Replace hard coded references to the 32-byte key length with a constant, add utilities for copying data to and from fixed sized arrays

3 files changed, 60 insertions, 17 deletions

diff --git a/include/olm/crypto.hh b/include/olm/crypto.hh
index b845bfe..7a05f8d 100644
--- a/include/olm/crypto.hh
+++ b/include/olm/crypto.hh
@@ -20,28 +20,27 @@
 
 namespace olm {
 
+static const std::size_t KEY_LENGTH = 32;
+static const std::size_t SIGNATURE_LENGTH = 64;
+static const std::size_t IV_LENGTH = 16;
 
 struct Curve25519PublicKey {
-    static const int LENGTH = 32;
-    std::uint8_t public_key[32];
+    std::uint8_t public_key[KEY_LENGTH];
 };
 
 
 struct Curve25519KeyPair : public Curve25519PublicKey {
-    static const int LENGTH = 64;
-    std::uint8_t private_key[32];
+    std::uint8_t private_key[KEY_LENGTH];
 };
 
 
 struct Ed25519PublicKey {
-    static const int LENGTH = 32;
-    std::uint8_t public_key[32];
+    std::uint8_t public_key[KEY_LENGTH];
 };
 
 
 struct Ed25519KeyPair : public Ed25519PublicKey {
-    static const int LENGTH = 64;
-    std::uint8_t private_key[32];
+    std::uint8_t private_key[KEY_LENGTH];
 };
 
 
@@ -52,9 +51,6 @@ void curve25519_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(
@@ -109,14 +105,12 @@ bool ed25519_verify(
 
 
 struct Aes256Key {
-    static const int LENGTH = 32;
-    std::uint8_t key[32];
+    std::uint8_t key[KEY_LENGTH];
 };
 
 
 struct Aes256Iv {
-    static const int LENGTH = 16;
-    std::uint8_t iv[16];
+    std::uint8_t iv[IV_LENGTH];
 };
 
 
@@ -156,7 +150,7 @@ void sha256(
 );
 
 
-const std::size_t HMAC_SHA256_OUTPUT_LENGTH = 32;
+const std::size_t SHA256_OUTPUT_LENGTH = 32;
 
 
 /** HMAC: Keyed-Hashing for Message Authentication
diff --git a/include/olm/memory.hh b/include/olm/memory.hh
index b19c74b..128990a 100644
--- a/include/olm/memory.hh
+++ b/include/olm/memory.hh
@@ -14,6 +14,8 @@
  */
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
+#include <type_traits>
 
 namespace olm {
 
@@ -35,4 +37,51 @@ bool is_equal(
     std::size_t length
 );
 
+/** Check if two fixed size arrays are equals */
+template<typename T>
+bool array_equal(
+    T const & array_a,
+    T const & array_b
+) {
+    static_assert(
+        std::is_array<T>::value
+            && std::is_convertible<T, std::uint8_t *>::value
+            && sizeof(T) > 0,
+        "Arguments to array_equal must be std::uint8_t arrays[]."
+    );
+    return is_equal(array_a, array_b, sizeof(T));
+}
+
+/** Copy into a fixed size array */
+template<typename T>
+std::uint8_t const * load_array(
+    T & destination,
+    std::uint8_t const * source
+) {
+    static_assert(
+        std::is_array<T>::value
+            && std::is_convertible<T, std::uint8_t *>::value
+            && sizeof(T) > 0,
+        "The first argument to load_array must be a std::uint8_t array[]."
+    );
+    std::memcpy(destination, source, sizeof(T));
+    return source + sizeof(T);
+}
+
+/** Copy from a fixed size array */
+template<typename T>
+std::uint8_t * store_array(
+    std::uint8_t * destination,
+    T const & source
+) {
+    static_assert(
+        std::is_array<T>::value
+            && std::is_convertible<T, std::uint8_t *>::value
+            && sizeof(T) > 0,
+        "The second argument to store_array must be a std::uint8_t array[]."
+    );
+    std::memcpy(destination, source, sizeof(T));
+    return destination + sizeof(T);
+}
+
 } // namespace olm
diff --git a/include/olm/ratchet.hh b/include/olm/ratchet.hh
index 7274255..2393e5b 100644
--- a/include/olm/ratchet.hh
+++ b/include/olm/ratchet.hh
@@ -21,7 +21,7 @@ namespace olm {
 
 class Cipher;
 
-typedef std::uint8_t SharedKey[32];
+typedef std::uint8_t SharedKey[olm::KEY_LENGTH];
 
 
 struct ChainKey {