From: Theodore Ts'o Subject: [PATCH RFC 1/2] ext4 crypto: add ciphertext_access mount option Date: Tue, 8 Dec 2015 15:51:04 -0500 Message-ID: <1449607865-21913-1-git-send-email-tytso@mit.edu> Cc: mhalcrow@google.com, Theodore Ts'o To: Ext4 Developers List Return-path: Received: from imap.thunk.org ([74.207.234.97]:46408 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657AbbLHUvL (ORCPT ); Tue, 8 Dec 2015 15:51:11 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 --- 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