v2api: implement Getxattr, Setxattr, Removexattr, Listxattr

gocryptfs/tests/xattr passes.

1 files changed, 86 insertions, 0 deletions

diff --git a/internal/fusefrontend/node_xattr.go b/internal/fusefrontend/node_xattr.go
new file mode 100644
index 0000000..de40915
--- /dev/null
+++ b/internal/fusefrontend/node_xattr.go
@@ -0,0 +1,86 @@
+// Package fusefrontend interfaces directly with the go-fuse library.
+package fusefrontend
+
+import (
+	"bytes"
+	"context"
+	"strings"
+	"syscall"
+
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+// xattr names are encrypted like file names, but with a fixed IV.
+// Padded with "_xx" for length 16.
+var xattrNameIV = []byte("xattr_name_iv_xx")
+
+// We store encrypted xattrs under this prefix plus the base64-encoded
+// encrypted original name.
+var xattrStorePrefix = "user.gocryptfs."
+
+// GetXAttr - FUSE call. Reads the value of extended attribute "attr".
+//
+// This function is symlink-safe through Fgetxattr.
+func (n *Node) Getxattr(ctx context.Context, attr string, dest []byte) (uint32, syscall.Errno) {
+	rn := n.rootNode()
+	cAttr := rn.encryptXattrName(attr)
+	cData, errno := n.getXAttr(cAttr)
+	if errno != 0 {
+		return 0, errno
+	}
+	data, err := rn.decryptXattrValue(cData)
+	if err != nil {
+		tlog.Warn.Printf("GetXAttr: %v", err)
+		return ^uint32(0), syscall.EIO
+	}
+	l := copy(dest, data)
+	return uint32(l), 0
+}
+
+// SetXAttr - FUSE call. Set extended attribute.
+//
+// This function is symlink-safe through Fsetxattr.
+func (n *Node) Setxattr(ctx context.Context, attr string, data []byte, flags uint32) syscall.Errno {
+	rn := n.rootNode()
+	flags = uint32(filterXattrSetFlags(int(flags)))
+	cAttr := rn.encryptXattrName(attr)
+	cData := rn.encryptXattrValue(data)
+	return n.setXAttr(cAttr, cData, flags)
+}
+
+// RemoveXAttr - FUSE call.
+//
+// This function is symlink-safe through Fremovexattr.
+func (n *Node) Removexattr(ctx context.Context, attr string) syscall.Errno {
+	rn := n.rootNode()
+	cAttr := rn.encryptXattrName(attr)
+	return n.removeXAttr(cAttr)
+}
+
+// ListXAttr - FUSE call. Lists extended attributes on the file at "relPath".
+//
+// This function is symlink-safe through Flistxattr.
+func (n *Node) Listxattr(ctx context.Context, dest []byte) (uint32, syscall.Errno) {
+	cNames, errno := n.listXAttr()
+	if errno != 0 {
+		return 0, errno
+	}
+	rn := n.rootNode()
+	var buf bytes.Buffer
+	for _, curName := range cNames {
+		if !strings.HasPrefix(curName, xattrStorePrefix) {
+			continue
+		}
+		name, err := rn.decryptXattrName(curName)
+		if err != nil {
+			tlog.Warn.Printf("ListXAttr: invalid xattr name %q: %v", curName, err)
+			rn.reportMitigatedCorruption(curName)
+			continue
+		}
+		buf.WriteString(name + "\000")
+	}
+	if buf.Len() > len(dest) {
+		return ^uint32(0), syscall.ERANGE
+	}
+	return uint32(copy(dest, buf.Bytes())), 0
+}