[PR #2035] fix mkvlang_params_check: prevent panic on multi-byte characters

**Original Pull Request:** https://github.com/CCExtractor/ccextractor/pull/2035 **State:** closed **Merged:** Yes ---  **In raising this pull request, I confirm the following (please check boxes):** - [x] I have read and understood the [contributors guide](https://github.com/CCExtractor/ccextractor/blob/master/.github/CONTRIBUTING.md). - [x] I have checked that another pull request for this purpose does not exist. - [x] I have considered, and confirmed that this submission will be valuable to others. - [x] I accept that this submission may not be used, and the pull request closed at the will of the maintainer. - [x] I give this submission freely, and claim no ownership to its content. - [x] **I have mentioned this change in the [changelog](https://github.com/CCExtractor/ccextractor/blob/master/docs/CHANGES.TXT).** **My familiarity with the project is as follows (check one):** - [ ] I have never used CCExtractor. - [ ] I have used CCExtractor just a couple of times. - [ ] I absolutely love CCExtractor, but have not contributed previously. - [x] I am an active contributor to CCExtractor. --- ### Description The mkvlang_params_check function validates language codes in MKV files, but the previous implementation assumed 1 byte per character and used string indices derived from to_lowercase(). This caused panics when multi-byte characters (like ç) were used, because slicing by byte indices can go out-of-bounds. ### Problem - Multi-byte characters break the original index-based logic. - Inputs like "ç,eng" would trigger a runtime panic. - Standard ISO codes (like "chi,eng") worked, but any non-ASCII input was unsafe. ### Fix - Split the input string on commas using lang.split(','). - Count characters with chars().count() instead of relying on byte indices. - Enforce the same rules as before: each code must be 3–6 characters, and 6-character codes must include a - - Handles non-ASCII input safely without panicking. Example after fix - "chi,eng" → passes validation (3 chars each) - "chi-tra,eng" → passes validation (6 chars with -) - "ç,eng" → triggers a controlled fatal error, but does not panic

claunia commented

2026-01-29 17:24:11 +00:00

Owner

Original Pull Request: https://github.com/CCExtractor/ccextractor/pull/2035

State: closed
Merged: Yes

In raising this pull request, I confirm the following (please check boxes):

I have read and understood the contributors guide.
I have checked that another pull request for this purpose does not exist.
I have considered, and confirmed that this submission will be valuable to others.
I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
I give this submission freely, and claim no ownership to its content.
I have mentioned this change in the changelog.

My familiarity with the project is as follows (check one):

I have never used CCExtractor.
I have used CCExtractor just a couple of times.
I absolutely love CCExtractor, but have not contributed previously.
I am an active contributor to CCExtractor.

Description

The mkvlang_params_check function validates language codes in MKV files, but the previous implementation assumed 1 byte per character and used string indices derived from to_lowercase(). This caused panics when multi-byte characters (like ç) were used, because slicing by byte indices can go out-of-bounds.

Problem

Multi-byte characters break the original index-based logic.
Inputs like "ç,eng" would trigger a runtime panic.
Standard ISO codes (like "chi,eng") worked, but any non-ASCII input was unsafe.

Fix

Split the input string on commas using lang.split(',').
Count characters with chars().count() instead of relying on byte indices.
Enforce the same rules as before: each code must be 3–6 characters, and 6-character codes must include a -
Handles non-ASCII input safely without panicking.

Example after fix

"chi,eng" → passes validation (3 chars each)
"chi-tra,eng" → passes validation (6 chars with -)
"ç,eng" → triggers a controlled fatal error, but does not panic

claunia added the pull-request label 2026-01-29 17:24:11 +00:00

claunia closed this issue

2026-01-29 17:24:12 +00:00

[PR #2035] fix mkvlang_params_check: prevent panic on multi-byte characters #2842

Description

Problem

Fix