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authorJakob Unterwurzacher2018-11-11 17:43:48 +0100
committerJakob Unterwurzacher2019-01-01 16:24:25 +0100
commit2286372603f506cf719654a9901de0749c544b12 (patch)
tree3281d54570b9a06e5be756a57d049900848db182 /internal
parentb97d7d1d33d1274c6872d899692a56bd4070a6d9 (diff)
fusefrontend: make GetXAttr() symlink-safe on Linux
Uses the /proc/self/fd trick, which does not work on Darwin.
Diffstat (limited to 'internal')
-rw-r--r--internal/fusefrontend/names.go1
-rw-r--r--internal/fusefrontend/xattr.go20
-rw-r--r--internal/fusefrontend/xattr_darwin.go19
-rw-r--r--internal/fusefrontend/xattr_linux.go53
4 files changed, 80 insertions, 13 deletions
diff --git a/internal/fusefrontend/names.go b/internal/fusefrontend/names.go
index 6997177..5d6951c 100644
--- a/internal/fusefrontend/names.go
+++ b/internal/fusefrontend/names.go
@@ -35,6 +35,7 @@ func (fs *FS) isFiltered(path string) bool {
// from the relative plaintext path "relPath"
//
// TODO: this function is NOT symlink-safe.
+// TODO: Move to xattr_darwin.go.
func (fs *FS) getBackingPath(relPath string) (string, error) {
cPath, err := fs.encryptPath(relPath)
if err != nil {
diff --git a/internal/fusefrontend/xattr.go b/internal/fusefrontend/xattr.go
index 74b3790..caf1e15 100644
--- a/internal/fusefrontend/xattr.go
+++ b/internal/fusefrontend/xattr.go
@@ -25,24 +25,22 @@ var xattrStorePrefix = "user.gocryptfs."
// GetXAttr - FUSE call. Reads the value of extended attribute "attr".
//
-// TODO: Make symlink-safe. Blocker: package xattr does not provide fgetxattr(2).
-func (fs *FS) GetXAttr(path string, attr string, context *fuse.Context) ([]byte, fuse.Status) {
- if fs.isFiltered(path) {
+// This function is symlink-safe on Linux.
+// Darwin does not have fgetxattr(2) nor /proc. How to implement this on Darwin
+// in a symlink-safe way?
+func (fs *FS) GetXAttr(relPath string, attr string, context *fuse.Context) ([]byte, fuse.Status) {
+ if fs.isFiltered(relPath) {
return nil, fuse.EPERM
}
if disallowedXAttrName(attr) {
return nil, _EOPNOTSUPP
}
cAttr := fs.encryptXattrName(attr)
- cPath, err := fs.getBackingPath(path)
- if err != nil {
- return nil, fuse.ToStatus(err)
- }
- encryptedData, err := xattr.LGet(cPath, cAttr)
- if err != nil {
- return nil, unpackXattrErr(err)
+ cData, status := fs.getXattr(relPath, cAttr, context)
+ if !status.Ok() {
+ return nil, status
}
- data, err := fs.decryptXattrValue(encryptedData)
+ data, err := fs.decryptXattrValue(cData)
if err != nil {
tlog.Warn.Printf("GetXAttr: %v", err)
return nil, fuse.EIO
diff --git a/internal/fusefrontend/xattr_darwin.go b/internal/fusefrontend/xattr_darwin.go
index b626006..cf48d13 100644
--- a/internal/fusefrontend/xattr_darwin.go
+++ b/internal/fusefrontend/xattr_darwin.go
@@ -3,7 +3,11 @@
// Package fusefrontend interfaces directly with the go-fuse library.
package fusefrontend
-import "github.com/pkg/xattr"
+import (
+ "github.com/pkg/xattr"
+
+ "github.com/hanwen/go-fuse/fuse"
+)
func disallowedXAttrName(attr string) bool {
return false
@@ -13,3 +17,16 @@ func disallowedXAttrName(attr string) bool {
func filterXattrSetFlags(flags int) int {
return flags &^ xattr.XATTR_NOSECURITY
}
+
+// This function is NOT symlink-safe because Darwin lacks fgetxattr().
+func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]byte, fuse.Status) {
+ cPath, err := fs.getBackingPath(relPath)
+ if err != nil {
+ return nil, fuse.ToStatus(err)
+ }
+ cData, err := xattr.LGet(cPath, cAttr)
+ if err != nil {
+ return nil, unpackXattrErr(err)
+ }
+ return cData, fuse.OK
+}
diff --git a/internal/fusefrontend/xattr_linux.go b/internal/fusefrontend/xattr_linux.go
index 61b90e3..5a189db 100644
--- a/internal/fusefrontend/xattr_linux.go
+++ b/internal/fusefrontend/xattr_linux.go
@@ -3,7 +3,17 @@
// Package fusefrontend interfaces directly with the go-fuse library.
package fusefrontend
-import "strings"
+import (
+ "fmt"
+ "strings"
+ "syscall"
+
+ "github.com/hanwen/go-fuse/fuse"
+
+ "github.com/pkg/xattr"
+
+ "github.com/rfjakob/gocryptfs/internal/tlog"
+)
// Only allow the "user" namespace, block "trusted" and "security", as
// these may be interpreted by the system, and we don't want to cause
@@ -17,3 +27,44 @@ func disallowedXAttrName(attr string) bool {
func filterXattrSetFlags(flags int) int {
return flags
}
+
+func procFd(fd int) string {
+ return fmt.Sprintf("/proc/self/fd/%d", fd)
+}
+
+// getFileFd calls fs.Open() on relative plaintext path "relPath" and returns
+// the resulting fusefrontend.*File along with the underlying fd. The caller
+// MUST call file.Release() when done with the file.
+//
+// Used by xattrGet() and friends.
+func (fs *FS) getFileFd(relPath string, context *fuse.Context) (*File, int, fuse.Status) {
+ fuseFile, status := fs.Open(relPath, syscall.O_RDONLY, context)
+ if !status.Ok() {
+ return nil, -1, status
+ }
+ file, ok := fuseFile.(*File)
+ if !ok {
+ tlog.Warn.Printf("BUG: xattrGet: cast to *File failed")
+ fuseFile.Release()
+ return nil, -1, fuse.EIO
+ }
+ return file, file.intFd(), fuse.OK
+}
+
+// getXattr - read encrypted xattr name "cAttr" from the file at relative
+// plaintext path "relPath". Returns the encrypted xattr value.
+//
+// This function is symlink-safe.
+func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]byte, fuse.Status) {
+ file, fd, status := fs.getFileFd(relPath, context)
+ if !status.Ok() {
+ return nil, status
+ }
+ defer file.Release()
+
+ cData, err := xattr.Get(procFd(fd), cAttr)
+ if err != nil {
+ return nil, unpackXattrErr(err)
+ }
+ return cData, fuse.OK
+}