From 35be6432c72f5e6fe7f7d8f6e494e854c7e74e19 Mon Sep 17 00:00:00 2001
From: Philipp Mieden <dreadl0ck@protonmail.ch>
Date: Tue, 11 Aug 2020 20:47:11 +0200
Subject: [PATCH] jailer: construct path to chrooted filesystem when applying
 the Handler, simplify API and code

Signed-off-by: Philipp Mieden <dreadl0ck@protonmail.ch>
---
 jailer.go | 43 +++++++++++++++++++------------------------
 1 file changed, 19 insertions(+), 24 deletions(-)

diff --git a/jailer.go b/jailer.go
index 931d92c5..56d89265 100644
--- a/jailer.go
+++ b/jailer.go
@@ -345,17 +345,9 @@ func jail(ctx context.Context, m *Machine, cfg *Config) error {
 	return nil
 }
 
-func linkFileToRootFS(cfg *JailerConfig, dst, src string) error {
-	if err := os.Link(src, dst); err != nil {
-		return err
-	}
-
-	return nil
-}
-
 // LinkFilesHandler creates a new link files handler that will link files to
 // the rootfs
-func LinkFilesHandler(rootfs, kernelImageFileName string) Handler {
+func LinkFilesHandler(kernelImageFileName string) Handler {
 	return Handler{
 		Name: LinkFilesToRootFSHandlerName,
 		Fn: func(ctx context.Context, m *Machine) error {
@@ -363,11 +355,18 @@ func LinkFilesHandler(rootfs, kernelImageFileName string) Handler {
 				return ErrMissingJailerConfig
 			}
 
+			// assemble the path to the jailed root folder on the host
+			rootfs := filepath.Join(
+				m.Cfg.JailerCfg.ChrootBaseDir,
+				filepath.Base(m.Cfg.JailerCfg.ExecFile),
+				m.Cfg.JailerCfg.ID,
+				rootfsFolderName,
+			)
+
 			// copy kernel image to root fs
-			if err := linkFileToRootFS(
-				m.Cfg.JailerCfg,
-				filepath.Join(rootfs, kernelImageFileName),
+			if err := os.Link(
 				m.Cfg.KernelImagePath,
+				filepath.Join(rootfs, kernelImageFileName),
 			); err != nil {
 				return err
 			}
@@ -376,10 +375,9 @@ func LinkFilesHandler(rootfs, kernelImageFileName string) Handler {
 			if m.Cfg.InitrdPath != "" {
 				initrdFilename := filepath.Base(m.Cfg.InitrdPath)
 				// copy initrd to root fs
-				if err := linkFileToRootFS(
-					m.Cfg.JailerCfg,
-					filepath.Join(rootfs, initrdFilename),
+				if err := os.Link(
 					m.Cfg.InitrdPath,
+					filepath.Join(rootfs, initrdFilename),
 				); err != nil {
 					return err
 				}
@@ -390,10 +388,9 @@ func LinkFilesHandler(rootfs, kernelImageFileName string) Handler {
 				hostPath := StringValue(drive.PathOnHost)
 				driveFileName := filepath.Base(hostPath)
 
-				if err := linkFileToRootFS(
-					m.Cfg.JailerCfg,
-					filepath.Join(rootfs, driveFileName),
+				if err := os.Link(
 					hostPath,
+					filepath.Join(rootfs, driveFileName),
 				); err != nil {
 					return err
 				}
@@ -412,10 +409,9 @@ func LinkFilesHandler(rootfs, kernelImageFileName string) Handler {
 				}
 
 				fileName := filepath.Base(*fifoPath)
-				if err := linkFileToRootFS(
-					m.Cfg.JailerCfg,
-					filepath.Join(rootfs, fileName),
+				if err := os.Link(
 					*fifoPath,
+					filepath.Join(rootfs, fileName),
 				); err != nil {
 					return err
 				}
@@ -441,9 +437,8 @@ type NaiveChrootStrategy struct {
 }
 
 // NewNaiveChrootStrategy returns a new NaivceChrootStrategy
-func NewNaiveChrootStrategy(rootfs, kernelImagePath string) NaiveChrootStrategy {
+func NewNaiveChrootStrategy(kernelImagePath string) NaiveChrootStrategy {
 	return NaiveChrootStrategy{
-		Rootfs:          rootfs,
 		KernelImagePath: kernelImagePath,
 	}
 }
@@ -460,7 +455,7 @@ func (s NaiveChrootStrategy) AdaptHandlers(handlers *Handlers) error {
 
 	handlers.FcInit = handlers.FcInit.AppendAfter(
 		CreateLogFilesHandlerName,
-		LinkFilesHandler(filepath.Join(s.Rootfs, rootfsFolderName), filepath.Base(s.KernelImagePath)),
+		LinkFilesHandler(filepath.Base(s.KernelImagePath)),
 	)
 
 	return nil