mysql replication and GRANT that doesn't quite grant

I am trying to set up mysql replication. All's well, but I see an error 1045 for the slave:

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Connecting to master
                  Master_Host: 
                  Master_User: slave_user
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000001
          Read_Master_Log_Pos: 107
               Relay_Log_File: mysqld-relay-bin.000003
                Relay_Log_Pos: 4
        Relay_Master_Log_File: mysql-bin.000001
             Slave_IO_Running: Connecting
            Slave_SQL_Running: Yes
              Replicate_Do_DB: my_db_name
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 107
              Relay_Log_Space: 107
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 1045
                Last_IO_Error: error connecting to master 'slave_user@my.host.ip:3306' - retry-time: 60  retries: 86400
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 0
1 row in set (0.00 sec)

mysql>

I try connecting manually, it starts out fine, but I've a permission problem. I can connect but I can't see anything but the info database:

```
$ mysql -h my-host-name -u slave_user -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.

While MySQL does not impose a password length limit, replication does. (I have not been able to find this in the MySQL documentation, but, empirically, it holds.)

This is all the less obvious, because the longer password works for login but fails for replication. So, in the end, reducing the password to 32 characters solved the problem.

StackExchange Database Administrators Q#139583, answer score: 3