feat: Integrate CIE authentication flow

common/Crypto.cc

@@ -1,6 +1,9 @@
 #include "common/Crypto.h"
 
 #include <drogon/utils/Utilities.h>
+#include <openssl/crypto.h>
+#include <openssl/hmac.h>
+
 #include <iomanip>
 #include <random>
 #include <sstream>
@@ -27,6 +30,29 @@ std::string sha256(const std::string &value)
     return drogon::utils::getSha256(value);
 }
 
+std::string hmacSha256Hex(const std::string &key, const std::string &value)
+{
+    unsigned char digest[EVP_MAX_MD_SIZE];
+    unsigned int digestSize = 0;
+    HMAC(EVP_sha256(),
+         key.data(),
+         static_cast<int>(key.size()),
+         reinterpret_cast<const unsigned char *>(value.data()),
+         value.size(),
+         digest,
+         &digestSize);
+    return toHex(digest, digestSize);
+}
+
+bool constantTimeEquals(const std::string &left, const std::string &right)
+{
+    if (left.size() != right.size())
+    {
+        return false;
+    }
+    return CRYPTO_memcmp(left.data(), right.data(), left.size()) == 0;
+}
+
 std::string randomNumericCode(int digits)
 {
     std::random_device device;