More work on key exhcnage negotiation

Signed-off-by: Luca Fulchir <luca.fulchir@runesauth.com>

src/config/mod.rs

@@ -1,6 +1,10 @@
 //!
 //! Configuration to initialize the Fenrir networking library
 
+use crate::{
+    connection::handshake::HandshakeID,
+    enc::{asym::KeyExchange, hkdf::HkdfKind, sym::CipherKind},
+};
 use ::std::{
     net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr},
     num::NonZeroUsize,
@@ -18,6 +22,14 @@ pub struct Config {
     pub listen: Vec<SocketAddr>,
     /// List of DNS resolvers to use
     pub resolvers: Vec<SocketAddr>,
+    /// Supported handshakes
+    pub handshakes: Vec<HandshakeID>,
+    /// Supported key exchanges
+    pub key_exchanges: Vec<KeyExchange>,
+    /// Supported Hkdfs
+    pub hkdfs: Vec<HkdfKind>,
+    /// Supported Ciphers
+    pub ciphers: Vec<CipherKind>,
 }
 
 impl Default for Config {
@@ -34,6 +46,10 @@ impl Default for Config {
                 ),
             ],
             resolvers: Vec::new(),
+            handshakes: [HandshakeID::DirectorySynchronized].to_vec(),
+            key_exchanges: [KeyExchange::X25519DiffieHellman].to_vec(),
+            hkdfs: [HkdfKind::Sha3].to_vec(),
+            ciphers: [CipherKind::XChaCha20Poly1305].to_vec(),
         }
     }
 }

src/connection/handshake/dirsync.rs

@@ -14,13 +14,41 @@ use crate::{
     connection::{ProtocolVersion, ID},
     enc::{
         asym::{ExchangePubKey, KeyExchange, KeyID},
+        hkdf::HkdfKind,
         sym::{CipherKind, HeadLen, Secret, TagLen},
+        Random,
     },
 };
 
 use ::arrayref::array_mut_ref;
 
-type Nonce = [u8; 16];
+// TODO: merge with crate::enc::sym::Nonce
+/// random nonce
+#[derive(Debug, Clone, Copy)]
+pub struct Nonce([u8; 16]);
+
+impl Nonce {
+    /// Create a new random Nonce
+    pub fn new(rnd: &Random) -> Self {
+        use ::core::mem::MaybeUninit;
+        let mut out: MaybeUninit<[u8; 16]>;
+        #[allow(unsafe_code)]
+        unsafe {
+            out = MaybeUninit::uninit();
+            let _ = rnd.fill(out.assume_init_mut());
+            Self(out.assume_init())
+        }
+    }
+    /// Length of the serialized Nonce
+    pub const fn len() -> usize {
+        16
+    }
+}
+impl From<&[u8; 16]> for Nonce {
+    fn from(raw: &[u8; 16]) -> Self {
+        Self(raw.clone())
+    }
+}
 
 /// Parsed handshake
 #[derive(Debug, Clone)]
@@ -61,6 +89,8 @@ pub struct Req {
     pub key_id: KeyID,
     /// Selected key exchange
     pub exchange: KeyExchange,
+    /// Selected hkdf
+    pub hkdf: HkdfKind,
     /// Selected cipher
     pub cipher: CipherKind,
     /// Client ephemeral public key used for key exchanges
@@ -77,6 +107,7 @@ impl Req {
         ProtocolVersion::len()
             + KeyID::len()
             + KeyExchange::len()
+            + HkdfKind::len()
             + CipherKind::len()
             + self.exchange_key.kind().pub_len()
     }
@@ -91,6 +122,7 @@ impl Req {
     pub fn len(&self) -> usize {
         KeyID::len()
             + KeyExchange::len()
+            + HkdfKind::len()
             + CipherKind::len()
             + self.exchange_key.kind().pub_len()
             + self.data.len()
@@ -121,18 +153,23 @@ impl super::HandshakeParsing for Req {
             Some(exchange) => exchange,
             None => return Err(Error::Parsing),
         };
-        let cipher: CipherKind = match CipherKind::from_u8(raw[3]) {
+        let hkdf: HkdfKind = match HkdfKind::from_u8(raw[3]) {
+            Some(exchange) => exchange,
+            None => return Err(Error::Parsing),
+        };
+        let cipher: CipherKind = match CipherKind::from_u8(raw[4]) {
             Some(cipher) => cipher,
             None => return Err(Error::Parsing),
         };
-        let (exchange_key, len) = match ExchangePubKey::from_slice(&raw[4..]) {
+        let (exchange_key, len) = match ExchangePubKey::from_slice(&raw[5..]) {
             Ok(exchange_key) => exchange_key,
             Err(e) => return Err(e.into()),
         };
-        let data = ReqInner::CipherText(raw.len() - (4 + len));
+        let data = ReqInner::CipherText(raw.len() - (5 + len));
         Ok(HandshakeData::DirSync(DirSync::Req(Self {
             key_id,
             exchange,
+            hkdf,
             cipher,
             exchange_key,
             data,
@@ -253,7 +290,7 @@ pub struct ReqData {
 impl ReqData {
     /// actual length of the request data
     pub fn len(&self) -> usize {
-        self.nonce.len() + KeyID::len() + ID::len() + self.auth.len()
+        Nonce::len() + KeyID::len() + ID::len() + self.auth.len()
     }
     /// Minimum byte length of the request data
     pub const MIN_PKT_LEN: usize =
@@ -265,7 +302,8 @@ impl ReqData {
         }
         let mut start = 0;
         let mut end = 16;
-        let nonce: Nonce = raw[start..end].try_into().unwrap();
+        let raw_sized: &[u8; 16] = raw[start..end].try_into().unwrap();
+        let nonce: Nonce = raw_sized.into();
         start = end;
         end = end + KeyID::len();
         let client_key_id =
@@ -440,7 +478,7 @@ impl RespData {
         assert!(out.len() == Self::len(), "wrong buffer size");
         let mut start = 0;
         let mut end = Self::NONCE_LEN;
-        out[start..end].copy_from_slice(&self.client_nonce);
+        out[start..end].copy_from_slice(&self.client_nonce.0);
         start = end;
         end = end + Self::NONCE_LEN;
         self.id.serialize(&mut out[start..end]);

src/connection/handshake/mod.rs

@@ -27,6 +27,37 @@ pub enum Error {
     NotEnoughData,
 }
 
+/// List of possible handshakes
+#[derive(::num_derive::FromPrimitive, Debug, Clone, Copy, PartialEq)]
+#[repr(u8)]
+pub enum HandshakeID {
+    /// 1-RTT Directory synchronized handshake. Fast, no forward secrecy
+    DirectorySynchronized = 0,
+    /// 2-RTT Stateful exchange. Little DDos protection
+    Stateful,
+    /// 3-RTT stateless exchange. Forward secrecy and ddos protection
+    Stateless,
+}
+
+impl TryFrom<&str> for HandshakeID {
+    type Error = ::std::io::Error;
+    // TODO: from actual names, not only numeric
+    fn try_from(raw: &str) -> Result<Self, Self::Error> {
+        if let Ok(handshake_u8) = raw.parse::<u8>() {
+            if handshake_u8 >= 1 {
+                if let Some(handshake) = HandshakeID::from_u8(handshake_u8 - 1)
+                {
+                    return Ok(handshake);
+                }
+            }
+        }
+        return Err(::std::io::Error::new(
+            ::std::io::ErrorKind::InvalidData,
+            "Unknown handshake ID",
+        ));
+    }
+}
+
 pub(crate) struct HandshakeServer {
     pub id: crate::enc::asym::KeyID,
     pub key: crate::enc::asym::PrivKey,

src/dnssec/record.rs

@@ -19,15 +19,15 @@
 //!     * 2..4 priority (for failover)
 //!     * 5..7 weight between priority
 //!   * 1 byte: divided in half:
-//!     * half: num of public key ids
+//!     * half: num of public key indexes
-//!     * half: num of handhskae ids
+//!     * half: num of handshake ids
 //!   * 2 bytes: UDP port
-//!   * [ 1 byte per public key id ]
+//!   * [ HALF byte per public key idx ] (index on the list of public keys)
 //!   * [ 1 byte per handshake id ]
 //!   * X bytes: IP
 //! ]
-//! [ # list of pubkeys
+//! [ # list of pubkeys (max: 16)
-//!   * 1 byte: pubkey id
+//!   * 2 byte: pubkey id
 //!   * 1 byte: pubkey length
 //!   * 1 byte: pubkey type
 //!   * Y bytes: pubkey
@@ -42,11 +42,14 @@
 //!   * 1 byte for each cipher
 //! ]
 
-use crate::enc::{
+use crate::{
-    self,
+    connection::handshake::HandshakeID,
-    asym::{KeyExchange, PubKey},
+    enc::{
-    hkdf::HkdfKind,
+        self,
-    sym::CipherKind,
+        asym::{KeyExchange, KeyID, PubKey},
+        hkdf::HkdfKind,
+        sym::CipherKind,
+    },
 };
 use ::core::num::NonZeroU16;
 use ::num_traits::FromPrimitive;
@@ -55,22 +58,12 @@ use ::std::{net::IpAddr, vec::Vec};
  * Public key data
  */
 
-/// Public Key ID
+/// Public Key Index.
+/// this points to the index of the public key in the array of public keys.
+/// needed to have one byte less in the list of public keys
+/// supported by and address
 #[derive(Debug, Copy, Clone, PartialEq)]
-pub struct PublicKeyID(u8);
+pub struct PubKeyIdx(pub u8);
-
-impl TryFrom<&str> for PublicKeyID {
-    type Error = ::std::io::Error;
-    fn try_from(raw: &str) -> Result<Self, Self::Error> {
-        if let Ok(id_u8) = raw.parse::<u8>() {
-            return Ok(PublicKeyID(id_u8));
-        }
-        return Err(::std::io::Error::new(
-            ::std::io::ErrorKind::InvalidData,
-            "Public Key ID must be between 0 and 256",
-        ));
-    }
-}
 
 /*
  * Address data
@@ -168,37 +161,6 @@ impl TryFrom<&str> for AddressWeight {
     }
 }
 
-/// List of possible handshakes
-#[derive(::num_derive::FromPrimitive, Debug, Clone, Copy)]
-#[repr(u8)]
-pub enum HandshakeID {
-    /// 1-RTT Directory synchronized handshake. Fast, no forward secrecy
-    DirectorySynchronized = 0,
-    /// 2-RTT Stateful exchange. Little DDos protection
-    Stateful,
-    /// 3-RTT stateless exchange. Forward secrecy and ddos protection
-    Stateless,
-}
-
-impl TryFrom<&str> for HandshakeID {
-    type Error = ::std::io::Error;
-    // TODO: from actual names, not only numeric
-    fn try_from(raw: &str) -> Result<Self, Self::Error> {
-        if let Ok(handshake_u8) = raw.parse::<u8>() {
-            if handshake_u8 >= 1 {
-                if let Some(handshake) = HandshakeID::from_u8(handshake_u8 - 1)
-                {
-                    return Ok(handshake);
-                }
-            }
-        }
-        return Err(::std::io::Error::new(
-            ::std::io::ErrorKind::InvalidData,
-            "Unknown handshake ID",
-        ));
-    }
-}
-
 /// Authentication server address information:
 /// * ip
 /// * udp port
@@ -220,14 +182,16 @@ pub struct Address {
     /// List of supported handshakes
     pub handshake_ids: Vec<HandshakeID>,
     /// Public key IDs used by this address
-    pub public_key_ids: Vec<PublicKeyID>,
+    pub public_key_idx: Vec<PubKeyIdx>,
 }
 
 impl Address {
     fn raw_len(&self) -> usize {
         // UDP port + Priority + Weight + pubkey_len + handshake_len
         let mut size = 6;
-        size = size + self.public_key_ids.len() + self.handshake_ids.len();
+        let num_pubkey_idx = self.public_key_idx.len();
+        let idx_bytes = (num_pubkey_idx / 2) + (num_pubkey_idx % 2);
+        size = size + idx_bytes + self.handshake_ids.len();
         size + match self.ip {
             IpAddr::V4(_) => size + 4,
             IpAddr::V6(_) => size + 16,
@@ -244,7 +208,7 @@ impl Address {
         bitfield |= self.weight as u8;
 
         raw.push(bitfield);
-        let len_combined: u8 = self.public_key_ids.len() as u8;
+        let len_combined: u8 = self.public_key_idx.len() as u8;
         let len_combined = len_combined << 4;
         let len_combined = len_combined | self.handshake_ids.len() as u8;
         raw.push(len_combined);
@@ -256,8 +220,18 @@ impl Address {
             }),
         );
 
-        for id in self.public_key_ids.iter() {
+        // pair every idx, since the max is 16
-            raw.push(id.0);
+        for chunk in self.public_key_idx.chunks(2) {
+            let second = {
+                if chunk.len() == 2 {
+                    chunk[1].0
+                } else {
+                    0
+                }
+            };
+            let tmp = chunk[0].0 << 4;
+            let tmp = tmp | second;
+            raw.push(tmp);
         }
         for id in self.handshake_ids.iter() {
             raw.push(*id as u8);
@@ -301,21 +275,29 @@ impl Address {
         };
 
         // Add publickey ids
-        let num_pubkey_ids = (raw[3] >> 4) as usize;
+        let num_pubkey_idx = (raw[3] >> 4) as usize;
         let num_handshake_ids = (raw[3] & 0x0F) as usize;
-        if raw.len() <= 3 + num_pubkey_ids + num_handshake_ids {
+        if raw.len() <= 3 + num_pubkey_idx + num_handshake_ids {
             return Err(Error::NotEnoughData(3));
         }
         let mut bytes_parsed = 4;
-        let mut public_key_ids = Vec::with_capacity(num_pubkey_ids);
+        let mut public_key_idx = Vec::with_capacity(num_pubkey_idx);
-        for raw_pubkey_id in
+        let idx_bytes = (num_pubkey_idx / 2) + (num_pubkey_idx % 2);
-            raw[bytes_parsed..(bytes_parsed + num_pubkey_ids)].iter()
+        let mut idx_added = 0;
+        for raw_pubkey_idx_pair in
+            raw[bytes_parsed..(bytes_parsed + idx_bytes)].iter()
         {
-            public_key_ids.push(PublicKeyID(*raw_pubkey_id));
+            let first = PubKeyIdx(raw_pubkey_idx_pair >> 4);
+            let second = PubKeyIdx(raw_pubkey_idx_pair & 0x0F);
+            public_key_idx.push(first);
+            if num_pubkey_idx - idx_added >= 2 {
+                public_key_idx.push(second);
+            }
+            idx_added = idx_added + 2;
         }
 
         // add handshake ids
-        bytes_parsed = bytes_parsed + num_pubkey_ids;
+        bytes_parsed = bytes_parsed + idx_bytes;
         let mut handshake_ids = Vec::with_capacity(num_handshake_ids);
         for raw_handshake_id in
             raw[bytes_parsed..(bytes_parsed + num_handshake_ids)].iter()
@@ -358,7 +340,7 @@ impl Address {
                 port,
                 priority,
                 weight,
-                public_key_ids,
+                public_key_idx,
                 handshake_ids,
             },
             bytes_parsed,
@@ -374,7 +356,7 @@ impl Address {
 #[derive(Debug, Clone)]
 pub struct Record {
     /// Public keys used by any authentication server
-    pub public_keys: Vec<(PublicKeyID, PubKey)>,
+    pub public_keys: Vec<(KeyID, PubKey)>,
     /// List of all authentication servers' addresses.
     /// Multiple ones can point to the same authentication server
     pub addresses: Vec<Address>,
@@ -443,7 +425,8 @@ impl Record {
             address.encode_into(&mut raw);
         }
         for (public_key_id, public_key) in self.public_keys.iter() {
-            raw.push(public_key_id.0);
+            let key_id_bytes = public_key_id.0.to_le_bytes();
+            raw.extend_from_slice(&key_id_bytes);
             raw.push(public_key.kind().pub_len() as u8);
             raw.push(public_key.kind() as u8);
             public_key.serialize_into(&mut raw);
@@ -462,8 +445,8 @@ impl Record {
     }
     /// Decode from base85 to the actual object
     pub fn decode(raw: &[u8]) -> Result<Self, Error> {
-        // bare minimum for 1 address,  1 key,  1 key exchange and 1 cipher
+        // bare minimum for lengths, (1 address),  (1 key),  cipher negotiation
-        const MIN_RAW_LENGTH: usize = 1 + 1 + 1 + 8 + 9 + 1 + 1;
+        const MIN_RAW_LENGTH: usize = 3 + (6 + 4) + (4 + 32) + 1 + 1 + 1;
         if raw.len() <= MIN_RAW_LENGTH {
             return Err(Error::NotEnoughData(0));
         }
@@ -499,11 +482,14 @@ impl Record {
             num_addresses = num_addresses - 1;
         }
         while num_public_keys > 0 {
-            if bytes_parsed + 2 >= raw.len() {
+            if bytes_parsed + 3 >= raw.len() {
                 return Err(Error::NotEnoughData(bytes_parsed));
             }
-            let id = PublicKeyID(raw[bytes_parsed]);
+
-            bytes_parsed = bytes_parsed + 1;
+            let raw_key_id =
+                u16::from_le_bytes([raw[bytes_parsed], raw[bytes_parsed + 1]]);
+            let id = KeyID(raw_key_id);
+            bytes_parsed = bytes_parsed + 2;
             let pubkey_length = raw[bytes_parsed] as usize;
             bytes_parsed = bytes_parsed + 1;
             if pubkey_length + bytes_parsed >= raw.len() {
@@ -590,6 +576,13 @@ impl Record {
             result.ciphers.push(cipher);
             num_ciphers = num_ciphers - 1;
         }
+        for addr in result.addresses.iter() {
+            for idx in addr.public_key_idx.iter() {
+                if idx.0 as usize >= result.public_keys.len() {
+                    return Err(Error::Max16PublicKeys);
+                }
+            }
+        }
         if bytes_parsed != raw.len() {
             Err(Error::UnknownData(bytes_parsed))
         } else {

src/enc/asym.rs

@@ -3,7 +3,10 @@
 use ::num_traits::FromPrimitive;
 
 use super::Error;
-use crate::enc::{sym::Secret, Random};
+use crate::{
+    config::Config,
+    enc::{sym::Secret, Random},
+};
 
 /// Public key ID
 #[derive(Debug, Copy, Clone, PartialEq)]
@@ -68,8 +71,19 @@ impl KeyKind {
             KeyKind::X25519 => KeyCapabilities::Exchange,
         }
     }
+    /// Returns the key exchanges supported by this key
+    pub fn key_exchanges(&self) -> &'static [KeyExchange] {
+        const EMPTY: [KeyExchange; 0] = [];
+        const X25519_KEY_EXCHANGES: [KeyExchange; 1] =
+            [KeyExchange::X25519DiffieHellman];
+        match self {
+            KeyKind::Ed25519 => &EMPTY,
+            KeyKind::X25519 => &X25519_KEY_EXCHANGES,
+        }
+    }
 }
 
+// FIXME: rename in KeyExchangeKind
 /// Kind of key exchange
 #[derive(Debug, Copy, Clone, PartialEq, ::num_derive::FromPrimitive)]
 #[non_exhaustive]
@@ -279,7 +293,28 @@ impl ExchangePubKey {
     }
 }
 
-/// Build a new pair of private/public key pair
+/// Select the best key exchange from our supported list
-pub fn new_keypair(kind: KeyKind, rnd: &Random) -> (PrivKey, PubKey) {
+/// and the other endpoint supported list.
-    todo!()
+/// Give priority to our list
+pub fn server_select_key_exchange(
+    cfg: &Config,
+    client_supported: &Vec<KeyExchange>,
+) -> Option<KeyExchange> {
+    cfg.key_exchanges
+        .iter()
+        .find(|k| client_supported.contains(k))
+        .copied()
+}
+/// Select the best key exchange from our supported list
+/// and the other endpoint supported list.
+/// Give priority to the server list
+/// This is used only in the Directory Synchronized handshake
+pub fn client_select_key_exchange(
+    cfg: &Config,
+    server_supported: &Vec<KeyExchange>,
+) -> Option<KeyExchange> {
+    server_supported
+        .iter()
+        .find(|k| cfg.key_exchanges.contains(k))
+        .copied()
 }

src/enc/hkdf.rs

@@ -4,7 +4,7 @@
 use ::sha3::Sha3_256;
 use ::zeroize::Zeroize;
 
-use crate::enc::sym::Secret;
+use crate::{config::Config, enc::sym::Secret};
 
 /// Kind of HKDF
 #[derive(Debug, Copy, Clone, PartialEq, ::num_derive::FromPrimitive)]
@@ -14,6 +14,12 @@ pub enum HkdfKind {
     /// Sha3
     Sha3 = 0,
 }
+impl HkdfKind {
+    /// Length of the serialized type
+    pub const fn len() -> usize {
+        1
+    }
+}
 
 /// Generic wrapper on Hkdfs
 #[derive(Clone)]
@@ -52,6 +58,8 @@ impl Hkdf {
 // we can't use #[derive(Zeroing)] either.
 // So we craete a union with a Zeroing object, and drop both manually.
 
+// TODO: move this to Hkdf instead of Sha3
+
 #[derive(Zeroize)]
 #[zeroize(drop)]
 struct Zeroable([u8; ::core::mem::size_of::<::hkdf::Hkdf<Sha3_256>>()]);
@@ -89,7 +97,7 @@ pub struct HkdfSha3 {
 
 impl HkdfSha3 {
     /// Instantiate a new HKDF with Sha3-256
-    pub fn new(salt: &[u8], key: Secret) -> Self {
+    pub(crate) fn new(salt: &[u8], key: Secret) -> Self {
         let hkdf = ::hkdf::Hkdf::<Sha3_256>::new(Some(salt), key.as_ref());
         Self {
             inner: HkdfInner {
@@ -98,7 +106,7 @@ impl HkdfSha3 {
         }
     }
     /// Get a secret generated from the key and a given context
-    pub fn get_secret(&self, context: &[u8]) -> Secret {
+    pub(crate) fn get_secret(&self, context: &[u8]) -> Secret {
         let mut out: [u8; 32] = [0; 32];
         #[allow(unsafe_code)]
         unsafe {
@@ -117,3 +125,29 @@ impl ::core::fmt::Debug for HkdfSha3 {
         ::core::fmt::Debug::fmt("[hidden hkdf]", f)
     }
 }
+
+/// Select the best hkdf from our supported list
+/// and the other endpoint supported list.
+/// Give priority to our list
+pub fn server_select_hkdf(
+    cfg: &Config,
+    client_supported: &Vec<HkdfKind>,
+) -> Option<HkdfKind> {
+    cfg.hkdfs
+        .iter()
+        .find(|h| client_supported.contains(h))
+        .copied()
+}
+/// Select the best hkdf from our supported list
+/// and the other endpoint supported list.
+/// Give priority to the server list
+/// this is used only in the directory synchronized handshake
+pub fn client_select_hkdf(
+    cfg: &Config,
+    server_supported: &Vec<HkdfKind>,
+) -> Option<HkdfKind> {
+    server_supported
+        .iter()
+        .find(|h| cfg.hkdfs.contains(h))
+        .copied()
+}

src/enc/sym.rs

@@ -1,7 +1,7 @@
 //! Symmetric cypher stuff
 
 use super::Error;
-use crate::enc::Random;
+use crate::{config::Config, enc::Random};
 use ::zeroize::Zeroize;
 
 /// Secret, used for keys.
@@ -299,7 +299,7 @@ impl XChaCha20Poly1305 {
 }
 
 //
-// TODO: For efficiency "Nonce" should become a reference.
+// TODO: Merge crate::{enc::sym::Nonce, connection::handshake::dirsync::Nonce}
 //
 
 #[derive(Debug, Copy, Clone)]
@@ -387,3 +387,28 @@ impl NonceSync {
         old_nonce
     }
 }
+/// Select the best cipher from our supported list
+/// and the other endpoint supported list.
+/// Give priority to our list
+pub fn server_select_cipher(
+    cfg: &Config,
+    client_supported: &Vec<CipherKind>,
+) -> Option<CipherKind> {
+    cfg.ciphers
+        .iter()
+        .find(|c| client_supported.contains(c))
+        .copied()
+}
+/// Select the best cipher from our supported list
+/// and the other endpoint supported list.
+/// Give priority to the server list
+/// This is used only in the Directory synchronized handshake
+pub fn client_select_cipher(
+    cfg: &Config,
+    server_supported: &Vec<CipherKind>,
+) -> Option<CipherKind> {
+    server_supported
+        .iter()
+        .find(|c| cfg.ciphers.contains(c))
+        .copied()
+}

src/inner/worker.rs

@@ -1,6 +1,7 @@
 //! Worker thread implementation
 use crate::{
     auth::{ServiceID, TokenChecker},
+    config::Config,
     connection::{
         self,
         handshake::{
@@ -12,9 +13,9 @@ use crate::{
     },
     dnssec,
     enc::{
-        asym::PubKey,
+        asym::{self, PubKey},
-        hkdf::{Hkdf, HkdfKind},
+        hkdf::{self, Hkdf, HkdfKind},
-        sym::Secret,
+        sym::{self, Secret},
         Random,
     },
     inner::{HandshakeAction, HandshakeTracker, ThreadTracker},
@@ -53,6 +54,7 @@ pub(crate) enum WorkAnswer {
 
 /// Actual worker implementation.
 pub(crate) struct Worker {
+    cfg: Config,
     thread_id: ThreadTracker,
     // PERF: rand uses syscalls. how to do that async?
     rand: Random,
@@ -67,6 +69,7 @@ pub(crate) struct Worker {
 
 impl Worker {
     pub(crate) async fn new_and_loop(
+        cfg: Config,
         thread_id: ThreadTracker,
         stop_working: ::tokio::sync::broadcast::Receiver<bool>,
         token_check: Option<Arc<Mutex<TokenChecker>>>,
@@ -75,6 +78,7 @@ impl Worker {
     ) -> ::std::io::Result<()> {
         // TODO: get a channel to send back information, and send the error
         let mut worker = Self::new(
+            cfg,
             thread_id,
             stop_working,
             token_check,
@@ -86,6 +90,7 @@ impl Worker {
         Ok(())
     }
     pub(crate) async fn new(
+        cfg: Config,
         thread_id: ThreadTracker,
         stop_working: ::tokio::sync::broadcast::Receiver<bool>,
         token_check: Option<Arc<Mutex<TokenChecker>>>,
@@ -126,6 +131,7 @@ impl Worker {
         };
 
         Ok(Self {
+            cfg,
             thread_id,
             rand: Random::new(),
             stop_working,
@@ -156,19 +162,52 @@ impl Worker {
                     let _ = sender.send(conn_num);
                 }
                 Work::Connect((send_res, dnssec_record, _service_id)) => {
+                    // PERF: geolocation
+
+                    // Find the first destination with a coherent
+                    // pubkey/key exchange
                     let destination =
                         dnssec_record.addresses.iter().find_map(|addr| {
-                            let maybe_key =
+                            if addr
-                                dnssec_record.public_keys.iter().find(
+                                .handshake_ids
-                                    |(id, _)| addr.public_key_ids.contains(id),
+                                .iter()
-                                );
+                                .find(|h_srv| {
-                            match maybe_key {
+                                    self.cfg.handshakes.contains(h_srv)
-                                Some(key) => Some((addr, key)),
+                                })
-                                None => None,
+                                .is_none()
+                            {
+                                // skip servers with no corresponding
+                                // handshake types
+                                return None;
                             }
+
+                            for idx in addr.public_key_idx.iter() {
+                                let key_supported_k_x =
+                                    dnssec_record.public_keys[idx.0 as usize]
+                                        .1
+                                        .kind()
+                                        .key_exchanges();
+                                match self
+                                    .cfg
+                                    .key_exchanges
+                                    .iter()
+                                    .find(|x| key_supported_k_x.contains(x))
+                                {
+                                    Some(exchange) => {
+                                        return Some((
+                                            addr,
+                                            dnssec_record.public_keys
+                                                [idx.0 as usize],
+                                            exchange,
+                                        ))
+                                    }
+                                    None => return None,
+                                }
+                            }
+                            return None;
                         });
-                    let (addr, key) = match destination {
+                    let (addr, key, exchange) = match destination {
-                        Some((addr, key)) => (addr, key),
+                        Some((addr, key, exchange)) => (addr, key, exchange),
                         None => {
                             let _ =
                                 send_res.send(Err(crate::Error::Resolution(
@@ -178,8 +217,29 @@ impl Worker {
                             continue 'mainloop;
                         }
                     };
-                    use crate::enc::asym;
+                    let hkdf = match hkdf::client_select_hkdf(
-                    let exchange = asym::KeyExchange::X25519DiffieHellman;
+                        &self.cfg,
+                        &dnssec_record.hkdfs,
+                    ) {
+                        Some(hkdf) => hkdf,
+                        None => {
+                            let _ = send_res
+                                .send(Err(crate::Error::HandshakeNegotiation));
+                            continue 'mainloop;
+                        }
+                    };
+                    let cipher = match sym::client_select_cipher(
+                        &self.cfg,
+                        &dnssec_record.ciphers,
+                    ) {
+                        Some(cipher) => cipher,
+                        None => {
+                            let _ = send_res
+                                .send(Err(crate::Error::HandshakeNegotiation));
+                            continue 'mainloop;
+                        }
+                    };
+
                     let (priv_key, pub_key) =
                         match exchange.new_keypair(&self.rand) {
                             Ok(pair) => pair,
@@ -187,10 +247,15 @@ impl Worker {
                         };
                     // build request
                     /*
+                    let req_data = dirsync::ReqData {
+                        nonce: dirsync::Nonce::new(&self.rand),
+                        client_key_id:
+                    };
                     let req = dirsync::Req {
                         key_id: key.0,
-                        exchange: exchange,
+                        exchange,
-                        cipher: 42,
+                        hkdf,
+                        cipher,
                         exchange_key: client_pub_key,
                         data: 42,
                     };

src/lib.rs

@@ -62,6 +62,9 @@ pub enum Error {
     /// Resolution problems. wrong or incomplete DNSSEC data
     #[error("DNSSEC resolution: {0}")]
     Resolution(String),
+    /// No common cryptographic primitives
+    #[error("No common cryptographic primitives")]
+    HandshakeNegotiation,
 }
 
 /// Instance of a fenrir endpoint
@@ -381,6 +384,7 @@ impl Fenrir {
             ::tracing::debug!("Spawning thread {}", core);
             let th_topology = hw_topology.clone();
             let th_tokio_rt = tokio_rt.clone();
+            let th_config = self.cfg.clone();
             let (work_send, work_recv) = ::async_channel::unbounded::<Work>();
             let th_stop_working = self.stop_working.subscribe();
             let th_token_check = self.token_check.clone();
@@ -417,6 +421,7 @@ impl Fenrir {
                 let _ = tk_local.block_on(
                     &th_tokio_rt,
                     Worker::new_and_loop(
+                        th_config,
                         thread_id,
                         th_stop_working,
                         th_token_check,