Implement more comprehensive SSRF mitigation #6362
Merged
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Motivation and context
The current mitigation approach (resolving the IP address and checking if it's in the private range) is insufficient for a few reasons:
It is susceptible to DNS rebinding (an attacker-controlled DNS name resolving to a public IP address when queried during the check, and to a private IP address afterwards).
It is susceptible to redirect-based attacks (a server with a public address redirecting to a server with a private address).
It is only applied when downloading remote files of tasks (and is not easily reusable).
Replace it with an approach based on smokescreen, a proxy that blocks connections to private IP addresses. In addition, use this proxy for webhooks, since they also make requests to untrusted URLs.
The benefits of smokescreen are as follows:
It's not susceptible to the problems listed above.
It's configurable, so system administrators can allow certain private IP ranges if necessary. This configurability is exposed via the
SMOKESCREEN_OPTS
environment variable.It doesn't require much code to use.
The drawbacks of smokescreen are:
It's not as clear when the request fails due to smokescreen (compared to manual IP validation). To compensate, make the error message in
_download_data
more verbose.The smokescreen project seems to be in early development (judging by the 0.0.x version numbers). Still, Stripe itself uses it, so it should be good enough. It's also not very convenient to set up (on account of not providing binaries), so disable it in development environments.
Keep the scheme check from
_validate_url
. I don't think this check prevents any attacks (as requests only supports http/https to begin with), but it provides a friendly error message in case the user tries to use an unsupported scheme.How has this been tested?
Manual testing.
Checklist
develop
branch[ ] I have updated the documentation accordingly[ ] I have added tests to cover my changes[ ] I have linked related issues (see GitHub docs)[ ] I have increased versions of npm packages if it is necessary(cvat-canvas,
cvat-core,
cvat-data and
cvat-ui)
License
Feel free to contact the maintainers if that's a concern.