diff options
| -rw-r--r-- | include/axolotl/crypto.hh | 2 | ||||
| -rw-r--r-- | include/axolotl/memory.hh | 17 | ||||
| -rw-r--r-- | src/axolotl.cpp | 37 | ||||
| -rw-r--r-- | src/crypto.cpp | 20 | ||||
| -rw-r--r-- | src/memory.cpp | 11 |
5 files changed, 59 insertions, 28 deletions
diff --git a/include/axolotl/crypto.hh b/include/axolotl/crypto.hh index 09e5b8e..162099f 100644 --- a/include/axolotl/crypto.hh +++ b/include/axolotl/crypto.hh @@ -28,6 +28,7 @@ struct Curve25519KeyPair : public Curve25519PublicKey { std::uint8_t private_key[32]; }; + /** Generate a curve25519 key pair from 32 random bytes. */ void generate_key( std::uint8_t const * random_32_bytes, @@ -37,6 +38,7 @@ void generate_key( const std::size_t CURVE25519_SHARED_SECRET_LENGTH = 32; + /** Create a shared secret using our private key and their public key. * The output buffer must be at least 32 bytes long. */ void curve25519_shared_secret( diff --git a/include/axolotl/memory.hh b/include/axolotl/memory.hh new file mode 100644 index 0000000..7749c54 --- /dev/null +++ b/include/axolotl/memory.hh @@ -0,0 +1,17 @@ +#include <cstddef> + +namespace axolotl { + +/** Clear the memory held in the buffer */ +void unset( + volatile void * buffer, std::size_t buffer_length +); + +/** Clear the memory backing an object */ +template<typename T> +void unset(T & value) { + unset(reinterpret_cast<volatile void *>(&value), sizeof(T)); +} + + +} // namespace axolotl diff --git a/src/axolotl.cpp b/src/axolotl.cpp index cf49d31..0f0d226 100644 --- a/src/axolotl.cpp +++ b/src/axolotl.cpp @@ -14,6 +14,7 @@ */ #include "axolotl/axolotl.hh" #include "axolotl/message.hh" +#include "axolotl/memory.hh" #include <cstring> @@ -26,14 +27,6 @@ std::uint8_t MESSAGE_KEY_SEED[1] = {0x01}; std::uint8_t CHAIN_KEY_SEED[1] = {0x02}; std::size_t MAX_MESSAGE_GAP = 2000; -template<typename T> -void unset( - T & value -) { - std::memset(&value, 0, sizeof(T)); -} - - void create_chain_key( axolotl::SharedKey const & root_key, axolotl::Curve25519KeyPair const & our_key, @@ -54,8 +47,8 @@ void create_chain_key( std::memcpy(new_root_key, derived_secrets, 32); std::memcpy(new_chain_key.key, derived_secrets + 32, 32); new_chain_key.index = 0; - unset(derived_secrets); - unset(secret); + axolotl::unset(derived_secrets); + axolotl::unset(secret); } @@ -94,8 +87,8 @@ void create_message_keys( std::memcpy(message_key.mac_key, derived_secrets + 32, 32); std::memcpy(message_key.iv.iv, derived_secrets + 64, 16); message_key.index = chain_key.index; - unset(derived_secrets); - unset(secret); + axolotl::unset(derived_secrets); + axolotl::unset(secret); } @@ -112,7 +105,7 @@ bool verify_mac( ); bool result = std::memcmp(mac, reader.mac, MAC_LENGTH) == 0; - unset(mac); + axolotl::unset(mac); return result; } @@ -142,7 +135,7 @@ bool verify_mac_for_existing_chain( create_message_keys(new_chain, session.kdf_info, message_key); bool result = verify_mac(message_key, input, reader); - unset(new_chain); + axolotl::unset(new_chain); return result; } @@ -178,8 +171,8 @@ bool verify_mac_for_new_chain( bool result = verify_mac_for_existing_chain( session, new_chain.chain_key, input, reader ); - unset(new_root_key); - unset(new_chain); + axolotl::unset(new_root_key); + axolotl::unset(new_chain); return result; } @@ -207,7 +200,7 @@ void axolotl::Session::initialise_as_bob( std::memcpy(root_key, derived_secrets, 32); std::memcpy(receiver_chains[0].chain_key.key, derived_secrets + 32, 32); receiver_chains[0].ratchet_key = their_ratchet_key; - unset(derived_secrets); + axolotl::unset(derived_secrets); } @@ -226,7 +219,7 @@ void axolotl::Session::initialise_as_alice( std::memcpy(root_key, derived_secrets, 32); std::memcpy(sender_chain[0].chain_key.key, derived_secrets + 32, 32); sender_chain[0].ratchet_key = our_ratchet_key; - unset(derived_secrets); + axolotl::unset(derived_secrets); } @@ -303,7 +296,7 @@ std::size_t axolotl::Session::encrypt( ); std::memcpy(writer.mac, mac, MAC_LENGTH); - unset(keys); + axolotl::unset(keys); return writer.body_length + MAC_LENGTH; } @@ -385,7 +378,7 @@ std::size_t axolotl::Session::decrypt( /* Remove the key from the skipped keys now that we've * decoded the message it corresponds to. */ - unset(skipped); + axolotl::unset(skipped); skipped_message_keys.erase(&skipped); return result; } @@ -414,7 +407,7 @@ std::size_t axolotl::Session::decrypt( root_key, sender_chain[0].ratchet_key, chain->ratchet_key, kdf_info, root_key, chain->chain_key ); - unset(sender_chain[0]); + axolotl::unset(sender_chain[0]); sender_chain.erase(sender_chain.begin()); } @@ -433,7 +426,7 @@ std::size_t axolotl::Session::decrypt( reader.ciphertext, reader.ciphertext_length, plaintext ); - unset(message_key); + axolotl::unset(message_key); advance_chain_key(chain->chain_key, chain->chain_key); diff --git a/src/crypto.cpp b/src/crypto.cpp index a219f36..57f31cd 100644 --- a/src/crypto.cpp +++ b/src/crypto.cpp @@ -13,6 +13,8 @@ * limitations under the License. */ #include "axolotl/crypto.hh" +#include "axolotl/memory.hh" + #include <cstring> extern "C" { @@ -76,7 +78,7 @@ inline void hmac_sha256_init( } ::sha256_init(context); ::sha256_update(context, i_pad, SHA256_BLOCK_LENGTH); - std::memset(i_pad, 0, sizeof(i_pad)); + axolotl::unset(i_pad); } @@ -95,7 +97,8 @@ inline void hmac_sha256_final( ::sha256_init(&final_context); ::sha256_update(&final_context, o_pad, sizeof(o_pad)); ::sha256_final(&final_context, output); - std::memset(o_pad, 0, sizeof(o_pad)); + axolotl::unset(final_context); + axolotl::unset(o_pad); } } // namespace @@ -154,8 +157,8 @@ void axolotl::aes_encrypt_cbc( input_block[i] ^= AES_BLOCK_LENGTH - input_length; } ::aes_encrypt(input_block, output, key_schedule, 256); - std::memset(key_schedule, 0, sizeof(key_schedule)); - std::memset(input_block, 0, sizeof(AES_BLOCK_LENGTH)); + axolotl::unset(key_schedule); + axolotl::unset(input_block); } @@ -175,7 +178,7 @@ std::size_t axolotl::aes_decrypt_cbc( xor_block<AES_BLOCK_LENGTH>(&output[i], &input[i - AES_BLOCK_LENGTH]); } } - std::memset(key_schedule, 0, sizeof(key_schedule)); + axolotl::unset(key_schedule); std::size_t padding = output[input_length - 1]; return (padding > input_length) ? std::size_t(-1) : (input_length - padding); } @@ -189,6 +192,7 @@ void axolotl::sha256( ::sha256_init(&context); ::sha256_update(&context, input, input_length); ::sha256_final(&context, output); + axolotl::unset(context); } void axolotl::hmac_sha256( @@ -202,7 +206,8 @@ void axolotl::hmac_sha256( hmac_sha256_init(&context, hmac_key); ::sha256_update(&context, input, input_length); hmac_sha256_final(&context, hmac_key, output); - std::memset(hmac_key, 0, sizeof(hmac_key)); + axolotl::unset(hmac_key); + axolotl::unset(context); } @@ -245,4 +250,7 @@ void axolotl::hkdf_sha256( hmac_sha256_final(&context, hmac_key, step_result); } std::memcpy(output, step_result, bytes_remaining); + axolotl::unset(context); + axolotl::unset(hmac_key); + axolotl::unset(step_result); } diff --git a/src/memory.cpp b/src/memory.cpp new file mode 100644 index 0000000..14c95dd --- /dev/null +++ b/src/memory.cpp @@ -0,0 +1,11 @@ +#include "axolotl/memory.hh" + +void axolotl::unset( + volatile void * buffer, std::size_t buffer_length +) { + volatile char * pos = reinterpret_cast<volatile char *>(buffer); + volatile char * end = pos + buffer_length; + while (pos != end) { + *(pos++) = 0; + } +} |