[RFC PATCH v3 02/16] fscrypt: export fscrypt_base64_encode and fscrypt_base64_decode

Jeff Layton
2020-09-14T19:19:17Z

Ceph will need to base64-encode some encrypted inode names, so make
these routines, and FSCRYPT_BASE64_CHARS available to modules.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/crypto/fname.c | 59 ++++++++++++++++++++++++++++++++++-------
include/linux/fscrypt.h | 4 +++
2 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index eb13408b50a7..a1cb6c2c50c4 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -187,10 +187,8 @@ 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.
@@ -200,7 +198,7 @@ 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;
@@ -218,8 +216,9 @@ 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)
+int fscrypt_base64_decode(const char *src, int len, u8 *dst)
{
int i, bits = 0, ac = 0;
const char *p;
@@ -241,6 +240,7 @@ 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,
@@ -272,7 +272,7 @@ 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);
+ const u32 max_encoded_len = FSCRYPT_BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX);
u32 max_presented_len;

max_presented_len = max(max_encoded_len, max_encrypted_len);
@@ -300,6 +300,45 @@ void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
}
EXPORT_SYMBOL(fscrypt_fname_free_buffer);

+void fscrypt_encode_nokey_name(u32 hash, u32 minor_hash,
+ const struct fscrypt_str *iname,
+ struct fscrypt_str *oname)
+{
+ struct fscrypt_nokey_name nokey_name;
+ u32 size; /* size of the unencoded no-key name */
+
+ /*
+ * Sanity check that struct fscrypt_nokey_name doesn't have padding
+ * between fields and that its encoded size never exceeds NAME_MAX.
+ */
+ BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, dirhash) !=
+ offsetof(struct fscrypt_nokey_name, bytes));
+ BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, bytes) !=
+ offsetof(struct fscrypt_nokey_name, sha256));
+ BUILD_BUG_ON(FSCRYPT_BASE64_CHARS(FSCRYPT_NOKEY_NAME_MAX) > NAME_MAX);
+
+ if (hash) {
+ nokey_name.dirhash[0] = hash;
+ nokey_name.dirhash[1] = minor_hash;
+ } else {
+ nokey_name.dirhash[0] = 0;
+ nokey_name.dirhash[1] = 0;
+ }
+ if (iname->len <= sizeof(nokey_name.bytes)) {
+ memcpy(nokey_name.bytes, iname->name, iname->len);
+ size = offsetof(struct fscrypt_nokey_name, bytes[iname->len]);
+ } else {
+ memcpy(nokey_name.bytes, iname->name, sizeof(nokey_name.bytes));
+ /* Compute strong hash of remaining part of name. */
+ fscrypt_do_sha256(&iname->name[sizeof(nokey_name.bytes)],
+ iname->len - sizeof(nokey_name.bytes),
+ nokey_name.sha256);
+ size = FSCRYPT_NOKEY_NAME_MAX;
+ }
+ oname->len = fscrypt_base64_encode((const u8 *)&nokey_name, size, oname->name);
+}
+EXPORT_SYMBOL(fscrypt_encode_nokey_name);
+
/**
* fscrypt_fname_disk_to_usr() - convert an encrypted filename to
* user-presentable form
@@ -351,7 +390,7 @@ 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;
@@ -371,7 +410,7 @@ 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);
@@ -445,14 +484,14 @@ 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 b3b0c5675c6b..95dddba3ed00 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -182,6 +182,10 @@ void fscrypt_free_inode(struct inode *inode);
int fscrypt_drop_inode(struct inode *inode);

/* fname.c */
+#define FSCRYPT_BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
+
+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);

--
2.26.2