XXE Mitigation #870
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XXE Mitigation #870
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…XXE attacks. The existing functionality resolving svg11.dtd references to the embedded version was preserved.
…to URIs that look like DTD requests. Only checking for 'svg' could match a directory named 'svg' containing a different resource.
mrbean-bremen
approved these changes
May 7, 2021
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Thank you for the contribution, this looks good! Can you please add an entry in the release notes?
H1Gdev
reviewed
May 8, 2021
| private const string SvgTextId = "secretText"; | ||
| private const string Secret = "This is a secret!"; | ||
| } | ||
| } |
H1Gdev
approved these changes
May 9, 2021
|
Added "change" to release notes, as requested. |
|
Thank you! |
github-actions bot
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May 10, 2021
…s Nuget README.md Samples Source Tests doc docfx.json index.md license.txt No longer resolves external resources in DTDs by default, to prevent XXE attacks. The existing functionality resolving svg11.dtd references to the embedded version was preserved. BuildProcessTemplates CONTRIBUTING.md Generators Nuget README.md Samples Source Tests doc docfx.json index.md license.txt Added tests to show the vulnerability and the mitigation. BuildProcessTemplates CONTRIBUTING.md Generators Nuget README.md Samples Source Tests doc docfx.json index.md license.txt Narrowed the check around whether to serve up the embedded svg11.dtd to URIs that look like DTD requests. Only checking for 'svg' could match a directory named 'svg' containing a different resource.
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What perfect timing! We just noticed this problem too. Do you know anything about when the next release will be? Thanks a lot, @gmwalker! ♥ |
This was referenced May 11, 2021
github-actions bot
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Jul 31, 2021
…nerators Nuget README.md Samples Source Tests doc docfx.json index.md license.txt No longer resolves external resources in DTDs by default, to prevent XXE attacks. The existing functionality resolving svg11.dtd references to the embedded version was preserved. BuildProcessTemplates CONTRIBUTING.md Generators Nuget README.md Samples Source Tests doc docfx.json index.md license.txt Added tests to show the vulnerability and the mitigation. BuildProcessTemplates CONTRIBUTING.md Generators Nuget README.md Samples Source Tests doc docfx.json index.md license.txt Narrowed the check around whether to serve up the embedded svg11.dtd to URIs that look like DTD requests. Only checking for 'svg' could match a directory named 'svg' containing a different resource.
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Reference Issue
Fixes #869
What does this implement/fix? Explain your changes.
This address the issue of XXE Vulnerability by changing
SvgDtdResolverso it only resolves external resources ifSvgDocument.ResolveExternalResourcesistrue.SvgDocumentwill no longer resolve external resources by default, to be on the safe side as suggested in the issue.Any other comments?
In
SvgDtdResolverI narrowed the check around whether to serve up the embedded svg11.dtd to URIs that look like DTD requests. Only checking for 'svg' could match a directory named 'svg' containing a different resource altogether - which was a problem I encountered making the unit tests for this pull request.This is my first contribution to this project and I'm looking forward to collaborating with you all.