Support for NIST P-521 public keys

russh-keys/Cargo.toml

@@ -65,6 +65,7 @@ tokio = { version = "1.17.0", features = [
 ] }
 tokio-stream = { version = "0.1", features = ["net"] }
 yasna = { version = "0.5.0", features = ["bit-vec", "num-bigint"] }
+p521 = "0.13.3"
 
 [features]
 vendored-openssl = ["openssl", "openssl/vendored"]

russh-keys/src/agent/client.rs

@@ -278,11 +278,19 @@ impl<S: AsyncRead + AsyncWrite + Unpin> AgentClient<S> {
                     b"ecdsa-sha2-nistp256" => {
                         let curve = r.read_string()?;
                         if curve != b"nistp256" {
-                            return Err(Error::P256KeyError(p256::elliptic_curve::Error));
+                            return Err(Error::EcdsaKeyError(p256::elliptic_curve::Error));
                         }
                         let key = r.read_string()?;
                         keys.push(PublicKey::P256(p256::PublicKey::from_sec1_bytes(key)?));
                     }
+                    b"ecdsa-sha2-nistp512" => {
+                        let curve = r.read_string()?;
+                        if curve != b"nistp521" {
+                            return Err(Error::EcdsaKeyError(p521::elliptic_curve::Error));
+                        }
+                        let key = r.read_string()?;
+                        keys.push(PublicKey::P521(p521::PublicKey::from_sec1_bytes(key)?));
+                    }
                     t => {
                         info!("Unsupported key type: {:?}", std::str::from_utf8(t))
                     }
@@ -542,7 +550,7 @@ fn key_blob(public: &key::PublicKey, buf: &mut CryptoVec) -> Result<(), Error> {
             #[allow(clippy::indexing_slicing)] // length is known
             BigEndian::write_u32(&mut buf[5..], (len1 - len0) as u32);
         }
-        PublicKey::P256(_) => {
+        PublicKey::P256(_) | PublicKey::P521(_) => {
             buf.extend_ssh_string(&public.public_key_bytes());
         }
     }

russh-keys/src/key.rs

@@ -14,6 +14,7 @@
 //
 use std::convert::TryFrom;
 
+use block_padding::generic_array::GenericArray;
 use ed25519_dalek::{Signer, Verifier};
 #[cfg(feature = "openssl")]
 use openssl::pkey::{Private, Public};
@@ -38,6 +39,8 @@ impl AsRef<str> for Name {
 
 /// The name of the ecdsa-sha2-nistp256 algorithm for SSH.
 pub const ECDSA_SHA2_NISTP256: Name = Name("ecdsa-sha2-nistp256");
+/// The name of the ecdsa-sha2-nistp521 algorithm for SSH.
+pub const ECDSA_SHA2_NISTP521: Name = Name("ecdsa-sha2-nistp521");
 /// The name of the Ed25519 algorithm for SSH.
 pub const ED25519: Name = Name("ssh-ed25519");
 /// The name of the ssh-sha2-512 algorithm for SSH.
@@ -53,7 +56,7 @@ impl Name {
     /// Base name of the private key file for a key name.
     pub fn identity_file(&self) -> &'static str {
         match *self {
-            ECDSA_SHA2_NISTP256 => "id_ecdsa",
+            ECDSA_SHA2_NISTP256 | ECDSA_SHA2_NISTP521 => "id_ecdsa",
             ED25519 => "id_ed25519",
             RSA_SHA2_512 => "id_rsa",
             RSA_SHA2_256 => "id_rsa",
@@ -123,6 +126,8 @@ pub enum PublicKey {
     },
     #[doc(hidden)]
     P256(p256::PublicKey),
+    #[doc(hidden)]
+    P521(p521::PublicKey),
 }
 
 impl PartialEq for PublicKey {
@@ -132,6 +137,7 @@ impl PartialEq for PublicKey {
             (Self::RSA { key: a, .. }, Self::RSA { key: b, .. }) => a == b,
             (Self::Ed25519(a), Self::Ed25519(b)) => a == b,
             (Self::P256(a), Self::P256(b)) => a == b,
+            (Self::P521(a), Self::P521(b)) => a == b,
             _ => false,
         }
     }
@@ -223,6 +229,18 @@ impl PublicKey {
                     .map_err(|_| Error::CouldNotReadKey)?;
                 Ok(PublicKey::P256(key))
             }
+            b"ecdsa-sha2-nistp521" => {
+                let mut p = pubkey.reader(0);
+                let key_algo = p.read_string()?;
+                let curve = p.read_string()?;
+                if key_algo != b"ecdsa-sha2-nistp521" || curve != b"nistp521" {
+                    return Err(Error::CouldNotReadKey);
+                }
+                let sec1_bytes = p.read_string()?;
+                let key = p521::PublicKey::from_sec1_bytes(sec1_bytes)
+                    .map_err(|_| Error::CouldNotReadKey)?;
+                Ok(PublicKey::P521(key))
+            }
             _ => Err(Error::CouldNotReadKey),
         }
     }
@@ -234,6 +252,7 @@ impl PublicKey {
             #[cfg(feature = "openssl")]
             PublicKey::RSA { ref hash, .. } => hash.name().0,
             PublicKey::P256(_) => ECDSA_SHA2_NISTP256.0,
+            PublicKey::P521(_) => ECDSA_SHA2_NISTP521.0,
         }
     }
 
@@ -282,6 +301,31 @@ impl PublicKey {
                     .verify(buffer, &signature)
                     .is_ok()
             }
+            PublicKey::P521(ref public) => {
+                const FIELD_LEN: usize =
+                    <p521::NistP521 as p256::elliptic_curve::Curve>::FieldBytesSize::USIZE;
+                let mut reader = sig.reader(0);
+                let mut read_field = || -> Option<p521::FieldBytes> {
+                    let f = reader.read_mpint().ok()?;
+                    let f = f.strip_prefix(&[0]).unwrap_or(f);
+                    let mut result = [0; FIELD_LEN];
+                    if f.len() > FIELD_LEN {
+                        return None;
+                    }
+                    #[allow(clippy::indexing_slicing)] // length is known
+                    result[FIELD_LEN - f.len()..].copy_from_slice(f);
+                    // Some(result.into())
+                    Some(GenericArray::clone_from_slice(&result)) // ew
+                };
+                let Some(r) = read_field() else { return false };
+                let Some(s) = read_field() else { return false };
+                let Ok(signature) = p521::ecdsa::Signature::from_scalars(r, s) else {
+                    return false;
+                };
+                p521::ecdsa::VerifyingKey::from_sec1_bytes(&public.to_sec1_bytes()).unwrap() // also ew
+                    .verify(buffer, &signature)
+                    .is_ok()
+            }
         }
     }
 
@@ -560,5 +604,13 @@ pub fn parse_public_key(
         let key = p256::PublicKey::from_sec1_bytes(sec1_bytes)?;
         return Ok(PublicKey::P256(key));
     }
+    if t == b"ecdsa-sha2-nistp521" {
+        if pos.read_string()? != b"nistp521" {
+            return Err(Error::CouldNotReadKey);
+        }
+        let sec1_bytes = pos.read_string()?;
+        let key = p521::PublicKey::from_sec1_bytes(sec1_bytes)?;
+        return Ok(PublicKey::P521(key));
+    }
     Err(Error::CouldNotReadKey)
 }

russh-keys/src/lib.rs

@@ -102,8 +102,8 @@ pub enum Error {
     #[error("Invalid Ed25519 key data")]
     Ed25519KeyError(#[from] ed25519_dalek::SignatureError),
     /// The type of the key is unsupported
-    #[error("Invalid NIST-P256 key data")]
-    P256KeyError(#[from] p256::elliptic_curve::Error),
+    #[error("Invalid ECDSA key data")]
+    EcdsaKeyError(#[from] p256::elliptic_curve::Error),
     /// The key is encrypted (should supply a password?)
     #[error("The key is encrypted")]
     KeyIsEncrypted,
@@ -242,6 +242,12 @@ impl PublicKeyBase64 for key::PublicKey {
                 s.extend_ssh_string(b"nistp256");
                 s.extend_ssh_string(&publickey.to_sec1_bytes());
             }
+            key::PublicKey::P521(ref publickey) => {
+                use encoding::Encoding;
+                s.extend_ssh_string(b"ecdsa-sha2-nistp521");
+                s.extend_ssh_string(b"nistp521");
+                s.extend_ssh_string(&publickey.to_sec1_bytes());
+            }
         }
         s
     }

russh/src/negotiation.rs

@@ -87,6 +87,7 @@ impl Preferred {
         key: &[
             key::ED25519,
             key::ECDSA_SHA2_NISTP256,
+            key::ECDSA_SHA2_NISTP521,
             #[cfg(feature = "openssl")]
             key::RSA_SHA2_256,
             #[cfg(feature = "openssl")]
@@ -126,13 +127,14 @@ impl Named for () {
 
 #[cfg(feature = "openssl")]
 use russh_keys::key::SSH_RSA;
-use russh_keys::key::{ECDSA_SHA2_NISTP256, ED25519};
+use russh_keys::key::{ECDSA_SHA2_NISTP256, ECDSA_SHA2_NISTP521, ED25519};
 
 impl Named for PublicKey {
     fn name(&self) -> &'static str {
         match self {
             PublicKey::Ed25519(_) => ED25519.0,
             PublicKey::P256(_) => ECDSA_SHA2_NISTP256.0,
+            PublicKey::P521(_) => ECDSA_SHA2_NISTP521.0,
             #[cfg(feature = "openssl")]
             PublicKey::RSA { .. } => SSH_RSA.0,
         }