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authorJakob Unterwurzacher2018-11-11 17:57:24 +0100
committerJakob Unterwurzacher2019-01-01 16:24:25 +0100
commit810d2a8b474e0102a8be3f6b00a3855e182dbd43 (patch)
tree67fd54b970e45c6f02ce1ec1f318c69c8859175b /internal/fusefrontend
parent2286372603f506cf719654a9901de0749c544b12 (diff)
fusefrontend: make SetXAttr() symlink-safe on Linux
Uses the /proc/self/fd trick.
Diffstat (limited to 'internal/fusefrontend')
-rw-r--r--internal/fusefrontend/xattr.go25
-rw-r--r--internal/fusefrontend/xattr_darwin.go9
-rw-r--r--internal/fusefrontend/xattr_linux.go20
3 files changed, 37 insertions, 17 deletions
diff --git a/internal/fusefrontend/xattr.go b/internal/fusefrontend/xattr.go
index caf1e15..b511bcf 100644
--- a/internal/fusefrontend/xattr.go
+++ b/internal/fusefrontend/xattr.go
@@ -26,8 +26,8 @@ var xattrStorePrefix = "user.gocryptfs."
// GetXAttr - FUSE call. Reads the value of extended attribute "attr".
//
// 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?
+// Darwin does not have fgetxattr(2) nor /proc/self/fd. 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
@@ -48,27 +48,22 @@ func (fs *FS) GetXAttr(relPath string, attr string, context *fuse.Context) ([]by
return data, fuse.OK
}
-// SetXAttr - FUSE call.
+// SetXAttr - FUSE call. Set extended attribute.
//
-// TODO: Make symlink-safe. Currently blocked because the xattr package does
-// not provide fsetxattr.
-func (fs *FS) SetXAttr(path string, attr string, data []byte, flags int, context *fuse.Context) fuse.Status {
- if fs.isFiltered(path) {
+// This function is symlink-safe on Linux.
+// Darwin does not have fsetxattr(2) nor /proc/self/fd. How to implement this
+// on Darwin in a symlink-safe way?
+func (fs *FS) SetXAttr(relPath string, attr string, data []byte, flags int, context *fuse.Context) fuse.Status {
+ if fs.isFiltered(relPath) {
return fuse.EPERM
}
if disallowedXAttrName(attr) {
return _EOPNOTSUPP
}
-
flags = filterXattrSetFlags(flags)
-
- cPath, err := fs.getBackingPath(path)
- if err != nil {
- return fuse.ToStatus(err)
- }
cAttr := fs.encryptXattrName(attr)
cData := fs.encryptXattrValue(data)
- return unpackXattrErr(xattr.LSetWithFlags(cPath, cAttr, cData, flags))
+ return fs.setXattr(relPath, cAttr, cData, flags, context)
}
// RemoveXAttr - FUSE call.
@@ -175,7 +170,7 @@ func (fs *FS) decryptXattrValue(cData []byte) (data []byte, err error) {
}
// unpackXattrErr unpacks an error value that we got from xattr.LGet/LSet/etc
-// and converts it to a fuse status.
+// and converts it to a fuse status. If err == nil, it returns fuse.OK.
func unpackXattrErr(err error) fuse.Status {
if err == nil {
return fuse.OK
diff --git a/internal/fusefrontend/xattr_darwin.go b/internal/fusefrontend/xattr_darwin.go
index cf48d13..e605f83 100644
--- a/internal/fusefrontend/xattr_darwin.go
+++ b/internal/fusefrontend/xattr_darwin.go
@@ -30,3 +30,12 @@ func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]b
}
return cData, fuse.OK
}
+
+func (fs *FS) setXattr(relPath string, cAttr string, cData []byte, flags int, context *fuse.Context) fuse.Status {
+ cPath, err := fs.getBackingPath(relPath)
+ if err != nil {
+ return fuse.ToStatus(err)
+ }
+ err = xattr.LSetWithFlags(cPath, cAttr, cData, flags)
+ return unpackXattrErr(err)
+}
diff --git a/internal/fusefrontend/xattr_linux.go b/internal/fusefrontend/xattr_linux.go
index 5a189db..659657d 100644
--- a/internal/fusefrontend/xattr_linux.go
+++ b/internal/fusefrontend/xattr_linux.go
@@ -28,6 +28,7 @@ func filterXattrSetFlags(flags int) int {
return flags
}
+// procFd returns the path to file descriptor "fd" in /proc/self/fd.
func procFd(fd int) string {
return fmt.Sprintf("/proc/self/fd/%d", fd)
}
@@ -51,10 +52,10 @@ func (fs *FS) getFileFd(relPath string, context *fuse.Context) (*File, int, fuse
return file, file.intFd(), fuse.OK
}
-// getXattr - read encrypted xattr name "cAttr" from the file at relative
+// getXattr - read encrypted xattr name "cAttr" from relative
// plaintext path "relPath". Returns the encrypted xattr value.
//
-// This function is symlink-safe.
+// This function is symlink-safe by using /proc/self/fd.
func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]byte, fuse.Status) {
file, fd, status := fs.getFileFd(relPath, context)
if !status.Ok() {
@@ -68,3 +69,18 @@ func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]b
}
return cData, fuse.OK
}
+
+// setXattr - set encrypted xattr name "cAttr" to value "cData" on plaintext
+// path "relPath".
+//
+// This function is symlink-safe by using /proc/self/fd.
+func (fs *FS) setXattr(relPath string, cAttr string, cData []byte, flags int, context *fuse.Context) fuse.Status {
+ file, fd, status := fs.getFileFd(relPath, context)
+ if !status.Ok() {
+ return status
+ }
+ defer file.Release()
+
+ err := xattr.SetWithFlags(procFd(fd), cAttr, cData, flags)
+ return unpackXattrErr(err)
+}