feat: require varints to be minimally encoded#19
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This also removes outdated information about how go implements |
This was referenced Sep 18, 2019
daviddias
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Stebalien
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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
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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
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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.
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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