Have cipher modes also verify that the nonce is set prior to use

2 files changed, 12 insertions, 5 deletions

diff --git a/src/lib/modes/cbc/cbc.cpp b/src/lib/modes/cbc/cbc.cpp
index c67664a6e..76b78e4f6 100644
--- a/src/lib/modes/cbc/cbc.cpp
+++ b/src/lib/modes/cbc/cbc.cpp
@@ -15,9 +15,9 @@ namespace Botan {
 CBC_Mode::CBC_Mode(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :
    m_cipher(cipher),
    m_padding(padding),
-   m_state(m_cipher->block_size())
+   m_block_size(cipher->block_size())
    {
-   if(m_padding && !m_padding->valid_blocksize(cipher->block_size()))
+   if(m_padding && !m_padding->valid_blocksize(m_block_size))
       throw Invalid_Argument("Padding " + m_padding->name() +
                              " cannot be used with " +
                              cipher->name() + "/CBC");
@@ -31,7 +31,7 @@ void CBC_Mode::clear()
 
 void CBC_Mode::reset()
    {
-   zeroise(m_state);
+   m_state.clear();
    }
 
 std::string CBC_Mode::name() const
@@ -79,6 +79,9 @@ void CBC_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
    */
    if(nonce_len)
       m_state.assign(nonce, nonce + nonce_len);
+   else if(m_state.empty())
+      m_state.resize(m_cipher->block_size());
+   // else leave the state alone
    }
 
 size_t CBC_Encryption::minimum_final_size() const
@@ -96,6 +99,7 @@ size_t CBC_Encryption::output_length(size_t input_length) const
 
 size_t CBC_Encryption::process(uint8_t buf[], size_t sz)
    {
+   BOTAN_STATE_CHECK(state().empty() == false);
    const size_t BS = block_size();
 
    BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");
@@ -205,6 +209,8 @@ size_t CBC_Decryption::minimum_final_size() const
 
 size_t CBC_Decryption::process(uint8_t buf[], size_t sz)
    {
+   BOTAN_STATE_CHECK(state().empty() == false);
+
    const size_t BS = block_size();
 
    BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");
diff --git a/src/lib/modes/cbc/cbc.h b/src/lib/modes/cbc/cbc.h
index 65b639511..aaa425712 100644
--- a/src/lib/modes/cbc/cbc.h
+++ b/src/lib/modes/cbc/cbc.h
@@ -46,9 +46,9 @@ class BOTAN_PUBLIC_API(2,0) CBC_Mode : public Cipher_Mode
          return *m_padding;
          }
 
-      secure_vector<uint8_t>& state() { return m_state; }
+      size_t block_size() const { return m_block_size; }
 
-      size_t block_size() const { return m_state.size(); }
+      secure_vector<uint8_t>& state() { return m_state; }
 
       uint8_t* state_ptr() { return m_state.data(); }
 
@@ -60,6 +60,7 @@ class BOTAN_PUBLIC_API(2,0) CBC_Mode : public Cipher_Mode
       std::unique_ptr<BlockCipher> m_cipher;
       std::unique_ptr<BlockCipherModePaddingMethod> m_padding;
       secure_vector<uint8_t> m_state;
+      size_t m_block_size;
    };
 
 /**