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ext4 crypto: add symlink encryption 

Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2015-04-16 01:55:00 -04:00
parent 4461471107
commit f348c25232
5 changed files with 184 additions and 23 deletions
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1
fs/ext4/ext4.h
View File

@ -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,

20
fs/ext4/ext4_crypto.h
View File

@ -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 */

5
fs/ext4/inode.c
View File

@ -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);

85
fs/ext4/namei.c
View File

@ -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 (l > EXT4_N_BLOCKS * 4) {
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 ((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;

96
fs/ext4/symlink.c
View File

@ -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,