Extend scheme validation to inner schemes of jar: URLs#636
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Builds on #633 by recursively validating the inner URL of a jar: URL against the same scheme and host allow-lists. This deliberately changes the previous semantics: for `jar:http://host/...` to be accepted, both `jar` and `http` must appear in the allow-list, and the inner host must satisfy the host allow-list. An alternative considered was the grammar documented by [`XMLConstants`](https://docs.oracle.com/en/java/javase/25/docs/api/java.xml/javax/xml/XMLConstants.html), where tokens like `jar:file` or `jar:http` would explicitly allow specific inner schemes. That grammar is documented but not honored by the JDK reference implementation: `jdk.xml.internal.SecuritySupport.checkAccess` (verified on JDK 8, 17 and 25) strips the `jar:` prefix and matches only the inner scheme as a bare token, so a `jar:http` entry in the allow-list never matches anything. Aligning with the documented spec would have added marginal expressiveness at the cost of diverging from what JDKs actually do.
The classical inversion bug. 😉
garydgregory
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May 12, 2026
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Thank you for the PR @ppkarwasz
- I think I saw some failures fly by on Java 25 due, possibly, to different Java versions throwing different exceptions for missing hosts.
- I left comments scattered throughout.
Thank you!
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Builds on #633 by recursively validating the inner URL of a jar: URL against the same scheme and host allow-lists.
This deliberately changes the previous semantics: for
jar:http://host/...to be accepted, bothjarandhttpmust appear in the allow-list, and the inner host must satisfy the host allow-list.An alternative considered was the grammar documented by
XMLConstants, where tokens likejar:fileorjar:httpwould explicitly allow specific inner schemes. That grammar is documented but not honored by the JDK reference implementation:jdk.xml.internal.SecuritySupport.checkAccess(verified on JDK 8, 17 and 25) strips thejar:prefix and matches only the inner scheme as a bare token, so ajar:httpentry in the allow-list never matches anything. Aligning with the documented spec would have added marginal expressiveness at the cost of diverging from what JDKs actually do.