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[Libcdio-devel] Rock Ridge and libisofs/xorriso 'AL' extension

From: Pete Batard
Subject: [Libcdio-devel] Rock Ridge and libisofs/xorriso 'AL' extension
Date: Tue, 25 Jul 2017 00:08:27 +0100
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1


I recently found that some Rock Ridge ISOs processed using the latest libcdio were mangling file names. Instead names being returned with the expected Rock Ridge data, I found that I got something like "FILENAME.EXT;1" from libcdio, which created issues with my downstream code. I was also able to confirm that this behaviour wasn't happening with some older versions of the library.

Looking further into this, I identified that the commit that brought this change was 8b96bd3f ("Guard against malformed rockridge iso" from 2015.05.08), where the Rock Ridge SUSPs are now being checked against a set of supported extensions, and that the issue happened if the ISO being processed (such as kali-linux-2017.1-amd64.iso) was using the nonstandard Rock Ridge extension 'AL'.

Obviously, as per the switch statement around line 172 of rock.c, libcdio does not currently recognize 'AL' as a valid Rock Ridge extension (whereas previous code just let it pass through), hence the problem observed.

Digging further into this still, I eventually managed to determine that the 'AL' Rock Ridge extension is something that the libburnia people (the developers behind libisofs & xorriso) introduced as part of their custom "Arbitrary Attribute Interchange Protocol" or AAIP, which they have documented at

From what I gather, they created AAIP along with the 'AL' generic extension mostly in order to carry POSIX ACLs into an ISO 9660 filesystem. These can then get added to the Rock Ridge data with the -acl option of xorriso.

My questions therefore are:

- Should libcdio add support for the 'AL' Rock Ridge extension?
- If so, is there anybody on this list willing to do it?



NB: There also

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