[Qemu-devel] [PATCH v6 06/11] block: add generic full disk encryption driver

[Daniel P. Berrange]

Add a block driver that is capable of supporting any full disk
encryption format. This utilizes the previously added block
encryption code, and at this time supports the LUKS format.

The driver code is capable of supporting any format supported
by the QCryptoBlock module, so it registers one block driver
for each format. This patch only registers the "luks" driver
since the "qcow" driver is there only for back-compatibility
with existing qcow built-in encryption.

New LUKS compatible volumes can be formatted using qemu-img
with defaults for all settings.

$ qemu-img create --object secret,data=123456,id=sec0 \
      -f luks -o key-secret=sec0 demo.luks 10G

Alternatively the cryptographic settings can be explicitly
set

$ qemu-img create --object secret,data=123456,id=sec0 \
      -f luks -o key-secret=sec0,cipher-alg=aes-256,\
                 cipher-mode=cbc,ivgen-alg=plain64,hash-alg=sha256 \
      demo.luks 10G

And query its size

$ qemu-img info demo.img
image: demo.img
file format: luks
virtual size: 10G (10737418240 bytes)
disk size: 132K
encrypted: yes

Note that it was not necessary to provide the password
when querying info for the volume. The password is only
required when performing I/O on the volume

All volumes created by this new 'luks' driver should be
capable of being opened by the kernel dm-crypt driver.

The only algorithms listed in the LUKS spec that are
not currently supported by this impl are sha512 and
ripemd160 hashes and cast6 cipher.

Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Daniel P. Berrange <address@hidden>
---
 block/Makefile.objs  |   2 +
 block/crypto.c       | 586 +++++++++++++++++++++++++++++++++++++++++++++++++++
 qapi/block-core.json |  22 +-
 3 files changed, 608 insertions(+), 2 deletions(-)
 create mode 100644 block/crypto.c

diff --git a/block/Makefile.objs b/block/Makefile.objs
index cdd8655..3426a15 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -23,6 +23,8 @@ block-obj-$(CONFIG_LIBSSH2) += ssh.o
 block-obj-y += accounting.o dirty-bitmap.o
 block-obj-y += write-threshold.o
 
+block-obj-y += crypto.o
+
 common-obj-y += stream.o
 common-obj-y += commit.o
 common-obj-y += backup.o
diff --git a/block/crypto.c b/block/crypto.c
new file mode 100644
index 0000000..e3467d5
--- /dev/null
+++ b/block/crypto.c
@@ -0,0 +1,586 @@
+/*
+ * QEMU block full disk encryption
+ *
+ * Copyright (c) 2015-2016 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include "block/block_int.h"
+#include "sysemu/block-backend.h"
+#include "crypto/block.h"
+#include "qapi/opts-visitor.h"
+#include "qapi-visit.h"
+
+#define BLOCK_CRYPTO_OPT_LUKS_KEY_SECRET "key-secret"
+#define BLOCK_CRYPTO_OPT_LUKS_CIPHER_ALG "cipher-alg"
+#define BLOCK_CRYPTO_OPT_LUKS_CIPHER_MODE "cipher-mode"
+#define BLOCK_CRYPTO_OPT_LUKS_IVGEN_ALG "ivgen-alg"
+#define BLOCK_CRYPTO_OPT_LUKS_IVGEN_HASH_ALG "ivgen-hash-alg"
+#define BLOCK_CRYPTO_OPT_LUKS_HASH_ALG "hash-alg"
+
+typedef struct BlockCrypto BlockCrypto;
+
+struct BlockCrypto {
+    QCryptoBlock *block;
+};
+
+
+static int block_crypto_probe_generic(QCryptoBlockFormat format,
+                                      const uint8_t *buf,
+                                      int buf_size,
+                                      const char *filename)
+{
+    if (qcrypto_block_has_format(format, buf, buf_size)) {
+        return 100;
+    } else {
+        return 0;
+    }
+}
+
+
+static ssize_t block_crypto_read_func(QCryptoBlock *block,
+                                      size_t offset,
+                                      uint8_t *buf,
+                                      size_t buflen,
+                                      Error **errp,
+                                      void *opaque)
+{
+    BlockDriverState *bs = opaque;
+    ssize_t ret;
+
+    ret = bdrv_pread(bs->file->bs, offset, buf, buflen);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not read encryption header");
+        return ret;
+    }
+    return ret;
+}
+
+
+struct BlockCryptoCreateData {
+    const char *filename;
+    QemuOpts *opts;
+    BlockBackend *blk;
+    uint64_t size;
+};
+
+
+static ssize_t block_crypto_write_func(QCryptoBlock *block,
+                                       size_t offset,
+                                       const uint8_t *buf,
+                                       size_t buflen,
+                                       Error **errp,
+                                       void *opaque)
+{
+    struct BlockCryptoCreateData *data = opaque;
+    ssize_t ret;
+
+    ret = blk_pwrite(data->blk, offset, buf, buflen);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not write encryption header");
+        return ret;
+    }
+    return ret;
+}
+
+
+static ssize_t block_crypto_init_func(QCryptoBlock *block,
+                                      size_t headerlen,
+                                      Error **errp,
+                                      void *opaque)
+{
+    struct BlockCryptoCreateData *data = opaque;
+    int ret;
+
+    /* User provided size should reflect amount of space made
+     * available to the guest, so we must take account of that
+     * which will be used by the crypto header
+     */
+    data->size += headerlen;
+
+    qemu_opt_set_number(data->opts, BLOCK_OPT_SIZE, data->size, &error_abort);
+    ret = bdrv_create_file(data->filename, data->opts, errp);
+    if (ret < 0) {
+        return -1;
+    }
+
+    data->blk = blk_new_open(data->filename, NULL, NULL,
+                             BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
+                             errp);
+    if (!data->blk) {
+        return -1;
+    }
+
+    return 0;
+}
+
+
+static QemuOptsList block_crypto_runtime_opts_luks = {
+    .name = "crypto",
+    .head = QTAILQ_HEAD_INITIALIZER(block_crypto_runtime_opts_luks.head),
+    .desc = {
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_KEY_SECRET,
+            .type = QEMU_OPT_STRING,
+            .help = "ID of the secret that provides the encryption key",
+        },
+        { /* end of list */ }
+    },
+};
+
+
+static QemuOptsList block_crypto_create_opts_luks = {
+    .name = "crypto",
+    .head = QTAILQ_HEAD_INITIALIZER(block_crypto_create_opts_luks.head),
+    .desc = {
+        {
+            .name = BLOCK_OPT_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Virtual disk size"
+        },
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_KEY_SECRET,
+            .type = QEMU_OPT_STRING,
+            .help = "ID of the secret that provides the encryption key",
+        },
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_CIPHER_ALG,
+            .type = QEMU_OPT_STRING,
+            .help = "Name of encryption cipher algorithm",
+        },
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_CIPHER_MODE,
+            .type = QEMU_OPT_STRING,
+            .help = "Name of encryption cipher mode",
+        },
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_IVGEN_ALG,
+            .type = QEMU_OPT_STRING,
+            .help = "Name of IV generator algorithm",
+        },
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_IVGEN_HASH_ALG,
+            .type = QEMU_OPT_STRING,
+            .help = "Name of IV generator hash algorithm",
+        },
+        {
+            .name = BLOCK_CRYPTO_OPT_LUKS_HASH_ALG,
+            .type = QEMU_OPT_STRING,
+            .help = "Name of encryption hash algorithm",
+        },
+        { /* end of list */ }
+    },
+};
+
+
+static QCryptoBlockOpenOptions *
+block_crypto_open_opts_init(QCryptoBlockFormat format,
+                            QemuOpts *opts,
+                            Error **errp)
+{
+    OptsVisitor *ov;
+    QCryptoBlockOpenOptions *ret = NULL;
+    Error *local_err = NULL;
+
+    ret = g_new0(QCryptoBlockOpenOptions, 1);
+    ret->format = format;
+
+    ov = opts_visitor_new(opts);
+
+    visit_start_struct(opts_get_visitor(ov),
+                       NULL, NULL, 0, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    switch (format) {
+    case Q_CRYPTO_BLOCK_FORMAT_LUKS:
+        visit_type_QCryptoBlockOptionsLUKS_members(
+            opts_get_visitor(ov), &ret->u.luks, &local_err);
+        break;
+
+    default:
+        error_setg(&local_err, "Unsupported block format %d", format);
+        break;
+    }
+    error_propagate(errp, local_err);
+    local_err = NULL;
+
+    visit_end_struct(opts_get_visitor(ov), &local_err);
+
+ out:
+    if (local_err) {
+        error_propagate(errp, local_err);
+        qapi_free_QCryptoBlockOpenOptions(ret);
+        ret = NULL;
+    }
+    opts_visitor_cleanup(ov);
+    return ret;
+}
+
+
+static QCryptoBlockCreateOptions *
+block_crypto_create_opts_init(QCryptoBlockFormat format,
+                              QemuOpts *opts,
+                              Error **errp)
+{
+    OptsVisitor *ov;
+    QCryptoBlockCreateOptions *ret = NULL;
+    Error *local_err = NULL;
+
+    ret = g_new0(QCryptoBlockCreateOptions, 1);
+    ret->format = format;
+
+    ov = opts_visitor_new(opts);
+
+    visit_start_struct(opts_get_visitor(ov),
+                       NULL, NULL, 0, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    switch (format) {
+    case Q_CRYPTO_BLOCK_FORMAT_LUKS:
+        visit_type_QCryptoBlockCreateOptionsLUKS_members(
+            opts_get_visitor(ov), &ret->u.luks, &local_err);
+        break;
+
+    default:
+        error_setg(&local_err, "Unsupported block format %d", format);
+        break;
+    }
+    error_propagate(errp, local_err);
+    local_err = NULL;
+
+    visit_end_struct(opts_get_visitor(ov), &local_err);
+
+ out:
+    if (local_err) {
+        error_propagate(errp, local_err);
+        qapi_free_QCryptoBlockCreateOptions(ret);
+        ret = NULL;
+    }
+    opts_visitor_cleanup(ov);
+    return ret;
+}
+
+
+static int block_crypto_open_generic(QCryptoBlockFormat format,
+                                     QemuOptsList *opts_spec,
+                                     BlockDriverState *bs,
+                                     QDict *options,
+                                     int flags,
+                                     Error **errp)
+{
+    BlockCrypto *crypto = bs->opaque;
+    QemuOpts *opts = NULL;
+    Error *local_err = NULL;
+    int ret = -EINVAL;
+    QCryptoBlockOpenOptions *open_opts = NULL;
+    unsigned int cflags = 0;
+
+    opts = qemu_opts_create(opts_spec, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto cleanup;
+    }
+
+    open_opts = block_crypto_open_opts_init(format, opts, errp);
+    if (!open_opts) {
+        goto cleanup;
+    }
+
+    if (flags & BDRV_O_NO_IO) {
+        cflags |= QCRYPTO_BLOCK_OPEN_NO_IO;
+    }
+    crypto->block = qcrypto_block_open(open_opts,
+                                       block_crypto_read_func,
+                                       bs,
+                                       cflags,
+                                       errp);
+
+    if (!crypto->block) {
+        ret = -EIO;
+        goto cleanup;
+    }
+
+    bs->encrypted = 1;
+    bs->valid_key = 1;
+
+    ret = 0;
+ cleanup:
+    qapi_free_QCryptoBlockOpenOptions(open_opts);
+    return ret;
+}
+
+
+static int block_crypto_create_generic(QCryptoBlockFormat format,
+                                       const char *filename,
+                                       QemuOpts *opts,
+                                       Error **errp)
+{
+    int ret = -EINVAL;
+    QCryptoBlockCreateOptions *create_opts = NULL;
+    QCryptoBlock *crypto = NULL;
+    struct BlockCryptoCreateData data = {
+        .size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
+                         BDRV_SECTOR_SIZE),
+        .opts = opts,
+        .filename = filename,
+    };
+
+    create_opts = block_crypto_create_opts_init(format, opts, errp);
+    if (!create_opts) {
+        return -1;
+    }
+
+    crypto = qcrypto_block_create(create_opts,
+                                  block_crypto_init_func,
+                                  block_crypto_write_func,
+                                  &data,
+                                  errp);
+
+    if (!crypto) {
+        ret = -EIO;
+        goto cleanup;
+    }
+
+    ret = 0;
+ cleanup:
+    qcrypto_block_free(crypto);
+    blk_unref(data.blk);
+    qapi_free_QCryptoBlockCreateOptions(create_opts);
+    return ret;
+}
+
+static int block_crypto_truncate(BlockDriverState *bs, int64_t offset)
+{
+    BlockCrypto *crypto = bs->opaque;
+    size_t payload_offset =
+        qcrypto_block_get_payload_offset(crypto->block);
+
+    offset += payload_offset;
+
+    return bdrv_truncate(bs->file->bs, offset);
+}
+
+static void block_crypto_close(BlockDriverState *bs)
+{
+    BlockCrypto *crypto = bs->opaque;
+    qcrypto_block_free(crypto->block);
+}
+
+
+#define BLOCK_CRYPTO_MAX_SECTORS 32
+
+static coroutine_fn int
+block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
+                      int remaining_sectors, QEMUIOVector *qiov)
+{
+    BlockCrypto *crypto = bs->opaque;
+    int cur_nr_sectors; /* number of sectors in current iteration */
+    uint64_t bytes_done = 0;
+    uint8_t *cipher_data = NULL;
+    QEMUIOVector hd_qiov;
+    int ret = 0;
+    size_t payload_offset =
+        qcrypto_block_get_payload_offset(crypto->block) / 512;
+
+    qemu_iovec_init(&hd_qiov, qiov->niov);
+
+    /* Bounce buffer so we have a linear mem region for
+     * entire sector. XXX optimize so we avoid bounce
+     * buffer in case that qiov->niov == 1
+     */
+    cipher_data =
+        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
+                                              qiov->size));
+    if (cipher_data == NULL) {
+        ret = -ENOMEM;
+        goto cleanup;
+    }
+
+    while (remaining_sectors) {
+        cur_nr_sectors = remaining_sectors;
+
+        if (cur_nr_sectors > BLOCK_CRYPTO_MAX_SECTORS) {
+            cur_nr_sectors = BLOCK_CRYPTO_MAX_SECTORS;
+        }
+
+        qemu_iovec_reset(&hd_qiov);
+        qemu_iovec_add(&hd_qiov, cipher_data, cur_nr_sectors * 512);
+
+        ret = bdrv_co_readv(bs->file->bs,
+                            payload_offset + sector_num,
+                            cur_nr_sectors, &hd_qiov);
+        if (ret < 0) {
+            goto cleanup;
+        }
+
+        if (qcrypto_block_decrypt(crypto->block,
+                                  sector_num,
+                                  cipher_data, cur_nr_sectors * 512,
+                                  NULL) < 0) {
+            ret = -EIO;
+            goto cleanup;
+        }
+
+        qemu_iovec_from_buf(qiov, bytes_done,
+                            cipher_data, cur_nr_sectors * 512);
+
+        remaining_sectors -= cur_nr_sectors;
+        sector_num += cur_nr_sectors;
+        bytes_done += cur_nr_sectors * 512;
+    }
+
+ cleanup:
+    qemu_iovec_destroy(&hd_qiov);
+    qemu_vfree(cipher_data);
+
+    return ret;
+}
+
+
+static coroutine_fn int
+block_crypto_co_writev(BlockDriverState *bs, int64_t sector_num,
+                       int remaining_sectors, QEMUIOVector *qiov)
+{
+    BlockCrypto *crypto = bs->opaque;
+    int cur_nr_sectors; /* number of sectors in current iteration */
+    uint64_t bytes_done = 0;
+    uint8_t *cipher_data = NULL;
+    QEMUIOVector hd_qiov;
+    int ret = 0;
+    size_t payload_offset =
+        qcrypto_block_get_payload_offset(crypto->block) / 512;
+
+    qemu_iovec_init(&hd_qiov, qiov->niov);
+
+    /* Bounce buffer so we have a linear mem region for
+     * entire sector. XXX optimize so we avoid bounce
+     * buffer in case that qiov->niov == 1
+     */
+    cipher_data =
+        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
+                                              qiov->size));
+    if (cipher_data == NULL) {
+        ret = -ENOMEM;
+        goto cleanup;
+    }
+
+    while (remaining_sectors) {
+        cur_nr_sectors = remaining_sectors;
+
+        if (cur_nr_sectors > BLOCK_CRYPTO_MAX_SECTORS) {
+            cur_nr_sectors = BLOCK_CRYPTO_MAX_SECTORS;
+        }
+
+        qemu_iovec_to_buf(qiov, bytes_done,
+                          cipher_data, cur_nr_sectors * 512);
+
+        if (qcrypto_block_encrypt(crypto->block,
+                                  sector_num,
+                                  cipher_data, cur_nr_sectors * 512,
+                                  NULL) < 0) {
+            ret = -EIO;
+            goto cleanup;
+        }
+
+        qemu_iovec_reset(&hd_qiov);
+        qemu_iovec_add(&hd_qiov, cipher_data, cur_nr_sectors * 512);
+
+        ret = bdrv_co_writev(bs->file->bs,
+                             payload_offset + sector_num,
+                             cur_nr_sectors, &hd_qiov);
+        if (ret < 0) {
+            goto cleanup;
+        }
+
+        remaining_sectors -= cur_nr_sectors;
+        sector_num += cur_nr_sectors;
+        bytes_done += cur_nr_sectors * 512;
+    }
+
+ cleanup:
+    qemu_iovec_destroy(&hd_qiov);
+    qemu_vfree(cipher_data);
+
+    return ret;
+}
+
+
+static int64_t block_crypto_getlength(BlockDriverState *bs)
+{
+    BlockCrypto *crypto = bs->opaque;
+    int64_t len = bdrv_getlength(bs->file->bs);
+
+    ssize_t offset = qcrypto_block_get_payload_offset(crypto->block);
+
+    len -= offset;
+
+    return len;
+}
+
+
+static int block_crypto_probe_luks(const uint8_t *buf,
+                                   int buf_size,
+                                   const char *filename) {
+    return block_crypto_probe_generic(Q_CRYPTO_BLOCK_FORMAT_LUKS,
+                                      buf, buf_size, filename);
+}
+
+static int block_crypto_open_luks(BlockDriverState *bs,
+                                  QDict *options,
+                                  int flags,
+                                  Error **errp)
+{
+    return block_crypto_open_generic(Q_CRYPTO_BLOCK_FORMAT_LUKS,
+                                     &block_crypto_runtime_opts_luks,
+                                     bs, options, flags, errp);
+}
+
+static int block_crypto_create_luks(const char *filename,
+                                    QemuOpts *opts,
+                                    Error **errp)
+{
+    return block_crypto_create_generic(Q_CRYPTO_BLOCK_FORMAT_LUKS,
+                                       filename, opts, errp);
+}
+
+BlockDriver bdrv_crypto_luks = {
+    .format_name        = "luks",
+    .instance_size      = sizeof(BlockCrypto),
+    .bdrv_probe         = block_crypto_probe_luks,
+    .bdrv_open          = block_crypto_open_luks,
+    .bdrv_close         = block_crypto_close,
+    .bdrv_create        = block_crypto_create_luks,
+    .bdrv_truncate      = block_crypto_truncate,
+    .create_opts        = &block_crypto_create_opts_luks,
+
+    .bdrv_co_readv      = block_crypto_co_readv,
+    .bdrv_co_writev     = block_crypto_co_writev,
+    .bdrv_getlength     = block_crypto_getlength,
+};
+
+static void block_crypto_init(void)
+{
+    bdrv_register(&bdrv_crypto_luks);
+}
+
+block_init(block_crypto_init);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index b1cf77d..8d41d95 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -242,11 +242,12 @@
 # @drv: the name of the block format used to open the backing device. As of
 #       0.14.0 this can be: 'blkdebug', 'bochs', 'cloop', 'cow', 'dmg',
 #       'file', 'file', 'ftp', 'ftps', 'host_cdrom', 'host_device',
-#       'http', 'https', 'nbd', 'parallels', 'qcow',
+#       'http', 'https', 'luks', 'nbd', 'parallels', 'qcow',
 #       'qcow2', 'raw', 'tftp', 'vdi', 'vmdk', 'vpc', 'vvfat'
 #       2.2: 'archipelago' added, 'cow' dropped
 #       2.3: 'host_floppy' deprecated
 #       2.5: 'host_floppy' dropped
+#       2.6: 'luks' added
 #
 # @backing_file: #optional the name of the backing file (for copy-on-write)
 #
@@ -1639,7 +1640,7 @@
 { 'enum': 'BlockdevDriver',
   'data': [ 'archipelago', 'blkdebug', 'blkverify', 'bochs', 'cloop',
             'dmg', 'file', 'ftp', 'ftps', 'host_cdrom', 'host_device',
-            'http', 'https', 'null-aio', 'null-co', 'parallels',
+            'http', 'https', 'luks', 'null-aio', 'null-co', 'parallels',
             'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'tftp', 'vdi', 'vhdx',
             'vmdk', 'vpc', 'vvfat' ] }
 
@@ -1706,6 +1707,22 @@
   'data': { 'file': 'BlockdevRef' } }
 
 ##
+# @BlockdevOptionsLUKS
+#
+# Driver specific block device options for LUKS.
+#
+# @key-secret: #optional the ID of a QCryptoSecret object providing
+#              the decryption key (since 2.6). Mandatory except when
+#              doing a metadata-only probe of the image.
+#
+# Since: 2.6
+##
+{ 'struct': 'BlockdevOptionsLUKS',
+  'base': 'BlockdevOptionsGenericFormat',
+  'data': { '*key-secret': 'str' } }
+
+
+##
 # @BlockdevOptionsGenericCOWFormat
 #
 # Driver specific block device options for image format that have no option
@@ -2085,6 +2102,7 @@
       'http':       'BlockdevOptionsFile',
       'https':      'BlockdevOptionsFile',
 # TODO iscsi: Wait for structured options
+      'luks':       'BlockdevOptionsLUKS',
 # TODO nbd: Should take InetSocketAddress for 'host'?
 # TODO nfs: Wait for structured options
       'null-aio':   'BlockdevOptionsNull',
-- 
2.5.0