feat: require varints to be minimally encoded #19
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
|
This also removes outdated information about how go implements |
This was referenced Sep 18, 2019
daviddias
approved these changes
Sep 18, 2019
Stebalien
added a commit
to Stebalien/unsigned-varint
that referenced
this pull request
Oct 27, 2021
ULEB128 technically allows any number trailing "MSB" zeros. However, this means that there are multiple ways to encode a single number. This is usually fine but can lead to security issues when the user assumes that a varint will round-trip and/or that there's exactly one encoding for some varint. For example, code may check "is this a CID of type X" by matching the prefix against a known-byte string. This check only works when there's exactly one way to encode a varint. As of multiformats/unsigned-varint#19, the multiformats unsigned varint spec requires minimal encoding.
Stebalien
added a commit
to Stebalien/unsigned-varint
that referenced
this pull request
Nov 6, 2021
ULEB128 technically allows any number trailing "MSB" zeros. However, this means that there are multiple ways to encode a single number. This is usually fine but can lead to security issues when the user assumes that a varint will round-trip and/or that there's exactly one encoding for some varint. For example, code may check "is this a CID of type X" by matching the prefix against a known-byte string. This check only works when there's exactly one way to encode a varint. As of multiformats/unsigned-varint#19, the multiformats unsigned varint spec requires minimal encoding.
Stebalien
added a commit
to Stebalien/unsigned-varint
that referenced
this pull request
Nov 6, 2021
ULEB128 technically allows any number trailing "MSB" zeros. However, this means that there are multiple ways to encode a single number. This is usually fine but can lead to security issues when the user assumes that a varint will round-trip and/or that there's exactly one encoding for some varint. For example, code may check "is this a CID of type X" by matching the prefix against a known-byte string. This check only works when there's exactly one way to encode a varint. As of multiformats/unsigned-varint#19, the multiformats unsigned varint spec requires minimal encoding.
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.
It has been pointed out that
{0x81 0x01}is technically a valid varint encoding of 0x1. Given that we tend to compare varints in byte strings, we need a 1-1 mapping between unsigned integers and encoded varints.Library where we can enforce our constraints: https://github.com/multiformats/go-varint