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Message-Id: <20171215174225.31583-22-ebiggers3@gmail.com>
Date: Fri, 15 Dec 2017 09:42:22 -0800
From: Eric Biggers <ebiggers3@...il.com>
To: linux-fscrypt@...r.kernel.org
Cc: "Theodore Y . Ts'o" <tytso@....edu>,
Jaegeuk Kim <jaegeuk@...nel.org>, linux-ext4@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-mtd@...ts.infradead.org, Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH 21/24] fscrypt: calculate NUL-padding length in one place only
From: Eric Biggers <ebiggers@...gle.com>
Currently, when encrypting a filename (either a real filename or a
symlink target) we calculate the amount of NUL-padding twice: once
before encryption and once during encryption in fname_encrypt(). It is
needed before encryption to allocate the needed buffer size as well as
calculate the size the symlink target will take up on-disk before
creating the symlink inode. Calculating the size during encryption as
well is redundant.
Remove this redundancy by always calculating the exact size beforehand,
and making fname_encrypt() just add as much NUL padding as is needed to
fill the output buffer.
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
fs/crypto/fname.c | 53 ++++++++++++++++++++++-----------------------
fs/crypto/fscrypt_private.h | 4 ++--
fs/crypto/hooks.c | 7 +-----
3 files changed, 29 insertions(+), 35 deletions(-)
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index cae7d1bcc8c5..65424b89a1d1 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -30,39 +30,29 @@ static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
/**
* fname_encrypt() - encrypt a filename
*
- * The caller must have allocated sufficient memory for the @oname string.
+ * The output buffer must be at least as large as the input buffer.
+ * Any extra space is filled with NUL padding before encryption.
*
* Return: 0 on success, -errno on failure
*/
-int fname_encrypt(struct inode *inode,
- const struct qstr *iname, struct fscrypt_str *oname)
+int fname_encrypt(struct inode *inode, const struct qstr *iname,
+ u8 *out, unsigned int olen)
{
struct skcipher_request *req = NULL;
DECLARE_CRYPTO_WAIT(wait);
- struct fscrypt_info *ci = inode->i_crypt_info;
- struct crypto_skcipher *tfm = ci->ci_ctfm;
+ struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm;
int res = 0;
char iv[FS_CRYPTO_BLOCK_SIZE];
struct scatterlist sg;
- int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
- unsigned int lim;
- unsigned int cryptlen;
-
- lim = inode->i_sb->s_cop->max_namelen(inode);
- if (iname->len <= 0 || iname->len > lim)
- return -EIO;
/*
* Copy the filename to the output buffer for encrypting in-place and
* pad it with the needed number of NUL bytes.
*/
- if (WARN_ON(oname->len < iname->len))
+ if (WARN_ON(olen < iname->len))
return -ENOBUFS;
- cryptlen = max_t(unsigned int, iname->len, FS_CRYPTO_BLOCK_SIZE);
- cryptlen = round_up(cryptlen, padding);
- cryptlen = min3(cryptlen, lim, oname->len);
- memcpy(oname->name, iname->name, iname->len);
- memset(oname->name + iname->len, 0, cryptlen - iname->len);
+ memcpy(out, iname->name, iname->len);
+ memset(out + iname->len, 0, olen - iname->len);
/* Initialize the IV */
memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
@@ -77,8 +67,8 @@ int fname_encrypt(struct inode *inode,
skcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &wait);
- sg_init_one(&sg, oname->name, cryptlen);
- skcipher_request_set_crypt(req, &sg, &sg, cryptlen, iv);
+ sg_init_one(&sg, out, olen);
+ skcipher_request_set_crypt(req, &sg, &sg, olen, iv);
/* Do the encryption */
res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
@@ -89,7 +79,6 @@ int fname_encrypt(struct inode *inode,
return res;
}
- oname->len = cryptlen;
return 0;
}
@@ -354,11 +343,21 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
return ret;
if (dir->i_crypt_info) {
- ret = fscrypt_fname_alloc_buffer(dir, iname->len,
- &fname->crypto_buf);
- if (ret)
- return ret;
- ret = fname_encrypt(dir, iname, &fname->crypto_buf);
+ unsigned int max_len = dir->i_sb->s_cop->max_namelen(dir);
+
+ if (iname->len > max_len)
+ return -ENAMETOOLONG;
+
+ fname->crypto_buf.len =
+ min(fscrypt_fname_encrypted_size(dir, iname->len),
+ max_len);
+ fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
+ GFP_NOFS);
+ if (!fname->crypto_buf.name)
+ return -ENOMEM;
+
+ ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
+ fname->crypto_buf.len);
if (ret)
goto errout;
fname->disk_name.name = fname->crypto_buf.name;
@@ -410,7 +409,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
return 0;
errout:
- fscrypt_fname_free_buffer(&fname->crypto_buf);
+ kfree(fname->crypto_buf.name);
return ret;
}
EXPORT_SYMBOL(fscrypt_setup_filename);
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index cec9ce309f41..053917587200 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -108,8 +108,8 @@ extern struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
gfp_t gfp_flags);
/* fname.c */
-extern int fname_encrypt(struct inode *inode,
- const struct qstr *iname, struct fscrypt_str *oname);
+extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
+ u8 *out, unsigned int olen);
/* keyinfo.c */
extern void __exit fscrypt_essiv_cleanup(void);
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 0f103a5cb1aa..ff20cacdea94 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -157,7 +157,6 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
struct qstr iname = { .name = target, .len = len };
struct fscrypt_symlink_data *sd;
unsigned int ciphertext_len;
- struct fscrypt_str oname;
err = fscrypt_require_key(inode);
if (err)
@@ -174,16 +173,12 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
ciphertext_len = disk_link->len - sizeof(*sd);
sd->len = cpu_to_le16(ciphertext_len);
- oname.name = sd->encrypted_path;
- oname.len = ciphertext_len;
- err = fname_encrypt(inode, &iname, &oname);
+ err = fname_encrypt(inode, &iname, sd->encrypted_path, ciphertext_len);
if (err) {
if (!disk_link->name)
kfree(sd);
return err;
}
- BUG_ON(oname.len != ciphertext_len);
-
/*
* Null-terminating the ciphertext doesn't make sense, but we still
* count the null terminator in the length, so we might as well
--
2.15.1
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