evince fails to open .cbt document from read-only media

[Jean-Baptiste Lallement]

Binary package hint: evince

Evince fails to open .cbt documents from read-only media with error
"Unable to open document
Error opening file: Permission denied"

Test Case:
1. Mount a device containing a .cbt file (comic book in tar format) read-only
2. Open the file with evince
   - > It fails with the error above
3. Copy the file to a RW device and open it
    -> Success

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: evince 2.32.0-0ubuntu5
ProcVersionSignature: Ubuntu 2.6.37-12.26-generic 2.6.37
Uname: Linux 2.6.37-12-generic i686
Architecture: i386
Date: Tue Jan 25 12:54:52 2011
EcryptfsInUse: Yes
ProcEnviron:
 LANGUAGE=en_US:en
 PATH=(custom, user)
 LANG=en_US.utf8
 LC_MESSAGES=en_US.utf8
 SHELL=/bin/bash
ProcVersionSignature_: Ubuntu 2.6.37-12.26-generic 2.6.37
SourcePackage: evince

[bbordwell (benbordwell)]

Could you please upload an example .cbt file to help reproduce this issue? thank you.

[Jean-Baptiste Lallement (jibel)]

Here it is.

[bbordwell (benbordwell)]

Steps I used to reproduce:
1. download example .cbt
2. save it on a flash drive
3. change permisions on said flash drive to read only
4. open .cbt file: permission denied while a .pdf on the same drive still opens.

[tyle (tyle7)]

I had a similar problem with opening cbt-files. Only cbt files in my home directory would open, and not cbt files on other drives.
Checking /etc/apparmor.d/abstractions/evince I found the following line under supported file formats:

/**.[cC][bB][rRzZ7] r,

so I changed that to

/**.[cC][bB][rRtTzZ7] r,

to account for cbt files as well as cbr, cbz, cb7.

I then restarted apparmor:
sudo /etc/init.d/apparmor restart
and now cbt files work everywhere. No idea why it worked in some cases earlier despite being missing from the list.