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python - Python SQL query has the wrong type

问题描述

I want to execute a SQL Statement from my python program. For this I use the MySQLdb library. This is my code: 

def execute(sql_statement):
    db = MySQLdb.connect("<DatabaseIP>", "<DatabaseUserName>", "<DatabasePassword>", "<DatabaseName>")
    cursor = db.cursor()
    cursor.execute(sql_statement)
    data = cursor.fetchone()
    db.close()
    return data

def look_up_user_id(username, password):
    print(type(username))
    print(type(password))
    sql_statement = "SELECT ID FROM user WHERE name = '" + username + "' AND password = '" + password + "'"
    print(sql_statement)
    return Database.execute(sql_statement)

This is the method in which the username and password are extracted from the request and the method that actually calls the Database class method.

@app.route('/auth', methods=['GET'])
def log_in():
    return AuthenticationManager.log_in(request.authorization.username, request.authorization.password)

def log_in(username, password):
    return Database.execute(SQLStatementBuilder.look_up_user_id(username, password))[0]

When I execute print(look_up_user_id("me", "password")) everything works as wanted and I get the ID of the user. But when I send a HTTP-Request to my Program with username and password in a basic authentication header, I get 

File "<PythonPath>\Python\Python38\Lib\site-packages\MySQLdb\cursors.py", line 208, in execute
   assert isinstance(query, (bytes, bytearray))
AssertionError

This is the method in which the Error is raised

    def execute(self, query, args=None):
        """Execute a query.

        query -- string, query to execute on server
        args -- optional sequence or mapping, parameters to use with query.

        Note: If args is a sequence, then %s must be used as the
        parameter placeholder in the query. If a mapping is used,
        %(key)s must be used as the placeholder.

        Returns integer represents rows affected, if any
        """
        while self.nextset():
            pass
        db = self._get_db()

        if isinstance(query, unicode):
            query = query.encode(db.encoding)

        if args is not None:
            if isinstance(args, dict):
                nargs = {}
                for key, item in args.items():
                    if isinstance(key, unicode):
                        key = key.encode(db.encoding)
                    nargs[key] = db.literal(item)
                args = nargs
            else:
                args = tuple(map(db.literal, args))
            try:
                query = query % args
            except TypeError as m:
                raise ProgrammingError(str(m))
        assert isinstance(query, (bytes, bytearray))
        res = self._query(query)
        return res

The two calls of print in the method look_up_user_idjust return <class 'str'> in both test cases and for password and name.

Thanks for any help!

Edit: added method that raises Error

标签： pythondatabasetypesdatabase-connectionassertion

解决方案

问题是lookup_user_id正在返回结果，Database.execute(sql_statement)并且该结果被再次传递给Database.execute在的返回语句中AuthorizationManager。要解决此问题，请使用SQLStatementBuilderreturn sql_statement。另请注意，log_in视图应返回字符串或类似内容。

另外，考虑执行如下 SQL 语句：

res = cursor.execute("""SELECT id FROM user WHERE name = %s and password = %s""",
                     (username, password))

以防止 SQL 注入攻击。

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