From f348c252320b98e11176074fe04223f22bddaf0d Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Thu, 16 Apr 2015 01:55:00 -0400 Subject: [PATCH] ext4 crypto: add symlink encryption Signed-off-by: Uday Savagaonkar Signed-off-by: Theodore Ts'o --- fs/ext4/ext4.h | 1 + fs/ext4/ext4_crypto.h | 20 +++++++++ fs/ext4/inode.c | 5 ++- fs/ext4/namei.c | 85 +++++++++++++++++++++++++++++--------- fs/ext4/symlink.c | 96 ++++++++++++++++++++++++++++++++++++++++++- 5 files changed, 184 insertions(+), 23 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 5146e67e8d51..86d15706d27a 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2233,6 +2233,7 @@ extern int ext4_group_add_blocks(handle_t *handle, struct super_block *sb, extern int ext4_trim_fs(struct super_block *, struct fstrim_range *); /* inode.c */ +int ext4_inode_is_fast_symlink(struct inode *inode); struct buffer_head *ext4_getblk(handle_t *, struct inode *, ext4_lblk_t, int); struct buffer_head *ext4_bread(handle_t *, struct inode *, ext4_lblk_t, int); int ext4_get_block_write(struct inode *inode, sector_t iblock, diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h index f7d46e8dc9d3..c2ba35a914b6 100644 --- a/fs/ext4/ext4_crypto.h +++ b/fs/ext4/ext4_crypto.h @@ -124,4 +124,24 @@ struct ext4_fname_crypto_ctx { unsigned ctfm_key_is_ready : 1; }; +/** + * For encrypted symlinks, the ciphertext length is stored at the beginning + * of the string in little-endian format. + */ +struct ext4_encrypted_symlink_data { + __le16 len; + char encrypted_path[1]; +} __attribute__((__packed__)); + +/** + * This function is used to calculate the disk space required to + * store a filename of length l in encrypted symlink format. + */ +static inline u32 encrypted_symlink_data_len(u32 l) +{ + if (l < EXT4_CRYPTO_BLOCK_SIZE) + l = EXT4_CRYPTO_BLOCK_SIZE; + return (l + sizeof(struct ext4_encrypted_symlink_data) - 1); +} + #endif /* _EXT4_CRYPTO_H */ diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 8b4fe626919a..f6b35d8a4a5b 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -139,7 +139,7 @@ static int ext4_meta_trans_blocks(struct inode *inode, int lblocks, /* * Test whether an inode is a fast symlink. */ -static int ext4_inode_is_fast_symlink(struct inode *inode) +int ext4_inode_is_fast_symlink(struct inode *inode) { int ea_blocks = EXT4_I(inode)->i_file_acl ? EXT4_CLUSTER_SIZE(inode->i_sb) >> 9 : 0; @@ -4215,7 +4215,8 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino) inode->i_op = &ext4_dir_inode_operations; inode->i_fop = &ext4_dir_operations; } else if (S_ISLNK(inode->i_mode)) { - if (ext4_inode_is_fast_symlink(inode)) { + if (ext4_inode_is_fast_symlink(inode) && + !ext4_encrypted_inode(inode)) { inode->i_op = &ext4_fast_symlink_inode_operations; nd_terminate_link(ei->i_data, inode->i_size, sizeof(ei->i_data) - 1); diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 4c84db862891..d201426b8d39 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -3193,16 +3193,24 @@ static int ext4_symlink(struct inode *dir, { handle_t *handle; struct inode *inode; - int l, err, retries = 0; + int err, len = strlen(symname); int credits; + bool encryption_required; + struct ext4_str disk_link; + struct ext4_encrypted_symlink_data *sd = NULL; - l = strlen(symname)+1; - if (l > dir->i_sb->s_blocksize) + disk_link.len = len + 1; + disk_link.name = (char *) symname; + + encryption_required = ext4_encrypted_inode(dir); + if (encryption_required) + disk_link.len = encrypted_symlink_data_len(len) + 1; + if (disk_link.len > dir->i_sb->s_blocksize) return -ENAMETOOLONG; dquot_initialize(dir); - if (l > EXT4_N_BLOCKS * 4) { + if ((disk_link.len > EXT4_N_BLOCKS * 4)) { /* * For non-fast symlinks, we just allocate inode and put it on * orphan list in the first transaction => we need bitmap, @@ -3221,16 +3229,49 @@ static int ext4_symlink(struct inode *dir, credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) + EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3; } -retry: + inode = ext4_new_inode_start_handle(dir, S_IFLNK|S_IRWXUGO, &dentry->d_name, 0, NULL, EXT4_HT_DIR, credits); handle = ext4_journal_current_handle(); - err = PTR_ERR(inode); - if (IS_ERR(inode)) - goto out_stop; + if (IS_ERR(inode)) { + if (handle) + ext4_journal_stop(handle); + return PTR_ERR(inode); + } + + if (encryption_required) { + struct ext4_fname_crypto_ctx *ctx = NULL; + struct qstr istr; + struct ext4_str ostr; + + sd = kzalloc(disk_link.len, GFP_NOFS); + if (!sd) { + err = -ENOMEM; + goto err_drop_inode; + } + err = ext4_inherit_context(dir, inode); + if (err) + goto err_drop_inode; + ctx = ext4_get_fname_crypto_ctx(inode, + inode->i_sb->s_blocksize); + if (IS_ERR_OR_NULL(ctx)) { + /* We just set the policy, so ctx should not be NULL */ + err = (ctx == NULL) ? -EIO : PTR_ERR(ctx); + goto err_drop_inode; + } + istr.name = (const unsigned char *) symname; + istr.len = len; + ostr.name = sd->encrypted_path; + err = ext4_fname_usr_to_disk(ctx, &istr, &ostr); + ext4_put_fname_crypto_ctx(&ctx); + if (err < 0) + goto err_drop_inode; + sd->len = cpu_to_le16(ostr.len); + disk_link.name = (char *) sd; + } - if (l > EXT4_N_BLOCKS * 4) { + if ((disk_link.len > EXT4_N_BLOCKS * 4)) { inode->i_op = &ext4_symlink_inode_operations; ext4_set_aops(inode); /* @@ -3246,9 +3287,10 @@ retry: drop_nlink(inode); err = ext4_orphan_add(handle, inode); ext4_journal_stop(handle); + handle = NULL; if (err) goto err_drop_inode; - err = __page_symlink(inode, symname, l, 1); + err = __page_symlink(inode, disk_link.name, disk_link.len, 1); if (err) goto err_drop_inode; /* @@ -3260,34 +3302,37 @@ retry: EXT4_INDEX_EXTRA_TRANS_BLOCKS + 1); if (IS_ERR(handle)) { err = PTR_ERR(handle); + handle = NULL; goto err_drop_inode; } set_nlink(inode, 1); err = ext4_orphan_del(handle, inode); - if (err) { - ext4_journal_stop(handle); - clear_nlink(inode); + if (err) goto err_drop_inode; - } } else { /* clear the extent format for fast symlink */ ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS); - inode->i_op = &ext4_fast_symlink_inode_operations; - memcpy((char *)&EXT4_I(inode)->i_data, symname, l); - inode->i_size = l-1; + inode->i_op = encryption_required ? + &ext4_symlink_inode_operations : + &ext4_fast_symlink_inode_operations; + memcpy((char *)&EXT4_I(inode)->i_data, disk_link.name, + disk_link.len); + inode->i_size = disk_link.len - 1; } EXT4_I(inode)->i_disksize = inode->i_size; err = ext4_add_nondir(handle, dentry, inode); if (!err && IS_DIRSYNC(dir)) ext4_handle_sync(handle); -out_stop: if (handle) ext4_journal_stop(handle); - if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries)) - goto retry; + kfree(sd); return err; err_drop_inode: + if (handle) + ext4_journal_stop(handle); + kfree(sd); + clear_nlink(inode); unlock_new_inode(inode); iput(inode); return err; diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c index 489b34333ea4..136ca0e911fd 100644 --- a/fs/ext4/symlink.c +++ b/fs/ext4/symlink.c @@ -22,7 +22,96 @@ #include "ext4.h" #include "xattr.h" +#ifdef CONFIG_EXT4_FS_ENCRYPTION static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd) +{ + struct page *cpage = NULL; + char *caddr, *paddr = NULL; + struct ext4_str cstr, pstr; + struct inode *inode = dentry->d_inode; + struct ext4_fname_crypto_ctx *ctx = NULL; + struct ext4_encrypted_symlink_data *sd; + loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1); + int res; + u32 plen, max_size = inode->i_sb->s_blocksize; + + if (!ext4_encrypted_inode(inode)) + return page_follow_link_light(dentry, nd); + + ctx = ext4_get_fname_crypto_ctx(inode, inode->i_sb->s_blocksize); + if (IS_ERR(ctx)) + return ctx; + + if (ext4_inode_is_fast_symlink(inode)) { + caddr = (char *) EXT4_I(dentry->d_inode)->i_data; + max_size = sizeof(EXT4_I(dentry->d_inode)->i_data); + } else { + cpage = read_mapping_page(inode->i_mapping, 0, NULL); + if (IS_ERR(cpage)) { + ext4_put_fname_crypto_ctx(&ctx); + return cpage; + } + caddr = kmap(cpage); + caddr[size] = 0; + } + + /* Symlink is encrypted */ + sd = (struct ext4_encrypted_symlink_data *)caddr; + cstr.name = sd->encrypted_path; + cstr.len = le32_to_cpu(sd->len); + if ((cstr.len + + sizeof(struct ext4_encrypted_symlink_data) - 1) > + max_size) { + /* Symlink data on the disk is corrupted */ + res = -EIO; + goto errout; + } + plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ? + EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len; + paddr = kmalloc(plen + 1, GFP_NOFS); + if (!paddr) { + res = -ENOMEM; + goto errout; + } + pstr.name = paddr; + res = _ext4_fname_disk_to_usr(ctx, &cstr, &pstr); + if (res < 0) + goto errout; + /* Null-terminate the name */ + if (res <= plen) + paddr[res] = '\0'; + nd_set_link(nd, paddr); + ext4_put_fname_crypto_ctx(&ctx); + if (cpage) { + kunmap(cpage); + page_cache_release(cpage); + } + return NULL; +errout: + ext4_put_fname_crypto_ctx(&ctx); + if (cpage) { + kunmap(cpage); + page_cache_release(cpage); + } + kfree(paddr); + return ERR_PTR(res); +} + +static void ext4_put_link(struct dentry *dentry, struct nameidata *nd, + void *cookie) +{ + struct page *page = cookie; + + if (!page) { + kfree(nd_get_link(nd)); + } else { + kunmap(page); + page_cache_release(page); + } +} +#endif + +static void *ext4_follow_fast_link(struct dentry *dentry, struct nameidata *nd) { struct ext4_inode_info *ei = EXT4_I(dentry->d_inode); nd_set_link(nd, (char *) ei->i_data); @@ -31,8 +120,13 @@ static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd) const struct inode_operations ext4_symlink_inode_operations = { .readlink = generic_readlink, +#ifdef CONFIG_EXT4_FS_ENCRYPTION + .follow_link = ext4_follow_link, + .put_link = ext4_put_link, +#else .follow_link = page_follow_link_light, .put_link = page_put_link, +#endif .setattr = ext4_setattr, .setxattr = generic_setxattr, .getxattr = generic_getxattr, @@ -42,7 +136,7 @@ const struct inode_operations ext4_symlink_inode_operations = { const struct inode_operations ext4_fast_symlink_inode_operations = { .readlink = generic_readlink, - .follow_link = ext4_follow_link, + .follow_link = ext4_follow_fast_link, .setattr = ext4_setattr, .setxattr = generic_setxattr, .getxattr = generic_getxattr, -- 2.20.1