feat: dutctl: validate transmitted file names against cmdline content

To prevent the agent from requesting or sending arbitrary files,
the files to be transferred must somehow be included in the cmdline
sent with the Run-RPC.

Signed-off-by: Jens Drenhaus <jens.drenhaus@blindspot.software>

cmds/dutctl/rpc.go

@@ -9,6 +9,7 @@ import (
 	"io/fs"
 	"log"
 	"os"
+	"strings"
 	"sync"
 
 	"connectrpc.com/connect"
@@ -116,6 +117,10 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {
 				path := msg.FileRequest.GetPath()
 				log.Printf("File request for: %q\n", path)
 
+				if !isPartOfArgs(cmdArgs, path) {
+					log.Fatalf("Invalid file request: Requested file %q was not named in the command's arguments", path)
+				}
+
 				content, err := os.ReadFile(path)
 				if err != nil {
 					log.Fatal(err)
@@ -141,6 +146,10 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {
 
 				log.Printf("Received file: %q\n", path)
 
+				if !isPartOfArgs(cmdArgs, path) {
+					log.Fatalf("Invalid file transmission: Sent file %q was not named in the command's arguments", path)
+				}
+
 				if len(content) == 0 {
 					log.Println("Received empty file content")
 				}
@@ -192,3 +201,13 @@ func (app *application) runRPC(device, command string, cmdArgs []string) error {
 
 	return nil
 }
+
+func isPartOfArgs(args []string, token string) bool {
+	for _, arg := range args {
+		if strings.Contains(arg, token) {
+			return true
+		}
+	}
+
+	return false
+}

pkg/module/dummy/dummy_file_transfer.go

@@ -53,12 +53,13 @@ func (d *FT) Run(_ context.Context, s module.Session, args ...string) error {
 	str := fmt.Sprintf("Called with %d arguments", len(args))
 	s.Print(str)
 
-	if len(args) != 1 {
-		return fmt.Errorf("expected 1 argument, got %d", len(args))
+	const expectedArgsCnt = 2
+	if len(args) != expectedArgsCnt {
+		return fmt.Errorf("expected 2 arguments, got %d", len(args))
 	}
 
 	inFile := args[0]
-	str = fmt.Sprintf("Requesting file %q passed in arg[0]", inFile)
+	str = fmt.Sprintf("Requesting file %q passed in arg[0] as input", inFile)
 	s.Print(str)
 
 	fileReader, err := s.RequestFile(inFile)
@@ -83,14 +84,16 @@ func (d *FT) Run(_ context.Context, s module.Session, args ...string) error {
 		return fmt.Errorf("failed to process file: %v", err)
 	}
 
-	log.Print("dummy.FT module: Sending back processed file")
+	outFile := args[1]
+	log.Printf("dummy.FT module: Sending back processed file %q", outFile)
 
-	err = s.SendFile("processed.txt", bytes.NewBuffer(result))
+	err = s.SendFile(outFile, bytes.NewBuffer(result))
 	if err != nil {
 		return fmt.Errorf("failed to send file: %v", err)
 	}
 
-	s.Print("File operated successfully, check processed.txt")
+	str = fmt.Sprintf("File operated successfully, delivered %q as passed in arg[1] as output", outFile)
+	s.Print(str)
 
 	return nil
 }