TLS Policy support

  * --policy works for TLS Server and TLS Client
  * Example policy BSI_TR-02102-2.txt
  * Fine granular configuration for TLS 1.0, 1.1, 1.2 and DTLS 1.0 and 1.2
  * Minimum ecdh and rsa group size

6 files changed, 153 insertions, 24 deletions

diff --git a/src/lib/tls/msg_certificate.cpp b/src/lib/tls/msg_certificate.cpp
index 5be9379bd..fd998cd5e 100644
--- a/src/lib/tls/msg_certificate.cpp
+++ b/src/lib/tls/msg_certificate.cpp
@@ -31,7 +31,7 @@ Certificate::Certificate(Handshake_IO& io,
 /**
 * Deserialize a Certificate message
 */
-Certificate::Certificate(const std::vector<byte>& buf)
+Certificate::Certificate(const std::vector<byte>& buf, const Policy &policy)
    {
    if(buf.size() < 3)
       throw Decoding_Error("Certificate: Message malformed");
@@ -54,7 +54,45 @@ Certificate::Certificate(const std::vector<byte>& buf)
          throw Decoding_Error("Certificate: Message malformed");
 
       DataSource_Memory cert_buf(&certs[3], cert_size);
-      m_certs.push_back(X509_Certificate(cert_buf));
+      X509_Certificate cert(cert_buf);
+      
+	  std::unique_ptr<Public_Key> cert_pub_key(cert.subject_public_key());
+          
+      const std::string algo_name = cert_pub_key->algo_name();
+      const size_t keylength = cert_pub_key->max_input_bits();
+      if(algo_name == "RSA")
+         {
+         const size_t expected_keylength = policy.minimum_rsa_bits();
+         if(keylength < expected_keylength)
+            throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
+                                "The peer sent RSA certificate of " +
+                                std::to_string(keylength) +
+                                " bits, policy requires at least " +
+                                std::to_string(expected_keylength));
+      }
+      else if(algo_name == "DH")
+         {
+         const size_t expected_keylength = policy.minimum_dh_group_size();
+         if(keylength < expected_keylength)
+            throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
+                                "The peer sent DH certificate of " +
+                                std::to_string(keylength) +
+                                " bits, policy requires at least " +
+                                std::to_string(expected_keylength));          
+      }
+      else if(algo_name == "ECDH")
+         {
+         const size_t expected_keylength = policy.minimum_ecdh_group_size();
+         if(keylength < expected_keylength)
+            throw TLS_Exception(Alert::INSUFFICIENT_SECURITY,
+                                "The peer sent ECDH certificate of " +
+                                std::to_string(keylength) +
+                                " bits, policy requires at least " +
+                                std::to_string(expected_keylength));
+          
+      }
+      
+      m_certs.push_back(cert);
 
       certs += cert_size + 3;
       }
diff --git a/src/lib/tls/tls_client.cpp b/src/lib/tls/tls_client.cpp
index 301c77c6b..0423b6536 100644
--- a/src/lib/tls/tls_client.cpp
+++ b/src/lib/tls/tls_client.cpp
@@ -352,7 +352,7 @@ void Client::process_handshake_msg(const Handshake_State* active_state,
          state.set_expected_next(SERVER_HELLO_DONE);
          }
 
-      state.server_certs(new Certificate(contents));
+      state.server_certs(new Certificate(contents, policy()));
 
       const std::vector<X509_Certificate>& server_certs =
          state.server_certs()->cert_chain();
diff --git a/src/lib/tls/tls_messages.h b/src/lib/tls/tls_messages.h
index 3bee89e13..cbeb9ad05 100644
--- a/src/lib/tls/tls_messages.h
+++ b/src/lib/tls/tls_messages.h
@@ -341,7 +341,7 @@ class Certificate final : public Handshake_Message
                   Handshake_Hash& hash,
                   const std::vector<X509_Certificate>& certs);
 
-      explicit Certificate(const std::vector<byte>& buf);
+      explicit Certificate(const std::vector<byte>& buf, const Policy &policy);
    private:
       std::vector<byte> serialize() const override;
 
diff --git a/src/lib/tls/tls_policy.cpp b/src/lib/tls/tls_policy.cpp
index 10b193215..b98f1106c 100644
--- a/src/lib/tls/tls_policy.cpp
+++ b/src/lib/tls/tls_policy.cpp
@@ -127,6 +127,17 @@ size_t Policy::minimum_dh_group_size() const
    return 1024;
    }
 
+size_t Policy::minimum_ecdh_group_size() const
+   {
+   return 159;
+   }
+
+
+size_t Policy::minimum_rsa_bits() const
+   {
+   return 1000; // Not 1024, since some certificates use, e.g., only 1023 bits
+   }
+
 /*
 * Return allowed compression algorithms
 */
@@ -147,10 +158,17 @@ bool Policy::send_fallback_scsv(Protocol_Version version) const
 
 bool Policy::acceptable_protocol_version(Protocol_Version version) const
    {
-   if(version.is_datagram_protocol())
-      return (version >= Protocol_Version::DTLS_V12);
-   else
-      return (version >= Protocol_Version::TLS_V10);
+        // Uses boolean optimization:
+        // First check the current version (left part), then if it is allowed 
+        // (right part)
+        // checks are ordered according to their probability
+        return (
+           ( ( version == Protocol_Version::TLS_V10)  && allow_tls10()  ) ||
+           ( ( version == Protocol_Version::TLS_V12)  && allow_tls12()  ) ||
+           ( ( version == Protocol_Version::TLS_V11)  && allow_tls11()  ) ||
+           ( ( version == Protocol_Version::DTLS_V12) && allow_dtls12() ) ||
+           ( ( version == Protocol_Version::DTLS_V10) && allow_dtls10() )
+        );
    }
 
 Protocol_Version Policy::latest_supported_version(bool datagram) const
@@ -168,6 +186,11 @@ bool Policy::acceptable_ciphersuite(const Ciphersuite&) const
 
 bool Policy::allow_server_initiated_renegotiation() const { return false; }
 bool Policy::allow_insecure_renegotiation() const { return false; }
+bool Policy::allow_tls10()  const { return true; }
+bool Policy::allow_tls11()  const { return true; }
+bool Policy::allow_tls12()  const { return true; }
+bool Policy::allow_dtls10() const { return false; }
+bool Policy::allow_dtls12() const { return true; }
 bool Policy::include_time_in_hello_random() const { return true; }
 bool Policy::hide_unknown_users() const { return false; }
 bool Policy::server_uses_own_ciphersuite_preferences() const { return true; }
@@ -339,6 +362,11 @@ void print_bool(std::ostream& o,
 
 void Policy::print(std::ostream& o) const
    {
+   print_bool(o, "allow_tls10", allow_tls10());
+   print_bool(o, "allow_tls11", allow_tls11());
+   print_bool(o, "allow_tls12", allow_tls12());
+   print_bool(o, "allow_dtls10", allow_dtls10());
+   print_bool(o, "allow_dtls12", allow_dtls12());
    print_vec(o, "ciphers", allowed_ciphers());
    print_vec(o, "macs", allowed_macs());
    print_vec(o, "signature_hashes", allowed_signature_hashes());
@@ -354,6 +382,8 @@ void Policy::print(std::ostream& o) const
    o << "session_ticket_lifetime = " << session_ticket_lifetime() << '\n';
    o << "dh_group = " << dh_group() << '\n';
    o << "minimum_dh_group_size = " << minimum_dh_group_size() << '\n';
+   o << "minimum_ecdh_group_size = " << minimum_ecdh_group_size() << '\n';
+   o << "minimum_rsa_bits = " << minimum_rsa_bits() << '\n';
    }
 
 std::vector<std::string> Strict_Policy::allowed_ciphers() const
@@ -376,13 +406,11 @@ std::vector<std::string> Strict_Policy::allowed_key_exchange_methods() const
    return { "ECDH" };
    }
 
-bool Strict_Policy::acceptable_protocol_version(Protocol_Version version) const
-   {
-   if(version.is_datagram_protocol())
-      return (version >= Protocol_Version::DTLS_V12);
-   else
-      return (version >= Protocol_Version::TLS_V12);
-   }
+bool Strict_Policy::allow_tls10()  const { return false; }
+bool Strict_Policy::allow_tls11()  const { return false; }
+bool Strict_Policy::allow_tls12()  const { return true;  }
+bool Strict_Policy::allow_dtls10() const { return false; }
+bool Strict_Policy::allow_dtls12() const { return true;  }
 
 }
 
diff --git a/src/lib/tls/tls_policy.h b/src/lib/tls/tls_policy.h
index f8262cdee..4ae84b833 100644
--- a/src/lib/tls/tls_policy.h
+++ b/src/lib/tls/tls_policy.h
@@ -101,6 +101,31 @@ class BOTAN_DLL Policy
       * Allow servers to initiate a new handshake
       */
       virtual bool allow_server_initiated_renegotiation() const;
+      
+      /**
+      * Allow TLS v1.0
+      */
+      virtual bool allow_tls10() const;
+      
+      /**
+      * Allow TLS v1.1
+      */
+      virtual bool allow_tls11() const;
+      
+      /**
+      * Allow TLS v1.2
+      */
+      virtual bool allow_tls12() const;
+      
+      /**
+      * Allow DTLS v1.0
+      */
+      virtual bool allow_dtls10() const;
+      
+      /**
+      * Allow DTLS v1.2
+      */
+      virtual bool allow_dtls12() const;
 
       virtual std::string dh_group() const;
 
@@ -108,7 +133,17 @@ class BOTAN_DLL Policy
       * Return the minimum DH group size we're willing to use
       */
       virtual size_t minimum_dh_group_size() const;
-
+      
+      /**
+      * Return the minimum ECDH group size we're willing to use
+      */
+      virtual size_t minimum_ecdh_group_size() const;
+      
+      /**
+      * Return the minimum RSA bit size we're willing to use
+      */
+      virtual size_t minimum_rsa_bits() const;
+      
       /**
       * If this function returns false, unknown SRP/PSK identifiers
       * will be rejected with an unknown_psk_identifier alert as soon
@@ -207,9 +242,12 @@ class BOTAN_DLL NSA_Suite_B_128 : public Policy
 
       std::vector<std::string> allowed_ecc_curves() const override
          { return std::vector<std::string>({"secp256r1"}); }
-
-      bool acceptable_protocol_version(Protocol_Version version) const override
-         { return version == Protocol_Version::TLS_V12; }
+            
+      bool allow_tls10()  const override { return false; }
+      bool allow_tls11()  const override { return false; }
+      bool allow_tls12()  const override { return true;  }
+      bool allow_dtls10() const override { return false; }
+      bool allow_dtls12() const override { return false; }
    };
 
 /**
@@ -220,9 +258,12 @@ class BOTAN_DLL Datagram_Policy : public Policy
    public:
       std::vector<std::string> allowed_macs() const override
          { return std::vector<std::string>({"AEAD"}); }
-
-      bool acceptable_protocol_version(Protocol_Version version) const override
-         { return version == Protocol_Version::DTLS_V12; }
+            
+      bool allow_tls10()  const override { return false; }
+      bool allow_tls11()  const override { return false; }
+      bool allow_tls12()  const override { return false; }
+      bool allow_dtls10() const override { return false; }
+      bool allow_dtls12() const override { return true;  }
    };
 
 /*
@@ -243,7 +284,11 @@ class BOTAN_DLL Strict_Policy : public Policy
 
       std::vector<std::string> allowed_key_exchange_methods() const override;
 
-      bool acceptable_protocol_version(Protocol_Version version) const override;
+      bool allow_tls10()  const override;
+      bool allow_tls11()  const override;
+      bool allow_tls12()  const override;
+      bool allow_dtls10() const override;
+      bool allow_dtls12() const override;
    };
 
 class BOTAN_DLL Text_Policy : public Policy
@@ -267,6 +312,21 @@ class BOTAN_DLL Text_Policy : public Policy
 
       std::vector<std::string> allowed_ecc_curves() const override
          { return get_list("ecc_curves", Policy::allowed_ecc_curves()); }
+      
+      bool allow_tls10() const override
+         { return get_bool("allow_tls10", Policy::allow_tls10()); }
+      
+      bool allow_tls11() const override
+         { return get_bool("allow_tls11", Policy::allow_tls11()); }
+      
+      bool allow_tls12() const override
+         { return get_bool("allow_tls12", Policy::allow_tls12()); }
+      
+      bool allow_dtls10() const override
+         { return get_bool("allow_dtls10", Policy::allow_dtls10()); }
+      
+      bool allow_dtls12() const override
+         { return get_bool("allow_dtls12", Policy::allow_dtls12()); }
 
       bool allow_insecure_renegotiation() const override
          { return get_bool("allow_insecure_renegotiation", Policy::allow_insecure_renegotiation()); }
@@ -286,6 +346,9 @@ class BOTAN_DLL Text_Policy : public Policy
       size_t minimum_dh_group_size() const override
          { return get_len("minimum_dh_group_size", Policy::minimum_dh_group_size()); }
 
+      size_t minimum_rsa_bits() const override
+         { return get_len("minimum_rsa_bits", Policy::minimum_rsa_bits()); }
+      
       bool hide_unknown_users() const override
          { return get_bool("hide_unknown_users", Policy::hide_unknown_users()); }
 
diff --git a/src/lib/tls/tls_server.cpp b/src/lib/tls/tls_server.cpp
index 41b14ae08..39b5afd65 100644
--- a/src/lib/tls/tls_server.cpp
+++ b/src/lib/tls/tls_server.cpp
@@ -591,7 +591,7 @@ void Server::process_handshake_msg(const Handshake_State* active_state,
       }
    else if(type == CERTIFICATE)
       {
-      state.client_certs(new Certificate(contents));
+      state.client_certs(new Certificate(contents, policy()));
 
       state.set_expected_next(CLIENT_KEX);
       }