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package fusefrontend_reverse
import (
"context"
"path/filepath"
"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/configfile"
"github.com/rfjakob/gocryptfs/internal/pathiv"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
)
const (
// File names are padded to 16-byte multiples, encrypted and
// base64-encoded. We can encode at most 176 bytes to stay below the 255
// bytes limit:
// * base64(176 bytes) = 235 bytes
// * base64(192 bytes) = 256 bytes (over 255!)
// But the PKCS#7 padding is at least one byte. This means we can only use
// 175 bytes for the file name.
shortNameMax = 175
)
// translateSize translates the ciphertext size in `out` into plaintext size.
func (n *Node) translateSize(dirfd int, cName string, pName string, out *fuse.Attr) {
if out.IsRegular() {
rn := n.rootNode()
out.Size = rn.contentEnc.PlainSizeToCipherSize(out.Size)
} else if out.IsSymlink() {
cLink, _ := n.readlink(dirfd, cName, pName)
out.Size = uint64(len(cLink))
}
}
// 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, pName string, errno syscall.Errno) {
p := n.Path()
if child != "" {
p = filepath.Join(p, child)
}
rn := n.rootNode()
dirfd, pName, 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)
}
// isRoot returns true if this node is the root node
func (n *Node) isRoot() bool {
rn := n.rootNode()
return &rn.Node == n
}
func (n *Node) lookupLongnameName(ctx context.Context, nameFile string, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
dirfd, pName1, errno := n.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd)
// Find the file the gocryptfs.longname.XYZ.name file belongs to in the
// directory listing
fd, err := syscallcompat.Openat(dirfd, pName1, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err != nil {
errno = fs.ToErrno(err)
return
}
diriv := pathiv.Derive(n.Path(), pathiv.PurposeDirIV)
rn := n.rootNode()
pName, cFullname, errno := rn.findLongnameParent(fd, diriv, nameFile)
if errno != 0 {
return
}
// Get attrs from parent file
st, err := syscallcompat.Fstatat2(dirfd, pName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
errno = fs.ToErrno(err)
return
}
var vf *VirtualMemNode
vf, errno = n.newVirtualMemNode([]byte(cFullname), st, inoTagNameFile)
if errno != 0 {
return nil, errno
}
out.Attr = vf.attr
// Create child node
id := fs.StableAttr{Mode: uint32(vf.attr.Mode), Gen: 1, Ino: vf.attr.Ino}
ch = n.NewInode(ctx, vf, id)
return
}
// lookupDiriv returns a new Inode for a gocryptfs.diriv file inside `n`.
func (n *Node) lookupDiriv(ctx context.Context, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
dirfd, pName, errno := n.prepareAtSyscall("")
if errno != 0 {
return
}
defer syscall.Close(dirfd)
st, err := syscallcompat.Fstatat2(dirfd, pName, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
errno = fs.ToErrno(err)
return
}
content := pathiv.Derive(n.Path(), pathiv.PurposeDirIV)
var vf *VirtualMemNode
vf, errno = n.newVirtualMemNode(content, st, inoTagDirIV)
if errno != 0 {
return nil, errno
}
out.Attr = vf.attr
// Create child node
id := fs.StableAttr{Mode: uint32(vf.attr.Mode), Gen: 1, Ino: vf.attr.Ino}
ch = n.NewInode(ctx, vf, id)
return
}
// lookupConf returns a new Inode for the gocryptfs.conf file
func (n *Node) lookupConf(ctx context.Context, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
rn := n.rootNode()
p := filepath.Join(rn.args.Cipherdir, configfile.ConfReverseName)
var st syscall.Stat_t
err := syscall.Stat(p, &st)
if err != nil {
errno = fs.ToErrno(err)
return
}
// Get unique inode number
rn.inoMap.TranslateStat(&st)
out.Attr.FromStat(&st)
// Create child node
id := fs.StableAttr{
Mode: uint32(st.Mode),
Gen: 1,
Ino: st.Ino,
}
node := &VirtualConfNode{path: p}
ch = n.NewInode(ctx, node, id)
return
}
// readlink reads and encrypts a symlink. Used by Readlink, Getattr, Lookup.
func (n *Node) readlink(dirfd int, cName string, pName string) (out []byte, errno syscall.Errno) {
plainTarget, err := syscallcompat.Readlinkat(dirfd, pName)
if err != nil {
errno = fs.ToErrno(err)
return
}
rn := n.rootNode()
if rn.args.PlaintextNames {
return []byte(plainTarget), 0
}
// Nonce is derived from the relative *ciphertext* path
p := filepath.Join(n.Path(), cName)
nonce := pathiv.Derive(p, pathiv.PurposeSymlinkIV)
// Symlinks are encrypted like file contents and base64-encoded
cBinTarget := rn.contentEnc.EncryptBlockNonce([]byte(plainTarget), 0, nil, nonce)
cTarget := rn.nameTransform.B64EncodeToString(cBinTarget)
// The kernel will reject a symlink target above 4096 chars and return
// and I/O error to the user. Better emit the proper error ourselves.
if len(cTarget) > syscallcompat.PATH_MAX {
errno = syscall.ENAMETOOLONG
return
}
return []byte(cTarget), 0
}
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