[Qemu-devel] [PATCH v2 14/17] qcow: convert QCow to use QCryptoBlock for encryption

["Daniel P. Berrange" <berrange@redhat.com>]

This converts the qcow2 driver to make use of the QCryptoBlock
APIs for encrypting image content. This is only wired up to
permit use of the legacy QCow encryption format. Users who wish
to have the strong LUKS format should switch to qcow2 instead.

With this change it is now required to use the QCryptoSecret
object for providing passwords, instead of the current block
password APIs / interactive prompting.

  $QEMU \
    -object secret,id=sec0,filename=/home/berrange/encrypted.pw \
    -drive file=/home/berrange/encrypted.qcow,key-secret=sec0

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 block/qcow.c         | 173 +++++++++++++++++++++++----------------------------
 qapi/block-core.json |  17 ++++-
 2 files changed, 93 insertions(+), 97 deletions(-)

diff --git a/block/qcow.c b/block/qcow.c
index 5a4f310..3b7c2b9 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -26,7 +26,9 @@
 #include "qemu/module.h"
 #include <zlib.h>
 #include "qapi/qmp/qerror.h"
-#include "crypto/cipher.h"
+#include "crypto/block.h"
+#include "qapi/opts-visitor.h"
+#include "qapi-visit.h"
 #include "migration/migration.h"
 
 /**************************************************************/
@@ -40,6 +42,8 @@
 
 #define QCOW_OFLAG_COMPRESSED (1LL << 63)
 
+#define QCOW_OPT_KEY_SECRET "key-secret"
+
 typedef struct QCowHeader {
     uint32_t magic;
     uint32_t version;
@@ -72,7 +76,7 @@ typedef struct BDRVQcowState {
     uint8_t *cluster_cache;
     uint8_t *cluster_data;
     uint64_t cluster_cache_offset;
-    QCryptoCipher *cipher; /* NULL if no key yet */
+    QCryptoBlock *crypto; /* Disk encryption format driver */
     uint32_t crypt_method_header;
     CoMutex lock;
     Error *migration_blocker;
@@ -92,6 +96,19 @@ static int qcow_probe(const uint8_t *buf, int buf_size, const char *filename)
         return 0;
 }
 
+static QemuOptsList qcow_runtime_opts = {
+    .name = "qcow",
+    .head = QTAILQ_HEAD_INITIALIZER(qcow_runtime_opts.head),
+    .desc = {
+        {
+            .name = QCOW_OPT_KEY_SECRET,
+            .type = QEMU_OPT_STRING,
+            .help = "ID of the secret that provides the encryption key",
+        },
+        { /* end of list */ }
+    },
+};
+
 static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp)
 {
@@ -99,6 +116,11 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
     unsigned int len, i, shift;
     int ret;
     QCowHeader header;
+    QemuOpts *opts = NULL;
+    Error *local_err = NULL;
+    QCryptoBlockOpenOptions *crypto_opts = NULL;
+    unsigned int cflags = 0;
+    OptsVisitor *ov;
 
     ret = bdrv_pread(bs->file->bs, 0, &header, sizeof(header));
     if (ret < 0) {
@@ -147,19 +169,50 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
-    if (header.crypt_method > QCOW_CRYPT_AES) {
-        error_setg(errp, "invalid encryption method in qcow header");
-        ret = -EINVAL;
-        goto fail;
-    }
-    if (!qcrypto_cipher_supports(QCRYPTO_CIPHER_ALG_AES_128)) {
-        error_setg(errp, "AES cipher not available");
+    opts = qemu_opts_create(&qcow_runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
         ret = -EINVAL;
         goto fail;
     }
+
     s->crypt_method_header = header.crypt_method;
     if (s->crypt_method_header) {
+        if (s->crypt_method_header == QCOW_CRYPT_AES) {
+            ov = opts_visitor_new(opts);
+
+            crypto_opts = g_new0(QCryptoBlockOpenOptions, 1);
+            crypto_opts->format = Q_CRYPTO_BLOCK_FORMAT_QCOW;
+            crypto_opts->u.qcow = g_new0(QCryptoBlockOptionsQCow, 1);
+            visit_type_QCryptoBlockOptionsQCow(opts_get_visitor(ov),
+                                               &crypto_opts->u.qcow,
+                                               "qcow", &local_err);
+            if (local_err) {
+                error_propagate(errp, local_err);
+                opts_visitor_cleanup(ov);
+                ret = -EINVAL;
+                goto fail;
+            }
+            opts_visitor_cleanup(ov);
+
+            if (flags & BDRV_O_NO_IO) {
+                cflags |= QCRYPTO_BLOCK_OPEN_NO_IO;
+            }
+            s->crypto = qcrypto_block_open(crypto_opts, NULL, NULL,
+                                           cflags, errp);
+            if (!s->crypto) {
+                error_setg(errp, "Could not setup encryption layer");
+                ret = -EINVAL;
+                goto fail;
+            }
+        } else {
+            error_setg(errp, "invalid encryption method in qcow header");
+            ret = -EINVAL;
+            goto fail;
+        }
         bs->encrypted = 1;
+        bs->valid_key = 1;
     }
     s->cluster_bits = header.cluster_bits;
     s->cluster_size = 1 << s->cluster_bits;
@@ -238,6 +291,7 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
                bdrv_get_device_or_node_name(bs));
     migrate_add_blocker(s->migration_blocker);
 
+    qapi_free_QCryptoBlockOpenOptions(crypto_opts);
     qemu_co_mutex_init(&s->lock);
     return 0;
 
@@ -246,6 +300,7 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
     qemu_vfree(s->l2_cache);
     g_free(s->cluster_cache);
     g_free(s->cluster_data);
+    qapi_free_QCryptoBlockOpenOptions(crypto_opts);
     return ret;
 }
 
@@ -258,79 +313,6 @@ static int qcow_reopen_prepare(BDRVReopenState *state,
     return 0;
 }
 
-static int qcow_set_key(BlockDriverState *bs, const char *key)
-{
-    BDRVQcowState *s = bs->opaque;
-    uint8_t keybuf[16];
-    int len, i;
-    Error *err;
-
-    memset(keybuf, 0, 16);
-    len = strlen(key);
-    if (len > 16)
-        len = 16;
-    /* XXX: we could compress the chars to 7 bits to increase
-       entropy */
-    for(i = 0;i < len;i++) {
-        keybuf[i] = key[i];
-    }
-    assert(bs->encrypted);
-
-    qcrypto_cipher_free(s->cipher);
-    s->cipher = qcrypto_cipher_new(
-        QCRYPTO_CIPHER_ALG_AES_128,
-        QCRYPTO_CIPHER_MODE_CBC,
-        keybuf, G_N_ELEMENTS(keybuf),
-        &err);
-
-    if (!s->cipher) {
-        /* XXX would be nice if errors in this method could
-         * be properly propagate to the caller. Would need
-         * the bdrv_set_key() API signature to be fixed. */
-        error_free(err);
-        return -1;
-    }
-    return 0;
-}
-
-static int encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
-                           uint8_t *buf, int nb_sectors, bool enc,
-                           Error **errp)
-{
-    union {
-        uint64_t ll[2];
-        uint8_t b[16];
-    } ivec;
-    int i;
-    int ret;
-
-    for(i = 0; i < nb_sectors; i++) {
-        ivec.ll[0] = cpu_to_le64(sector_num);
-        ivec.ll[1] = 0;
-        if (qcrypto_cipher_setiv(s->cipher,
-                                 ivec.b, G_N_ELEMENTS(ivec.b),
-                                 errp) < 0) {
-            return -1;
-        }
-        if (enc) {
-            ret = qcrypto_cipher_encrypt(s->cipher,
-                                         buf, buf,
-                                         512,
-                                         errp);
-        } else {
-            ret = qcrypto_cipher_decrypt(s->cipher,
-                                         buf, buf,
-                                         512,
-                                         errp);
-        }
-        if (ret < 0) {
-            return -1;
-        }
-        sector_num++;
-        buf += 512;
-    }
-    return 0;
-}
 
 /* 'allocate' is:
  *
@@ -445,15 +427,15 @@ static uint64_t get_cluster_offset(BlockDriverState *bs,
                 if (bs->encrypted &&
                     (n_end - n_start) < s->cluster_sectors) {
                     uint64_t start_sect;
-                    assert(s->cipher);
+                    assert(s->crypto);
                     start_sect = (offset & ~(s->cluster_size - 1)) >> 9;
                     memset(s->cluster_data, 0x00, 512);
                     for(i = 0; i < s->cluster_sectors; i++) {
                         if (i < n_start || i >= n_end) {
                             Error *err = NULL;
-                            if (encrypt_sectors(s, start_sect + i,
-                                                s->cluster_data, 1,
-                                                true, &err) < 0) {
+                            if (qcrypto_block_encrypt(s->crypto, start_sect + i,
+                                                      s->cluster_data, 1,
+                                                      &err) < 0) {
                                 error_free(err);
                                 errno = EIO;
                                 return -1;
@@ -498,7 +480,7 @@ static int64_t coroutine_fn qcow_co_get_block_status(BlockDriverState *bs,
     if (!cluster_offset) {
         return 0;
     }
-    if ((cluster_offset & QCOW_OFLAG_COMPRESSED) || s->cipher) {
+    if ((cluster_offset & QCOW_OFLAG_COMPRESSED) || s->crypto) {
         return BDRV_BLOCK_DATA;
     }
     cluster_offset |= (index_in_cluster << BDRV_SECTOR_BITS);
@@ -629,9 +611,9 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
                 break;
             }
             if (bs->encrypted) {
-                assert(s->cipher);
-                if (encrypt_sectors(s, sector_num, buf,
-                                    n, false, &err) < 0) {
+                assert(s->crypto);
+                if (qcrypto_block_decrypt(s->crypto, sector_num, buf,
+                                          n, &err) < 0) {
                     goto fail;
                 }
             }
@@ -703,12 +685,12 @@ static coroutine_fn int qcow_co_writev(BlockDriverState *bs, int64_t sector_num,
         }
         if (bs->encrypted) {
             Error *err = NULL;
-            assert(s->cipher);
+            assert(s->crypto);
             if (!cluster_data) {
                 cluster_data = g_malloc0(s->cluster_size);
             }
-            if (encrypt_sectors(s, sector_num, buf,
-                                n, true, &err) < 0) {
+            if (qcrypto_block_encrypt(s->crypto, sector_num, buf,
+                                      n, &err) < 0) {
                 error_free(err);
                 ret = -EIO;
                 break;
@@ -746,8 +728,8 @@ static void qcow_close(BlockDriverState *bs)
 {
     BDRVQcowState *s = bs->opaque;
 
-    qcrypto_cipher_free(s->cipher);
-    s->cipher = NULL;
+    qcrypto_block_free(s->crypto);
+    s->crypto = NULL;
     g_free(s->l1_table);
     qemu_vfree(s->l2_cache);
     g_free(s->cluster_cache);
@@ -1012,7 +994,6 @@ static BlockDriver bdrv_qcow = {
     .bdrv_co_writev         = qcow_co_writev,
     .bdrv_co_get_block_status   = qcow_co_get_block_status,
 
-    .bdrv_set_key           = qcow_set_key,
     .bdrv_make_empty        = qcow_make_empty,
     .bdrv_write_compressed  = qcow_write_compressed,
     .bdrv_get_info          = qcow_get_info,
diff --git a/qapi/block-core.json b/qapi/block-core.json
index b704dd7..e0d423f 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1756,6 +1756,21 @@
             'mode':  'Qcow2OverlapCheckMode' } }
 
 ##
+# @BlockdevOptionsQcow
+#
+# Driver specific block device options for qcow.
+#
+# @key-secret:   #optional ID of the "secret" object providing the
+#                AES decryption key.
+#
+# Since: 2.6
+##
+{ 'struct': 'BlockdevOptionsQcow',
+  'base': 'BlockdevOptionsGenericCOWFormat',
+  'data': { '*key-secret': 'str' } }
+
+
+##
 # @BlockdevOptionsQcow2
 #
 # Driver specific block device options for qcow2.
@@ -2024,7 +2039,7 @@
       'null-co':    'BlockdevOptionsNull',
       'parallels':  'BlockdevOptionsGenericFormat',
       'qcow2':      'BlockdevOptionsQcow2',
-      'qcow':       'BlockdevOptionsGenericCOWFormat',
+      'qcow':       'BlockdevOptionsQcow',
       'qed':        'BlockdevOptionsGenericCOWFormat',
       'quorum':     'BlockdevOptionsQuorum',
       'raw':        'BlockdevOptionsGenericFormat',
-- 
2.5.0