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Message-ID: <20171027180257.GB10611@google.com>
Date: Fri, 27 Oct 2017 11:02:57 -0700
From: Michael Halcrow <mhalcrow@...gle.com>
To: Eric Biggers <ebiggers3@...il.com>
Cc: linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
linux-mtd@...ts.infradead.org, linux-api@...r.kernel.org,
keyrings@...r.kernel.org, "Theodore Y . Ts'o" <tytso@....edu>,
Jaegeuk Kim <jaegeuk@...nel.org>,
Gwendal Grignou <gwendal@...omium.org>,
Ryo Hashimoto <hashimoto@...omium.org>,
Sarthak Kukreti <sarthakkukreti@...omium.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Eric Biggers <ebiggers@...gle.com>
Subject: Re: [RFC PATCH 02/25] fscrypt: use FSCRYPT_ prefix for uapi constants
On Mon, Oct 23, 2017 at 02:40:35PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
>
> Prefix all filesystem encryption UAPI constants except the ioctl numbers
> with "FSCRYPT_" rather than with "FS_". This namespaces the constants
> more appropriately and makes it clear that they are related specifically
> to the filesystem encryption feature, and to the 'fscrypt_*' structures.
> With some of the old names like "FS_POLICY_FLAGS_VALID", it was not
> immediately clear that the constant had anything to do with encryption.
>
> This is also useful because we'll be adding more encryption-related
> constants, e.g. for the policy version, and we'd otherwise have to
> choose whether to use unclear names like FS_POLICY_VERSION_* or
> inconsistent names like FS_ENCRYPTION_POLICY_VERSION_*.
>
> For source compatibility with older userspace programs, keep the old
> names defined as aliases to the new ones. (It's debatable whether we
> really need this, though; the filesystem encryption API is new enough
> that most if not all programs that are using it have to declare it
> themselves anyway.)
>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Reviewed-by: Michael Halcrow <mhalcrow@...gle.com>
> ---
> Documentation/filesystems/fscrypt.rst | 14 ++++-----
> include/uapi/linux/fscrypt.h | 59 ++++++++++++++++++++++++-----------
> 2 files changed, 47 insertions(+), 26 deletions(-)
>
> diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
> index 776ddc655f79..f12956f3f1f8 100644
> --- a/Documentation/filesystems/fscrypt.rst
> +++ b/Documentation/filesystems/fscrypt.rst
> @@ -251,14 +251,14 @@ empty directory or verifies that a directory or regular file already
> has the specified encryption policy. It takes in a pointer to a
> :c:type:`struct fscrypt_policy`, defined as follows::
>
> - #define FS_KEY_DESCRIPTOR_SIZE 8
> + #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
>
> struct fscrypt_policy {
> __u8 version;
> __u8 contents_encryption_mode;
> __u8 filenames_encryption_mode;
> __u8 flags;
> - __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
> + __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
> };
>
> This structure must be initialized as follows:
> @@ -274,7 +274,7 @@ This structure must be initialized as follows:
>
> - ``flags`` must be set to a value from ``<linux/fs.h>`` which
> identifies the amount of NUL-padding to use when encrypting
> - filenames. If unsure, use FS_POLICY_FLAGS_PAD_32 (0x3).
> + filenames. If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3).
>
> - ``master_key_descriptor`` specifies how to find the master key in
> the keyring; see `Adding keys`_. It is up to userspace to choose a
> @@ -374,11 +374,11 @@ followed by the 16-character lower case hex representation of the
> ``master_key_descriptor`` that was set in the encryption policy. The
> key payload must conform to the following structure::
>
> - #define FS_MAX_KEY_SIZE 64
> + #define FSCRYPT_MAX_KEY_SIZE 64
>
> struct fscrypt_key {
> u32 mode;
> - u8 raw[FS_MAX_KEY_SIZE];
> + u8 raw[FSCRYPT_MAX_KEY_SIZE];
> u32 size;
> };
>
> @@ -533,7 +533,7 @@ much confusion if an encryption policy were to be added to or removed
> from anything other than an empty directory.) The struct is defined
> as follows::
>
> - #define FS_KEY_DESCRIPTOR_SIZE 8
> + #define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
> #define FS_KEY_DERIVATION_NONCE_SIZE 16
>
> struct fscrypt_context {
> @@ -541,7 +541,7 @@ as follows::
> u8 contents_encryption_mode;
> u8 filenames_encryption_mode;
> u8 flags;
> - u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
> + u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
> u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
> };
>
> diff --git a/include/uapi/linux/fscrypt.h b/include/uapi/linux/fscrypt.h
> index c09209fc42ea..26c381a40279 100644
> --- a/include/uapi/linux/fscrypt.h
> +++ b/include/uapi/linux/fscrypt.h
> @@ -7,30 +7,31 @@
> * File system encryption support
> */
> /* Policy provided via an ioctl on the topmost directory */
> -#define FS_KEY_DESCRIPTOR_SIZE 8
> +#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
>
> -#define FS_POLICY_FLAGS_PAD_4 0x00
> -#define FS_POLICY_FLAGS_PAD_8 0x01
> -#define FS_POLICY_FLAGS_PAD_16 0x02
> -#define FS_POLICY_FLAGS_PAD_32 0x03
> -#define FS_POLICY_FLAGS_PAD_MASK 0x03
> -#define FS_POLICY_FLAGS_VALID 0x03
> +/* Encryption policy flags */
> +#define FSCRYPT_POLICY_FLAGS_PAD_4 0x00
> +#define FSCRYPT_POLICY_FLAGS_PAD_8 0x01
> +#define FSCRYPT_POLICY_FLAGS_PAD_16 0x02
> +#define FSCRYPT_POLICY_FLAGS_PAD_32 0x03
> +#define FSCRYPT_POLICY_FLAGS_PAD_MASK 0x03
> +#define FSCRYPT_POLICY_FLAGS_VALID 0x03
>
> /* Encryption algorithms */
> -#define FS_ENCRYPTION_MODE_INVALID 0
> -#define FS_ENCRYPTION_MODE_AES_256_XTS 1
> -#define FS_ENCRYPTION_MODE_AES_256_GCM 2
> -#define FS_ENCRYPTION_MODE_AES_256_CBC 3
> -#define FS_ENCRYPTION_MODE_AES_256_CTS 4
> -#define FS_ENCRYPTION_MODE_AES_128_CBC 5
> -#define FS_ENCRYPTION_MODE_AES_128_CTS 6
> +#define FSCRYPT_MODE_INVALID 0
> +#define FSCRYPT_MODE_AES_256_XTS 1
> +#define FSCRYPT_MODE_AES_256_GCM 2
> +#define FSCRYPT_MODE_AES_256_CBC 3
> +#define FSCRYPT_MODE_AES_256_CTS 4
> +#define FSCRYPT_MODE_AES_128_CBC 5
> +#define FSCRYPT_MODE_AES_128_CTS 6
>
> struct fscrypt_policy {
> __u8 version;
> __u8 contents_encryption_mode;
> __u8 filenames_encryption_mode;
> __u8 flags;
> - __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
> + __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
> };
>
> #define FS_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct fscrypt_policy)
> @@ -38,16 +39,36 @@ struct fscrypt_policy {
> #define FS_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct fscrypt_policy)
>
> /* Parameters for passing an encryption key into the kernel keyring */
> -#define FS_KEY_DESC_PREFIX "fscrypt:"
> -#define FS_KEY_DESC_PREFIX_SIZE 8
> +#define FSCRYPT_KEY_DESC_PREFIX "fscrypt:"
> +#define FSCRYPT_KEY_DESC_PREFIX_SIZE 8
>
> /* Structure that userspace passes to the kernel keyring */
> -#define FS_MAX_KEY_SIZE 64
> +#define FSCRYPT_MAX_KEY_SIZE 64
>
> struct fscrypt_key {
> __u32 mode;
> - __u8 raw[FS_MAX_KEY_SIZE];
> + __u8 raw[FSCRYPT_MAX_KEY_SIZE];
> __u32 size;
> };
> +/**********************************************************************/
> +
> +/* old names; don't add anything new here! */
> +#define FS_POLICY_FLAGS_PAD_4 FSCRYPT_POLICY_FLAGS_PAD_4
> +#define FS_POLICY_FLAGS_PAD_8 FSCRYPT_POLICY_FLAGS_PAD_8
> +#define FS_POLICY_FLAGS_PAD_16 FSCRYPT_POLICY_FLAGS_PAD_16
> +#define FS_POLICY_FLAGS_PAD_32 FSCRYPT_POLICY_FLAGS_PAD_32
> +#define FS_POLICY_FLAGS_PAD_MASK FSCRYPT_POLICY_FLAGS_PAD_MASK
> +#define FS_POLICY_FLAGS_VALID FSCRYPT_POLICY_FLAGS_VALID
> +#define FS_KEY_DESCRIPTOR_SIZE FSCRYPT_KEY_DESCRIPTOR_SIZE
> +#define FS_ENCRYPTION_MODE_INVALID FSCRYPT_MODE_INVALID
> +#define FS_ENCRYPTION_MODE_AES_256_XTS FSCRYPT_MODE_AES_256_XTS
> +#define FS_ENCRYPTION_MODE_AES_256_GCM FSCRYPT_MODE_AES_256_GCM
> +#define FS_ENCRYPTION_MODE_AES_256_CBC FSCRYPT_MODE_AES_256_CBC
> +#define FS_ENCRYPTION_MODE_AES_256_CTS FSCRYPT_MODE_AES_256_CTS
> +#define FS_ENCRYPTION_MODE_AES_128_CBC FSCRYPT_MODE_AES_128_CBC
> +#define FS_ENCRYPTION_MODE_AES_128_CTS FSCRYPT_MODE_AES_128_CTS
> +#define FS_KEY_DESC_PREFIX FSCRYPT_KEY_DESC_PREFIX
> +#define FS_KEY_DESC_PREFIX_SIZE FSCRYPT_KEY_DESC_PREFIX_SIZE
> +#define FS_MAX_KEY_SIZE FSCRYPT_MAX_KEY_SIZE
>
> #endif /* _UAPI_LINUX_FSCRYPT_H */
> --
> 2.15.0.rc0.271.g36b669edcc-goog
>
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