Add Handshake Backup When Primary Protocol Detection Fails #335
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
…he strange case where a target improperly rejects our constructed ClientHello.
Owner
|
I've done some testing with this on various local stacks and not seen any issues from it - so looks good. I wonder exactly what it is they're running that's behaving in this way. Wouldn't it be great if people actually followed standards....? |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
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Outdated suggestions cannot be applied.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.
A user reported in #334 that TLSv1.2 was not being detected on a target. An investigation found that the target was terminating the connection because our constructed ClientHello includes a high number of ciphersuites (351; this is to increase the chances of a server responding). I strongly suspect this server behavior is not conformant to the TLS specs, but regardless, this PR works around the issue by making a second handshake attempt using OpenSSL's built-in functions (which include only 28 ciphersuites in the ClientHello message).
This workaround may be useful for detecting other non-standard TLS implementations as well.