[PATCH v4 3/3] f2fs: Handle casefolding with Encryption

From: Daniel Rosenberg
Date: Thu Nov 19 2020 - 01:09:34 EST

Expand f2fs's casefolding support to include encrypted directories. To
index casefolded+encrypted directories, we use the SipHash of the
casefolded name, keyed by a key derived from the directory's fscrypt
master key. This ensures that the dirhash doesn't leak information
about the plaintext filenames.

Encryption keys are unavailable during roll-forward recovery, so we
can't compute the dirhash when recovering a new dentry in an encrypted +
casefolded directory. To avoid having to force a checkpoint when a new
file is fsync'ed, store the dirhash on-disk appended to i_name.

This patch incorporates work by Eric Biggers <ebiggers@xxxxxxxxxx>
and Jaegeuk Kim <jaegeuk@xxxxxxxxxx>.

Co-developed-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Daniel Rosenberg <drosen@xxxxxxxxxx>
Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
fs/f2fs/dir.c | 98 +++++++++++++++++++++++++++++++++++-----------
fs/f2fs/f2fs.h | 8 ++--
fs/f2fs/hash.c | 11 +++++-
fs/f2fs/inline.c | 4 ++
fs/f2fs/recovery.c | 12 +++++-
fs/f2fs/super.c | 6 ---
6 files changed, 106 insertions(+), 33 deletions(-)

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 71fdf5076461..82b58d1f80eb 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -5,6 +5,7 @@
* Copyright (c) 2012 Samsung Electronics Co., Ltd.
* http://www.samsung.com/
*/
+#include <asm/unaligned.h>
#include <linux/fs.h>
#include <linux/f2fs_fs.h>
#include <linux/sched/signal.h>
@@ -206,30 +207,55 @@ static struct f2fs_dir_entry *find_in_block(struct inode *dir,
/*
* Test whether a case-insensitive directory entry matches the filename
* being searched for.
+ *
+ * Returns 1 for a match, 0 for no match, and -errno on an error.
*/
-static bool f2fs_match_ci_name(const struct inode *dir, const struct qstr *name,
+static int f2fs_match_ci_name(const struct inode *dir, const struct qstr *name,
const u8 *de_name, u32 de_name_len)
{
const struct super_block *sb = dir->i_sb;
const struct unicode_map *um = sb->s_encoding;
+ struct fscrypt_str decrypted_name = FSTR_INIT(NULL, de_name_len);
struct qstr entry = QSTR_INIT(de_name, de_name_len);
int res;

+ if (IS_ENCRYPTED(dir)) {
+ const struct fscrypt_str encrypted_name =
+ FSTR_INIT((u8 *)de_name, de_name_len);
+
+ if (WARN_ON_ONCE(!fscrypt_has_encryption_key(dir)))
+ return -EINVAL;
+
+ decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
+ if (!decrypted_name.name)
+ return -ENOMEM;
+ res = fscrypt_fname_disk_to_usr(dir, 0, 0, &encrypted_name,
+ &decrypted_name);
+ if (res < 0)
+ goto out;
+ entry.name = decrypted_name.name;
+ entry.len = decrypted_name.len;
+ }
+
res = utf8_strncasecmp_folded(um, name, &entry);
- if (res < 0) {
- /*
- * In strict mode, ignore invalid names. In non-strict mode,
- * fall back to treating them as opaque byte sequences.
- */
- if (sb_has_strict_encoding(sb) || name->len != entry.len)
- return false;
- return !memcmp(name->name, entry.name, name->len);
+ /*
+ * In strict mode, ignore invalid names. In non-strict mode,
+ * fall back to treating them as opaque byte sequences.
+ */
+ if (res < 0 && !sb_has_strict_encoding(sb)) {
+ res = name->len == entry.len &&
+ memcmp(name->name, entry.name, name->len) == 0;
+ } else {
+ /* utf8_strncasecmp_folded returns 0 on match */
+ res = (res == 0);
}
- return res == 0;
+out:
+ kfree(decrypted_name.name);
+ return res;
}
#endif /* CONFIG_UNICODE */

-static inline bool f2fs_match_name(const struct inode *dir,
+static inline int f2fs_match_name(const struct inode *dir,
const struct f2fs_filename *fname,
const u8 *de_name, u32 de_name_len)
{
@@ -256,6 +282,7 @@ struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
struct f2fs_dir_entry *de;
unsigned long bit_pos = 0;
int max_len = 0;
+ int res = 0;

if (max_slots)
*max_slots = 0;
@@ -273,10 +300,15 @@ struct f2fs_dir_entry *f2fs_find_target_dentry(const struct f2fs_dentry_ptr *d,
continue;
}

- if (de->hash_code == fname->hash &&
- f2fs_match_name(d->inode, fname, d->filename[bit_pos],
- le16_to_cpu(de->name_len)))
- goto found;
+ if (de->hash_code == fname->hash) {
+ res = f2fs_match_name(d->inode, fname,
+ d->filename[bit_pos],
+ le16_to_cpu(de->name_len));
+ if (res < 0)
+ return ERR_PTR(res);
+ if (res)
+ goto found;
+ }

if (max_slots && max_len > *max_slots)
*max_slots = max_len;
@@ -326,7 +358,11 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
}

de = find_in_block(dir, dentry_page, fname, &max_slots);
- if (de) {
+ if (IS_ERR(de)) {
+ *res_page = ERR_CAST(de);
+ de = NULL;
+ break;
+ } else if (de) {
*res_page = dentry_page;
break;
}
@@ -448,17 +484,39 @@ void f2fs_set_link(struct inode *dir, struct f2fs_dir_entry *de,
f2fs_put_page(page, 1);
}

-static void init_dent_inode(const struct f2fs_filename *fname,
+static void init_dent_inode(struct inode *dir, struct inode *inode,
+ const struct f2fs_filename *fname,
struct page *ipage)
{
struct f2fs_inode *ri;

+ if (!fname) /* tmpfile case? */
+ return;
+
f2fs_wait_on_page_writeback(ipage, NODE, true, true);

/* copy name info. to this inode page */
ri = F2FS_INODE(ipage);
ri->i_namelen = cpu_to_le32(fname->disk_name.len);
memcpy(ri->i_name, fname->disk_name.name, fname->disk_name.len);
+ if (IS_ENCRYPTED(dir)) {
+ file_set_enc_name(inode);
+ /*
+ * Roll-forward recovery doesn't have encryption keys available,
+ * so it can't compute the dirhash for encrypted+casefolded
+ * filenames. Append it to i_name if possible. Else, disable
+ * roll-forward recovery of the dentry (i.e., make fsync'ing the
+ * file force a checkpoint) by setting LOST_PINO.
+ */
+ if (IS_CASEFOLDED(dir)) {
+ if (fname->disk_name.len + sizeof(f2fs_hash_t) <=
+ F2FS_NAME_LEN)
+ put_unaligned(fname->hash, (f2fs_hash_t *)
+ &ri->i_name[fname->disk_name.len]);
+ else
+ file_lost_pino(inode);
+ }
+ }
set_page_dirty(ipage);
}

@@ -541,11 +599,7 @@ struct page *f2fs_init_inode_metadata(struct inode *inode, struct inode *dir,
return page;
}

- if (fname) {
- init_dent_inode(fname, page);
- if (IS_ENCRYPTED(dir))
- file_set_enc_name(inode);
- }
+ init_dent_inode(dir, inode, fname, page);

/*
* This file should be checkpointed during fsync.
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 62b4f31d30e2..878308736761 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -533,9 +533,11 @@ struct f2fs_filename {
#ifdef CONFIG_UNICODE
/*
* For casefolded directories: the casefolded name, but it's left NULL
- * if the original name is not valid Unicode or if the filesystem is
- * doing an internal operation where usr_fname is also NULL. In these
- * cases we fall back to treating the name as an opaque byte sequence.
+ * if the original name is not valid Unicode, if the directory is both
+ * casefolded and encrypted and its encryption key is unavailable, or if
+ * the filesystem is doing an internal operation where usr_fname is also
+ * NULL. In all these cases we fall back to treating the name as an
+ * opaque byte sequence.
*/
struct fscrypt_str cf_name;
#endif
diff --git a/fs/f2fs/hash.c b/fs/f2fs/hash.c
index de841aaf3c43..e3beac546c63 100644
--- a/fs/f2fs/hash.c
+++ b/fs/f2fs/hash.c
@@ -111,7 +111,9 @@ void f2fs_hash_filename(const struct inode *dir, struct f2fs_filename *fname)
* If the casefolded name is provided, hash it instead of the
* on-disk name. If the casefolded name is *not* provided, that
* should only be because the name wasn't valid Unicode, so fall
- * back to treating the name as an opaque byte sequence.
+ * back to treating the name as an opaque byte sequence. Note
+ * that to handle encrypted directories, the fallback must use
+ * usr_fname (plaintext) rather than disk_name (ciphertext).
*/
WARN_ON_ONCE(!fname->usr_fname->name);
if (fname->cf_name.name) {
@@ -121,6 +123,13 @@ void f2fs_hash_filename(const struct inode *dir, struct f2fs_filename *fname)
name = fname->usr_fname->name;
len = fname->usr_fname->len;
}
+ if (IS_ENCRYPTED(dir)) {
+ struct qstr tmp = QSTR_INIT(name, len);
+
+ fname->hash =
+ cpu_to_le32(fscrypt_fname_siphash(dir, &tmp));
+ return;
+ }
}
#endif
fname->hash = cpu_to_le32(TEA_hash_name(name, len));
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 70384e31788d..92e9852d316a 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -332,6 +332,10 @@ struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
make_dentry_ptr_inline(dir, &d, inline_dentry);
de = f2fs_find_target_dentry(&d, fname, NULL);
unlock_page(ipage);
+ if (IS_ERR(de)) {
+ *res_page = ERR_CAST(de);
+ de = NULL;
+ }
if (de)
*res_page = ipage;
else
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 4f12ade6410a..0947d36af1a8 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -5,6 +5,7 @@
* Copyright (c) 2012 Samsung Electronics Co., Ltd.
* http://www.samsung.com/
*/
+#include <asm/unaligned.h>
#include <linux/fs.h>
#include <linux/f2fs_fs.h>
#include "f2fs.h"
@@ -128,7 +129,16 @@ static int init_recovered_filename(const struct inode *dir,
}

/* Compute the hash of the filename */
- if (IS_CASEFOLDED(dir)) {
+ if (IS_ENCRYPTED(dir) && IS_CASEFOLDED(dir)) {
+ /*
+ * In this case the hash isn't computable without the key, so it
+ * was saved on-disk.
+ */
+ if (fname->disk_name.len + sizeof(f2fs_hash_t) > F2FS_NAME_LEN)
+ return -EINVAL;
+ fname->hash = get_unaligned((f2fs_hash_t *)
+ &raw_inode->i_name[fname->disk_name.len]);
+ } else if (IS_CASEFOLDED(dir)) {
err = f2fs_init_casefolded_name(dir, fname);
if (err)
return err;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index f51d52591c99..42293b7ceaf2 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3399,12 +3399,6 @@ static int f2fs_setup_casefold(struct f2fs_sb_info *sbi)
struct unicode_map *encoding;
__u16 encoding_flags;

- if (f2fs_sb_has_encrypt(sbi)) {
- f2fs_err(sbi,
- "Can't mount with encoding and encryption");
- return -EINVAL;
- }
-
if (f2fs_sb_read_encoding(sbi->raw_super, &encoding_info,
&encoding_flags)) {
f2fs_err(sbi,
--
2.29.2.454.gaff20da3a2-goog