diff mbox series

[RFC,v5,03/19] fscrypt: export fscrypt_fname_encrypt and fscrypt_fname_encrypted_size

Message ID 20210326173227.96363-4-jlayton@kernel.org (mailing list archive)
State New, archived
Headers show
Series ceph+fscrypt: context, filename and symlink support | expand

Commit Message

Jeff Layton March 26, 2021, 5:32 p.m. UTC 
For ceph, we want to use our own scheme for handling filenames that are
are longer than NAME_MAX after encryption and base64 encoding. This
allows us to have a consistent view of the encrypted filenames for
clients that don't support fscrypt and clients that do but that don't
have the key.

Export fscrypt_fname_encrypt. Rename fscrypt_fname_encrypted_size to
__fscrypt_fname_encrypted_size and add a new wrapper called
fscrypt_fname_encrypted_size that takes an inode argument rahter than
a pointer to a fscrypt_policy union.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/crypto/fname.c           | 19 ++++++++++++++-----
 fs/crypto/fscrypt_private.h |  9 +++------
 fs/crypto/hooks.c           |  6 +++---
 include/linux/fscrypt.h     |  4 ++++
 4 files changed, 24 insertions(+), 14 deletions(-)

Comments

Eric Biggers April 8, 2021, 1:19 a.m. UTC | #1 
On Fri, Mar 26, 2021 at 01:32:11PM -0400, Jeff Layton wrote:
> For ceph, we want to use our own scheme for handling filenames that are
> are longer than NAME_MAX after encryption and base64 encoding. This
> allows us to have a consistent view of the encrypted filenames for
> clients that don't support fscrypt and clients that do but that don't
> have the key.
> 
> Export fscrypt_fname_encrypt. Rename fscrypt_fname_encrypted_size to
> __fscrypt_fname_encrypted_size and add a new wrapper called
> fscrypt_fname_encrypted_size that takes an inode argument rahter than
> a pointer to a fscrypt_policy union.

This explanation seems to be missing a logical connection between the first and
second paragraphs.  I think it's missing something along the lines of:
"Currently, fs/crypto/ only supports filenames encryption using
fscrypt_setup_filename(), which also handles decoding no-key names.  Ceph can't
use that because it needs to handle no-key names in a different way.  So, we
need to export the functions needed to encrypt filenames separately."

(I might have gotten the explanation a bit wrong... Point is, it's the type of
thing that seems to be missing here.)

- Eric
diff mbox series

Patch

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 32b1f50433ba..5a794de7f61d 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -126,6 +126,7 @@  int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
 
 	return 0;
 }
+EXPORT_SYMBOL(fscrypt_fname_encrypt);
 
 /**
  * fname_decrypt() - decrypt a filename
@@ -244,9 +245,9 @@  int fscrypt_base64_decode(const char *src, int len, u8 *dst)
 }
 EXPORT_SYMBOL(fscrypt_base64_decode);
 
-bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
-				  u32 orig_len, u32 max_len,
-				  u32 *encrypted_len_ret)
+bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
+				    u32 orig_len, u32 max_len,
+				    u32 *encrypted_len_ret)
 {
 	int padding = 4 << (fscrypt_policy_flags(policy) &
 			    FSCRYPT_POLICY_FLAGS_PAD_MASK);
@@ -260,6 +261,15 @@  bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
 	return true;
 }
 
+bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
+				  u32 max_len, u32 *encrypted_len_ret)
+{
+	return __fscrypt_fname_encrypted_size(&inode->i_crypt_info->ci_policy,
+					      orig_len, max_len,
+					      encrypted_len_ret);
+}
+EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
+
 /**
  * fscrypt_fname_alloc_buffer() - allocate a buffer for presented filenames
  * @max_encrypted_len: maximum length of encrypted filenames the buffer will be
@@ -422,8 +432,7 @@  int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 		return ret;
 
 	if (fscrypt_has_encryption_key(dir)) {
-		if (!fscrypt_fname_encrypted_size(&dir->i_crypt_info->ci_policy,
-						  iname->len,
+		if (!fscrypt_fname_encrypted_size(dir, iname->len,
 						  dir->i_sb->s_cop->max_namelen,
 						  &fname->crypto_buf.len))
 			return -ENAMETOOLONG;
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 3fa965eb3336..195de6d0db40 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -292,14 +292,11 @@  void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 			 const struct fscrypt_info *ci);
 
 /* fname.c */
-int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
-			  u8 *out, unsigned int olen);
-bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
-				  u32 orig_len, u32 max_len,
-				  u32 *encrypted_len_ret);
+bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
+				    u32 orig_len, u32 max_len,
+                                    u32 *encrypted_len_ret);
 
 /* hkdf.c */
-
 struct fscrypt_hkdf {
 	struct crypto_shash *hmac_tfm;
 };
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index a73b0376e6f3..e65c19aae041 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -228,9 +228,9 @@  int fscrypt_prepare_symlink(struct inode *dir, const char *target,
 	 * counting it (even though it is meaningless for ciphertext) is simpler
 	 * for now since filesystems will assume it is there and subtract it.
 	 */
-	if (!fscrypt_fname_encrypted_size(policy, len,
-					  max_len - sizeof(struct fscrypt_symlink_data),
-					  &disk_link->len))
+	if (!__fscrypt_fname_encrypted_size(policy, len,
+					    max_len - sizeof(struct fscrypt_symlink_data),
+					    &disk_link->len))
 		return -ENAMETOOLONG;
 	disk_link->len += sizeof(struct fscrypt_symlink_data);
 
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index e300f6145ddc..b5c31baaa8bf 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -212,6 +212,10 @@  int fscrypt_drop_inode(struct inode *inode);
 /* fname.c */
 int fscrypt_base64_encode(const u8 *src, int len, char *dst);
 int fscrypt_base64_decode(const char *src, int len, u8 *dst);
+bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
+				  u32 max_len, u32 *encrypted_len_ret);
+int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
+			  u8 *out, unsigned int olen);
 int fscrypt_setup_filename(struct inode *inode, const struct qstr *iname,
 			   int lookup, struct fscrypt_name *fname);