From ebdf58b9ebf366ac6dbf500c0f4f4d211451bb44 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Sun, 21 Jun 2020 12:42:18 +0200
Subject: v2api: implement GetAttr and Readdir

---
 internal/fusefrontend/node.go         | 27 ++++++++--
 internal/fusefrontend/node_dir_ops.go | 97 +++++++++++++++++++++++++++++++++++
 internal/fusefrontend/root_node.go    | 24 +++++++++
 3 files changed, 144 insertions(+), 4 deletions(-)
 create mode 100644 internal/fusefrontend/node_dir_ops.go
 create mode 100644 internal/fusefrontend/root_node.go

diff --git a/internal/fusefrontend/node.go b/internal/fusefrontend/node.go
index f246408..f4359a2 100644
--- a/internal/fusefrontend/node.go
+++ b/internal/fusefrontend/node.go
@@ -31,6 +31,15 @@ type RootNode struct {
 	nameTransform nametransform.NameTransformer
 	// Content encryption helper
 	contentEnc *contentenc.ContentEnc
+	// MitigatedCorruptions is used to report data corruption that is internally
+	// mitigated by ignoring the corrupt item. For example, when OpenDir() finds
+	// a corrupt filename, we still return the other valid filenames.
+	// The corruption is logged to syslog to inform the user,	and in addition,
+	// the corrupt filename is logged to this channel via
+	// reportMitigatedCorruption().
+	// "gocryptfs -fsck" reads from the channel to also catch these transparently-
+	// mitigated corruptions.
+	MitigatedCorruptions chan string
 	// IsIdle flag is set to zero each time fs.isFiltered() is called
 	// (uint32 so that it can be reset with CompareAndSwapUint32).
 	// When -idle was used when mounting, idleMonitor() sets it to 1
@@ -68,6 +77,7 @@ func (n *Node) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (*fs
 	if err != nil {
 		return nil, fs.ToErrno(err)
 	}
+	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 {
@@ -88,9 +98,18 @@ func (n *Node) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (*fs
 }
 
 func (n *Node) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) syscall.Errno {
-	return 1
-}
+	rn := n.rootNode()
+	dirfd, cName, err := rn.openBackingDir(n.path())
+	if err != nil {
+		return fs.ToErrno(err)
+	}
+	defer syscall.Close(dirfd)
 
-func (n *Node) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
-	return nil, 1
+	st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
+	if err != nil {
+		return fs.ToErrno(err)
+	}
+	rn.inoMap.TranslateStat(st)
+	out.Attr.FromStat(st)
+	return 0
 }
diff --git a/internal/fusefrontend/node_dir_ops.go b/internal/fusefrontend/node_dir_ops.go
new file mode 100644
index 0000000..38d0940
--- /dev/null
+++ b/internal/fusefrontend/node_dir_ops.go
@@ -0,0 +1,97 @@
+package fusefrontend
+
+import (
+	"context"
+	"path/filepath"
+	"syscall"
+
+	"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/nametransform"
+	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+func (n *Node) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
+	rn := n.rootNode()
+	p := n.path()
+	dirName := filepath.Base(p)
+	parentDirFd, cDirName, err := rn.openBackingDir(p)
+	if err != nil {
+		return nil, fs.ToErrno(err)
+	}
+	defer syscall.Close(parentDirFd)
+
+	// Read ciphertext directory
+	var cipherEntries []fuse.DirEntry
+	fd, err := syscallcompat.Openat(parentDirFd, cDirName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
+	if err != nil {
+		return nil, fs.ToErrno(err)
+	}
+	defer syscall.Close(fd)
+	cipherEntries, err = syscallcompat.Getdents(fd)
+	if err != nil {
+		return nil, fs.ToErrno(err)
+	}
+	// Get DirIV (stays nil if PlaintextNames is used)
+	var cachedIV []byte
+	if !rn.args.PlaintextNames {
+		// Read the DirIV from disk
+		cachedIV, err = nametransform.ReadDirIVAt(fd)
+		if err != nil {
+			tlog.Warn.Printf("OpenDir %q: could not read %s: %v", cDirName, nametransform.DirIVFilename, err)
+			return nil, syscall.EIO
+		}
+	}
+	// Decrypted directory entries
+	var plain []fuse.DirEntry
+	// Filter and decrypt filenames
+	for i := range cipherEntries {
+		cName := cipherEntries[i].Name
+		if dirName == "." && cName == configfile.ConfDefaultName {
+			// silently ignore "gocryptfs.conf" in the top level dir
+			continue
+		}
+		if rn.args.PlaintextNames {
+			plain = append(plain, cipherEntries[i])
+			continue
+		}
+		if cName == nametransform.DirIVFilename {
+			// silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
+			continue
+		}
+		// Handle long file name
+		isLong := nametransform.LongNameNone
+		if rn.args.LongNames {
+			isLong = nametransform.NameType(cName)
+		}
+		if isLong == nametransform.LongNameContent {
+			cNameLong, err := nametransform.ReadLongNameAt(fd, cName)
+			if err != nil {
+				tlog.Warn.Printf("OpenDir %q: invalid entry %q: Could not read .name: %v",
+					cDirName, cName, err)
+				rn.reportMitigatedCorruption(cName)
+				continue
+			}
+			cName = cNameLong
+		} else if isLong == nametransform.LongNameFilename {
+			// ignore "gocryptfs.longname.*.name"
+			continue
+		}
+		name, err := rn.nameTransform.DecryptName(cName, cachedIV)
+		if err != nil {
+			tlog.Warn.Printf("OpenDir %q: invalid entry %q: %v",
+				cDirName, cName, err)
+			rn.reportMitigatedCorruption(cName)
+			continue
+		}
+		// Override the ciphertext name with the plaintext name but reuse the rest
+		// of the structure
+		cipherEntries[i].Name = name
+		plain = append(plain, cipherEntries[i])
+	}
+
+	return fs.NewListDirStream(plain), 0
+}
diff --git a/internal/fusefrontend/root_node.go b/internal/fusefrontend/root_node.go
new file mode 100644
index 0000000..94fd021
--- /dev/null
+++ b/internal/fusefrontend/root_node.go
@@ -0,0 +1,24 @@
+package fusefrontend
+
+import (
+	"time"
+
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+// reportMitigatedCorruption is used to report a corruption that was transparently
+// mitigated and did not return an error to the user. Pass the name of the corrupt
+// item (filename for OpenDir(), xattr name for ListXAttr() etc).
+// See the MitigatedCorruptions channel for more info.
+func (rn *RootNode) reportMitigatedCorruption(item string) {
+	if rn.MitigatedCorruptions == nil {
+		return
+	}
+	select {
+	case rn.MitigatedCorruptions <- item:
+	case <-time.After(1 * time.Second):
+		tlog.Warn.Printf("BUG: reportCorruptItem: timeout")
+		//debug.PrintStack()
+		return
+	}
+}
-- 
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