wire: Reject non-canonically encoded varints. #507
Merged
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
The Bitcoin wire protocol includes several fields with their lengths encoded according to a variable length integer encoding scheme that does not enforce a unique encoding for all numbers. This can lead to a situation where deserializing and re-serializing the same data can result in different bytes. There are no currently known issues due to this, but it is safer to reject such subtle differences as they could potentially lead to exploits. Consequently, this commit modifies the varint decoding function to error when the value is not canonically encoded which effectively means that all messages with varints that are not canonically encoded will now be rejected. This will not cause issues with old client versions in regards to blocks and transactions since the data is deserialized into memory and then reserialized before being relayed thereby effectively erasing any non-canonical encodings. Also, new tests have been added to ensure non-canonical encodings are properly rejected and exercise the new code, and the default user agent version for wire has been bumped to version 0.2.1 to differentiate the new behavior. The equivalent logic was implemented in Bitcoin Core by PR 2884.
|
ok |
|
Looks good. OK. |
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Outdated suggestions cannot be applied.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 Bitcoin wire protocol includes several fields with their lengths encoded according to a variable length integer encoding scheme that does not enforce a unique encoding for all numbers.
This can lead to a situation where deserializing and re-serializing the same data can result in different bytes. There are no currently known issues due to this, but it is safer to reject such subtle differences as
they could potentially lead to exploits.
Consequently, this pull request modifies the varint decoding function to error when the value is not canonically encoded which effectively means that all messages with varints that are not canonically encoded will now be rejected. This will not cause issues with old client versions in regards to blocks and transactions since the data is deserialized into memory and then reserialized before being relayed thereby effectively erasing any non-canonical encodings.
Also, new tests have been added to ensure non-canonical encodings are properly rejected and exercise the new code, and the default user agent version for wire has been bumped to version 0.2.1 to differentiate the new behavior.
The equivalent logic was implemented in Bitcoin Core by PR 2884.