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Message-Id: <1428012659-12709-21-git-send-email-tytso@mit.edu>
Date: Thu, 2 Apr 2015 18:10:57 -0400
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: jaegeuk@...nel.org, mhalcrow@...gle.com,
Theodore Ts'o <tytso@....edu>,
Uday Savagaonkar <savagaon@...gle.com>
Subject: [PATCH 20/22] ext4 crypto: Add symlink encryption
Change-Id: Ic92ebe4c615721650ccaf16b3175c2f4e931af2d
Signed-off-by: Uday Savagaonkar <savagaon@...gle.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
fs/ext4/ext4_crypto.h | 20 ++++++++++
fs/ext4/namei.c | 63 +++++++++++++++++++++++++++---
fs/ext4/symlink.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 180 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h
index 68e95d8..4597530 100644
--- a/fs/ext4/ext4_crypto.h
+++ b/fs/ext4/ext4_crypto.h
@@ -117,4 +117,24 @@ 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 {
+ __le32 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)
+{
+ return ((l + EXT4_CRYPTO_BLOCK_SIZE - 1) / EXT4_CRYPTO_BLOCK_SIZE)
+ * EXT4_CRYPTO_BLOCK_SIZE
+ + sizeof(struct ext4_encrypted_symlink_data) - 1;
+}
+
#endif /* _EXT4_CRYPTO_H */
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 80a3979..57db793 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3198,14 +3198,31 @@ static int ext4_symlink(struct inode *dir,
struct inode *inode;
int l, err, retries = 0;
int credits;
+ bool encryption_required = false;
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ int l2;
+ struct ext4_fname_crypto_ctx *ctx = NULL;
+ struct qstr istr;
+ struct ext4_str ostr;
+ struct ext4_encrypted_symlink_data *sd = NULL;
+ struct ext4_sb_info *sbi = EXT4_SB(dir->i_sb);
+#endif
- l = strlen(symname)+1;
+ l = strlen(symname) + 1;
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ l2 = encrypted_symlink_data_len(l - 1);
+ encryption_required = (ext4_encrypted_inode(dir) ||
+ unlikely(sbi->s_mount_flags &
+ EXT4_MF_TEST_DUMMY_ENCRYPTION));
+ if (encryption_required && l2 > dir->i_sb->s_blocksize)
+#else
if (l > dir->i_sb->s_blocksize)
+#endif
return -ENAMETOOLONG;
dquot_initialize(dir);
- if (l > EXT4_N_BLOCKS * 4) {
+ if ((l > EXT4_N_BLOCKS * 4) || encryption_required) {
/*
* For non-fast symlinks, we just allocate inode and put it on
* orphan list in the first transaction => we need bitmap,
@@ -3233,7 +3250,7 @@ retry:
if (IS_ERR(inode))
goto out_stop;
- if (l > EXT4_N_BLOCKS * 4) {
+ if ((l > EXT4_N_BLOCKS * 4) || encryption_required) {
inode->i_op = &ext4_symlink_inode_operations;
ext4_set_aops(inode);
/*
@@ -3251,9 +3268,40 @@ retry:
ext4_journal_stop(handle);
if (err)
goto err_drop_inode;
- err = __page_symlink(inode, symname, l, 1);
- if (err)
- goto err_drop_inode;
+ if (!encryption_required) {
+ err = __page_symlink(inode, symname, l, 1);
+ if (err)
+ goto err_drop_inode;
+ }
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ else {
+ sd = kmalloc(l2 + 1, GFP_NOFS);
+ if (!sd) {
+ err = -ENOMEM;
+ goto err_drop_inode;
+ }
+ sd->encrypted_path[l2] = '\0';
+ err = ext4_inherit_context(dir, 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 = l - 1;
+ 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_le32(ostr.len);
+ err = __page_symlink(inode, (char *)sd, l2 + 1, 1);
+
+ }
+#endif
/*
* Now inode is being linked into dir (EXT4_DATA_TRANS_BLOCKS
* + EXT4_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified
@@ -3293,6 +3341,9 @@ out_stop:
err_drop_inode:
unlock_new_inode(inode);
iput(inode);
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ kfree(sd);
+#endif
return err;
}
diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
index ff37119..d788891 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -22,9 +22,106 @@
#include <linux/namei.h>
#include "ext4.h"
#include "xattr.h"
+#include "ext4_crypto.h"
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
{
+ struct page *cpage = NULL;
+ char *caddr, *paddr;
+ 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(inode->i_size, (loff_t) PAGE_SIZE-1);
+ int res;
+ u32 plen, plen2;
+
+ ctx = ext4_get_fname_crypto_ctx(inode, inode->i_sb->s_blocksize);
+ if (IS_ERR(ctx))
+ return ctx;
+
+ 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;
+
+ if (!ctx) {
+ /* Symlink is unencrypted */
+ plen = strnlen((char *)caddr, inode->i_sb->s_blocksize);
+ plen2 = (plen < inode->i_sb->s_blocksize) ? plen + 1 : plen;
+ paddr = kmalloc(plen2, GFP_NOFS);
+ if (!paddr) {
+ ext4_put_fname_crypto_ctx(&ctx);
+ kunmap(cpage);
+ page_cache_release(cpage);
+ return ERR_PTR(-ENOMEM);
+ }
+ memcpy(paddr, caddr, plen);
+ if (plen < inode->i_sb->s_blocksize)
+ paddr[plen] = '\0';
+ } else {
+ /* 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)
+ > inode->i_sb->s_blocksize) {
+ /* Symlink data on the disk is corrupted */
+ kunmap(cpage);
+ page_cache_release(cpage);
+ return ERR_PTR(-EIO);
+ }
+ 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) {
+ ext4_put_fname_crypto_ctx(&ctx);
+ kunmap(cpage);
+ page_cache_release(cpage);
+ return ERR_PTR(-ENOMEM);
+ }
+ pstr.name = paddr;
+ res = _ext4_fname_disk_to_usr(ctx, &cstr, &pstr);
+ if (res < 0) {
+ ext4_put_fname_crypto_ctx(&ctx);
+ kunmap(cpage);
+ page_cache_release(cpage);
+ kfree(paddr);
+ return ERR_PTR(res);
+ }
+ /* Null-terminate the name */
+ if (res <= plen)
+ paddr[res] = '\0';
+ }
+ nd_set_link(nd, paddr);
+ ext4_put_fname_crypto_ctx(&ctx);
+ return cpage;
+}
+
+static void ext4_put_link(struct dentry *dentry, struct nameidata *nd,
+ void *cookie)
+{
+ struct page *page = cookie;
+ char *buf = nd_get_link(nd);
+
+ if (page) {
+ kunmap(page);
+ page_cache_release(page);
+ }
+ if (buf) {
+ nd_set_link(nd, NULL);
+ kfree(buf);
+ }
+}
+#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;
@@ -32,8 +129,13 @@ 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,
@@ -43,7 +145,7 @@ 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,
--
2.3.0
--
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