Re: [PATCH proxmox v4 02/31] wireguard: utilize x25519 for public key generation

[Stefan Hanreich <s.hanreich@proxmox.com>]

@Christoph could you please double-check this in particular?


On 5/7/26 2:38 PM, Stefan Hanreich wrote:
> Previously, proxmox-wireguard used ed25519 for generating the public
> keys, which is the wrong algorithm for deriving suitable public keys
> for WireGuard - since ed25519 is a digital signature algorithm. x25519
> is for conducting DH key exchanges, which is what is utilized in the
> WireGuard protocol.
> 
> The generated public keys from the tests have been checked against the
> output from wg pubkey - to make sure that generated keys are exactly
> the same as the ones generated by the userspace wg(8) tool.
> 
> Signed-off-by: Stefan Hanreich <s.hanreich@proxmox.com>
> ---
>  proxmox-wireguard/Cargo.toml |  1 +
>  proxmox-wireguard/src/lib.rs | 56 +++++++++++++-----------------------
>  2 files changed, 21 insertions(+), 36 deletions(-)
> 
> diff --git a/proxmox-wireguard/Cargo.toml b/proxmox-wireguard/Cargo.toml
> index b1abae3d..ae3236a8 100644
> --- a/proxmox-wireguard/Cargo.toml
> +++ b/proxmox-wireguard/Cargo.toml
> @@ -11,6 +11,7 @@ rust-version.workspace = true
>  
>  [dependencies]
>  ed25519-dalek = "2.1"
> +x25519-dalek = { version = "2.0.1", features = ["getrandom", "static_secrets"] }
>  serde = { workspace = true, features = [ "derive" ] }
>  thiserror.workspace = true
>  proxmox-schema = { workspace = true, optional = true, features = ["api-types"] }
> diff --git a/proxmox-wireguard/src/lib.rs b/proxmox-wireguard/src/lib.rs
> index 08579775..bf6ea8ad 100644
> --- a/proxmox-wireguard/src/lib.rs
> +++ b/proxmox-wireguard/src/lib.rs
> @@ -12,9 +12,11 @@
>  
>  #![forbid(unsafe_code, missing_docs)]
>  
> +use std::fmt;
> +
>  use ed25519_dalek::SigningKey;
>  use serde::{Deserialize, Serialize};
> -use std::fmt;
> +use x25519_dalek::StaticSecret;
>  
>  use proxmox_network_types::{endpoint::ServiceEndpoint, ip_address::Cidr};
>  #[cfg(feature = "api-types")]
> @@ -42,9 +44,7 @@ impl From<proxmox_ini::Error> for Error {
>  /// Public key of a WireGuard peer.
>  #[derive(Clone, Copy, Deserialize, Serialize, Hash, Debug)]
>  #[serde(transparent)]
> -pub struct PublicKey(
> -    #[serde(with = "proxmox_serde::byte_array_as_base64")] [u8; ed25519_dalek::PUBLIC_KEY_LENGTH],
> -);
> +pub struct PublicKey(#[serde(with = "proxmox_serde::byte_array_as_base64")] [u8; 32]);
>  
>  #[cfg(feature = "api-types")]
>  impl ApiType for PublicKey {
> @@ -62,9 +62,7 @@ impl UpdaterType for PublicKey {
>  /// Private key of a WireGuard peer.
>  #[derive(Serialize)]
>  #[serde(transparent)]
> -pub struct PrivateKey(
> -    #[serde(with = "proxmox_serde::byte_array_as_base64")] ed25519_dalek::SecretKey,
> -);
> +pub struct PrivateKey(#[serde(with = "proxmox_serde::byte_array_as_base64")] [u8; 32]);
>  
>  impl fmt::Debug for PrivateKey {
>      fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> @@ -73,42 +71,27 @@ impl fmt::Debug for PrivateKey {
>  }
>  
>  impl PrivateKey {
> -    /// Length of the raw private key data in bytes.
> -    pub const RAW_LENGTH: usize = ed25519_dalek::SECRET_KEY_LENGTH;
> -
>      /// Generates a new private key suitable for use with WireGuard.
>      #[cfg(feature = "key-generation")]
>      pub fn generate() -> Result<Self, Error> {
> -        generate_key().map(Self)
> +        Ok(Self(StaticSecret::random().to_bytes()))
>      }
>  
>      /// Calculates the public key from the private key.
>      pub fn public_key(&self) -> PublicKey {
> -        PublicKey(
> -            ed25519_dalek::SigningKey::from_bytes(&self.0)
> -                .verifying_key()
> -                .to_bytes(),
> -        )
> -    }
> -
> -    /// Builds a new [`PrivateKey`] from raw key material.
> -    #[must_use]
> -    pub fn from_raw(data: ed25519_dalek::SecretKey) -> Self {
> -        // [`SigningKey`] takes care of correct key clamping.
> -        Self(SigningKey::from(&data).to_bytes())
> +        PublicKey(x25519_dalek::PublicKey::from(&StaticSecret::from(self.0)).to_bytes())
>      }
>  }
>  
> -impl From<ed25519_dalek::SecretKey> for PrivateKey {
> -    fn from(value: ed25519_dalek::SecretKey) -> Self {
> +impl From<[u8; 32]> for PrivateKey {
> +    fn from(value: [u8; 32]) -> Self {
>          Self(value)
>      }
>  }
>  
> -impl AsRef<ed25519_dalek::SecretKey> for PrivateKey {
> -    /// Returns the raw private key material.
> -    fn as_ref(&self) -> &ed25519_dalek::SecretKey {
> -        &self.0
> +impl From<x25519_dalek::StaticSecret> for PrivateKey {
> +    fn from(value: x25519_dalek::StaticSecret) -> Self {
> +        Self(value.to_bytes())
>      }
>  }
>  
> @@ -239,7 +222,8 @@ mod tests {
>  
>      fn mock_private_key(v: u8) -> PrivateKey {
>          let base = v * 32;
> -        PrivateKey((base..base + 32).collect::<Vec<u8>>().try_into().unwrap())
> +        let key: [u8; 32] = (base..base + 32).collect::<Vec<u8>>().try_into().unwrap();
> +        PrivateKey(key.into())
>      }
>  
>      fn mock_preshared_key(v: u8) -> PresharedKey {
> @@ -272,7 +256,7 @@ ListenPort = 51820
>  FwMark = 127
>  
>  [Peer]
> -PublicKey = Kay64UG8yvCyLhqU000LxzYeUm0L/hLIl5S8kyKWbdc=
> +PublicKey = NYBy1jZYgNGu6jKa35EhODhR7SGijjt16WXQ0s0WYlQ=
>  PresharedKey = ICEiIyQlJicoKSorLC0uLzAxMjM0NTY3ODk6Ozw9Pj8=
>  AllowedIPs = 192.168.0.0/24
>  Endpoint = foo.example.com:51820
> @@ -328,24 +312,24 @@ PrivateKey = AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8=
>  ListenPort = 51820
>  
>  [Peer]
> -PublicKey = Kay64UG8yvCyLhqU000LxzYeUm0L/hLIl5S8kyKWbdc=
> +PublicKey = NYBy1jZYgNGu6jKa35EhODhR7SGijjt16WXQ0s0WYlQ=
>  PresharedKey = ICEiIyQlJicoKSorLC0uLzAxMjM0NTY3ODk6Ozw9Pj8=
>  AllowedIPs = 192.168.0.0/24
>  Endpoint = foo.example.com:51820
>  
>  [Peer]
> -PublicKey = JUO5L/EJVRFHatyDadtt3JM2ZaEZeN2hQE7hBmypVZ0=
> +PublicKey = eaYx7t4b+cmPEgMs3q3Q56B5OY/HhriMyEbsia+FpRo=
>  PresharedKey = QEFCQ0RFRkdISUpLTE1OT1BRUlNUVVZXWFlaW1xdXl8=
>  AllowedIPs = 192.168.1.0/24
>  PersistentKeepalive = 25
>  
>  [Peer]
> -PublicKey = F0VTtFbd38aQjsqxwQH+arIeK6oGF3lbfUOmNIKZP9U=
> +PublicKey = Z13VdO13iTELPS52gfN5C0ZsdzsVIf7PNld5WDcepS8=
>  PresharedKey = YGFiY2RlZmdoaWprbG1ub3BxcnN0dXZ3eHl6e3x9fn8=
>  AllowedIPs = 192.168.2.0/24
>  
>  [Peer]
> -PublicKey = zRSzf5VulTGU/3+3Oz2B3MVh1hp1OAlLfD4aZD7l86o=
> +PublicKey = ST6C/HRGSlkmiBdiPSBTxeuOLMSpiLT+4XnsawENUx0=
>  PresharedKey = gIGCg4SFhoeIiYqLjI2Oj5CRkpOUlZaXmJmam5ydnp8=
>  Endpoint = 10.0.0.1:51820
>  PersistentKeepalive = 25
> @@ -376,7 +360,7 @@ PersistentKeepalive = 25
>  PrivateKey = AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8=
>  
>  [Peer]
> -PublicKey = Kay64UG8yvCyLhqU000LxzYeUm0L/hLIl5S8kyKWbdc=
> +PublicKey = NYBy1jZYgNGu6jKa35EhODhR7SGijjt16WXQ0s0WYlQ=
>  PresharedKey = ICEiIyQlJicoKSorLC0uLzAxMjM0NTY3ODk6Ozw9Pj8=
>  AllowedIPs = 192.168.0.0/24
>  Endpoint = 10.0.0.1:51820