[PATCH] eCryptfs: Encrypted passthrough

Provide an option to provide a view of the encrypted files such that the
metadata is always in the header of the files, regardless of whether the
metadata is actually in the header or in the extended attribute.  This mode of
operation is useful for applications like incremental backup utilities that do
not preserve the extended attributes when directly accessing the lower files.

With this option enabled, the files under the eCryptfs mount point will be
read-only.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 6b45b2908f17..bbc1b4f666fe 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -289,6 +289,7 @@ static struct dentry *ecryptfs_lookup(struct inode *dir, struct dentry *dentry,
         char *encoded_name;
         unsigned int encoded_namelen;
         struct ecryptfs_crypt_stat *crypt_stat = NULL;
+        struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
         char *page_virt = NULL;
         struct inode *lower_inode;
         u64 file_size;
@@ -388,8 +389,18 @@ static struct dentry *ecryptfs_lookup(struct inode *dir, struct dentry *dentry,
                 }
                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
         }
-        memcpy(&file_size, page_virt, sizeof(file_size));
-        file_size = be64_to_cpu(file_size);
+        mount_crypt_stat = &ecryptfs_superblock_to_private(
+                dentry->d_sb)->mount_crypt_stat;
+        if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED) {
+                if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
+                        file_size = (crypt_stat->header_extent_size
+                                     + i_size_read(lower_dentry->d_inode));
+                else
+                        file_size = i_size_read(lower_dentry->d_inode);
+        } else {
+                memcpy(&file_size, page_virt, sizeof(file_size));
+                file_size = be64_to_cpu(file_size);
+        }
         i_size_write(dentry->d_inode, (loff_t)file_size);
         kmem_cache_free(ecryptfs_header_cache_2, page_virt);
         goto out;