If the maximum fragment extension was negotiated, enforce it. Also

enforce the 2^14 byte plaintext limit in the reader (previously only
the 2^14+2048 byte ciphertext size limit was enforced).

4 files changed, 32 insertions, 2 deletions

diff --git a/src/tls/rec_read.cpp b/src/tls/rec_read.cpp
index 080d6a1f8..518540bab 100644
--- a/src/tls/rec_read.cpp
+++ b/src/tls/rec_read.cpp
@@ -9,10 +9,18 @@
 #include <botan/lookup.h>
 #include <botan/loadstor.h>
 #include <botan/internal/tls_session_key.h>
+#include <botan/internal/rounding.h>
 #include <botan/internal/assert.h>
 
 namespace Botan {
 
+Record_Reader::Record_Reader()
+   {
+   m_mac = 0;
+   reset();
+   set_maximum_fragment_size(0);
+   }
+
 /*
 * Reset the state
 */
@@ -28,6 +36,15 @@ void Record_Reader::reset()
    m_iv_size = 0;
    m_major = m_minor = 0;
    m_seq_no = 0;
+   set_maximum_fragment_size(0);
+   }
+
+void Record_Reader::set_maximum_fragment_size(size_t max_fragment)
+   {
+   if(max_fragment == 0)
+      m_max_fragment = MAX_PLAINTEXT_SIZE;
+   else
+      m_max_fragment = clamp(max_fragment, 128, MAX_PLAINTEXT_SIZE);
    }
 
 /*
@@ -252,6 +269,9 @@ size_t Record_Reader::get_record(byte& msg_type,
 
    const u16bit plain_length = m_readbuf.size() - (m_mac_size + pad_size + m_iv_size);
 
+   if(plain_length > m_max_fragment)
+      throw TLS_Exception(RECORD_OVERFLOW, "Plaintext record is too large");
+
    m_mac->update_be(m_seq_no);
    m_mac->update(header[0]); // msg_type
 
diff --git a/src/tls/rec_wri.cpp b/src/tls/rec_wri.cpp
index d9f86492d..4ccec58d9 100644
--- a/src/tls/rec_wri.cpp
+++ b/src/tls/rec_wri.cpp
@@ -20,10 +20,11 @@ namespace Botan {
 * Record_Writer Constructor
 */
 Record_Writer::Record_Writer(std::tr1::function<void (const byte[], size_t)> out) :
-   m_output_fn(out), m_max_fragment(MAX_PLAINTEXT_SIZE)
+   m_output_fn(out)
    {
    m_mac = 0;
    reset();
+   set_maximum_fragment_size(0);
    }
 
 void Record_Writer::set_maximum_fragment_size(size_t max_fragment)
@@ -39,6 +40,7 @@ void Record_Writer::set_maximum_fragment_size(size_t max_fragment)
 */
 void Record_Writer::reset()
    {
+   set_maximum_fragment_size(0);
    m_cipher.reset();
 
    delete m_mac;
diff --git a/src/tls/tls_record.h b/src/tls/tls_record.h
index 052fd43d8..8e89b9f8a 100644
--- a/src/tls/tls_record.h
+++ b/src/tls/tls_record.h
@@ -104,7 +104,9 @@ class BOTAN_DLL Record_Reader
 
       bool currently_empty() const { return m_input_queue.size() == 0; }
 
-      Record_Reader() { m_mac = 0; reset(); }
+      void set_maximum_fragment_size(size_t max_fragment);
+
+      Record_Reader();
 
       ~Record_Reader() { delete m_mac; }
    private:
diff --git a/src/tls/tls_server.cpp b/src/tls/tls_server.cpp
index 17f2b51b9..e66936771 100644
--- a/src/tls/tls_server.cpp
+++ b/src/tls/tls_server.cpp
@@ -200,7 +200,10 @@ void TLS_Server::process_handshake_msg(Handshake_Type type,
             rng);
 
          if(session_info.fragment_size())
+            {
+            reader.set_maximum_fragment_size(session_info.fragment_size());
             writer.set_maximum_fragment_size(session_info.fragment_size());
+            }
 
          state->suite = TLS_Cipher_Suite(state->server_hello->ciphersuite());
 
@@ -250,7 +253,10 @@ void TLS_Server::process_handshake_msg(Handshake_Type type,
             rng);
 
          if(state->client_hello->fragment_size())
+            {
+            reader.set_maximum_fragment_size(state->client_hello->fragment_size());
             writer.set_maximum_fragment_size(state->client_hello->fragment_size());
+            }
 
          state->suite = TLS_Cipher_Suite(state->server_hello->ciphersuite());