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Date: Tue, 8 Dec 2015 15:51:04 -0500
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: mhalcrow@...gle.com, Theodore Ts'o <tytso@....edu>
Subject: [PATCH RFC 1/2] ext4 crypto: add ciphertext_access mount option
Add a mount option which allows root to be able to access the
ciphertext of a file by reading it using O_DIRECT.
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
fs/ext4/ext4.h | 1 +
fs/ext4/file.c | 5 ++++-
fs/ext4/inode.c | 15 ++++++++-------
fs/ext4/super.c | 5 +++++
4 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 1e20fa9..44278aa7 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1052,6 +1052,7 @@ struct ext4_inode_info {
#define EXT4_MOUNT_DIOREAD_NOLOCK 0x400000 /* Enable support for dio read nolocking */
#define EXT4_MOUNT_JOURNAL_CHECKSUM 0x800000 /* Journal checksums */
#define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal Async Commit */
+#define EXT4_MOUNT_CIPHERTEXT_ACCESS 0x2000000 /* Direct I/O to ciphertext */
#define EXT4_MOUNT_DELALLOC 0x8000000 /* Delalloc support */
#define EXT4_MOUNT_DATA_ERR_ABORT 0x10000000 /* Abort on file data write */
#define EXT4_MOUNT_BLOCK_VALIDITY 0x20000000 /* Block validity checking */
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 749b222..60683ab 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -388,7 +388,10 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
ret = ext4_get_encryption_info(inode);
if (ret)
return -EACCES;
- if (ext4_encryption_info(inode) == NULL)
+ if ((ext4_encryption_info(inode) == NULL) &&
+ !(test_opt(inode->i_sb, CIPHERTEXT_ACCESS) &&
+ ((filp->f_flags & O_ACCMODE) == O_RDONLY) &&
+ capable(CAP_SYS_ADMIN)))
return -ENOKEY;
}
/*
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ff2f3cd..4b21bff 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3279,9 +3279,6 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
get_block_func = ext4_get_block_write;
dio_flags = DIO_LOCKING;
}
-#ifdef CONFIG_EXT4_FS_ENCRYPTION
- BUG_ON(ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode));
-#endif
if (IS_DAX(inode))
ret = dax_do_io(iocb, inode, iter, offset, get_block_func,
ext4_end_io_dio, dio_flags);
@@ -3344,10 +3341,14 @@ static ssize_t ext4_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
size_t count = iov_iter_count(iter);
ssize_t ret;
-#ifdef CONFIG_EXT4_FS_ENCRYPTION
- if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode))
- return 0;
-#endif
+ if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode)) {
+ if (test_opt(inode->i_sb, CIPHERTEXT_ACCESS) &&
+ capable(CAP_SYS_ADMIN)) {
+ if (iov_iter_rw(iter) == WRITE)
+ return -EPERM;
+ } else
+ return 0;
+ }
/*
* If we are doing data journalling we don't support O_DIRECT
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 486e869..de875b4 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1182,6 +1182,7 @@ enum {
Opt_journal_path, Opt_journal_checksum, Opt_journal_async_commit,
Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
Opt_data_err_abort, Opt_data_err_ignore, Opt_test_dummy_encryption,
+ Opt_ciphertext_access, Opt_nociphertext_access,
Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
Opt_noquota, Opt_barrier, Opt_nobarrier, Opt_err,
@@ -1273,6 +1274,8 @@ static const match_table_t tokens = {
{Opt_noinit_itable, "noinit_itable"},
{Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
{Opt_test_dummy_encryption, "test_dummy_encryption"},
+ {Opt_ciphertext_access, "ciphertext_access"},
+ {Opt_nociphertext_access, "nociphertext_access"},
{Opt_removed, "check=none"}, /* mount option from ext2/3 */
{Opt_removed, "nocheck"}, /* mount option from ext2/3 */
{Opt_removed, "reservation"}, /* mount option from ext2/3 */
@@ -1475,6 +1478,8 @@ static const struct mount_opts {
{Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
{Opt_max_dir_size_kb, 0, MOPT_GTE0},
{Opt_test_dummy_encryption, 0, MOPT_GTE0},
+ {Opt_ciphertext_access, EXT4_MOUNT_CIPHERTEXT_ACCESS, MOPT_SET},
+ {Opt_nociphertext_access, EXT4_MOUNT_CIPHERTEXT_ACCESS, MOPT_CLEAR},
{Opt_err, 0, 0}
};
--
2.5.0
--
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