Support downloading remote files to a server via the API

Co-authored-by: Dane Everitt <dane@daneeveritt.com>

router/middleware.go

@@ -1,6 +1,7 @@
 package router
 
 import (
+	"errors"
 	"github.com/gin-gonic/gin"
 	"github.com/google/uuid"
 	"github.com/pterodactyl/wings/config"
@@ -60,6 +61,9 @@ func AuthorizationMiddleware(c *gin.Context) {
 }
 
 // Helper function to fetch a server out of the servers collection stored in memory.
+//
+// This function should not be used in new controllers, prefer ExtractServer where
+// possible.
 func GetServer(uuid string) *server.Server {
 	return server.GetServers().Find(func(s *server.Server) bool {
 		return uuid == s.Id()
@@ -70,12 +74,24 @@ func GetServer(uuid string) *server.Server {
 // locate it.
 func ServerExists(c *gin.Context) {
 	u, err := uuid.Parse(c.Param("server"))
-	if err != nil || GetServer(u.String()) == nil {
+	if err == nil {
+		if s := GetServer(u.String()); s != nil {
+			c.Set("server", s)
+			c.Next()
+			return
+		}
+	}
 	c.AbortWithStatusJSON(http.StatusNotFound, gin.H{
 		"error": "The resource you requested does not exist.",
 	})
-		return
 }
 
-	c.Next()
+// Returns the server instance from the gin context. If there is no server set in the
+// context (e.g. calling from a controller not protected by ServerExists) this function
+// will panic.
+func ExtractServer(c *gin.Context) *server.Server {
+	if s, ok := c.Get("server"); ok {
+		return s.(*server.Server)
+	}
+	panic(errors.New("cannot extract server, missing on gin context"))
 }

router/router.go

@@ -83,6 +83,7 @@ func Configure() *gin.Engine {
 			files.PUT("/rename", putServerRenameFiles)
 			files.POST("/copy", postServerCopyFile)
 			files.POST("/write", postServerWriteFile)
+			files.POST("/writeUrl", postServerDownloadRemoteFile)
 			files.POST("/create-directory", postServerCreateDirectory)
 			files.POST("/delete", postServerDeleteFiles)
 			files.POST("/compress", postServerCompressFiles)

router/router_server_files.go

@@ -225,6 +225,51 @@ func postServerWriteFile(c *gin.Context) {
 	c.Status(http.StatusNoContent)
 }
 
+// Writes the contents of the remote URL to a file on a server.
+func postServerDownloadRemoteFile(c *gin.Context) {
+	s := ExtractServer(c)
+	var data struct {
+		URL      string `binding:"required" json:"url"`
+		BasePath string `json:"path"`
+	}
+	if err := c.BindJSON(&data); err != nil {
+		return
+	}
+
+	u, err := url.Parse(data.URL)
+	if err != nil {
+		if e, ok := err.(*url.Error); ok {
+			c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
+				"error": "An error occurred while parsing that URL: " + e.Err.Error(),
+			})
+			return
+		}
+		TrackedServerError(err, s).AbortWithServerError(c)
+		return
+	}
+
+	resp, err := http.Get(u.String())
+	if err != nil {
+		TrackedServerError(err, s).AbortWithServerError(c)
+		return
+	}
+	defer resp.Body.Close()
+
+	filename := strings.Split(u.Path, "/")
+	if err := s.Filesystem().Writefile(filepath.Join(data.BasePath, filename[len(filename)-1]), resp.Body); err != nil {
+		if errors.Is(err, filesystem.ErrIsDirectory) {
+			c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{
+				"error": "Cannot write file, name conflicts with an existing directory by the same name.",
+			})
+			return
+		}
+		TrackedServerError(err, s).AbortFilesystemError(c)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
 // Create a directory on a server.
 func postServerCreateDirectory(c *gin.Context) {
 	s := GetServer(c.Param("server"))