tls_ciphersuite.cpp

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/*
* TLS Cipher Suite
* (C) 2004-2010,2012,2013 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/tls_ciphersuite.h>
 
#include <botan/block_cipher.h>
#include <botan/exceptn.h>
#include <botan/hash.h>
#include <botan/stream_cipher.h>
#include <botan/internal/parsing.h>
#include <algorithm>
 
namespace Botan::TLS {
 
size_t Ciphersuite::nonce_bytes_from_handshake() const {
   switch(m_nonce_format) {
      case Nonce_Format::CBC_MODE: {
         if(cipher_algo() == "3DES") {
            return 8;
         } else {
            return 16;
         }
      }
      case Nonce_Format::AEAD_IMPLICIT_4:
         return 4;
      case Nonce_Format::AEAD_XOR_12:
         return 12;
   }
 
   throw Invalid_State("In Ciphersuite::nonce_bytes_from_handshake invalid enum value");
}
 
size_t Ciphersuite::nonce_bytes_from_record(Protocol_Version version) const {
   BOTAN_UNUSED(version);
   switch(m_nonce_format) {
      case Nonce_Format::CBC_MODE:
         return cipher_algo() == "3DES" ? 8 : 16;
      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
   return (suite == 0x00FF || suite == 0x5600);
}
 
bool Ciphersuite::psk_ciphersuite() const {
   return kex_method() == Kex_Algo::PSK || kex_method() == Kex_Algo::ECDHE_PSK;
}
 
bool Ciphersuite::ecc_ciphersuite() const {
   return kex_method() == Kex_Algo::ECDH || kex_method() == Kex_Algo::ECDHE_PSK || auth_method() == Auth_Method::ECDSA;
}
 
bool Ciphersuite::usable_in_version(Protocol_Version version) const {
   // RFC 8446 B.4.:
   //   Although TLS 1.3 uses the same cipher suite space as previous
   //   versions of TLS, TLS 1.3 cipher suites are defined differently, only
   //   specifying the symmetric ciphers, and cannot be used for TLS 1.2.
   //   Similarly, cipher suites for TLS 1.2 and lower cannot be used with
   //   TLS 1.3.
   //
   // Currently cipher suite codes {0x13,0x01} through {0x13,0x05} are
   // allowed for TLS 1.3. This may change in the future.
   const auto is_legacy_suite = (ciphersuite_code() & 0xFF00) != 0x1300;
   return version.is_pre_tls_13() == is_legacy_suite;
}
 
bool Ciphersuite::cbc_ciphersuite() const {
   return (mac_algo() != "AEAD");
}
 
bool Ciphersuite::aead_ciphersuite() const {
   return (mac_algo() == "AEAD");
}
 
bool Ciphersuite::signature_used() const {
   return auth_method() != Auth_Method::IMPLICIT;
}
 
std::optional<Ciphersuite> Ciphersuite::by_id(uint16_t suite) {
   const std::vector<Ciphersuite>& all_suites = all_known_ciphersuites();
   auto s = std::lower_bound(all_suites.begin(), all_suites.end(), suite);
 
   if(s != all_suites.end() && s->ciphersuite_code() == suite) {
      return *s;
   }
 
   return std::nullopt;  // some unknown ciphersuite
}
 
std::optional<Ciphersuite> Ciphersuite::from_name(std::string_view name) {
   const std::vector<Ciphersuite>& all_suites = all_known_ciphersuites();
 
   for(auto suite : all_suites) {
      if(suite.to_string() == name) {
         return suite;
      }
   }
 
   return std::nullopt;  // some unknown ciphersuite
}
 
namespace {
 
bool have_hash(std::string_view prf) {
   return (!HashFunction::providers(prf).empty());
}
 
bool have_cipher(std::string_view cipher) {
   return (!BlockCipher::providers(cipher).empty()) || (!StreamCipher::providers(cipher).empty());
}
 
}  // namespace
 
bool Ciphersuite::is_usable() const {
   if(!m_cipher_keylen) {  // uninitialized object
      return false;
   }
 
   if(!have_hash(prf_algo())) {
      return false;
   }
 
#if !defined(BOTAN_HAS_TLS_CBC)
   if(cbc_ciphersuite())
      return false;
#endif
 
   if(mac_algo() == "AEAD") {
      if(cipher_algo() == "ChaCha20Poly1305") {
#if !defined(BOTAN_HAS_AEAD_CHACHA20_POLY1305)
         return false;
#endif
      } else {
         auto cipher_and_mode = split_on(cipher_algo(), '/');
         BOTAN_ASSERT(cipher_and_mode.size() == 2, "Expected format for AEAD algo");
         if(!have_cipher(cipher_and_mode[0])) {
            return false;
         }
 
         const auto mode = cipher_and_mode[1];
 
#if !defined(BOTAN_HAS_AEAD_CCM)
         if(mode == "CCM" || mode == "CCM-8")
            return false;
#endif
 
#if !defined(BOTAN_HAS_AEAD_GCM)
         if(mode == "GCM")
            return false;
#endif
 
#if !defined(BOTAN_HAS_AEAD_OCB)
         if(mode == "OCB(12)" || mode == "OCB")
            return false;
#endif
      }
   } else {
      // Old non-AEAD schemes
      if(!have_cipher(cipher_algo())) {
         return false;
      }
      if(!have_hash(mac_algo())) {  // HMAC
         return false;
      }
   }
 
   if(kex_method() == Kex_Algo::ECDH || kex_method() == Kex_Algo::ECDHE_PSK) {
#if !defined(BOTAN_HAS_ECDH)
      return false;
#endif
   } else if(kex_method() == Kex_Algo::DH) {
#if !defined(BOTAN_HAS_DIFFIE_HELLMAN)
      return false;
#endif
   }
 
   if(auth_method() == Auth_Method::ECDSA) {
#if !defined(BOTAN_HAS_ECDSA)
      return false;
#endif
   } else if(auth_method() == Auth_Method::RSA) {
#if !defined(BOTAN_HAS_RSA)
      return false;
#endif
   }
 
   return true;
}
 
}  // namespace Botan::TLS