Implement authentication

internal/authentication/authentication.go

@@ -0,0 +1,26 @@
+package authentication
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"strings"
+)
+
+// https://learn.microsoft.com/en-us/rest/api/cosmos-db/access-control-on-cosmosdb-resources
+func GenerateSignature(verb string, resourceType string, resourceId string, date string, masterKey string) string {
+	payload := fmt.Sprintf(
+		"%s\n%s\n%s\n%s\n%s\n",
+		strings.ToLower(verb),
+		strings.ToLower(resourceType),
+		resourceId,
+		strings.ToLower(date),
+		"")
+
+	masterKeyBytes, _ := base64.StdEncoding.DecodeString(masterKey)
+	hash := hmac.New(sha256.New, masterKeyBytes)
+	hash.Write([]byte(payload))
+	signature := base64.StdEncoding.EncodeToString(hash.Sum(nil))
+	return signature
+}