Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756669AbcCBScN (ORCPT ); Wed, 2 Mar 2016 13:32:13 -0500 Received: from mail.kernel.org ([198.145.29.136]:48424 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756554AbcCBScC (ORCPT ); Wed, 2 Mar 2016 13:32:02 -0500 From: Jaegeuk Kim To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, tytso@mit.edu Cc: Jaegeuk Kim , Uday Savagaonkar , Ildar Muslukhov , Michael Halcrow Subject: [PATCH 05/10] fs crypto: add fname.c to support filename encryption Date: Wed, 2 Mar 2016 10:31:13 -0800 Message-Id: <1456943478-11107-6-git-send-email-jaegeuk@kernel.org> X-Mailer: git-send-email 2.6.3 In-Reply-To: <1456943478-11107-1-git-send-email-jaegeuk@kernel.org> References: <1456943478-11107-1-git-send-email-jaegeuk@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 14734 Lines: 540 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 Signed-off-by: Ildar Muslukhov Signed-off-by: Michael Halcrow Signed-off-by: Theodore Ts'o Signed-off-by: Jaegeuk Kim --- fs/crypto/fname.c | 427 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fscrypto.h | 66 ++++++++ 2 files changed, 493 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..5e4ddee --- /dev/null +++ b/fs/crypto/fname.c @@ -0,0 +1,427 @@ +/* + * 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 +#include +#include +#include +#include +#include +#include +#include + +static u32 size_round_up(size_t size, size_t blksize) +{ + return ((size + blksize - 1) / blksize) * blksize; +} + +/** + * 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; +} + +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; + struct fscrypt_info *ci = inode->i_crypt_info; + + if (ci) + padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK); + 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; + + if (inode->i_crypt_info) + return fname_decrypt(inode, iname, oname); + + 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; + } + if (inode->i_crypt_info) + return fname_encrypt(inode, iname, oname); + /* + * 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; + + 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; + } + 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 0720292..144541b 100644 --- a/include/linux/fscrypto.h +++ b/include/linux/fscrypto.h @@ -262,6 +262,19 @@ extern int fscrypt_inherit_context(struct inode *, struct inode *, extern int get_crypt_info(struct inode *); extern int fscrypt_get_encryption_info(struct inode *); extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *); + +/* fname.c */ +extern int fscrypt_setup_filename(struct inode *, const struct qstr *, + int lookup, struct fscrypt_name *); +extern void fscrypt_free_filename(struct fscrypt_name *); +extern u32 fscrypt_fname_encrypted_size(struct inode *, u32); +extern int fscrypt_fname_alloc_buffer(struct inode *, u32, + struct fscrypt_str *); +extern void fscrypt_fname_free_buffer(struct fscrypt_str *); +extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32, + const struct fscrypt_str *, struct fscrypt_str *); +extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *, + struct fscrypt_str *); #endif /* crypto.c */ @@ -344,4 +357,57 @@ static inline void fscrypt_notsupp_put_encryption_info(struct inode *i, { return; } + + /* fname.c */ +static inline int fscrypt_notsupp_setup_filename(struct inode *dir, + const struct qstr *iname, + int lookup, struct fscrypt_name *fname) +{ + if (dir->i_sb->s_cop->is_encrypted(dir)) + return -EOPNOTSUPP; + + memset(fname, 0, sizeof(struct fscrypt_name)); + fname->usr_fname = iname; + fname->disk_name.name = (unsigned char *)iname->name; + fname->disk_name.len = iname->len; + return 0; +} + +static inline void fscrypt_notsupp_free_filename(struct fscrypt_name *fname) +{ + return; +} + +static inline u32 fscrypt_notsupp_fname_encrypted_size(struct inode *i, u32 s) +{ + /* never happens */ + WARN_ON(1); + return 0; +} + +static inline int fscrypt_notsupp_fname_alloc_buffer(struct inode *inode, + u32 ilen, struct fscrypt_str *crypto_str) +{ + return -EOPNOTSUPP; +} + +static inline void fscrypt_notsupp_fname_free_buffer(struct fscrypt_str *c) +{ + return; +} + +static inline int fscrypt_notsupp_fname_disk_to_usr(struct inode *inode, + u32 hash, u32 minor_hash, + const struct fscrypt_str *iname, + struct fscrypt_str *oname) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_notsupp_fname_usr_to_disk(struct inode *inode, + const struct qstr *iname, + struct fscrypt_str *oname) +{ + return -EOPNOTSUPP; +} #endif /* _LINUX_FSCRYPTO_H */ -- 2.6.3