[PATCH v6 3/5] f2fs: Handle casefolding with Encryption

[Daniel Rosenberg <drosen@google.com>]

This expands f2fs's casefolding support to include encrypted
directories. For encrypted directories, we use the siphash of the
casefolded name. This ensures there is no direct way to go from an
unencrypted name to the stored hash on disk without knowledge of the
encryption policy keys.

Additionally, we switch to using the vfs layer's casefolding support
instead of storing this information inside of f2fs's private data.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/f2fs/dir.c    | 65 ++++++++++++++++++++++++++++++++----------------
 fs/f2fs/f2fs.h   |  8 +++---
 fs/f2fs/hash.c   | 23 +++++++++++------
 fs/f2fs/inline.c |  9 ++++---
 fs/f2fs/super.c  |  6 -----
 5 files changed, 68 insertions(+), 43 deletions(-)

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index f1e7dc4ae5256..70daae4a16ed8 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -112,30 +112,50 @@ static struct f2fs_dir_entry *find_in_block(struct inode *dir,
  * doesn't match or less than zero on error.
  */
 int f2fs_ci_compare(const struct inode *parent, const struct qstr *name,
-				const struct qstr *entry, bool quick)
+		    unsigned char *name2, size_t len, bool quick)
 {
 	const struct super_block *sb = parent->i_sb;
 	const struct unicode_map *um = sb->s_encoding;
+	const struct fscrypt_str crypt_entry = FSTR_INIT(name2, len);
+	struct fscrypt_str decrypted_entry;
+	struct qstr decrypted;
+	struct qstr entry = QSTR_INIT(name2, len);
+	struct qstr *tocheck;
 	int ret;
 
+	decrypted_entry.name = NULL;
+
+	if (IS_ENCRYPTED(parent) && fscrypt_has_encryption_key(parent)) {
+		decrypted_entry.name = kmalloc(len, GFP_ATOMIC);
+		decrypted.name = decrypted_entry.name;
+		decrypted_entry.len = len;
+		decrypted.len = len;
+		if (!decrypted.name)
+			return -ENOMEM;
+		ret = fscrypt_fname_disk_to_usr(parent, 0, 0, &crypt_entry,
+							&decrypted_entry);
+		if (ret < 0)
+			goto out;
+	}
+	tocheck = decrypted_entry.name ? &decrypted : &entry;
+
 	if (quick)
-		ret = utf8_strncasecmp_folded(um, name, entry);
+		ret = utf8_strncasecmp_folded(um, name, tocheck);
 	else
-		ret = utf8_strncasecmp(um, name, entry);
-
+		ret = utf8_strncasecmp(um, name, tocheck);
 	if (ret < 0) {
 		/* Handle invalid character sequence as either an error
 		 * or as an opaque byte sequence.
 		 */
 		if (sb_has_enc_strict_mode(sb))
-			return -EINVAL;
-
-		if (name->len != entry->len)
-			return 1;
-
-		return !!memcmp(name->name, entry->name, name->len);
+			ret = -EINVAL;
+		else if (name->len != len)
+			ret = 1;
+		else
+			ret = !!memcmp(name->name, tocheck->name, len);
 	}
-
+out:
+	kfree(decrypted_entry.name);
 	return ret;
 }
 
@@ -173,24 +193,24 @@ static inline bool f2fs_match_name(struct f2fs_dentry_ptr *d,
 {
 #ifdef CONFIG_UNICODE
 	struct inode *parent = d->inode;
-	struct super_block *sb = parent->i_sb;
-	struct qstr entry;
+	unsigned char *name;
+	int len;
 #endif
 
 	if (de->hash_code != namehash)
 		return false;
 
 #ifdef CONFIG_UNICODE
-	entry.name = d->filename[bit_pos];
-	entry.len = de->name_len;
+	name = d->filename[bit_pos];
+	len = de->name_len;
 
-	if (sb->s_encoding && IS_CASEFOLDED(parent)) {
+	if (needs_casefold(parent)) {
 		if (cf_str->name) {
 			struct qstr cf = {.name = cf_str->name,
 					  .len = cf_str->len};
-			return !f2fs_ci_compare(parent, &cf, &entry, true);
+			return !f2fs_ci_compare(parent, &cf, name, len, true);
 		}
-		return !f2fs_ci_compare(parent, fname->usr_fname, &entry,
+		return !f2fs_ci_compare(parent, fname->usr_fname, name, len,
 					false);
 	}
 #endif
@@ -602,13 +622,13 @@ void f2fs_update_dentry(nid_t ino, umode_t mode, struct f2fs_dentry_ptr *d,
 
 int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
 				const struct qstr *orig_name,
+				f2fs_hash_t dentry_hash,
 				struct inode *inode, nid_t ino, umode_t mode)
 {
 	unsigned int bit_pos;
 	unsigned int level;
 	unsigned int current_depth;
 	unsigned long bidx, block;
-	f2fs_hash_t dentry_hash;
 	unsigned int nbucket, nblock;
 	struct page *dentry_page = NULL;
 	struct f2fs_dentry_block *dentry_blk = NULL;
@@ -618,7 +638,6 @@ int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
 
 	level = 0;
 	slots = GET_DENTRY_SLOTS(new_name->len);
-	dentry_hash = f2fs_dentry_hash(dir, new_name, NULL);
 
 	current_depth = F2FS_I(dir)->i_current_depth;
 	if (F2FS_I(dir)->chash == dentry_hash) {
@@ -704,17 +723,19 @@ int f2fs_add_dentry(struct inode *dir, struct fscrypt_name *fname,
 				struct inode *inode, nid_t ino, umode_t mode)
 {
 	struct qstr new_name;
+	f2fs_hash_t dentry_hash;
 	int err = -EAGAIN;
 
 	new_name.name = fname_name(fname);
 	new_name.len = fname_len(fname);
 
 	if (f2fs_has_inline_dentry(dir))
-		err = f2fs_add_inline_entry(dir, &new_name, fname->usr_fname,
+		err = f2fs_add_inline_entry(dir, &new_name, fname,
 							inode, ino, mode);
+	dentry_hash = f2fs_dentry_hash(dir, &new_name, fname);
 	if (err == -EAGAIN)
 		err = f2fs_add_regular_entry(dir, &new_name, fname->usr_fname,
-							inode, ino, mode);
+						dentry_hash, inode, ino, mode);
 
 	f2fs_update_time(F2FS_I_SB(dir), REQ_TIME);
 	return err;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index cc767dd4d5352..1d5d9df20cc67 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2967,7 +2967,7 @@ struct dentry *f2fs_get_parent(struct dentry *child);
 
 extern int f2fs_ci_compare(const struct inode *parent,
 			   const struct qstr *name,
-			   const struct qstr *entry,
+			   unsigned char *name2, size_t len,
 			   bool quick);
 
 /*
@@ -3001,7 +3001,7 @@ void f2fs_update_dentry(nid_t ino, umode_t mode, struct f2fs_dentry_ptr *d,
 			const struct qstr *name, f2fs_hash_t name_hash,
 			unsigned int bit_pos);
 int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
-			const struct qstr *orig_name,
+			const struct qstr *orig_name, f2fs_hash_t dentry_hash,
 			struct inode *inode, nid_t ino, umode_t mode);
 int f2fs_add_dentry(struct inode *dir, struct fscrypt_name *fname,
 			struct inode *inode, nid_t ino, umode_t mode);
@@ -3035,7 +3035,7 @@ int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi);
  * hash.c
  */
 f2fs_hash_t f2fs_dentry_hash(const struct inode *dir,
-		const struct qstr *name_info, struct fscrypt_name *fname);
+		const struct qstr *name_info, const struct fscrypt_name *fname);
 
 /*
  * node.c
@@ -3511,7 +3511,7 @@ struct f2fs_dir_entry *f2fs_find_in_inline_dir(struct inode *dir,
 int f2fs_make_empty_inline_dir(struct inode *inode, struct inode *parent,
 			struct page *ipage);
 int f2fs_add_inline_entry(struct inode *dir, const struct qstr *new_name,
-			const struct qstr *orig_name,
+			const struct fscrypt_name *fname,
 			struct inode *inode, nid_t ino, umode_t mode);
 void f2fs_delete_inline_entry(struct f2fs_dir_entry *dentry,
 				struct page *page, struct inode *dir,
diff --git a/fs/f2fs/hash.c b/fs/f2fs/hash.c
index 28acb24e7a7a8..6d7ddf2fd308f 100644
--- a/fs/f2fs/hash.c
+++ b/fs/f2fs/hash.c
@@ -68,8 +68,9 @@ static void str2hashbuf(const unsigned char *msg, size_t len,
 		*buf++ = pad;
 }
 
-static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
-				struct fscrypt_name *fname)
+static f2fs_hash_t __f2fs_dentry_hash(const struct inode *dir,
+				const struct qstr *name_info,
+				const struct fscrypt_name *fname)
 {
 	__u32 hash;
 	f2fs_hash_t f2fs_hash;
@@ -85,6 +86,11 @@ static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
 	if (is_dot_dotdot(name_info))
 		return 0;
 
+	if (IS_CASEFOLDED(dir) && IS_ENCRYPTED(dir)) {
+		f2fs_hash = fscrypt_fname_siphash(dir, name_info);
+		return f2fs_hash;
+	}
+
 	/* Initialize the default seed for the hash checksum functions */
 	buf[0] = 0x67452301;
 	buf[1] = 0xefcdab89;
@@ -106,7 +112,7 @@ static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
 }
 
 f2fs_hash_t f2fs_dentry_hash(const struct inode *dir,
-		const struct qstr *name_info, struct fscrypt_name *fname)
+		const struct qstr *name_info, const struct fscrypt_name *fname)
 {
 #ifdef CONFIG_UNICODE
 	struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);
@@ -114,27 +120,30 @@ f2fs_hash_t f2fs_dentry_hash(const struct inode *dir,
 	int r, dlen;
 	unsigned char *buff;
 	struct qstr folded;
+	const struct qstr *name = fname ? fname->usr_fname : name_info;
 
 	if (!name_info->len || !IS_CASEFOLDED(dir))
 		goto opaque_seq;
 
+	if (IS_ENCRYPTED(dir) && !fscrypt_has_encryption_key(dir))
+		goto opaque_seq;
+
 	buff = f2fs_kzalloc(sbi, sizeof(char) * PATH_MAX, GFP_KERNEL);
 	if (!buff)
 		return -ENOMEM;
-
-	dlen = utf8_casefold(um, name_info, buff, PATH_MAX);
+	dlen = utf8_casefold(um, name, buff, PATH_MAX);
 	if (dlen < 0) {
 		kvfree(buff);
 		goto opaque_seq;
 	}
 	folded.name = buff;
 	folded.len = dlen;
-	r = __f2fs_dentry_hash(&folded, fname);
+	r = __f2fs_dentry_hash(dir, &folded, fname);
 
 	kvfree(buff);
 	return r;
 
 opaque_seq:
 #endif
-	return __f2fs_dentry_hash(name_info, fname);
+	return __f2fs_dentry_hash(dir, name_info, fname);
 }
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 896db0416f0e6..3c37720941539 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -465,8 +465,8 @@ static int f2fs_add_inline_entries(struct inode *dir, void *inline_dentry)
 		ino = le32_to_cpu(de->ino);
 		fake_mode = f2fs_get_de_type(de) << S_SHIFT;
 
-		err = f2fs_add_regular_entry(dir, &new_name, NULL, NULL,
-							ino, fake_mode);
+		err = f2fs_add_regular_entry(dir, &new_name, NULL,
+					de->hash_code, NULL, ino, fake_mode);
 		if (err)
 			goto punch_dentry_pages;
 
@@ -540,7 +540,7 @@ static int f2fs_convert_inline_dir(struct inode *dir, struct page *ipage,
 }
 
 int f2fs_add_inline_entry(struct inode *dir, const struct qstr *new_name,
-				const struct qstr *orig_name,
+				const struct fscrypt_name *fname,
 				struct inode *inode, nid_t ino, umode_t mode)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(dir);
@@ -551,6 +551,7 @@ int f2fs_add_inline_entry(struct inode *dir, const struct qstr *new_name,
 	struct f2fs_dentry_ptr d;
 	int slots = GET_DENTRY_SLOTS(new_name->len);
 	struct page *page = NULL;
+	const struct qstr *orig_name = fname->usr_fname;
 	int err = 0;
 
 	ipage = f2fs_get_node_page(sbi, dir->i_ino);
@@ -581,7 +582,7 @@ int f2fs_add_inline_entry(struct inode *dir, const struct qstr *new_name,
 
 	f2fs_wait_on_page_writeback(ipage, NODE, true, true);
 
-	name_hash = f2fs_dentry_hash(dir, new_name, NULL);
+	name_hash = f2fs_dentry_hash(dir, new_name, fname);
 	f2fs_update_dentry(ino, mode, &d, new_name, name_hash, bit_pos);
 
 	set_page_dirty(ipage);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 0f7ef0896655a..2c6efff50d1c1 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3141,12 +3141,6 @@ 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,
-- 
2.25.0.341.g760bfbb309-goog


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