1.2 KiB
[advisory]
id = "RUSTSEC-2022-0093"
package = "ed25519-dalek"
date = "2022-06-11"
categories = ["crypto-failure"]
url = "https://github.com/MystenLabs/ed25519-unsafe-libs"
aliases = ["GHSA-w5vr-6qhr-36cc"]
[versions]
patched = [">= 2"]
Double Public Key Signing Function Oracle Attack on ed25519-dalek
Versions of ed25519-dalek prior to v2.0 model private and public keys as
separate types which can be assembled into a Keypair, and also provide APIs
for serializing and deserializing 64-byte private/public keypairs.
Such APIs and serializations are inherently unsafe as the public key is one of
the inputs used in the deterministic computation of the S part of the signature,
but not in the R value. An adversary could somehow use the signing function as
an oracle that allows arbitrary public keys as input can obtain two signatures
for the same message sharing the same R and only differ on the S part.
Unfortunately, when this happens, one can easily extract the private key.
Revised public APIs in v2.0 of ed25519-dalek do NOT allow a decoupled
private/public keypair as signing input, except as part of specially labeled
"hazmat" APIs which are clearly labeled as being dangerous if misused.