From 643fa9612bf1a29153eee46fd398117632f93cbe Mon Sep 17 00:00:00 2001 From: Chandan Rajendra Date: Wed, 12 Dec 2018 15:20:12 +0530 Subject: fscrypt: remove filesystem specific build config option In order to have a common code base for fscrypt "post read" processing for all filesystems which support encryption, this commit removes filesystem specific build config option (e.g. CONFIG_EXT4_FS_ENCRYPTION) and replaces it with a build option (i.e. CONFIG_FS_ENCRYPTION) whose value affects all the filesystems making use of fscrypt. Reviewed-by: Eric Biggers Signed-off-by: Chandan Rajendra Signed-off-by: Eric Biggers --- include/linux/fs.h | 4 +- include/linux/fscrypt.h | 416 +++++++++++++++++++++++++++++++++++++++- include/linux/fscrypt_notsupp.h | 231 ---------------------- include/linux/fscrypt_supp.h | 204 -------------------- 4 files changed, 410 insertions(+), 445 deletions(-) delete mode 100644 include/linux/fscrypt_notsupp.h delete mode 100644 include/linux/fscrypt_supp.h (limited to 'include') diff --git a/include/linux/fs.h b/include/linux/fs.h index 811c77743dad..ba7889bb9ef6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -698,7 +698,7 @@ struct inode { struct fsnotify_mark_connector __rcu *i_fsnotify_marks; #endif -#if IS_ENABLED(CONFIG_FS_ENCRYPTION) +#ifdef CONFIG_FS_ENCRYPTION struct fscrypt_info *i_crypt_info; #endif @@ -1403,7 +1403,7 @@ struct super_block { void *s_security; #endif const struct xattr_handler **s_xattr; -#if IS_ENABLED(CONFIG_FS_ENCRYPTION) +#ifdef CONFIG_FS_ENCRYPTION const struct fscrypt_operations *s_cop; #endif struct hlist_bl_head s_roots; /* alternate root dentries for NFS */ diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 952ab97af325..eec604840568 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -2,9 +2,8 @@ /* * fscrypt.h: declarations for per-file encryption * - * Filesystems that implement per-file encryption include this header - * file with the __FS_HAS_ENCRYPTION set according to whether that filesystem - * is being built with encryption support or not. + * Filesystems that implement per-file encryption must include this header + * file. * * Copyright (C) 2015, Google, Inc. * @@ -15,6 +14,8 @@ #define _LINUX_FSCRYPT_H #include +#include +#include #define FS_CRYPTO_BLOCK_SIZE 16 @@ -42,11 +43,410 @@ struct fscrypt_name { /* Maximum value for the third parameter of fscrypt_operations.set_context(). */ #define FSCRYPT_SET_CONTEXT_MAX_SIZE 28 -#if __FS_HAS_ENCRYPTION -#include -#else -#include -#endif +#ifdef CONFIG_FS_ENCRYPTION +/* + * fscrypt superblock flags + */ +#define FS_CFLG_OWN_PAGES (1U << 1) + +/* + * crypto operations for filesystems + */ +struct fscrypt_operations { + unsigned int flags; + const char *key_prefix; + int (*get_context)(struct inode *, void *, size_t); + int (*set_context)(struct inode *, const void *, size_t, void *); + bool (*dummy_context)(struct inode *); + bool (*empty_dir)(struct inode *); + unsigned int max_namelen; +}; + +struct fscrypt_ctx { + union { + struct { + struct page *bounce_page; /* Ciphertext page */ + struct page *control_page; /* Original page */ + } w; + struct { + struct bio *bio; + struct work_struct work; + } r; + struct list_head free_list; /* Free list */ + }; + u8 flags; /* Flags */ +}; + +static inline bool fscrypt_has_encryption_key(const struct inode *inode) +{ + return (inode->i_crypt_info != NULL); +} + +static inline bool fscrypt_dummy_context_enabled(struct inode *inode) +{ + return inode->i_sb->s_cop->dummy_context && + inode->i_sb->s_cop->dummy_context(inode); +} + +/* crypto.c */ +extern void fscrypt_enqueue_decrypt_work(struct work_struct *); +extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t); +extern void fscrypt_release_ctx(struct fscrypt_ctx *); +extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *, + unsigned int, unsigned int, + u64, gfp_t); +extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int, + unsigned int, u64); + +static inline struct page *fscrypt_control_page(struct page *page) +{ + return ((struct fscrypt_ctx *)page_private(page))->w.control_page; +} + +extern void fscrypt_restore_control_page(struct page *); + +/* policy.c */ +extern int fscrypt_ioctl_set_policy(struct file *, const void __user *); +extern int fscrypt_ioctl_get_policy(struct file *, void __user *); +extern int fscrypt_has_permitted_context(struct inode *, struct inode *); +extern int fscrypt_inherit_context(struct inode *, struct inode *, + void *, bool); +/* keyinfo.c */ +extern int fscrypt_get_encryption_info(struct inode *); +extern void fscrypt_put_encryption_info(struct inode *); + +/* fname.c */ +extern int fscrypt_setup_filename(struct inode *, const struct qstr *, + int lookup, struct fscrypt_name *); + +static inline void fscrypt_free_filename(struct fscrypt_name *fname) +{ + kfree(fname->crypto_buf.name); +} + +extern int fscrypt_fname_alloc_buffer(const 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 *); + +#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32 + +/* Extracts the second-to-last ciphertext block; see explanation below */ +#define FSCRYPT_FNAME_DIGEST(name, len) \ + ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \ + FS_CRYPTO_BLOCK_SIZE)) + +#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE + +/** + * fscrypt_digested_name - alternate identifier for an on-disk filename + * + * When userspace lists an encrypted directory without access to the key, + * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE + * bytes are shown in this abbreviated form (base64-encoded) rather than as the + * full ciphertext (base64-encoded). This is necessary to allow supporting + * filenames up to NAME_MAX bytes, since base64 encoding expands the length. + * + * To make it possible for filesystems to still find the correct directory entry + * despite not knowing the full on-disk name, we encode any filesystem-specific + * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups, + * followed by the second-to-last ciphertext block of the filename. Due to the + * use of the CBC-CTS encryption mode, the second-to-last ciphertext block + * depends on the full plaintext. (Note that ciphertext stealing causes the + * last two blocks to appear "flipped".) This makes accidental collisions very + * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they + * share the same filesystem-specific hashes. + * + * However, this scheme isn't immune to intentional collisions, which can be + * created by anyone able to create arbitrary plaintext filenames and view them + * without the key. Making the "digest" be a real cryptographic hash like + * SHA-256 over the full ciphertext would prevent this, although it would be + * less efficient and harder to implement, especially since the filesystem would + * need to calculate it for each directory entry examined during a search. + */ +struct fscrypt_digested_name { + u32 hash; + u32 minor_hash; + u8 digest[FSCRYPT_FNAME_DIGEST_SIZE]; +}; + +/** + * fscrypt_match_name() - test whether the given name matches a directory entry + * @fname: the name being searched for + * @de_name: the name from the directory entry + * @de_name_len: the length of @de_name in bytes + * + * Normally @fname->disk_name will be set, and in that case we simply compare + * that to the name stored in the directory entry. The only exception is that + * if we don't have the key for an encrypted directory and a filename in it is + * very long, then we won't have the full disk_name and we'll instead need to + * match against the fscrypt_digested_name. + * + * Return: %true if the name matches, otherwise %false. + */ +static inline bool fscrypt_match_name(const struct fscrypt_name *fname, + const u8 *de_name, u32 de_name_len) +{ + if (unlikely(!fname->disk_name.name)) { + const struct fscrypt_digested_name *n = + (const void *)fname->crypto_buf.name; + if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_')) + return false; + if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) + return false; + return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len), + n->digest, FSCRYPT_FNAME_DIGEST_SIZE); + } + + if (de_name_len != fname->disk_name.len) + return false; + return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); +} + +/* bio.c */ +extern void fscrypt_decrypt_bio(struct bio *); +extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, + struct bio *bio); +extern void fscrypt_pullback_bio_page(struct page **, bool); +extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t, + unsigned int); + +/* hooks.c */ +extern int fscrypt_file_open(struct inode *inode, struct file *filp); +extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir); +extern int __fscrypt_prepare_rename(struct inode *old_dir, + struct dentry *old_dentry, + struct inode *new_dir, + struct dentry *new_dentry, + unsigned int flags); +extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry); +extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, + unsigned int max_len, + struct fscrypt_str *disk_link); +extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, + unsigned int len, + struct fscrypt_str *disk_link); +extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, + unsigned int max_size, + struct delayed_call *done); +#else /* !CONFIG_FS_ENCRYPTION */ + +static inline bool fscrypt_has_encryption_key(const struct inode *inode) +{ + return false; +} + +static inline bool fscrypt_dummy_context_enabled(struct inode *inode) +{ + return false; +} + +/* crypto.c */ +static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work) +{ +} + +static inline struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, + gfp_t gfp_flags) +{ + return ERR_PTR(-EOPNOTSUPP); +} + +static inline void fscrypt_release_ctx(struct fscrypt_ctx *ctx) +{ + return; +} + +static inline struct page *fscrypt_encrypt_page(const struct inode *inode, + struct page *page, + unsigned int len, + unsigned int offs, + u64 lblk_num, gfp_t gfp_flags) +{ + return ERR_PTR(-EOPNOTSUPP); +} + +static inline int fscrypt_decrypt_page(const struct inode *inode, + struct page *page, + unsigned int len, unsigned int offs, + u64 lblk_num) +{ + return -EOPNOTSUPP; +} + +static inline struct page *fscrypt_control_page(struct page *page) +{ + WARN_ON_ONCE(1); + return ERR_PTR(-EINVAL); +} + +static inline void fscrypt_restore_control_page(struct page *page) +{ + return; +} + +/* policy.c */ +static inline int fscrypt_ioctl_set_policy(struct file *filp, + const void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_has_permitted_context(struct inode *parent, + struct inode *child) +{ + return 0; +} + +static inline int fscrypt_inherit_context(struct inode *parent, + struct inode *child, + void *fs_data, bool preload) +{ + return -EOPNOTSUPP; +} + +/* keyinfo.c */ +static inline int fscrypt_get_encryption_info(struct inode *inode) +{ + return -EOPNOTSUPP; +} + +static inline void fscrypt_put_encryption_info(struct inode *inode) +{ + return; +} + + /* fname.c */ +static inline int fscrypt_setup_filename(struct inode *dir, + const struct qstr *iname, + int lookup, struct fscrypt_name *fname) +{ + if (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_free_filename(struct fscrypt_name *fname) +{ + return; +} + +static inline int fscrypt_fname_alloc_buffer(const struct inode *inode, + u32 max_encrypted_len, + struct fscrypt_str *crypto_str) +{ + return -EOPNOTSUPP; +} + +static inline void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) +{ + return; +} + +static inline int fscrypt_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 bool fscrypt_match_name(const struct fscrypt_name *fname, + const u8 *de_name, u32 de_name_len) +{ + /* Encryption support disabled; use standard comparison */ + if (de_name_len != fname->disk_name.len) + return false; + return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); +} + +/* bio.c */ +static inline void fscrypt_decrypt_bio(struct bio *bio) +{ +} + +static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, + struct bio *bio) +{ +} + +static inline void fscrypt_pullback_bio_page(struct page **page, bool restore) +{ + return; +} + +static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, + sector_t pblk, unsigned int len) +{ + return -EOPNOTSUPP; +} + +/* hooks.c */ + +static inline int fscrypt_file_open(struct inode *inode, struct file *filp) +{ + if (IS_ENCRYPTED(inode)) + return -EOPNOTSUPP; + return 0; +} + +static inline int __fscrypt_prepare_link(struct inode *inode, + struct inode *dir) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_rename(struct inode *old_dir, + struct dentry *old_dentry, + struct inode *new_dir, + struct dentry *new_dentry, + unsigned int flags) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_lookup(struct inode *dir, + struct dentry *dentry) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_symlink(struct inode *dir, + unsigned int len, + unsigned int max_len, + struct fscrypt_str *disk_link) +{ + return -EOPNOTSUPP; +} + + +static inline int __fscrypt_encrypt_symlink(struct inode *inode, + const char *target, + unsigned int len, + struct fscrypt_str *disk_link) +{ + return -EOPNOTSUPP; +} + +static inline const char *fscrypt_get_symlink(struct inode *inode, + const void *caddr, + unsigned int max_size, + struct delayed_call *done) +{ + return ERR_PTR(-EOPNOTSUPP); +} +#endif /* !CONFIG_FS_ENCRYPTION */ /** * fscrypt_require_key - require an inode's encryption key diff --git a/include/linux/fscrypt_notsupp.h b/include/linux/fscrypt_notsupp.h deleted file mode 100644 index ee8b43e4c15a..000000000000 --- a/include/linux/fscrypt_notsupp.h +++ /dev/null @@ -1,231 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -/* - * fscrypt_notsupp.h - * - * This stubs out the fscrypt functions for filesystems configured without - * encryption support. - * - * Do not include this file directly. Use fscrypt.h instead! - */ -#ifndef _LINUX_FSCRYPT_H -#error "Incorrect include of linux/fscrypt_notsupp.h!" -#endif - -#ifndef _LINUX_FSCRYPT_NOTSUPP_H -#define _LINUX_FSCRYPT_NOTSUPP_H - -static inline bool fscrypt_has_encryption_key(const struct inode *inode) -{ - return false; -} - -static inline bool fscrypt_dummy_context_enabled(struct inode *inode) -{ - return false; -} - -/* crypto.c */ -static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work) -{ -} - -static inline struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, - gfp_t gfp_flags) -{ - return ERR_PTR(-EOPNOTSUPP); -} - -static inline void fscrypt_release_ctx(struct fscrypt_ctx *ctx) -{ - return; -} - -static inline struct page *fscrypt_encrypt_page(const struct inode *inode, - struct page *page, - unsigned int len, - unsigned int offs, - u64 lblk_num, gfp_t gfp_flags) -{ - return ERR_PTR(-EOPNOTSUPP); -} - -static inline int fscrypt_decrypt_page(const struct inode *inode, - struct page *page, - unsigned int len, unsigned int offs, - u64 lblk_num) -{ - return -EOPNOTSUPP; -} - -static inline struct page *fscrypt_control_page(struct page *page) -{ - WARN_ON_ONCE(1); - return ERR_PTR(-EINVAL); -} - -static inline void fscrypt_restore_control_page(struct page *page) -{ - return; -} - -/* policy.c */ -static inline int fscrypt_ioctl_set_policy(struct file *filp, - const void __user *arg) -{ - return -EOPNOTSUPP; -} - -static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) -{ - return -EOPNOTSUPP; -} - -static inline int fscrypt_has_permitted_context(struct inode *parent, - struct inode *child) -{ - return 0; -} - -static inline int fscrypt_inherit_context(struct inode *parent, - struct inode *child, - void *fs_data, bool preload) -{ - return -EOPNOTSUPP; -} - -/* keyinfo.c */ -static inline int fscrypt_get_encryption_info(struct inode *inode) -{ - return -EOPNOTSUPP; -} - -static inline void fscrypt_put_encryption_info(struct inode *inode) -{ - return; -} - - /* fname.c */ -static inline int fscrypt_setup_filename(struct inode *dir, - const struct qstr *iname, - int lookup, struct fscrypt_name *fname) -{ - if (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_free_filename(struct fscrypt_name *fname) -{ - return; -} - -static inline int fscrypt_fname_alloc_buffer(const struct inode *inode, - u32 max_encrypted_len, - struct fscrypt_str *crypto_str) -{ - return -EOPNOTSUPP; -} - -static inline void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) -{ - return; -} - -static inline int fscrypt_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 bool fscrypt_match_name(const struct fscrypt_name *fname, - const u8 *de_name, u32 de_name_len) -{ - /* Encryption support disabled; use standard comparison */ - if (de_name_len != fname->disk_name.len) - return false; - return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); -} - -/* bio.c */ -static inline void fscrypt_decrypt_bio(struct bio *bio) -{ -} - -static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, - struct bio *bio) -{ -} - -static inline void fscrypt_pullback_bio_page(struct page **page, bool restore) -{ - return; -} - -static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, - sector_t pblk, unsigned int len) -{ - return -EOPNOTSUPP; -} - -/* hooks.c */ - -static inline int fscrypt_file_open(struct inode *inode, struct file *filp) -{ - if (IS_ENCRYPTED(inode)) - return -EOPNOTSUPP; - return 0; -} - -static inline int __fscrypt_prepare_link(struct inode *inode, - struct inode *dir) -{ - return -EOPNOTSUPP; -} - -static inline int __fscrypt_prepare_rename(struct inode *old_dir, - struct dentry *old_dentry, - struct inode *new_dir, - struct dentry *new_dentry, - unsigned int flags) -{ - return -EOPNOTSUPP; -} - -static inline int __fscrypt_prepare_lookup(struct inode *dir, - struct dentry *dentry) -{ - return -EOPNOTSUPP; -} - -static inline int __fscrypt_prepare_symlink(struct inode *dir, - unsigned int len, - unsigned int max_len, - struct fscrypt_str *disk_link) -{ - return -EOPNOTSUPP; -} - -static inline int __fscrypt_encrypt_symlink(struct inode *inode, - const char *target, - unsigned int len, - struct fscrypt_str *disk_link) -{ - return -EOPNOTSUPP; -} - -static inline const char *fscrypt_get_symlink(struct inode *inode, - const void *caddr, - unsigned int max_size, - struct delayed_call *done) -{ - return ERR_PTR(-EOPNOTSUPP); -} - -#endif /* _LINUX_FSCRYPT_NOTSUPP_H */ diff --git a/include/linux/fscrypt_supp.h b/include/linux/fscrypt_supp.h deleted file mode 100644 index 6456c6b2005f..000000000000 --- a/include/linux/fscrypt_supp.h +++ /dev/null @@ -1,204 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -/* - * fscrypt_supp.h - * - * Do not include this file directly. Use fscrypt.h instead! - */ -#ifndef _LINUX_FSCRYPT_H -#error "Incorrect include of linux/fscrypt_supp.h!" -#endif - -#ifndef _LINUX_FSCRYPT_SUPP_H -#define _LINUX_FSCRYPT_SUPP_H - -#include -#include - -/* - * fscrypt superblock flags - */ -#define FS_CFLG_OWN_PAGES (1U << 1) - -/* - * crypto operations for filesystems - */ -struct fscrypt_operations { - unsigned int flags; - const char *key_prefix; - int (*get_context)(struct inode *, void *, size_t); - int (*set_context)(struct inode *, const void *, size_t, void *); - bool (*dummy_context)(struct inode *); - bool (*empty_dir)(struct inode *); - unsigned int max_namelen; -}; - -struct fscrypt_ctx { - union { - struct { - struct page *bounce_page; /* Ciphertext page */ - struct page *control_page; /* Original page */ - } w; - struct { - struct bio *bio; - struct work_struct work; - } r; - struct list_head free_list; /* Free list */ - }; - u8 flags; /* Flags */ -}; - -static inline bool fscrypt_has_encryption_key(const struct inode *inode) -{ - return (inode->i_crypt_info != NULL); -} - -static inline bool fscrypt_dummy_context_enabled(struct inode *inode) -{ - return inode->i_sb->s_cop->dummy_context && - inode->i_sb->s_cop->dummy_context(inode); -} - -/* crypto.c */ -extern void fscrypt_enqueue_decrypt_work(struct work_struct *); -extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t); -extern void fscrypt_release_ctx(struct fscrypt_ctx *); -extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *, - unsigned int, unsigned int, - u64, gfp_t); -extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int, - unsigned int, u64); - -static inline struct page *fscrypt_control_page(struct page *page) -{ - return ((struct fscrypt_ctx *)page_private(page))->w.control_page; -} - -extern void fscrypt_restore_control_page(struct page *); - -/* policy.c */ -extern int fscrypt_ioctl_set_policy(struct file *, const void __user *); -extern int fscrypt_ioctl_get_policy(struct file *, void __user *); -extern int fscrypt_has_permitted_context(struct inode *, struct inode *); -extern int fscrypt_inherit_context(struct inode *, struct inode *, - void *, bool); -/* keyinfo.c */ -extern int fscrypt_get_encryption_info(struct inode *); -extern void fscrypt_put_encryption_info(struct inode *); - -/* fname.c */ -extern int fscrypt_setup_filename(struct inode *, const struct qstr *, - int lookup, struct fscrypt_name *); - -static inline void fscrypt_free_filename(struct fscrypt_name *fname) -{ - kfree(fname->crypto_buf.name); -} - -extern int fscrypt_fname_alloc_buffer(const 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 *); - -#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32 - -/* Extracts the second-to-last ciphertext block; see explanation below */ -#define FSCRYPT_FNAME_DIGEST(name, len) \ - ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \ - FS_CRYPTO_BLOCK_SIZE)) - -#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE - -/** - * fscrypt_digested_name - alternate identifier for an on-disk filename - * - * When userspace lists an encrypted directory without access to the key, - * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE - * bytes are shown in this abbreviated form (base64-encoded) rather than as the - * full ciphertext (base64-encoded). This is necessary to allow supporting - * filenames up to NAME_MAX bytes, since base64 encoding expands the length. - * - * To make it possible for filesystems to still find the correct directory entry - * despite not knowing the full on-disk name, we encode any filesystem-specific - * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups, - * followed by the second-to-last ciphertext block of the filename. Due to the - * use of the CBC-CTS encryption mode, the second-to-last ciphertext block - * depends on the full plaintext. (Note that ciphertext stealing causes the - * last two blocks to appear "flipped".) This makes accidental collisions very - * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they - * share the same filesystem-specific hashes. - * - * However, this scheme isn't immune to intentional collisions, which can be - * created by anyone able to create arbitrary plaintext filenames and view them - * without the key. Making the "digest" be a real cryptographic hash like - * SHA-256 over the full ciphertext would prevent this, although it would be - * less efficient and harder to implement, especially since the filesystem would - * need to calculate it for each directory entry examined during a search. - */ -struct fscrypt_digested_name { - u32 hash; - u32 minor_hash; - u8 digest[FSCRYPT_FNAME_DIGEST_SIZE]; -}; - -/** - * fscrypt_match_name() - test whether the given name matches a directory entry - * @fname: the name being searched for - * @de_name: the name from the directory entry - * @de_name_len: the length of @de_name in bytes - * - * Normally @fname->disk_name will be set, and in that case we simply compare - * that to the name stored in the directory entry. The only exception is that - * if we don't have the key for an encrypted directory and a filename in it is - * very long, then we won't have the full disk_name and we'll instead need to - * match against the fscrypt_digested_name. - * - * Return: %true if the name matches, otherwise %false. - */ -static inline bool fscrypt_match_name(const struct fscrypt_name *fname, - const u8 *de_name, u32 de_name_len) -{ - if (unlikely(!fname->disk_name.name)) { - const struct fscrypt_digested_name *n = - (const void *)fname->crypto_buf.name; - if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_')) - return false; - if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) - return false; - return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len), - n->digest, FSCRYPT_FNAME_DIGEST_SIZE); - } - - if (de_name_len != fname->disk_name.len) - return false; - return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); -} - -/* bio.c */ -extern void fscrypt_decrypt_bio(struct bio *); -extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, - struct bio *bio); -extern void fscrypt_pullback_bio_page(struct page **, bool); -extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t, - unsigned int); - -/* hooks.c */ -extern int fscrypt_file_open(struct inode *inode, struct file *filp); -extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir); -extern int __fscrypt_prepare_rename(struct inode *old_dir, - struct dentry *old_dentry, - struct inode *new_dir, - struct dentry *new_dentry, - unsigned int flags); -extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry); -extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, - unsigned int max_len, - struct fscrypt_str *disk_link); -extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, - unsigned int len, - struct fscrypt_str *disk_link); -extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, - unsigned int max_size, - struct delayed_call *done); - -#endif /* _LINUX_FSCRYPT_SUPP_H */ -- cgit v1.2.3 From f5e55e777cc93eae1416f0fa4908e8846b6d7825 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 22 Jan 2019 16:20:21 -0800 Subject: fscrypt: return -EXDEV for incompatible rename or link into encrypted dir Currently, trying to rename or link a regular file, directory, or symlink into an encrypted directory fails with EPERM when the source file is unencrypted or is encrypted with a different encryption policy, and is on the same mountpoint. It is correct for the operation to fail, but the choice of EPERM breaks tools like 'mv' that know to copy rather than rename if they see EXDEV, but don't know what to do with EPERM. Our original motivation for EPERM was to encourage users to securely handle their data. Encrypting files by "moving" them into an encrypted directory can be insecure because the unencrypted data may remain in free space on disk, where it can later be recovered by an attacker. It's much better to encrypt the data from the start, or at least try to securely delete the source data e.g. using the 'shred' program. However, the current behavior hasn't been effective at achieving its goal because users tend to be confused, hack around it, and complain; see e.g. https://github.com/google/fscrypt/issues/76. And in some cases it's actually inconsistent or unnecessary. For example, 'mv'-ing files between differently encrypted directories doesn't work even in cases where it can be secure, such as when in userspace the same passphrase protects both directories. Yet, you *can* already 'mv' unencrypted files into an encrypted directory if the source files are on a different mountpoint, even though doing so is often insecure. There are probably better ways to teach users to securely handle their files. For example, the 'fscrypt' userspace tool could provide a command that migrates unencrypted files into an encrypted directory, acting like 'shred' on the source files and providing appropriate warnings depending on the type of the source filesystem and disk. Receiving errors on unimportant files might also force some users to disable encryption, thus making the behavior counterproductive. It's desirable to make encryption as unobtrusive as possible. Therefore, change the error code from EPERM to EXDEV so that tools looking for EXDEV will fall back to a copy. This, of course, doesn't prevent users from still doing the right things to securely manage their files. Note that this also matches the behavior when a file is renamed between two project quota hierarchies; so there's precedent for using EXDEV for things other than mountpoints. xfstests generic/398 will require an update with this change. [Rewritten from an earlier patch series by Michael Halcrow.] Cc: Michael Halcrow Cc: Joe Richey Signed-off-by: Eric Biggers --- include/linux/fscrypt.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index eec604840568..e5194fc3983e 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -489,7 +489,7 @@ static inline int fscrypt_require_key(struct inode *inode) * in an encrypted directory tree use the same encryption policy. * * Return: 0 on success, -ENOKEY if the directory's encryption key is missing, - * -EPERM if the link would result in an inconsistent encryption policy, or + * -EXDEV if the link would result in an inconsistent encryption policy, or * another -errno code. */ static inline int fscrypt_prepare_link(struct dentry *old_dentry, @@ -519,7 +519,7 @@ static inline int fscrypt_prepare_link(struct dentry *old_dentry, * We also verify that the rename will not violate the constraint that all files * in an encrypted directory tree use the same encryption policy. * - * Return: 0 on success, -ENOKEY if an encryption key is missing, -EPERM if the + * Return: 0 on success, -ENOKEY if an encryption key is missing, -EXDEV if the * rename would cause inconsistent encryption policies, or another -errno code. */ static inline int fscrypt_prepare_rename(struct inode *old_dir, -- cgit v1.2.3