ext4 crypto: add symlink encryption
Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 5146e67..86d1570 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2233,6 +2233,7 @@
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 f7d46e8..c2ba35a 100644
--- a/fs/ext4/ext4_crypto.h
+++ b/fs/ext4/ext4_crypto.h
@@ -124,4 +124,24 @@
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 8b4fe62..f6b35d8 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -139,7 +139,7 @@
/*
* 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 @@
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 4c84db8..d201426 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3193,16 +3193,24 @@
{
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 @@
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 @@
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 @@
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 489b343..136ca0e 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -22,8 +22,97 @@
#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);
return NULL;
@@ -31,8 +120,13 @@
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_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,