directly.

Include tests for each case. Along with a check to make sure the last
time the value is accessed returns -1. This should be enough to make
sure Buffer::Fill() is receiving the correct value. Along with two tests
against process.binding directly.

Fixes: nodejs#9149
PR-URL: nodejs#9174
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <ranziska.hinkelmann@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
@trevnorris trevnorris merged commit 7bffe23 into nodejs:master Oct 20, 2016
jasnell pushed a commit that referenced this pull request Oct 20, 2016
Using the black magic of Symbol.toPrimitive the numeric value of
start/end can be changed when Uint32Value() is called once
Buffer::Fill() is entered. Allowing the CHECK() to be bypassed.

The bug report was only for "start", but the same can be done with
"end". Perform checks for both in node::Buffer::Fill() to make sure the
issue can't be triggered, even if process.binding is used directly.

Include tests for each case. Along with a check to make sure the last
time the value is accessed returns -1. This should be enough to make
sure Buffer::Fill() is receiving the correct value. Along with two tests
against process.binding directly.

Fixes: #9149
PR-URL: #9174
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <ranziska.hinkelmann@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
MylesBorins pushed a commit that referenced this pull request Dec 20, 2016
Using the black magic of Symbol.toPrimitive the numeric value of
start/end can be changed when Uint32Value() is called once
Buffer::Fill() is entered. Allowing the CHECK() to be bypassed.

The bug report was only for "start", but the same can be done with
"end". Perform checks for both in node::Buffer::Fill() to make sure the
issue can't be triggered, even if process.binding is used directly.

Include tests for each case. Along with a check to make sure the last
time the value is accessed returns -1. This should be enough to make
sure Buffer::Fill() is receiving the correct value. Along with two tests
against process.binding directly.

Fixes: #9149
PR-URL: #9174
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <ranziska.hinkelmann@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
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@trevnorris I've gone ahead and landed this on v6.x. If you would like to see it on v4.x please submit a manual backport. Otherwise could you change the label to dont-land-on-v4.x

MylesBorins pushed a commit that referenced this pull request Dec 21, 2016
Using the black magic of Symbol.toPrimitive the numeric value of
start/end can be changed when Uint32Value() is called once
Buffer::Fill() is entered. Allowing the CHECK() to be bypassed.

The bug report was only for "start", but the same can be done with
"end". Perform checks for both in node::Buffer::Fill() to make sure the
issue can't be triggered, even if process.binding is used directly.

Include tests for each case. Along with a check to make sure the last
time the value is accessed returns -1. This should be enough to make
sure Buffer::Fill() is receiving the correct value. Along with two tests
against process.binding directly.

Fixes: #9149
PR-URL: #9174
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <ranziska.hinkelmann@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
@MylesBorins MylesBorins mentioned this pull request Dec 21, 2016
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7 participants