bound capwap decap reads to caplen in dissectPacket#10487
Open
uwezkhan wants to merge 1 commit into
Open
Conversation
This file contains hidden or 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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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 CAPWAP UDP tunnel branch in dissectPacket reads the header-length byte at packet[ip_offset + 1] before checking that byte is inside the captured data, then advances ip_offset by that value and compares the result against h->len. h->len is the on-wire frame size, not h->caplen, so on a snaplen-truncated capture (caplen < len) the header-length read and the later packet[ip_offset - 2] and inner IP reads run past the end of the packet buffer. A crafted CAPWAP-data UDP packet triggers it, and tunnel decoding is on by default.
Before, this branch trusted h->len for the bound while every sibling tunnel case (GRE, ERSPAN, GTP, L2TP, 6in4) bounds against h->caplen. After, the header-length byte is guarded against h->caplen first and the advanced offset is compared to h->caplen as well. The tradeoff is that a CAPWAP frame whose header was clipped by the snap length is now dropped instead of parsed from uncaptured bytes, which is how the other decoders already behave.