Simplification in record layer

4 files changed, 34 insertions, 10 deletions

diff --git a/src/lib/tls/tls_ciphersuite.cpp b/src/lib/tls/tls_ciphersuite.cpp
index 88837387e..cf284e565 100644
--- a/src/lib/tls/tls_ciphersuite.cpp
+++ b/src/lib/tls/tls_ciphersuite.cpp
@@ -37,6 +37,30 @@ size_t Ciphersuite::nonce_bytes_from_handshake() const
    throw Invalid_State("In Ciphersuite::nonce_bytes_from_handshake invalid enum value");
    }
 
+size_t Ciphersuite::nonce_bytes_from_record(Protocol_Version version) const
+   {
+   switch(m_nonce_format)
+      {
+      case Nonce_Format::CBC_MODE:
+         {
+         if(version.supports_explicit_cbc_ivs())
+            {
+            return cipher_algo() == "3DES" ? 8 : 16;
+            }
+         else
+            {
+            return 0;
+            }
+         }
+      case Nonce_Format::AEAD_IMPLICIT_4:
+         return 8;
+      case Nonce_Format::AEAD_XOR_12:
+         return 0;
+      }
+
+   throw Invalid_State("In Ciphersuite::nonce_bytes_from_handshake invalid enum value");
+   }
+
 bool Ciphersuite::is_scsv(uint16_t suite)
    {
    // TODO: derive from IANA file in script
diff --git a/src/lib/tls/tls_ciphersuite.h b/src/lib/tls/tls_ciphersuite.h
index 7ef7623bb..1d23a6c4a 100644
--- a/src/lib/tls/tls_ciphersuite.h
+++ b/src/lib/tls/tls_ciphersuite.h
@@ -114,6 +114,8 @@ class BOTAN_PUBLIC_API(2,0) Ciphersuite final
 
       size_t nonce_bytes_from_handshake() const;
 
+      size_t nonce_bytes_from_record(Protocol_Version version) const;
+
       Nonce_Format nonce_format() const { return m_nonce_format; }
 
       size_t mac_keylen() const { return m_mac_keylen; }
diff --git a/src/lib/tls/tls_record.cpp b/src/lib/tls/tls_record.cpp
index 730751855..ccad351d2 100644
--- a/src/lib/tls/tls_record.cpp
+++ b/src/lib/tls/tls_record.cpp
@@ -50,8 +50,11 @@ Connection_Cipher_State::Connection_Cipher_State(Protocol_Version version,
       }
 
    m_nonce = unlock(iv.bits_of());
-   m_nonce_bytes_from_handshake = m_nonce.size();
    m_nonce_format = suite.nonce_format();
+   m_nonce_bytes_from_record = suite.nonce_bytes_from_record(version);
+   m_nonce_bytes_from_handshake = suite.nonce_bytes_from_handshake();
+
+   BOTAN_ASSERT_NOMSG(m_nonce.size() == m_nonce_bytes_from_handshake);
 
    if(nonce_format() == Nonce_Format::CBC_MODE)
       {
@@ -83,11 +86,7 @@ Connection_Cipher_State::Connection_Cipher_State(Protocol_Version version,
 
       m_aead->set_key(cipher_key + mac_key);
 
-      m_nonce_bytes_from_record = 0;
-
-      if(version.supports_explicit_cbc_ivs())
-         m_nonce_bytes_from_record = m_nonce_bytes_from_handshake;
-      else if(our_side == false)
+      if(our_side == false)
          m_aead->start(iv.bits_of());
 #else
       throw Internal_Error("Negotiated disabled TLS CBC+HMAC ciphersuite");
@@ -101,7 +100,6 @@ Connection_Cipher_State::Connection_Cipher_State(Protocol_Version version,
 
       if(nonce_format() == Nonce_Format::AEAD_IMPLICIT_4)
          {
-         m_nonce_bytes_from_record = 8;
          m_nonce.resize(m_nonce.size() + 8);
          }
       else if(nonce_format() != Nonce_Format::AEAD_XOR_12)
diff --git a/src/lib/tls/tls_record.h b/src/lib/tls/tls_record.h
index 7ccd78b86..7cf577217 100644
--- a/src/lib/tls/tls_record.h
+++ b/src/lib/tls/tls_record.h
@@ -68,9 +68,9 @@ class Connection_Cipher_State final
       std::unique_ptr<AEAD_Mode> m_aead;
 
       std::vector<uint8_t> m_nonce;
-      Nonce_Format m_nonce_format = Nonce_Format::CBC_MODE;
-      size_t m_nonce_bytes_from_handshake = 0;
-      size_t m_nonce_bytes_from_record = 0;
+      Nonce_Format m_nonce_format;
+      size_t m_nonce_bytes_from_handshake;
+      size_t m_nonce_bytes_from_record;
    };
 
 class Record final