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Message-Id: <1455588792-87825-5-git-send-email-jaegeuk@kernel.org>
Date: Mon, 15 Feb 2016 18:13:09 -0800
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, tytso@....edu
Cc: Jaegeuk Kim <jaegeuk@...nel.org>,
Uday Savagaonkar <savagaon@...gle.com>,
Ildar Muslukhov <ildarm@...gle.com>,
Michael Halcrow <mhalcrow@...gle.com>
Subject: [PATCH 5/8] fs crypto: add fname.c to support filename encryption
This patch adds fname.c supporting filename encryption.
1. general wrapper functions
- fscrypt_fname_disk_to_usr
- fscrypt_fname_usr_to_disk
- fscrypt_setup_filename
- fscrypt_free_filename
2. specific filename handling functions
- fscrypt_fname_alloc_buffer
- fscrypt_fname_free_buffer
Signed-off-by: Uday Savagaonkar <savagaon@...gle.com>
Signed-off-by: Ildar Muslukhov <ildarm@...gle.com>
Signed-off-by: Michael Halcrow <mhalcrow@...gle.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
fs/crypto/fname.c | 437 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fscrypto.h | 13 ++
2 files changed, 450 insertions(+)
create mode 100644 fs/crypto/fname.c
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
new file mode 100644
index 0000000..8488a96
--- /dev/null
+++ b/fs/crypto/fname.c
@@ -0,0 +1,437 @@
+/*
+ * This contains functions for filename crypto management
+ *
+ * Copyright (C) 2015, Google, Inc.
+ * Copyright (C) 2015, Motorola Mobility
+ *
+ * Written by Uday Savagaonkar, 2014.
+ * Modified by Jaegeuk Kim, 2015.
+ *
+ * This has not yet undergone a rigorous security audit.
+ */
+
+#include <crypto/hash.h>
+#include <crypto/sha.h>
+#include <keys/encrypted-type.h>
+#include <keys/user-type.h>
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+#include <linux/ratelimit.h>
+#include <linux/fscrypto.h>
+
+static u32 size_round_up(size_t size, size_t blksize)
+{
+ return ((size + blksize - 1) / blksize) * blksize;
+}
+
+#ifdef CONFIG_FS_ENCRYPTION
+/**
+ * dir_crypt_complete() -
+ */
+static void dir_crypt_complete(struct crypto_async_request *req, int res)
+{
+ struct fscrypt_completion_result *ecr = req->data;
+
+ if (res == -EINPROGRESS)
+ return;
+ ecr->res = res;
+ complete(&ecr->completion);
+}
+
+/**
+ * fname_encrypt() -
+ *
+ * This function encrypts the input filename, and returns the length of the
+ * ciphertext. Errors are returned as negative numbers. We trust the caller to
+ * allocate sufficient memory to oname string.
+ */
+static int fname_encrypt(struct inode *inode,
+ const struct qstr *iname, struct fscrypt_str *oname)
+{
+ u32 ciphertext_len;
+ struct ablkcipher_request *req = NULL;
+ DECLARE_FS_COMPLETION_RESULT(ecr);
+ struct fscrypt_info *ci = inode->i_crypt_info;
+ struct crypto_ablkcipher *tfm = ci->ci_ctfm;
+ int res = 0;
+ char iv[FS_CRYPTO_BLOCK_SIZE];
+ struct scatterlist src_sg, dst_sg;
+ int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
+ char *workbuf, buf[32], *alloc_buf = NULL;
+ unsigned lim;
+
+ lim = inode->i_sb->s_cop->max_namelen(inode);
+ if (iname->len <= 0 || iname->len > lim)
+ return -EIO;
+
+ ciphertext_len = (iname->len < FS_CRYPTO_BLOCK_SIZE) ?
+ FS_CRYPTO_BLOCK_SIZE : iname->len;
+ ciphertext_len = size_round_up(ciphertext_len, padding);
+ ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len;
+
+ if (ciphertext_len <= sizeof(buf)) {
+ workbuf = buf;
+ } else {
+ alloc_buf = kmalloc(ciphertext_len, GFP_NOFS);
+ if (!alloc_buf)
+ return -ENOMEM;
+ workbuf = alloc_buf;
+ }
+
+ /* Allocate request */
+ req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+ if (!req) {
+ printk_ratelimited(KERN_ERR
+ "%s: crypto_request_alloc() failed\n", __func__);
+ kfree(alloc_buf);
+ return -ENOMEM;
+ }
+ ablkcipher_request_set_callback(req,
+ CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+ dir_crypt_complete, &ecr);
+
+ /* Copy the input */
+ memcpy(workbuf, iname->name, iname->len);
+ if (iname->len < ciphertext_len)
+ memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
+
+ /* Initialize IV */
+ memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
+
+ /* Create encryption request */
+ sg_init_one(&src_sg, workbuf, ciphertext_len);
+ sg_init_one(&dst_sg, oname->name, ciphertext_len);
+ ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv);
+ res = crypto_ablkcipher_encrypt(req);
+ if (res == -EINPROGRESS || res == -EBUSY) {
+ wait_for_completion(&ecr.completion);
+ res = ecr.res;
+ }
+ kfree(alloc_buf);
+ ablkcipher_request_free(req);
+ if (res < 0)
+ printk_ratelimited(KERN_ERR
+ "%s: Error (error code %d)\n", __func__, res);
+
+ oname->len = ciphertext_len;
+ return res;
+}
+
+/*
+ * fname_decrypt()
+ * This function decrypts the input filename, and returns
+ * the length of the plaintext.
+ * Errors are returned as negative numbers.
+ * We trust the caller to allocate sufficient memory to oname string.
+ */
+static int fname_decrypt(struct inode *inode,
+ const struct fscrypt_str *iname,
+ struct fscrypt_str *oname)
+{
+ struct ablkcipher_request *req = NULL;
+ DECLARE_FS_COMPLETION_RESULT(ecr);
+ struct scatterlist src_sg, dst_sg;
+ struct fscrypt_info *ci = inode->i_crypt_info;
+ struct crypto_ablkcipher *tfm = ci->ci_ctfm;
+ int res = 0;
+ char iv[FS_CRYPTO_BLOCK_SIZE];
+ unsigned lim;
+
+ lim = inode->i_sb->s_cop->max_namelen(inode);
+ if (iname->len <= 0 || iname->len > lim)
+ return -EIO;
+
+ /* Allocate request */
+ req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+ if (!req) {
+ printk_ratelimited(KERN_ERR
+ "%s: crypto_request_alloc() failed\n", __func__);
+ return -ENOMEM;
+ }
+ ablkcipher_request_set_callback(req,
+ CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+ dir_crypt_complete, &ecr);
+
+ /* Initialize IV */
+ memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
+
+ /* Create decryption request */
+ sg_init_one(&src_sg, iname->name, iname->len);
+ sg_init_one(&dst_sg, oname->name, oname->len);
+ ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv);
+ res = crypto_ablkcipher_decrypt(req);
+ if (res == -EINPROGRESS || res == -EBUSY) {
+ wait_for_completion(&ecr.completion);
+ res = ecr.res;
+ }
+ ablkcipher_request_free(req);
+ if (res < 0) {
+ printk_ratelimited(KERN_ERR
+ "%s: Error (error code %d)\n", __func__, res);
+ return res;
+ }
+
+ oname->len = strnlen(oname->name, iname->len);
+ return oname->len;
+}
+#endif
+
+static const char *lookup_table =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
+
+/**
+ * digest_encode() -
+ *
+ * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
+ * The encoded string is roughly 4/3 times the size of the input string.
+ */
+static int digest_encode(const char *src, int len, char *dst)
+{
+ int i = 0, bits = 0, ac = 0;
+ char *cp = dst;
+
+ while (i < len) {
+ ac += (((unsigned char) src[i]) << bits);
+ bits += 8;
+ do {
+ *cp++ = lookup_table[ac & 0x3f];
+ ac >>= 6;
+ bits -= 6;
+ } while (bits >= 6);
+ i++;
+ }
+ if (bits)
+ *cp++ = lookup_table[ac & 0x3f];
+ return cp - dst;
+}
+
+static int digest_decode(const char *src, int len, char *dst)
+{
+ int i = 0, bits = 0, ac = 0;
+ const char *p;
+ char *cp = dst;
+
+ while (i < len) {
+ p = strchr(lookup_table, src[i]);
+ if (p == NULL || src[i] == 0)
+ return -2;
+ ac += (p - lookup_table) << bits;
+ bits += 6;
+ if (bits >= 8) {
+ *cp++ = ac & 0xff;
+ ac >>= 8;
+ bits -= 8;
+ }
+ i++;
+ }
+ if (ac)
+ return -1;
+ return cp - dst;
+}
+
+u32 fscrypt_fname_encrypted_size(struct inode *inode, u32 ilen)
+{
+ int padding = 32;
+#ifdef CONFIG_FS_ENCRYPTION
+ struct fscrypt_info *ci = inode->i_crypt_info;
+
+ if (ci)
+ padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
+#endif
+ if (ilen < FS_CRYPTO_BLOCK_SIZE)
+ ilen = FS_CRYPTO_BLOCK_SIZE;
+ return size_round_up(ilen, padding);
+}
+EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
+
+/**
+ * fscrypt_fname_crypto_alloc_obuff() -
+ *
+ * Allocates an output buffer that is sufficient for the crypto operation
+ * specified by the context and the direction.
+ */
+int fscrypt_fname_alloc_buffer(struct inode *inode,
+ u32 ilen, struct fscrypt_str *crypto_str)
+{
+ unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen);
+
+ crypto_str->len = olen;
+ if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2)
+ olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2;
+ /*
+ * Allocated buffer can hold one more character to null-terminate the
+ * string
+ */
+ crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
+ if (!(crypto_str->name))
+ return -ENOMEM;
+ return 0;
+}
+EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
+
+/**
+ * fscrypt_fname_crypto_free_buffer() -
+ *
+ * Frees the buffer allocated for crypto operation.
+ */
+void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
+{
+ if (!crypto_str)
+ return;
+ kfree(crypto_str->name);
+ crypto_str->name = NULL;
+}
+EXPORT_SYMBOL(fscrypt_fname_free_buffer);
+
+/**
+ * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user
+ * space
+ */
+int fscrypt_fname_disk_to_usr(struct inode *inode,
+ u32 hash, u32 minor_hash,
+ const struct fscrypt_str *iname,
+ struct fscrypt_str *oname)
+{
+ const struct qstr qname = FSTR_TO_QSTR(iname);
+ char buf[24];
+ int ret;
+
+ if (fscrypt_is_dot_dotdot(&qname)) {
+ oname->name[0] = '.';
+ oname->name[iname->len - 1] = '.';
+ oname->len = iname->len;
+ return oname->len;
+ }
+
+ if (iname->len < FS_CRYPTO_BLOCK_SIZE)
+ return -EUCLEAN;
+
+#ifdef CONFIG_FS_ENCRYPTION
+ if (inode->i_crypt_info)
+ return fname_decrypt(inode, iname, oname);
+#endif
+
+ if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) {
+ ret = digest_encode(iname->name, iname->len, oname->name);
+ oname->len = ret;
+ return ret;
+ }
+ if (hash) {
+ memcpy(buf, &hash, 4);
+ memcpy(buf + 4, &minor_hash, 4);
+ } else {
+ memset(buf, 0, 8);
+ }
+ memcpy(buf + 8, iname->name + iname->len - 16, 16);
+ oname->name[0] = '_';
+ ret = digest_encode(buf, 24, oname->name + 1);
+ oname->len = ret + 1;
+ return ret + 1;
+}
+EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
+
+/**
+ * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
+ * space
+ */
+int fscrypt_fname_usr_to_disk(struct inode *inode,
+ const struct qstr *iname,
+ struct fscrypt_str *oname)
+{
+ if (fscrypt_is_dot_dotdot(iname)) {
+ oname->name[0] = '.';
+ oname->name[iname->len - 1] = '.';
+ oname->len = iname->len;
+ return oname->len;
+ }
+#ifdef CONFIG_FS_ENCRYPTION
+ if (inode->i_crypt_info)
+ return fname_encrypt(inode, iname, oname);
+#endif
+ /*
+ * Without a proper key, a user is not allowed to modify the filenames
+ * in a directory. Consequently, a user space name cannot be mapped to
+ * a disk-space name
+ */
+ return -EACCES;
+}
+EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
+
+int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
+ int lookup, struct fscrypt_name *fname)
+{
+ int ret = 0, bigname = 0;
+
+ memset(fname, 0, sizeof(struct fscrypt_name));
+ fname->usr_fname = iname;
+
+ if (!dir->i_sb->s_cop->is_encrypted(dir) ||
+ fscrypt_is_dot_dotdot(iname)) {
+ fname->disk_name.name = (unsigned char *)iname->name;
+ fname->disk_name.len = iname->len;
+ return 0;
+ }
+ ret = get_crypt_info(dir);
+ if (ret && ret != -EOPNOTSUPP)
+ return ret;
+
+#ifdef CONFIG_FS_ENCRYPTION
+ if (dir->i_crypt_info) {
+ ret = fscrypt_fname_alloc_buffer(dir, iname->len,
+ &fname->crypto_buf);
+ if (ret < 0)
+ return ret;
+ ret = fname_encrypt(dir, iname, &fname->crypto_buf);
+ if (ret < 0)
+ goto errout;
+ fname->disk_name.name = fname->crypto_buf.name;
+ fname->disk_name.len = fname->crypto_buf.len;
+ return 0;
+ }
+#endif
+ if (!lookup)
+ return -EACCES;
+
+ /*
+ * We don't have the key and we are doing a lookup; decode the
+ * user-supplied name
+ */
+ if (iname->name[0] == '_')
+ bigname = 1;
+ if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43)))
+ return -ENOENT;
+
+ fname->crypto_buf.name = kmalloc(32, GFP_KERNEL);
+ if (fname->crypto_buf.name == NULL)
+ return -ENOMEM;
+
+ ret = digest_decode(iname->name + bigname, iname->len - bigname,
+ fname->crypto_buf.name);
+ if (ret < 0) {
+ ret = -ENOENT;
+ goto errout;
+ }
+ fname->crypto_buf.len = ret;
+ if (bigname) {
+ memcpy(&fname->hash, fname->crypto_buf.name, 4);
+ memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4);
+ } else {
+ fname->disk_name.name = fname->crypto_buf.name;
+ fname->disk_name.len = fname->crypto_buf.len;
+ }
+ return 0;
+
+errout:
+ fscrypt_fname_free_buffer(&fname->crypto_buf);
+ return ret;
+}
+EXPORT_SYMBOL(fscrypt_setup_filename);
+
+void fscrypt_free_filename(struct fscrypt_name *fname)
+{
+ kfree(fname->crypto_buf.name);
+ fname->crypto_buf.name = NULL;
+ fname->usr_fname = NULL;
+ fname->disk_name.name = NULL;
+}
+EXPORT_SYMBOL(fscrypt_free_filename);
diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h
index 4d17e10..41c7851 100644
--- a/include/linux/fscrypto.h
+++ b/include/linux/fscrypto.h
@@ -346,4 +346,17 @@ static inline void fscrypt_put_encryption_info(struct inode *i,
return;
}
#endif
+
+/* fname.c */
+int fscrypt_setup_filename(struct inode *, const struct qstr *,
+ int lookup, struct fscrypt_name *);
+void fscrypt_free_filename(struct fscrypt_name *);
+u32 fscrypt_fname_encrypted_size(struct inode *, u32);
+int fscrypt_fname_alloc_buffer(struct inode *, u32, struct fscrypt_str *);
+void fscrypt_fname_free_buffer(struct fscrypt_str *);
+int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
+ const struct fscrypt_str *, struct fscrypt_str *);
+int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
+ struct fscrypt_str *);
+
#endif /* _LINUX_FSCRYPTO_H */
--
2.6.3
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