RUSTSEC-2022-0093: Double Public Key Signing Function Oracle Attack on `ed25519-dalek`

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Double Public Key Signing Function Oracle Attack on ed25519-dalek

Details
Package	ed25519-dalek
Version	1.0.1
URL	https://github.com/MystenLabs/ed25519-unsafe-libs
Date	2022-06-11
Patched versions	>=2

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.

See advisory page for additional details.

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