diff --git a/internal/fusefrontend/node.go b/internal/fusefrontend/node.go index 5753053..bce4ea8 100644 --- a/internal/fusefrontend/node.go +++ b/internal/fusefrontend/node.go @@ -178,3 +178,34 @@ func (n *Node) Unlink(ctx context.Context, name string) syscall.Errno { } return fs.ToErrno(err) } + +// Readlink - FUSE call. +// +// Symlink-safe through openBackingDir() + Readlinkat(). +func (n *Node) Readlink(ctx context.Context) ([]byte, syscall.Errno) { + rn := n.rootNode() + p := n.path() + if rn.isFiltered(p) { + return nil, syscall.EPERM + } + dirfd, cName, err := rn.openBackingDir(p) + if err != nil { + return nil, fs.ToErrno(err) + } + defer syscall.Close(dirfd) + + cTarget, err := syscallcompat.Readlinkat(dirfd, cName) + if err != nil { + return nil, fs.ToErrno(err) + } + if rn.args.PlaintextNames { + return []byte(cTarget), 0 + } + // Symlinks are encrypted like file contents (GCM) and base64-encoded + target, err := rn.decryptSymlinkTarget(cTarget) + if err != nil { + tlog.Warn.Printf("Readlink %q: decrypting target failed: %v", cName, err) + return nil, syscall.EIO + } + return []byte(target), 0 +} diff --git a/internal/fusefrontend/node_api_check.go b/internal/fusefrontend/node_api_check.go index dcf62d3..dd2fd88 100644 --- a/internal/fusefrontend/node_api_check.go +++ b/internal/fusefrontend/node_api_check.go @@ -12,3 +12,4 @@ var _ = (fs.NodeCreater)((*Node)(nil)) var _ = (fs.NodeMkdirer)((*Node)(nil)) var _ = (fs.NodeRmdirer)((*Node)(nil)) var _ = (fs.NodeUnlinker)((*Node)(nil)) +var _ = (fs.NodeReadlinker)((*Node)(nil)) diff --git a/internal/fusefrontend/root_node.go b/internal/fusefrontend/root_node.go index be82851..7565018 100644 --- a/internal/fusefrontend/root_node.go +++ b/internal/fusefrontend/root_node.go @@ -117,3 +117,23 @@ func (rn *RootNode) isFiltered(path string) bool { // are exclusive return false } + +// decryptSymlinkTarget: "cData64" is base64-decoded and decrypted +// like file contents (GCM). +// The empty string decrypts to the empty string. +// +// This function does not do any I/O and is hence symlink-safe. +func (rn *RootNode) decryptSymlinkTarget(cData64 string) (string, error) { + if cData64 == "" { + return "", nil + } + cData, err := rn.nameTransform.B64DecodeString(cData64) + if err != nil { + return "", err + } + data, err := rn.contentEnc.DecryptBlock([]byte(cData), 0, nil) + if err != nil { + return "", err + } + return string(data), nil +}