This content originally appeared on Sass Blog and was authored by Natalie Weizenbaum
The Sass team was recently alerted by prolific external contributor @ntkme to a security issue in our release process.
TL;DR permalinkTL;DR
If you’re using Linux or Mac OS, run ls -ax path/to/sass. If the last group of
letters in the first column contains w, you’re vulnerable:
Vulnerable:
-rwxr-xrwx 1 nweiz primarygroup 407 Dec 13 12:33 sass-1.56.2/sass
Not vulnerable:
-rwxr-xr-x 1 nweiz primarygroup 407 Dec 13 12:33 sass-1.56.2/sass
If you’re using the sass-embedded package, do the same thing for
node_modules/sass-embedded/dist/lib/src/vendor/dart-sass-embedded/dart-sass-embedded.
Who’s Affected? permalinkWho’s Affected?
While we don’t expect this issue to be a problem for the vast majority of users, it does affect the following groups:
Users who downloaded the stand-alone Dart Sass, Dart Sass Embedded, or Sass Migrator
.tar.gzarchives from the Dart Sass website and extracted them as the Unix root user.Users who installed the
sass-embeddednpm package as the Unix root user prior to version 1.54.5.Users who installed the “non-native” version of the community-maintained
sass-embeddedRubyGems package as the Unix root user prior to version 1.56.2.Users on multi-user systems who downloaded the stand-alone Dart Sass, Dart Sass Embedded, or Sass Migrator
.tar.gzarchives from the Dart Sass website and explicitly passed the-p/--preserve-permissionsflag when extracting them.
Users who installed Dart Sass via the sass npm package, Homebrew, or
Chocolatey are categorically not at risk, nor are users on Windows.
We strongly recommend that users in these vulnerable groups delete and
re-install Sass. All the .tar.gz files on GitHub have been scrubbed to remove
the vulnerability, so you can reinstall the same version you were previously
using without needing to upgrade to the latest version.
This is a privilege-escalation issue, which means it could allow a hypothetical attacker with access to a low-privilege account on your computer to escalate their access to your account’s privileges. However, this also means that it’s not a risk unless an attacker already has access to an account on your machine.
What went wrong? permalinkWhat went wrong?
We were inadvertently uploading .tar.gz archives with permissions metadata
indicating that executable files could be overwritten by all users, not just the
owner.
In most cases, this metadata is ignored when extracting the archives and the
permissions are set to only be writable by the user doing the extraction.
However, when extracting archives as the Unix root user or explicitly passing
the -p/--preserve-permissions flag, the permissions for the extracted files
are set according to the archive’s metadata. Because the metadata was incorrect,
an attacker with access to a low-privilege account would be able to overwrite
the executable file and escalate their privileges once it’s executed.
How did this happen? permalinkHow did this happen?
Dart Sass is automatically deployed to various different release platforms using
a Dart package called cli_pkg, which is also written maintained by the Sass
team. This package uses the Dart archive package to generate .tar.gz files
for stand-alone release packages which are then uploaded to GitHub, and when
initially writing the code to use this package I wrote the following function:
ArchiveFile fileFromBytes(String path, List<int> data,
{bool executable = false}) =>
ArchiveFile(path, data.length, data)
..mode = executable ? 495 : 428
..lastModTime = DateTime.now().millisecondsSinceEpoch ~/ 1000;
My intention was to set the executable mode to 755 (read/write/execute for the
owner, read/execute only for the other users) and the non-executable mode to
644 (read/write for the owner, read-only for other users). However, Dart
doesn’t support literal octal numbers and I must have done the decimal-to-octal
conversion wrong. The actual permissions that got set were 757
(read/write/execute for the owner and other users, read/execute for the
group) and 654 (read/write for the owner, read/execute for the group, and
read-only for other users).
This went unnoticed for several years, until @ntkme notified us of the issue
last week and provided a fix to cli_pkg.
What’s been done? permalinkWhat’s been done?
We’ve released cli_pkg 2.1.7 which sets the archive permissions correctly. In
addition, we’ve updated all .tar.gz files in the Dart Sass, Dart Sass
Embedded, and Sass Migrator repositories to correctly limit write permissions to
only the owner of the files. We’re announcing the vulnerability here and on the
@SassCSS Twitter account.
This content originally appeared on Sass Blog and was authored by Natalie Weizenbaum
Natalie Weizenbaum | Sciencx (2022-12-10T00:00:00+00:00) Security Alert: Tar Permissions. Retrieved from https://www.scien.cx/2022/12/10/security-alert-tar-permissions/
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