Re: [PATCH 01/10] fs crypto: add basic definitions for per-file encryption
From: Randy Dunlap
Date: Mon Feb 29 2016 - 00:41:31 EST
On 02/25/16 11:25, Jaegeuk Kim wrote:
> This patch adds definitions for per-file encryption used by ext4 and f2fs.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> ---
> include/linux/fs.h | 8 ++
> include/linux/fscrypto.h | 239 +++++++++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/fs.h | 18 ++++
> 3 files changed, 265 insertions(+)
> create mode 100644 include/linux/fscrypto.h
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index ae68100..d8f57cf 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -53,6 +53,8 @@ struct swap_info_struct;
> struct seq_file;
> struct workqueue_struct;
> struct iov_iter;
> +struct fscrypt_info;
> +struct fscrypt_operations;
>
> extern void __init inode_init(void);
> extern void __init inode_init_early(void);
> @@ -678,6 +680,10 @@ struct inode {
> struct hlist_head i_fsnotify_marks;
> #endif
>
> +#ifdef CONFIG_FS_ENCRYPTION
> + struct fscrypt_info *i_crypt_info;
> +#endif
> +
> void *i_private; /* fs or device private pointer */
> };
>
> @@ -1323,6 +1329,8 @@ struct super_block {
> #endif
> const struct xattr_handler **s_xattr;
>
> + const struct fscrypt_operations *s_cop;
> +
> struct hlist_bl_head s_anon; /* anonymous dentries for (nfs) exporting */
> struct list_head s_mounts; /* list of mounts; _not_ for fs use */
> struct block_device *s_bdev;
> diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h
> new file mode 100644
> index 0000000..b0aed92
> --- /dev/null
> +++ b/include/linux/fscrypto.h
> @@ -0,0 +1,239 @@
> +/*
> + * General per-file encryption definition
> + *
> + * Copyright (C) 2015, Google, Inc.
> + *
> + * Written by Michael Halcrow, 2015.
> + * Modified by Jaegeuk Kim, 2015.
> + */
> +
> +#ifndef _LINUX_FSCRYPTO_H
> +#define _LINUX_FSCRYPTO_H
> +
> +#include <linux/key.h>
> +#include <linux/fs.h>
> +#include <linux/mm.h>
> +#include <linux/bio.h>
> +#include <linux/dcache.h>
> +#include <uapi/linux/fs.h>
> +
> +#define FS_KEY_DERIVATION_NONCE_SIZE 16
> +#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1
> +
> +#define FS_POLICY_FLAGS_PAD_4 0x00
> +#define FS_POLICY_FLAGS_PAD_8 0x01
> +#define FS_POLICY_FLAGS_PAD_16 0x02
> +#define FS_POLICY_FLAGS_PAD_32 0x03
> +#define FS_POLICY_FLAGS_PAD_MASK 0x03
> +#define FS_POLICY_FLAGS_VALID 0x03
> +
> +/* Encryption algorithms */
> +#define FS_ENCRYPTION_MODE_INVALID 0
> +#define FS_ENCRYPTION_MODE_AES_256_XTS 1
> +#define FS_ENCRYPTION_MODE_AES_256_GCM 2
> +#define FS_ENCRYPTION_MODE_AES_256_CBC 3
> +#define FS_ENCRYPTION_MODE_AES_256_CTS 4
> +
> +/**
> + * Encryption context for inode
> + *
> + * Protector format:
> + * 1 byte: Protector format (1 = this version)
> + * 1 byte: File contents encryption mode
> + * 1 byte: File names encryption mode
> + * 1 byte: Flags
> + * 8 bytes: Master Key descriptor
> + * 16 bytes: Encryption Key derivation nonce
> + */
> +struct fscrypt_context {
> + char format;
> + char contents_encryption_mode;
> + char filenames_encryption_mode;
> + char flags;
> + char master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
> + char nonce[FS_KEY_DERIVATION_NONCE_SIZE];
how about u8 instead of char?
> +} __packed;
> +
> +/* Encryption parameters */
> +#define FS_XTS_TWEAK_SIZE 16
> +#define FS_AES_128_ECB_KEY_SIZE 16
> +#define FS_AES_256_GCM_KEY_SIZE 32
> +#define FS_AES_256_CBC_KEY_SIZE 32
> +#define FS_AES_256_CTS_KEY_SIZE 32
> +#define FS_AES_256_XTS_KEY_SIZE 64
> +#define FS_MAX_KEY_SIZE 64
> +
> +#define FS_KEY_DESC_PREFIX "fscrypt:"
> +#define FS_KEY_DESC_PREFIX_SIZE 8
> +
> +/* This is passed in from userspace into the kernel keyring */
> +struct fscrypt_key {
> + __u32 mode;
> + char raw[FS_MAX_KEY_SIZE];
> + __u32 size;
> +} __packed;
> +
> +struct fscrypt_info {
> + char ci_data_mode;
> + char ci_filename_mode;
> + char ci_flags;
ditto
> + struct crypto_ablkcipher *ci_ctfm;
> + struct key *ci_keyring_key;
> + char ci_master_key[FS_KEY_DESCRIPTOR_SIZE];
> +};
> +
> +#define FS_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
> +#define FS_WRITE_PATH_FL 0x00000002
> +
> +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 */
> + };
> + char flags; /* Flags */
> + char mode; /* Encryption mode for tfm */
> +};
> +
> +struct fscrypt_completion_result {
> + struct completion completion;
> + int res;
> +};
> +
> +#define DECLARE_FS_COMPLETION_RESULT(ecr) \
> + struct fscrypt_completion_result ecr = { \
> + COMPLETION_INITIALIZER((ecr).completion), 0 }
> +
> +static inline int fscrypt_key_size(int mode)
> +{
> + switch (mode) {
> + case FS_ENCRYPTION_MODE_AES_256_XTS:
> + return FS_AES_256_XTS_KEY_SIZE;
> + case FS_ENCRYPTION_MODE_AES_256_GCM:
> + return FS_AES_256_GCM_KEY_SIZE;
> + case FS_ENCRYPTION_MODE_AES_256_CBC:
> + return FS_AES_256_CBC_KEY_SIZE;
> + case FS_ENCRYPTION_MODE_AES_256_CTS:
> + return FS_AES_256_CTS_KEY_SIZE;
> + default:
> + BUG();
> + }
> + return 0;
> +}
> +
> +#define FS_FNAME_NUM_SCATTER_ENTRIES 4
> +#define FS_CRYPTO_BLOCK_SIZE 16
> +#define FS_FNAME_CRYPTO_DIGEST_SIZE 32
> +
> +/**
> + * For encrypted symlinks, the ciphertext length is stored at the beginning
> + * of the string in little-endian format.
> + */
> +struct fscrypt_symlink_data {
> + __le16 len;
> + char encrypted_path[1];
> +} __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 fscrypt_symlink_data_len(u32 l)
> +{
> + if (l < FS_CRYPTO_BLOCK_SIZE)
> + l = FS_CRYPTO_BLOCK_SIZE;
> + return (l + sizeof(struct fscrypt_symlink_data) - 1);
> +}
> +
> +struct fscrypt_str {
> + unsigned char *name;
> + u32 len;
> +};
> +
> +struct fscrypt_name {
> + const struct qstr *usr_fname;
> + struct fscrypt_str disk_name;
> + u32 hash;
> + u32 minor_hash;
> + struct fscrypt_str crypto_buf;
> +};
> +
> +#define FSTR_INIT(n, l) { .name = n, .len = l }
> +#define FSTR_TO_QSTR(f) QSTR_INIT((f)->name, (f)->len)
> +#define fname_name(p) ((p)->disk_name.name)
> +#define fname_len(p) ((p)->disk_name.len)
> +
> +/*
> + * crypto opertions for filesystems
> + */
> +struct fscrypt_operations {
> + int (*get_context)(struct inode *, void *, size_t);
> + int (*prepare_context)(struct inode *);
> + int (*set_context)(struct inode *, const void *, size_t, void *);
> + int (*dummy_context)(struct inode *);
> + bool (*is_encrypted)(struct inode *);
> + bool (*empty_dir)(struct inode *);
> + unsigned (*max_namelen)(struct inode *);
> +};
> +
> +static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
> +{
> + if (inode->i_sb->s_cop->dummy_context &&
> + inode->i_sb->s_cop->dummy_context(inode))
> + return true;
> + return false;
> +}
> +
> +static inline bool fscrypt_valid_contents_enc_mode(u32 mode)
> +{
> + return (mode == FS_ENCRYPTION_MODE_AES_256_XTS);
> +}
> +
> +static inline bool fscrypt_valid_filenames_enc_mode(u32 mode)
> +{
> + return (mode == FS_ENCRYPTION_MODE_AES_256_CTS);
> +}
> +
> +static inline u32 fscrypt_validate_encryption_key_size(u32 mode, u32 size)
> +{
> + if (size == fscrypt_key_size(mode))
> + return size;
> + return 0;
> +}
> +
> +static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
> +{
> + if (str->len == 1 && str->name[0] == '.')
> + return true;
> +
> + if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
> + return true;
> +
> + return false;
> +}
> +
> +static inline struct page *fscrypt_control_page(struct page *page)
> +{
> +#ifdef CONFIG_FS_ENCRYPTION
> + return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
> +#else
> + WARN_ON_ONCE(1);
> + return ERR_PTR(-EINVAL);
> +#endif
> +}
> +
> +static inline int fscrypt_has_encryption_key(struct inode *inode)
> +{
> +#ifdef CONFIG_FS_ENCRYPTION
> + return (inode->i_crypt_info != NULL);
> +#else
> + return 0;
> +#endif
> +}
> +#endif /* _LINUX_FSCRYPTO_H */
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 149bec8..1d26276 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -247,6 +247,24 @@ struct fsxattr {
> #define FS_IOC_FSSETXATTR _IOW ('X', 32, struct fsxattr)
>
> /*
> + * File system encryption support
> + */
> +/* Policy provided via an ioctl on the topmost directory */
> +#define FS_KEY_DESCRIPTOR_SIZE 8
> +
> +struct fscrypt_policy {
> + char version;
> + char contents_encryption_mode;
> + char filenames_encryption_mode;
> + char flags;
> + char master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
ditto
> +} __packed;
> +
> +#define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy)
> +#define FS_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16])
> +#define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy)
> +
> +/*
> * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)
> *
> * Note: for historical reasons, these flags were originally used and
>
--
~Randy