fix: stabilize mini app login and safe area

src/GmRelay.Web/Services/TelegramAuthService.cs

@@ -1,6 +1,7 @@
 using System.Security.Cryptography;
 using System.Text;
 using System.Text.Json;
+using System.Text.Json.Serialization;
 using Microsoft.AspNetCore.WebUtilities;
 
 namespace GmRelay.Web.Services;
@@ -113,6 +114,69 @@ public sealed class TelegramAuthService(IConfiguration configuration)
         return TryReadWebAppUser(userJson.ToString(), out telegramId, out name);
     }
 
+    public bool VerifyLoginPayload(TelegramLoginPayload payload, out long telegramId, out string name)
+    {
+        telegramId = 0;
+        name = string.Empty;
+
+        if (payload.Id <= 0 ||
+            string.IsNullOrWhiteSpace(payload.FirstName) ||
+            payload.AuthDate <= 0 ||
+            string.IsNullOrWhiteSpace(payload.Hash))
+        {
+            return false;
+        }
+
+        var token = configuration["Telegram__BotToken"] ?? configuration["Telegram:BotToken"];
+        if (string.IsNullOrEmpty(token))
+            return false;
+
+        var values = new SortedDictionary<string, string>(StringComparer.Ordinal)
+        {
+            ["auth_date"] = payload.AuthDate.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            ["first_name"] = payload.FirstName,
+            ["id"] = payload.Id.ToString(System.Globalization.CultureInfo.InvariantCulture)
+        };
+
+        if (!string.IsNullOrWhiteSpace(payload.LastName))
+            values["last_name"] = payload.LastName;
+        if (!string.IsNullOrWhiteSpace(payload.PhotoUrl))
+            values["photo_url"] = payload.PhotoUrl;
+        if (!string.IsNullOrWhiteSpace(payload.Username))
+            values["username"] = payload.Username;
+
+        var dataCheckString = string.Join("\n", values.Select(pair => $"{pair.Key}={pair.Value}"));
+        var secretKey = SHA256.HashData(Encoding.UTF8.GetBytes(token));
+        var computedHashBytes = HMACSHA256.HashData(secretKey, Encoding.UTF8.GetBytes(dataCheckString));
+
+        byte[] hashBytes;
+        try
+        {
+            hashBytes = Convert.FromHexString(payload.Hash);
+        }
+        catch (FormatException)
+        {
+            return false;
+        }
+        catch (ArgumentException)
+        {
+            return false;
+        }
+
+        if (!CryptographicOperations.FixedTimeEquals(computedHashBytes, hashBytes))
+            return false;
+
+        var now = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
+        if (now - payload.AuthDate > 86400)
+            return false;
+
+        telegramId = payload.Id;
+        name = string.IsNullOrWhiteSpace(payload.LastName)
+            ? payload.FirstName
+            : $"{payload.FirstName} {payload.LastName}";
+        return true;
+    }
+
     private static bool TryReadWebAppUser(string userJson, out long telegramId, out string name)
     {
         telegramId = 0;
@@ -152,3 +216,12 @@ public sealed class TelegramAuthService(IConfiguration configuration)
         }
     }
 }
+
+public sealed record TelegramLoginPayload(
+    [property: JsonPropertyName("id")] long Id,
+    [property: JsonPropertyName("first_name")] string FirstName,
+    [property: JsonPropertyName("last_name")] string? LastName,
+    [property: JsonPropertyName("username")] string? Username,
+    [property: JsonPropertyName("photo_url")] string? PhotoUrl,
+    [property: JsonPropertyName("auth_date")] long AuthDate,
+    [property: JsonPropertyName("hash")] string Hash);