Authsocket : Where is the password verification ?

[Auntie Mangos]

@Patman128

http://getmangos.eu/community/post/136475/#p136475

@XtremeX

_HandleLogonChallenge is where the user's account info is loaded from the DB and used to calculate B.

In _HandleLogonProof, everything before lines 594-668 are the server's SRP6 algorithm (line 668 is the comparison against the client's proof) - anything that follows is handling success/failure of that comparison.

The password is never inspected/compared directly. SRP6 calculates a cryptographic hash of the password - you can read info on it here: http://srp.stanford.edu/design.html

[XtremeX]

Hello,

I've looked the "Authsocket.cpp" and "Authsocket.h" scripts for to understand how it works, but i don't understand where is the password verification.

I think it's here :

[== c++ ==]
  BigNumber A;

   A.SetBinary(lp.A, 32);

   // SRP safeguard: abort if A==0
   if (A.isZero())
       return false;

   Sha1Hash sha;
   sha.UpdateBigNumbers(&A, &B, NULL);
   sha.Finalize();
   BigNumber u;
   u.SetBinary(sha.GetDigest(), 20);
   BigNumber S = (A * (v.ModExp(u, N))).ModExp(b, N);

   uint8 t[32];
   uint8 t1[16];
   uint8 vK[40];
   memcpy(t, S.AsByteArray(32), 32);
   for (int i = 0; i < 16; ++i)
   {
       t1[i] = t[i * 2];
   }
   sha.Initialize();
   sha.UpdateData(t1, 16);
   sha.Finalize();
   for (int i = 0; i < 20; ++i)
   {
       vK[i * 2] = sha.GetDigest()[i];
   }
   for (int i = 0; i < 16; ++i)
   {
       t1[i] = t[i * 2 + 1];
   }
   sha.Initialize();
   sha.UpdateData(t1, 16);
   sha.Finalize();
   for (int i = 0; i < 20; ++i)
   {
       vK[i * 2 + 1] = sha.GetDigest()[i];
   }
   K.SetBinary(vK, 40);

   uint8 hash[20];

   sha.Initialize();
   sha.UpdateBigNumbers(&N, NULL);
   sha.Finalize();
   memcpy(hash, sha.GetDigest(), 20);
   sha.Initialize();
   sha.UpdateBigNumbers(&g, NULL);
   sha.Finalize();
   for (int i = 0; i < 20; ++i)
   {
       hash[i] ^= sha.GetDigest()[i];
   }
   BigNumber t3;
   t3.SetBinary(hash, 20);

   sha.Initialize();
   sha.UpdateData(_login);
   sha.Finalize();
   uint8 t4[sHA_DIGEST_LENGTH];
   memcpy(t4, sha.GetDigest(), SHA_DIGEST_LENGTH);

   sha.Initialize();
   sha.UpdateBigNumbers(&t3, NULL);
   sha.UpdateData(t4, SHA_DIGEST_LENGTH);
   sha.UpdateBigNumbers(&s, &A, &B, &K, NULL);
   sha.Finalize();
   BigNumber M;
   M.SetBinary(sha.GetDigest(), 20);

   ///- Check if SRP6 results match (password is correct), else send an error
   if (!memcmp(M.AsByteArray(), lp.M1, 20))
   {
       BASIC_LOG("User '%s' successfully authenticated", _login.c_str());

       ///- Update the sessionkey, last_ip, last login time and reset number of failed logins in the account table for this account
       // No SQL injection (escaped user name) and IP address as received by socket
       const char* K_hex = K.AsHexStr();
       LoginDatabase.PExecute("UPDATE account SET sessionkey = '%s', last_ip = '%s', last_login = NOW(), locale = '%u', failed_logins = 0 WHERE username = '%s'", K_hex, get_remote_address().c_str(), GetLocaleByName(_localizationName), _safelogin.c_str() );
       OPENSSL_free((void*)K_hex);

       ///- Finish SRP6 and send the final result to the client
       sha.Initialize();
       sha.UpdateBigNumbers(&A, &M, &K, NULL);
       sha.Finalize();

       SendProof(sha);

       ///- Set _authed to true!
       _authed = true;
   }
   else
   {
       if (_build > 6005) // > 1.12.2
       {
           char data[4] = { CMD_AUTH_LOGON_PROOF, WOW_FAIL_UNKNOWN_ACCOUNT, 3, 0};
           send(data, sizeof(data));
       }
       else
       {
           // 1.x not react incorrectly at 4-byte message use 3 as real error
           char data[2] = { CMD_AUTH_LOGON_PROOF, WOW_FAIL_UNKNOWN_ACCOUNT};
           send(data, sizeof(data));
       }
       BASIC_LOG("[AuthChallenge] account %s tried to login with wrong password!",_login.c_str ());

       uint32 MaxWrongPassCount = sConfig.GetIntDefault("WrongPass.MaxCount", 0);
       if(MaxWrongPassCount > 0)
       {
           //Increment number of failed logins by one and if it reaches the limit temporarily ban that account or IP
           LoginDatabase.PExecute("UPDATE account SET failed_logins = failed_logins + 1 WHERE username = '%s'",_safelogin.c_str());

           if(QueryResult *loginfail = LoginDatabase.PQuery("SELECT id, failed_logins FROM account WHERE username = '%s'", _safelogin.c_str()))
           {
               Field* fields = loginfail->Fetch();
               uint32 failed_logins = fields[1].GetUInt32();

               if( failed_logins >= MaxWrongPassCount )
               {
                   uint32 WrongPassBanTime = sConfig.GetIntDefault("WrongPass.BanTime", 600);
                   bool WrongPassBanType = sConfig.GetBoolDefault("WrongPass.BanType", false);

                   if(WrongPassBanType)
                   {
                       uint32 acc_id = fields[0].GetUInt32();
                       LoginDatabase.PExecute("INSERT INTO account_banned VALUES
('%u',UNIX_TIMESTAMP(),UNIX_TIMESTAMP()+'%u','MaNGOS realmd','Failed login autoban',1)",
                           acc_id, WrongPassBanTime);
                       BASIC_LOG("[AuthChallenge] account %s got banned for '%u' seconds because it failed to authenticate '%u' times",
                           _login.c_str(), WrongPassBanTime, failed_logins);
                   }
                   else
                   {
                       std::string current_ip = get_remote_address();
                       LoginDatabase.escape_string(current_ip);
                       LoginDatabase.PExecute("INSERT INTO ip_banned VALUES
('%s',UNIX_TIMESTAMP(),UNIX_TIMESTAMP()+'%u','MaNGOS realmd','Failed login autoban')",
                           current_ip.c_str(), WrongPassBanTime);
                       BASIC_LOG("[AuthChallenge] IP %s got banned for '%u' seconds because account %s failed to authenticate '%u' times",
                           current_ip.c_str(), WrongPassBanTime, _login.c_str(), failed_logins);
                   }
               }
               delete loginfail;
           }
       }
   }

But I don't understand where is the comparison with the password in the database..

Can someone help me to understand it please ?

[Patman128]

Is it just me or does the codebox turn it into a giant blob?

[XtremeX]

No, it's for all, would you like a screenshot?