[Bug] OPDS mime types for cbz/cbr are not the commonly used ones

[WorldTeacher]

What Went Wrong?

Another issue (#2484 ) reported not being able to download comic files using the opds. I confirmed this and reached out to Yomu and they confirmed that the error was partially on their side, but maybe in our opds implementation as well. Here's the part from the mail:

The app supports the following MIME types for CBZ and CBR comics, which are commonly used by OPDS servers:
application/x-cbz
application/x-cbr

It appears that BookLore has vendor-specific types for comics in the OPDS feed. I have now added these as an addition:
application/vnd.comicbook+zip
application/vnd.comicbook-rar

This change should be available in an upcoming v3.16.0 update, I hope this resolves the problem.

However, I think there might be an issue with BookLore's implementation as well. I noticed that the OPDS feed contains the application/vnd.comicbook+zip type for both CBZ and CBR books. As far as I know, the application/vnd.comicbook-rar type should be used for CBR comics.

When I tried to download CBR comics (file extension .cbr) the app failed to extract them. They cannot be recognised correctly by their type and zip/rar are different archive formats. Links to the IANA documentation are provided below, along with example screenshots and a feed extract.

- CBZ Comic
application/vnd.comicbook+zip
https://www.iana.org/assignments/media-types/application/vnd.comicbook+zip

- CBR Comic
application/vnd.comicbook-rar
https://www.iana.org/assignments/media-types/application/vnd.comicbook-rar

- BookLore
Version: v1.18.5
Docker: booklore/booklore:latest

How Can We Reproduce This?

1. use yomu prior to 3.16.0
2. use opds with cbz files
3. observe that the cbz files are not present

What Should Have Happened?

files should show up / maybe mime types need to be added?

Screenshots or Error Messages (Optional)

No response

Any Ideas on How to Fix This? (Optional)

No response

Your Setup

Booklore 1.18.5
Yomu Reader
Docker
Unraid

Before Submitting

• I've searched existing issues and confirmed this bug hasn't been reported yet

Edit:

Attach data sent from yomu dev
booklore-comic-issue.zip

[balazs-szucs]

But we are using the correct MIME types, though:

https://github.com/booklore-app/booklore/blob/a402f98e088a552b19228b7753ca685af6195175/booklore-api/src/main/java/com/adityachandel/booklore/service/opds/OpdsFeedService.java#L645C1-L667C18

it default to ZIP, which is true, but generally, if it correctly encoded the correct MIME type should assigned and NOT the default...

[balazs-szucs]

When I tried to download CBR comics (file extension .cbr) the app failed to extract them. They cannot be recognised correctly by their type and zip/rar are different archive formats. Links to the IANA documentation are provided below, along with example screenshots and a feed extract.

??????

[WorldTeacher]

no clue...

I can see both mime types in the code, maybe the issue is once again in yomu. If I remember and have time, I think I'll try to use the mime types they used to detect and see how yomu and other opds feeds behave

[balazs-szucs]

I can 100% guarantee you, we are NOT the problem, not one bit. We have Junit testing for that specific place see:

https://github.com/booklore-app/booklore/blob/develop/booklore-api/src/test/java/com/adityachandel/booklore/service/opds/OpdsFeedServiceMimeTypeTest.java

Like literally a whole-ass testing file just for MIME types in OPDS...

[WorldTeacher]

¯_(ツ)_/¯

I'll send them a message later

[balazs-szucs]

Ok, though, don't send my messages, they may come off a bit rude. 😅

I just had to deal with this 4 times already... I don't wanna any issues here, because it didn't become a well-tested area of the codebase because of nothing... As I said, I had to deal with this more times than I wanted to...

[WorldTeacher]

^^

I'll try to keep the mail formal and polite

[balazs-szucs]

application/x-cbz
application/x-cbr

He/she is wrong:
https://www.iana.org/assignments/media-types/application/vnd.comicbook-rar
https://www.iana.org/assignments/media-types/application/vnd.comicbook+zip

It literally says:

1. Deprecated alias names for this type: application/x-cbr
2. Magic number(s): none
3. File extension(s): .cbr
4. Macintosh file type code: N/A
5. Object Identifiers: N/A

1. Deprecated alias names for this type: application/x-cbr
2. Magic number(s): none
3. File extension(s): .cbz
4. Macintosh file type code: N/A
5. Object Identifiers: N/A

He is using deprecated alias... It not an us problem.

[WorldTeacher]

I'll let them know

[WorldTeacher]

@balazs-szucs
So they got back to be:

1) is not the problem, as I can add the additional types to support them. -> I let them know about the deprecated MIME types

The issue is with 2) Here I see the same type in the BookLore feed for both CBZ and CBR books. What I would expect instead is:
- CBZ file -> type = application/vnd.comicbook+zip
- CBR file -> type = application/vnd.comicbook-rar

Although the books are recognised as CBR format in BookLore (see previous attachment), they show up as vnd.comicbook+zip in the OPDS feed. Here are the links to two example files that fail (Download -> Continue with Download only):
https://www.dropbox.com/scl/fi/j4npbc450qoh3bppc1stb/Daredevil-606-2018-Digital-Zone-Empire.cbr?rlkey=s6h9l7njd34ky696q30y34nxu&st=oezl17tt&dl=0
https://www.dropbox.com/scl/fi/hvqtw0ucfdm270l3pt2zi/Amazing-Spider-Man-003-2018-Digital-Zone-Empire.cbr?rlkey=9q7kkzq3lsn79lqxo1zhja9ry&st=19hytjc4&dl=0

Hope this helps. I will leave this up to you.

[balazs-szucs]

I checked out the file. The reason it didn't work is because it was an ancient RAR version. We don't rely on file extensions when detecting file formats; rather, we use the magic numbers in file headers. I added the old RAR magic numbers to support this, which should resolve the issue.

FYI, the RAR utility hasn't used RAR v4 as the default since 2017. v5 was released in 2013, and we only used v5 RAR magic numbers to detect RAR files. Hence the problem.