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authorSebastian Lackner2019-01-12 21:22:52 +0100
committerSebastian Lackner2019-01-12 21:22:58 +0100
commitefc280330c68dc5cbf605921f6c840a54d5841bb (patch)
treed531534d3681342ad8a929765ce433d2eb6096f7
parent1fbe7798cf879d80cfbd755b05bdadae24bc5519 (diff)
fusefrontend: -allow_other: Use SymlinkatUser in Symlink FUSE call.
Instead of manually adjusting the user after creating the symlink, adjust effective permissions and let the kernel deal with it. Related to https://github.com/rfjakob/gocryptfs/issues/338.
-rw-r--r--internal/fusefrontend/fs.go21
-rw-r--r--internal/syscallcompat/sys_darwin.go5
-rw-r--r--internal/syscallcompat/sys_linux.go22
3 files changed, 34 insertions, 14 deletions
diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index 9637acf..c4b1a01 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -483,6 +483,10 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
+ // Make sure context is nil if we don't want to preserve the owner
+ if !fs.args.PreserveOwner {
+ context = nil
+ }
cTarget := target
if !fs.args.PlaintextNames {
// Symlinks are encrypted like file contents (GCM) and base64-encoded
@@ -495,26 +499,15 @@ func (fs *FS) Symlink(target string, linkName string, context *fuse.Context) (co
return fuse.ToStatus(err)
}
// Create "gocryptfs.longfile." symlink
- err = syscallcompat.Symlinkat(cTarget, dirfd, cName)
+ err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, context)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
}
} else {
// Create symlink
- err = syscallcompat.Symlinkat(cTarget, dirfd, cName)
- }
- if err != nil {
- return fuse.ToStatus(err)
- }
- // Set owner
- if fs.args.PreserveOwner {
- err = syscallcompat.Fchownat(dirfd, cName, int(context.Owner.Uid),
- int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
- if err != nil {
- tlog.Warn.Printf("Symlink: Fchownat failed: %v", err)
- }
+ err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, context)
}
- return fuse.OK
+ return fuse.ToStatus(err)
}
// Rename - FUSE call.
diff --git a/internal/syscallcompat/sys_darwin.go b/internal/syscallcompat/sys_darwin.go
index c9f3ad7..52803ab 100644
--- a/internal/syscallcompat/sys_darwin.go
+++ b/internal/syscallcompat/sys_darwin.go
@@ -80,6 +80,11 @@ func Symlinkat(oldpath string, newdirfd int, newpath string) (err error) {
return emulateSymlinkat(oldpath, newdirfd, newpath)
}
+func SymlinkatUser(oldpath string, newdirfd int, newpath string, context *fuse.Context) (err error) {
+ // FIXME: take into account context.Owner
+ return Symlinkat(oldpath, newdirfd, newpath)
+}
+
func Mkdirat(dirfd int, path string, mode uint32) (err error) {
return emulateMkdirat(dirfd, path, mode)
}
diff --git a/internal/syscallcompat/sys_linux.go b/internal/syscallcompat/sys_linux.go
index cf747b1..6f2a70d 100644
--- a/internal/syscallcompat/sys_linux.go
+++ b/internal/syscallcompat/sys_linux.go
@@ -197,6 +197,28 @@ func Symlinkat(oldpath string, newdirfd int, newpath string) (err error) {
return unix.Symlinkat(oldpath, newdirfd, newpath)
}
+// SymlinkatUser runs the Symlinkat syscall in the context of a different user.
+func SymlinkatUser(oldpath string, newdirfd int, newpath string, context *fuse.Context) (err error) {
+ if context != nil {
+ runtime.LockOSThread()
+ defer runtime.UnlockOSThread()
+
+ err = syscall.Setregid(-1, int(context.Owner.Gid))
+ if err != nil {
+ return err
+ }
+ defer syscall.Setregid(-1, 0)
+
+ err = syscall.Setreuid(-1, int(context.Owner.Uid))
+ if err != nil {
+ return err
+ }
+ defer syscall.Setreuid(-1, 0)
+ }
+
+ return Symlinkat(oldpath, newdirfd, newpath)
+}
+
// Mkdirat syscall.
func Mkdirat(dirfd int, path string, mode uint32) (err error) {
return syscall.Mkdirat(dirfd, path, mode)