From baebac5bec42743ea49644d4a836c6162cfe613f Mon Sep 17 00:00:00 2001
From: Mathias Hall-Andersen <mathias@hall-andersen.dk>
Date: Sat, 3 Aug 2019 14:45:45 +0200
Subject: Validate mac2 field

---
 src/handshake/macs.rs  | 35 ++++++++++++++++++++++-------------
 src/handshake/noise.rs |  1 -
 src/handshake/types.rs |  2 ++
 3 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/src/handshake/macs.rs b/src/handshake/macs.rs
index c65f2c8..d95489f 100644
--- a/src/handshake/macs.rs
+++ b/src/handshake/macs.rs
@@ -1,6 +1,5 @@
 use std::time::{Duration, Instant};
 
-use rand::rngs::OsRng;
 use rand::CryptoRng;
 use rand::RngCore;
 
@@ -194,7 +193,16 @@ impl Validator {
         }
     }
 
-    fn get_tau<T>(&self, rng: &mut T, addr: &[u8]) -> [u8; SIZE_COOKIE]
+    fn get_tau(&self, src: &[u8]) -> Result<[u8; SIZE_COOKIE], HandshakeError> {
+        let secret = self.secret.lock();
+        if secret.birth.elapsed() < Duration::from_secs(SECS_COOKIE_UPDATE) {
+            Ok(MAC!(&secret.value, src))
+        } else {
+            Err(HandshakeError::InvalidMac2)
+        }
+    }
+
+    fn get_set_tau<T>(&self, rng: &mut T, src: &[u8]) -> [u8; SIZE_COOKIE]
     where
         T: RngCore + CryptoRng,
     {
@@ -202,13 +210,13 @@ impl Validator {
 
         // check if current value is still valid
         if secret.birth.elapsed() < Duration::from_secs(SECS_COOKIE_UPDATE) {
-            return MAC!(&secret.value, addr);
+            return MAC!(&secret.value, src);
         };
 
         // generate new value
         rng.fill_bytes(&mut secret.value);
         secret.birth = Instant::now();
-        MAC!(&secret.value, addr)
+        MAC!(&secret.value, src)
     }
 
     fn create_cookie_reply<T>(
@@ -224,12 +232,12 @@ impl Validator {
         msg.f_receiver.set(receiver);
         rng.fill_bytes(&mut msg.f_nonce);
         XSEAL!(
-            &self.cookie_key,        // key
-            &msg.f_nonce,            // nonce
-            &macs.f_mac1,            // ad
-            &self.get_tau(rng, src), // pt
-            &mut msg.f_cookie,       // ct
-            &mut msg.f_cookie_tag    // tag
+            &self.cookie_key,            // key
+            &msg.f_nonce,                // nonce
+            &macs.f_mac1,                // ad
+            &self.get_set_tau(rng, src), // pt
+            &mut msg.f_cookie,           // ct
+            &mut msg.f_cookie_tag        // tag
         );
     }
 
@@ -261,9 +269,10 @@ impl Validator {
         src: &[u8],
         macs: &MacsFooter,
     ) -> Result<(), HandshakeError> {
-        let valid_mac1: bool = MAC!(&self.mac1_key, inner).ct_eq(&macs.f_mac1).into();
-        if !valid_mac1 {
-            Err(HandshakeError::InvalidMac1)
+        let tau = self.get_tau(src)?;
+        let valid_mac2: bool = MAC!(&tau, inner, macs.f_mac1).ct_eq(&macs.f_mac2).into();
+        if !valid_mac2 {
+            Err(HandshakeError::InvalidMac2)
         } else {
             Ok(())
         }
diff --git a/src/handshake/noise.rs b/src/handshake/noise.rs
index cf5238c..0534e97 100644
--- a/src/handshake/noise.rs
+++ b/src/handshake/noise.rs
@@ -322,7 +322,6 @@ pub fn create_response<T: Copy>(
     state: TemporaryState,   // state from "consume_initiation"
     msg: &mut NoiseResponse, // resulting response
 ) -> Result<KeyPair, HandshakeError> {
-    let mut rng = OsRng::new().unwrap();
     let (receiver, eph_r_pk, hs, ck) = state;
     let mut rng = OsRng::new().unwrap();
     msg.f_sender.set(sender);
diff --git a/src/handshake/types.rs b/src/handshake/types.rs
index 6a35e1c..38b044e 100644
--- a/src/handshake/types.rs
+++ b/src/handshake/types.rs
@@ -43,6 +43,7 @@ pub enum HandshakeError {
     OldTimestamp,
     InvalidState,
     InvalidMac1,
+    InvalidMac2
 }
 
 impl fmt::Display for HandshakeError {
@@ -57,6 +58,7 @@ impl fmt::Display for HandshakeError {
             HandshakeError::OldTimestamp => write!(f, "Timestamp is less/equal to the newest"),
             HandshakeError::InvalidState => write!(f, "Message does not apply to handshake state"),
             HandshakeError::InvalidMac1 => write!(f, "Message has invalid mac1 field"),
+            HandshakeError::InvalidMac2 => write!(f, "Message has invalid mac2 field"),
         }
     }
 }
-- 
cgit v1.2.3-59-g8ed1b