dhserver: Support DHCP clients that don't send the MESSAGETYPE as first option #1712
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…st option Signed-off-by: Jannis Achstetter <kripton@kripserver.net>
hathach
approved these changes
Nov 18, 2022
kripton
added a commit
to kripton/tinyusb
that referenced
this pull request
Feb 4, 2023
hathach
added a commit
that referenced
this pull request
Feb 13, 2023
dhserver: Fix a potential DoS vulnerability accidentially introduced by #1712
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The included DHCP server fails to process DHCP DISCOVER or REQUEST packages that don't contain the "DHCP MESSAGE TYPE" option as the first option in the package.
The initial report that triggered me was in OpenLightingProject/rp2040-dmxsun#53 and after some investigation, I found that the "dhcpcd" client (maybe others, too) don't send the MESSAGE TYPE as the first option (see Wireshark dump attached in the linked issue). This seems to be valid since the order of the options contained in the package shouldn't matter. However, tinyUSB's DHCP server expects the MESSAGE TYPE to be the first option.
This change uses the already existing function to extract the MESSAGE TYPE option from the options properly. It will also fail now, if the MESSAGE TYPE option doesn't exist at all, making the code safer than the current approach.