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authorJakob Unterwurzacher2020-08-01 21:13:00 +0200
committerJakob Unterwurzacher2020-08-01 21:14:33 +0200
commitf54d21c38427e68b598546c1c870a289cb5e99bb (patch)
treeeeb3a55f70a3cb105a0da8e46ad6423f98da0401
parent18b3bdb1584fd8e3dde89a95c0dfff910dd95ae1 (diff)
v2api/reverse: implement Lookup & Getattr
-rw-r--r--internal/fusefrontend_reverse/node.go66
-rw-r--r--internal/fusefrontend_reverse/node_helpers.go67
-rw-r--r--internal/fusefrontend_reverse/rpath.go102
3 files changed, 235 insertions, 0 deletions
diff --git a/internal/fusefrontend_reverse/node.go b/internal/fusefrontend_reverse/node.go
index 6a1294a..a102a66 100644
--- a/internal/fusefrontend_reverse/node.go
+++ b/internal/fusefrontend_reverse/node.go
@@ -1,7 +1,15 @@
package fusefrontend_reverse
import (
+ "context"
+ "syscall"
+
+ "golang.org/x/sys/unix"
+
"github.com/hanwen/go-fuse/v2/fs"
+ "github.com/hanwen/go-fuse/v2/fuse"
+
+ "github.com/rfjakob/gocryptfs/internal/syscallcompat"
)
// Node is a file or directory in the filesystem tree
@@ -9,3 +17,61 @@ import (
type Node struct {
fs.Inode
}
+
+// Lookup - FUSE call for discovering a file.
+// TODO handle virtual files
+func (n *Node) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
+ dirfd, cName, errno := n.prepareAtSyscall(name)
+ if errno != 0 {
+ return
+ }
+ defer syscall.Close(dirfd)
+
+ // Get device number and inode number into `st`
+ st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
+ if err != nil {
+ return nil, fs.ToErrno(err)
+ }
+
+ // Create new inode and fill `out`
+ ch = n.newChild(ctx, st, out)
+
+ // Translate ciphertext size in `out.Attr.Size` to plaintext size
+ n.translateSize(dirfd, cName, &out.Attr)
+
+ return ch, 0
+}
+
+// GetAttr - FUSE call for stat()ing a file.
+//
+// GetAttr is symlink-safe through use of openBackingDir() and Fstatat().
+func (n *Node) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) (errno syscall.Errno) {
+ // If the kernel gives us a file handle, use it.
+ if f != nil {
+ return f.(fs.FileGetattrer).Getattr(ctx, out)
+ }
+
+ dirfd, cName, errno := n.prepareAtSyscall("")
+ if errno != 0 {
+ return
+ }
+ defer syscall.Close(dirfd)
+
+ st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
+ if err != nil {
+ return fs.ToErrno(err)
+ }
+
+ // Fix inode number
+ rn := n.rootNode()
+ rn.inoMap.TranslateStat(st)
+ out.Attr.FromStat(st)
+
+ // Translate ciphertext size in `out.Attr.Size` to plaintext size
+ n.translateSize(dirfd, cName, &out.Attr)
+
+ if rn.args.ForceOwner != nil {
+ out.Owner = *rn.args.ForceOwner
+ }
+ return 0
+}
diff --git a/internal/fusefrontend_reverse/node_helpers.go b/internal/fusefrontend_reverse/node_helpers.go
new file mode 100644
index 0000000..a26ee81
--- /dev/null
+++ b/internal/fusefrontend_reverse/node_helpers.go
@@ -0,0 +1,67 @@
+package fusefrontend_reverse
+
+import (
+ "context"
+ "path/filepath"
+ "syscall"
+
+ "github.com/hanwen/go-fuse/v2/fs"
+ "github.com/hanwen/go-fuse/v2/fuse"
+)
+
+// translateSize translates the ciphertext size in `out` into plaintext size.
+func (n *Node) translateSize(dirfd int, cName string, out *fuse.Attr) {
+ if out.IsRegular() {
+ rn := n.rootNode()
+ out.Size = rn.contentEnc.PlainSizeToCipherSize(out.Size)
+ } else if out.IsSymlink() {
+ panic("todo: call readlink once it is implemented")
+ }
+}
+
+// Path returns the relative plaintext path of this node
+func (n *Node) Path() string {
+ return n.Inode.Path(n.Root())
+}
+
+// rootNode returns the Root Node of the filesystem.
+func (n *Node) rootNode() *RootNode {
+ return n.Root().Operations().(*RootNode)
+}
+
+// prepareAtSyscall returns a (dirfd, cName) pair that can be used
+// with the "___at" family of system calls (openat, fstatat, unlinkat...) to
+// access the backing encrypted directory.
+//
+// If you pass a `child` file name, the (dirfd, cName) pair will refer to
+// a child of this node.
+// If `child` is empty, the (dirfd, cName) pair refers to this node itself.
+func (n *Node) prepareAtSyscall(child string) (dirfd int, cName string, errno syscall.Errno) {
+ p := n.Path()
+ if child != "" {
+ p = filepath.Join(p, child)
+ }
+ rn := n.rootNode()
+ dirfd, cName, err := rn.openBackingDir(p)
+ if err != nil {
+ errno = fs.ToErrno(err)
+ }
+ return
+}
+
+// newChild attaches a new child inode to n.
+// The passed-in `st` will be modified to get a unique inode number.
+func (n *Node) newChild(ctx context.Context, st *syscall.Stat_t, out *fuse.EntryOut) *fs.Inode {
+ // Get unique inode number
+ rn := n.rootNode()
+ rn.inoMap.TranslateStat(st)
+ out.Attr.FromStat(st)
+ // Create child node
+ id := fs.StableAttr{
+ Mode: uint32(st.Mode),
+ Gen: 1,
+ Ino: st.Ino,
+ }
+ node := &Node{}
+ return n.NewInode(ctx, node, id)
+}
diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
new file mode 100644
index 0000000..ed37847
--- /dev/null
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -0,0 +1,102 @@
+package fusefrontend_reverse
+
+import (
+ "encoding/base64"
+ "path/filepath"
+ "strings"
+ "syscall"
+
+ "github.com/rfjakob/gocryptfs/internal/nametransform"
+ "github.com/rfjakob/gocryptfs/internal/pathiv"
+ "github.com/rfjakob/gocryptfs/internal/syscallcompat"
+ "github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+// abs basically returns storage dir + "/" + relPath.
+// It takes an error parameter so it can directly wrap decryptPath like this:
+// a, err := rfs.abs(rfs.decryptPath(relPath))
+// abs never generates an error on its own. In other words, abs(p, nil) never
+// fails.
+func (rfs *RootNode) abs(relPath string, err error) (string, error) {
+ if err != nil {
+ return "", err
+ }
+ return filepath.Join(rfs.args.Cipherdir, relPath), nil
+}
+
+// rDecryptName decrypts the ciphertext name "cName", given the dirIV of the
+// directory "cName" lies in. The relative plaintext path to the directory
+// "pDir" is used if a "gocryptfs.longname.XYZ.name" must be resolved.
+func (rfs *RootNode) rDecryptName(cName string, dirIV []byte, pDir string) (pName string, err error) {
+ nameType := nametransform.NameType(cName)
+ if nameType == nametransform.LongNameNone {
+ pName, err = rfs.nameTransform.DecryptName(cName, dirIV)
+ if err != nil {
+ // We get lots of decrypt requests for names like ".Trash" that
+ // are invalid base64. Convert them to ENOENT so the correct
+ // error gets returned to the user.
+ if _, ok := err.(base64.CorruptInputError); ok {
+ return "", syscall.ENOENT
+ }
+ // Stat attempts on the link target of encrypted symlinks.
+ // These are always valid base64 but the length is not a
+ // multiple of 16.
+ if err == syscall.EBADMSG {
+ return "", syscall.ENOENT
+ }
+ return "", err
+ }
+ } else if nameType == nametransform.LongNameContent {
+ panic("todo")
+ //pName, err = rfs.findLongnameParent(pDir, dirIV, cName)
+ if err != nil {
+ return "", err
+ }
+ } else {
+ // It makes no sense to decrypt a ".name" file. This is a virtual file
+ // that has no representation in the plaintext filesystem. ".name"
+ // files should have already been handled in virtualfile.go.
+ tlog.Warn.Printf("rDecryptName: cannot decrypt virtual file %q", cName)
+ return "", syscall.EINVAL
+ }
+ return pName, nil
+}
+
+// decryptPath decrypts a relative ciphertext path to a relative plaintext
+// path.
+func (rn *RootNode) decryptPath(relPath string) (string, error) {
+ if rn.args.PlaintextNames || relPath == "" {
+ return relPath, nil
+ }
+ parts := strings.Split(relPath, "/")
+ var transformedParts []string
+ for i := range parts {
+ // Start at the top and recurse
+ currentCipherDir := filepath.Join(parts[:i]...)
+ currentPlainDir := filepath.Join(transformedParts[:i]...)
+ dirIV := pathiv.Derive(currentCipherDir, pathiv.PurposeDirIV)
+ transformedPart, err := rn.rDecryptName(parts[i], dirIV, currentPlainDir)
+ if err != nil {
+ return "", err
+ }
+ transformedParts = append(transformedParts, transformedPart)
+ }
+ pRelPath := filepath.Join(transformedParts...)
+ return pRelPath, nil
+}
+
+// openBackingDir receives an already decrypted relative path
+// "pRelPath", opens the directory that contains the target file/dir
+// and returns the fd to the directory and the decrypted name of the
+// target file. The fd/name pair is intended for use with fchownat and
+// friends.
+func (rn *RootNode) openBackingDir(pRelPath string) (dirfd int, pName string, err error) {
+ // Open directory, safe against symlink races
+ pDir := filepath.Dir(pRelPath)
+ dirfd, err = syscallcompat.OpenDirNofollow(rn.args.Cipherdir, pDir)
+ if err != nil {
+ return -1, "", err
+ }
+ pName = filepath.Base(pRelPath)
+ return dirfd, pName, nil
+}