diff mbox series

[RFC,v5,02/19] fscrypt: export fscrypt_base64_encode and fscrypt_base64_decode

Message ID 20210326173227.96363-3-jlayton@kernel.org (mailing list archive)
State Superseded
Headers show
Series ceph+fscrypt: context, filename and symlink support | expand

Commit Message

Jeff Layton March 26, 2021, 5:32 p.m. UTC 
Ceph will need to base64-encode some encrypted filenames, so make
these routines, and FSCRYPT_BASE64_CHARS available to modules.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/crypto/fname.c       | 34 ++++++++++++++++++++++++----------
 include/linux/fscrypt.h |  5 +++++
 2 files changed, 29 insertions(+), 10 deletions(-)

Comments

Eric Biggers April 8, 2021, 1:06 a.m. UTC | #1 
On Fri, Mar 26, 2021 at 01:32:10PM -0400, Jeff Layton wrote:
> Ceph will need to base64-encode some encrypted filenames, so make
> these routines, and FSCRYPT_BASE64_CHARS available to modules.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>

It would be helpful to have a quick explanation here about *why* ceph has to do
base64 encoding/decoding itself.

- Eric
Jeff Layton April 8, 2021, 4:22 p.m. UTC | #2 
On Wed, 2021-04-07 at 18:06 -0700, Eric Biggers wrote:
> On Fri, Mar 26, 2021 at 01:32:10PM -0400, Jeff Layton wrote:
> > Ceph will need to base64-encode some encrypted filenames, so make
> > these routines, and FSCRYPT_BASE64_CHARS available to modules.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> 
> It would be helpful to have a quick explanation here about *why* ceph has to do
> base64 encoding/decoding itself.
> 

Sure. I'll plan to flesh out the changelogs a bit more before the next
posting.

The basic problem is that we want to use printable filenames for storage
on the MDS, but we don't want to tie the format we use to the fscrypt
nokey name format.

So, we have our own nokey name format that we use that's quite similar
to the one in fscrypt. So similar in fact, that we want to use the same
base64 encoding scheme that fscrypt uses for this -- hence the need to
make these available to modules.
diff mbox series

Patch

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 6ca7d16593ff..32b1f50433ba 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -178,10 +178,8 @@  static int fname_decrypt(const struct inode *inode,
 static const char lookup_table[65] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
 
-#define BASE64_CHARS(nbytes)	DIV_ROUND_UP((nbytes) * 4, 3)
-
 /**
- * base64_encode() - base64-encode some bytes
+ * fscrypt_base64_encode() - base64-encode some bytes
  * @src: the bytes to encode
  * @len: number of bytes to encode
  * @dst: (output) the base64-encoded string.  Not NUL-terminated.
@@ -191,7 +189,7 @@  static const char lookup_table[65] =
  *
  * Return: length of the encoded string
  */
-static int base64_encode(const u8 *src, int len, char *dst)
+int fscrypt_base64_encode(const u8 *src, int len, char *dst)
 {
 	int i, bits = 0, ac = 0;
 	char *cp = dst;
@@ -209,8 +207,20 @@  static int base64_encode(const u8 *src, int len, char *dst)
 		*cp++ = lookup_table[ac & 0x3f];
 	return cp - dst;
 }
+EXPORT_SYMBOL(fscrypt_base64_encode);
 
-static int base64_decode(const char *src, int len, u8 *dst)
+/**
+ * fscrypt_base64_decode() - base64-decode some bytes
+ * @src: the bytes to decode
+ * @len: number of bytes to decode
+ * @dst: (output) decoded binary data
+ *
+ * Decode an input string that was previously encoded using
+ * fscrypt_base64_encode.
+ *
+ * Return: length of the decoded binary data
+ */
+int fscrypt_base64_decode(const char *src, int len, u8 *dst)
 {
 	int i, bits = 0, ac = 0;
 	const char *p;
@@ -232,6 +242,7 @@  static int base64_decode(const char *src, int len, u8 *dst)
 		return -1;
 	return cp - dst;
 }
+EXPORT_SYMBOL(fscrypt_base64_decode);
 
 bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
 				  u32 orig_len, u32 max_len,
@@ -263,8 +274,9 @@  bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
 int fscrypt_fname_alloc_buffer(u32 max_encrypted_len,
 			       struct fscrypt_str *crypto_str)
 {
-	const u32 max_encoded_len = BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX);
 	u32 max_presented_len;
+	const u32 max_encoded_len =
+		FSCRYPT_BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX);
 
 	max_presented_len = max(max_encoded_len, max_encrypted_len);
 
@@ -342,7 +354,7 @@  int fscrypt_fname_disk_to_usr(const struct inode *inode,
 		     offsetof(struct fscrypt_nokey_name, bytes));
 	BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, bytes) !=
 		     offsetof(struct fscrypt_nokey_name, sha256));
-	BUILD_BUG_ON(BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX) > NAME_MAX);
+	BUILD_BUG_ON(FSCRYPT_BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX) > NAME_MAX);
 
 	if (hash) {
 		nokey_name.dirhash[0] = hash;
@@ -362,7 +374,8 @@  int fscrypt_fname_disk_to_usr(const struct inode *inode,
 		       nokey_name.sha256);
 		size = FSCRYPT_NOKEY_NAME_MAX;
 	}
-	oname->len = base64_encode((const u8 *)&nokey_name, size, oname->name);
+	oname->len = fscrypt_base64_encode((const u8 *)&nokey_name, size,
+					   oname->name);
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
@@ -436,14 +449,15 @@  int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 	 * user-supplied name
 	 */
 
-	if (iname->len > BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX))
+	if (iname->len > FSCRYPT_BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX))
 		return -ENOENT;
 
 	fname->crypto_buf.name = kmalloc(FSCRYPT_NOKEY_NAME_MAX, GFP_KERNEL);
 	if (fname->crypto_buf.name == NULL)
 		return -ENOMEM;
 
-	ret = base64_decode(iname->name, iname->len, fname->crypto_buf.name);
+	ret = fscrypt_base64_decode(iname->name, iname->len,
+				    fname->crypto_buf.name);
 	if (ret < (int)offsetof(struct fscrypt_nokey_name, bytes[1]) ||
 	    (ret > offsetof(struct fscrypt_nokey_name, sha256) &&
 	     ret != FSCRYPT_NOKEY_NAME_MAX)) {
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 2ea1387bb497..e300f6145ddc 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -46,6 +46,9 @@  struct fscrypt_name {
 /* Maximum value for the third parameter of fscrypt_operations.set_context(). */
 #define FSCRYPT_SET_CONTEXT_MAX_SIZE	40
 
+/* Calculate worst-case base64 encoding inflation */
+#define FSCRYPT_BASE64_CHARS(nbytes)	DIV_ROUND_UP((nbytes) * 4, 3)
+
 #ifdef CONFIG_FS_ENCRYPTION
 /*
  * fscrypt superblock flags
@@ -207,6 +210,8 @@  void fscrypt_free_inode(struct inode *inode);
 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);
 int fscrypt_setup_filename(struct inode *inode, const struct qstr *iname,
 			   int lookup, struct fscrypt_name *fname);