Fix off by one when decoding TLS-CBC ciphertexts

3 files changed, 30 insertions, 27 deletions

diff --git a/src/lib/tls/tls_cbc/tls_cbc.cpp b/src/lib/tls/tls_cbc/tls_cbc.cpp
index ca80a3d3c..a745a548b 100644
--- a/src/lib/tls/tls_cbc/tls_cbc.cpp
+++ b/src/lib/tls/tls_cbc/tls_cbc.cpp
@@ -24,26 +24,25 @@ namespace TLS {
 * TLS_CBC_HMAC_AEAD_Mode Constructor
 */
 TLS_CBC_HMAC_AEAD_Mode::TLS_CBC_HMAC_AEAD_Mode(Cipher_Dir dir,
-                                               const std::string& cipher_name,
+                                               std::unique_ptr<BlockCipher> cipher,
+                                               std::unique_ptr<MessageAuthenticationCode> mac,
                                                size_t cipher_keylen,
-                                               const std::string& mac_name,
                                                size_t mac_keylen,
                                                bool use_explicit_iv,
                                                bool use_encrypt_then_mac) :
-   m_cipher_name(cipher_name),
-   m_mac_name(mac_name),
+   m_cipher_name(cipher->name()),
+   m_mac_name(mac->name()),
    m_cipher_keylen(cipher_keylen),
    m_mac_keylen(mac_keylen),
    m_use_encrypt_then_mac(use_encrypt_then_mac)
    {
-   m_mac = MessageAuthenticationCode::create_or_throw("HMAC(" + m_mac_name + ")");
-   std::unique_ptr<BlockCipher> cipher = BlockCipher::create_or_throw(m_cipher_name);
-
-   m_tag_size = m_mac->output_length();
+   m_tag_size = mac->output_length();
    m_block_size = cipher->block_size();
 
    m_iv_size = use_explicit_iv ? m_block_size : 0;
 
+   m_mac = std::move(mac);
+
    if(dir == ENCRYPTION)
       m_cbc.reset(new CBC_Encryption(cipher.release(), new Null_Padding));
    else
@@ -419,7 +418,7 @@ void TLS_CBC_HMAC_AEAD_Decryption::finish(secure_vector<uint8_t>& buffer, size_t
       (sending empty records, instead of 1/(n-1) splitting)
       */
 
-      const uint16_t size_ok_mask = CT::is_lte<uint16_t>(static_cast<uint16_t>(tag_size() + pad_size), static_cast<uint16_t>(record_len + 1));
+      const uint16_t size_ok_mask = CT::is_lte<uint16_t>(static_cast<uint16_t>(tag_size() + pad_size), static_cast<uint16_t>(record_len));
       pad_size &= size_ok_mask;
 
       CT::unpoison(record_contents, record_len);
diff --git a/src/lib/tls/tls_cbc/tls_cbc.h b/src/lib/tls/tls_cbc/tls_cbc.h
index 012b9e51f..c8a808156 100644
--- a/src/lib/tls/tls_cbc/tls_cbc.h
+++ b/src/lib/tls/tls_cbc/tls_cbc.h
@@ -46,9 +46,9 @@ class BOTAN_TEST_API TLS_CBC_HMAC_AEAD_Mode : public AEAD_Mode
 
  protected:
       TLS_CBC_HMAC_AEAD_Mode(Cipher_Dir direction,
-                             const std::string& cipher_name,
+                             std::unique_ptr<BlockCipher> cipher,
+                             std::unique_ptr<MessageAuthenticationCode> mac,
                              size_t cipher_keylen,
-                             const std::string& mac_name,
                              size_t mac_keylen,
                              bool use_explicit_iv,
                              bool use_encrypt_then_mac);
@@ -104,16 +104,17 @@ class BOTAN_TEST_API TLS_CBC_HMAC_AEAD_Encryption final : public TLS_CBC_HMAC_AE
    public:
       /**
       */
-      TLS_CBC_HMAC_AEAD_Encryption(const std::string& cipher_algo,
-                                   const size_t cipher_keylen,
-                                   const std::string& mac_algo,
-                                   const size_t mac_keylen,
-                                   bool use_explicit_iv,
-                                   bool use_encrypt_then_mac) :
+      TLS_CBC_HMAC_AEAD_Encryption(
+                             std::unique_ptr<BlockCipher> cipher,
+                             std::unique_ptr<MessageAuthenticationCode> mac,
+                             const size_t cipher_keylen,
+                             const size_t mac_keylen,
+                             bool use_explicit_iv,
+                             bool use_encrypt_then_mac) :
          TLS_CBC_HMAC_AEAD_Mode(ENCRYPTION,
-                                cipher_algo,
+                                std::move(cipher),
+                                std::move(mac),
                                 cipher_keylen,
-                                mac_algo,
                                 mac_keylen,
                                 use_explicit_iv,
                                 use_encrypt_then_mac)
@@ -138,16 +139,16 @@ class BOTAN_TEST_API TLS_CBC_HMAC_AEAD_Decryption final : public TLS_CBC_HMAC_AE
    public:
       /**
       */
-      TLS_CBC_HMAC_AEAD_Decryption(const std::string& cipher_algo,
+      TLS_CBC_HMAC_AEAD_Decryption(std::unique_ptr<BlockCipher> cipher,
+                                   std::unique_ptr<MessageAuthenticationCode> mac,
                                    const size_t cipher_keylen,
-                                   const std::string& mac_algo,
                                    const size_t mac_keylen,
                                    bool use_explicit_iv,
                                    bool use_encrypt_then_mac) :
          TLS_CBC_HMAC_AEAD_Mode(DECRYPTION,
-                                cipher_algo,
+                                std::move(cipher),
+                                std::move(mac),
                                 cipher_keylen,
-                                mac_algo,
                                 mac_keylen,
                                 use_explicit_iv,
                                 use_encrypt_then_mac)
diff --git a/src/lib/tls/tls_record.cpp b/src/lib/tls/tls_record.cpp
index ded3831d0..1f564a689 100644
--- a/src/lib/tls/tls_record.cpp
+++ b/src/lib/tls/tls_record.cpp
@@ -57,12 +57,15 @@ Connection_Cipher_State::Connection_Cipher_State(Protocol_Version version,
       {
 #if defined(BOTAN_HAS_TLS_CBC)
       // legacy CBC+HMAC mode
+      auto mac = MessageAuthenticationCode::create_or_throw("HMAC(" + suite.mac_algo() + ")");
+      auto cipher = BlockCipher::create_or_throw(suite.cipher_algo());
+
       if(our_side)
          {
          m_aead.reset(new TLS_CBC_HMAC_AEAD_Encryption(
-                         suite.cipher_algo(),
+                         std::move(cipher),
+                         std::move(mac),
                          suite.cipher_keylen(),
-                         suite.mac_algo(),
                          suite.mac_keylen(),
                          version.supports_explicit_cbc_ivs(),
                          uses_encrypt_then_mac));
@@ -70,9 +73,9 @@ Connection_Cipher_State::Connection_Cipher_State(Protocol_Version version,
       else
          {
          m_aead.reset(new TLS_CBC_HMAC_AEAD_Decryption(
-                         suite.cipher_algo(),
+                         std::move(cipher),
+                         std::move(mac),
                          suite.cipher_keylen(),
-                         suite.mac_algo(),
                          suite.mac_keylen(),
                          version.supports_explicit_cbc_ivs(),
                          uses_encrypt_then_mac));