qcow2: convert QCow2 to use QCryptoBlock for encryption

This converts the qcow2 driver to make use of the QCryptoBlock
APIs for encrypting image content, using the legacy QCow2 AES
scheme.

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,file=/home/berrange/encrypted.pw \
    -drive file=/home/berrange/encrypted.qcow2,encrypt.key-secret=sec0

The test 087 could be simplified since there is no longer a
difference in behaviour when using blockdev_add with encrypted
images for the running vs stopped CPU state.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20170623162419.26068-12-berrange@redhat.com
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 152 insertions, 74 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index df9caa8773..1c66ec120e 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -37,6 +37,9 @@
 #include "qemu/option_int.h"
 #include "qemu/cutils.h"
 #include "qemu/bswap.h"
+#include "qapi/opts-visitor.h"
+#include "qapi-visit.h"
+#include "block/crypto.h"
 
 /*
   Differences with QCOW:
@@ -461,6 +464,7 @@ static QemuOptsList qcow2_runtime_opts = {
             .type = QEMU_OPT_NUMBER,
             .help = "Clean unused cache entries after this time (in seconds)",
         },
+        BLOCK_CRYPTO_OPT_DEF_QCOW_KEY_SECRET("encrypt."),
         { /* end of list */ }
     },
 };
@@ -585,6 +589,7 @@ typedef struct Qcow2ReopenState {
     int overlap_check;
     bool discard_passthrough[QCOW2_DISCARD_MAX];
     uint64_t cache_clean_interval;
+    QCryptoBlockOpenOptions *crypto_opts; /* Disk encryption runtime options */
 } Qcow2ReopenState;
 
 static int qcow2_update_options_prepare(BlockDriverState *bs,
@@ -598,9 +603,14 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
     int overlap_check_template = 0;
     uint64_t l2_cache_size, refcount_cache_size;
     int i;
+    const char *encryptfmt;
+    QDict *encryptopts = NULL;
     Error *local_err = NULL;
     int ret;
 
+    qdict_extract_subqdict(options, &encryptopts, "encrypt.");
+    encryptfmt = qdict_get_try_str(encryptopts, "format");
+
     opts = qemu_opts_create(&qcow2_runtime_opts, NULL, 0, &error_abort);
     qemu_opts_absorb_qdict(opts, options, &local_err);
     if (local_err) {
@@ -751,8 +761,42 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
     r->discard_passthrough[QCOW2_DISCARD_OTHER] =
         qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_OTHER, false);
 
+    switch (s->crypt_method_header) {
+    case QCOW_CRYPT_NONE:
+        if (encryptfmt) {
+            error_setg(errp, "No encryption in image header, but options "
+                       "specified format '%s'", encryptfmt);
+            ret = -EINVAL;
+            goto fail;
+        }
+        break;
+
+    case QCOW_CRYPT_AES:
+        if (encryptfmt && !g_str_equal(encryptfmt, "aes")) {
+            error_setg(errp,
+                       "Header reported 'aes' encryption format but "
+                       "options specify '%s'", encryptfmt);
+            ret = -EINVAL;
+            goto fail;
+        }
+        qdict_del(encryptopts, "format");
+        r->crypto_opts = block_crypto_open_opts_init(
+            Q_CRYPTO_BLOCK_FORMAT_QCOW, encryptopts, errp);
+        break;
+
+    default:
+        error_setg(errp, "Unsupported encryption method %d",
+                   s->crypt_method_header);
+        break;
+    }
+    if (s->crypt_method_header != QCOW_CRYPT_NONE && !r->crypto_opts) {
+        ret = -EINVAL;
+        goto fail;
+    }
+
     ret = 0;
 fail:
+    QDECREF(encryptopts);
     qemu_opts_del(opts);
     opts = NULL;
     return ret;
@@ -785,6 +829,9 @@ static void qcow2_update_options_commit(BlockDriverState *bs,
         s->cache_clean_interval = r->cache_clean_interval;
         cache_clean_timer_init(bs, bdrv_get_aio_context(bs));
     }
+
+    qapi_free_QCryptoBlockOpenOptions(s->crypto_opts);
+    s->crypto_opts = r->crypto_opts;
 }
 
 static void qcow2_update_options_abort(BlockDriverState *bs,
@@ -796,6 +843,7 @@ static void qcow2_update_options_abort(BlockDriverState *bs,
     if (r->refcount_block_cache) {
         qcow2_cache_destroy(bs, r->refcount_block_cache);
     }
+    qapi_free_QCryptoBlockOpenOptions(r->crypto_opts);
 }
 
 static int qcow2_update_options(BlockDriverState *bs, QDict *options,
@@ -967,12 +1015,6 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags,
         ret = -EINVAL;
         goto fail;
     }
-    if (!qcrypto_cipher_supports(QCRYPTO_CIPHER_ALG_AES_128,
-                                 QCRYPTO_CIPHER_MODE_CBC)) {
-        error_setg(errp, "AES cipher not available");
-        ret = -EINVAL;
-        goto fail;
-    }
     s->crypt_method_header = header.crypt_method;
     if (s->crypt_method_header) {
         if (bdrv_uses_whitelist() &&
@@ -990,6 +1032,7 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags,
         }
 
         bs->encrypted = true;
+        bs->valid_key = true;
     }
 
     s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
@@ -1122,6 +1165,19 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
+    if (s->crypt_method_header == QCOW_CRYPT_AES) {
+        unsigned int cflags = 0;
+        if (flags & BDRV_O_NO_IO) {
+            cflags |= QCRYPTO_BLOCK_OPEN_NO_IO;
+        }
+        s->crypto = qcrypto_block_open(s->crypto_opts, NULL, NULL,
+                                       cflags, errp);
+        if (!s->crypto) {
+            ret = -EINVAL;
+            goto fail;
+        }
+    }
+
     /* read the backing file name */
     if (header.backing_file_offset != 0) {
         len = header.backing_file_size;
@@ -1202,6 +1258,8 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags,
     }
     g_free(s->cluster_cache);
     qemu_vfree(s->cluster_data);
+    qcrypto_block_free(s->crypto);
+    qapi_free_QCryptoBlockOpenOptions(s->crypto_opts);
     return ret;
 }
 
@@ -1229,41 +1287,6 @@ static void qcow2_refresh_limits(BlockDriverState *bs, Error **errp)
     bs->bl.pdiscard_alignment = s->cluster_size;
 }
 
-static int qcow2_set_key(BlockDriverState *bs, const char *key)
-{
-    BDRVQcow2State *s = bs->opaque;
-    uint8_t keybuf[16];
-    int len, i;
-    Error *err = NULL;
-
-    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 qcow2_reopen_prepare(BDRVReopenState *state,
                                 BlockReopenQueue *queue, Error **errp)
 {
@@ -1379,7 +1402,7 @@ static int64_t coroutine_fn qcow2_co_get_block_status(BlockDriverState *bs,
     *pnum = bytes >> BDRV_SECTOR_BITS;
 
     if (cluster_offset != 0 && ret != QCOW2_CLUSTER_COMPRESSED &&
-        !s->cipher) {
+        !s->crypto) {
         index_in_cluster = sector_num & (s->cluster_sectors - 1);
         cluster_offset |= (index_in_cluster << BDRV_SECTOR_BITS);
         *file = bs->file->bs;
@@ -1436,7 +1459,7 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
 
         /* prepare next request */
         cur_bytes = MIN(bytes, INT_MAX);
-        if (s->cipher) {
+        if (s->crypto) {
             cur_bytes = MIN(cur_bytes,
                             QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
         }
@@ -1506,7 +1529,7 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
             }
 
             if (bs->encrypted) {
-                assert(s->cipher);
+                assert(s->crypto);
 
                 /*
                  * For encrypted images, read everything into a temporary
@@ -1538,14 +1561,15 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
                 goto fail;
             }
             if (bs->encrypted) {
-                assert(s->cipher);
+                assert(s->crypto);
                 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
                 assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
                 Error *err = NULL;
-                if (qcow2_encrypt_sectors(s, offset >> BDRV_SECTOR_BITS,
+                if (qcrypto_block_decrypt(s->crypto,
+                                          offset >> BDRV_SECTOR_BITS,
                                           cluster_data,
-                                          cur_bytes >> BDRV_SECTOR_BITS,
-                                          false, &err) < 0) {
+                                          cur_bytes,
+                                          &err) < 0) {
                     error_free(err);
                     ret = -EIO;
                     goto fail;
@@ -1661,7 +1685,7 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
 
         if (bs->encrypted) {
             Error *err = NULL;
-            assert(s->cipher);
+            assert(s->crypto);
             if (!cluster_data) {
                 cluster_data = qemu_try_blockalign(bs->file->bs,
                                                    QCOW_MAX_CRYPT_CLUSTERS
@@ -1676,10 +1700,9 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
                    QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);
             qemu_iovec_to_buf(&hd_qiov, 0, cluster_data, hd_qiov.size);
 
-            if (qcow2_encrypt_sectors(s, offset >> BDRV_SECTOR_BITS,
+            if (qcrypto_block_encrypt(s->crypto, offset >> BDRV_SECTOR_BITS,
                                       cluster_data,
-                                      cur_bytes >>BDRV_SECTOR_BITS,
-                                      true, &err) < 0) {
+                                      cur_bytes, &err) < 0) {
                 error_free(err);
                 ret = -EIO;
                 goto fail;
@@ -1804,8 +1827,8 @@ static void qcow2_close(BlockDriverState *bs)
     qcow2_cache_destroy(bs, s->l2_table_cache);
     qcow2_cache_destroy(bs, s->refcount_block_cache);
 
-    qcrypto_cipher_free(s->cipher);
-    s->cipher = NULL;
+    qcrypto_block_free(s->crypto);
+    s->crypto = NULL;
 
     g_free(s->unknown_header_fields);
     cleanup_unknown_header_ext(bs);
@@ -1823,7 +1846,7 @@ static void qcow2_invalidate_cache(BlockDriverState *bs, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     int flags = s->flags;
-    QCryptoCipher *cipher = NULL;
+    QCryptoBlock *crypto = NULL;
     QDict *options;
     Error *local_err = NULL;
     int ret;
@@ -1833,8 +1856,8 @@ static void qcow2_invalidate_cache(BlockDriverState *bs, Error **errp)
      * that means we don't have to worry about reopening them here.
      */
 
-    cipher = s->cipher;
-    s->cipher = NULL;
+    crypto = s->crypto;
+    s->crypto = NULL;
 
     qcow2_close(bs);
 
@@ -1855,7 +1878,7 @@ static void qcow2_invalidate_cache(BlockDriverState *bs, Error **errp)
         return;
     }
 
-    s->cipher = cipher;
+    s->crypto = crypto;
 }
 
 static size_t header_ext_add(char *buf, uint32_t magic, const void *s,
@@ -2079,6 +2102,56 @@ static int qcow2_change_backing_file(BlockDriverState *bs,
     return qcow2_update_header(bs);
 }
 
+
+static int qcow2_set_up_encryption(BlockDriverState *bs, const char *encryptfmt,
+                                   QemuOpts *opts, Error **errp)
+{
+    BDRVQcow2State *s = bs->opaque;
+    QCryptoBlockCreateOptions *cryptoopts = NULL;
+    QCryptoBlock *crypto = NULL;
+    int ret = -EINVAL;
+    QDict *options, *encryptopts;
+
+    options = qemu_opts_to_qdict(opts, NULL);
+    qdict_extract_subqdict(options, &encryptopts, "encrypt.");
+    QDECREF(options);
+
+    if (!g_str_equal(encryptfmt, "aes")) {
+        error_setg(errp, "Unknown encryption format '%s', expected 'aes'",
+                   encryptfmt);
+        ret = -EINVAL;
+        goto out;
+    }
+    cryptoopts = block_crypto_create_opts_init(
+        Q_CRYPTO_BLOCK_FORMAT_QCOW, encryptopts, errp);
+    if (!cryptoopts) {
+        ret = -EINVAL;
+        goto out;
+    }
+    s->crypt_method_header = QCOW_CRYPT_AES;
+
+    crypto = qcrypto_block_create(cryptoopts,
+                                  NULL, NULL,
+                                  bs, errp);
+    if (!crypto) {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    ret = qcow2_update_header(bs);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not write encryption header");
+        goto out;
+    }
+
+ out:
+    QDECREF(encryptopts);
+    qcrypto_block_free(crypto);
+    qapi_free_QCryptoBlockCreateOptions(cryptoopts);
+    return ret;
+}
+
+
 static int preallocate(BlockDriverState *bs)
 {
     uint64_t bytes;
@@ -2273,17 +2346,8 @@ static int qcow2_create2(const char *filename, int64_t total_size,
         .header_length              = cpu_to_be32(sizeof(*header)),
     };
 
-    if (encryptfmt) {
-        if (!g_str_equal(encryptfmt, "aes")) {
-            error_setg(errp, "Unknown encryption format '%s', expected 'aes'",
-                       encryptfmt);
-            ret = -EINVAL;
-            goto out;
-        }
-        header->crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
-    } else {
-        header->crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
-    }
+    /* We'll update this to correct value later */
+    header->crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
 
     if (flags & BLOCK_FLAG_LAZY_REFCOUNTS) {
         header->compatible_features |=
@@ -2362,6 +2426,14 @@ static int qcow2_create2(const char *filename, int64_t total_size,
         }
     }
 
+    /* Want encryption? There you go. */
+    if (encryptfmt) {
+        ret = qcow2_set_up_encryption(blk_bs(blk), encryptfmt, opts, errp);
+        if (ret < 0) {
+            goto out;
+        }
+    }
+
     /* And if we're supposed to preallocate metadata, do that now */
     if (prealloc != PREALLOC_MODE_OFF) {
         BDRVQcow2State *s = blk_bs(blk)->opaque;
@@ -2377,11 +2449,17 @@ static int qcow2_create2(const char *filename, int64_t total_size,
     blk_unref(blk);
     blk = NULL;
 
-    /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
+    /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning.
+     * Using BDRV_O_NO_IO, since encryption is now setup we don't want to
+     * have to setup decryption context. We're not doing any I/O on the top
+     * level BlockDriverState, only lower layers, where BDRV_O_NO_IO does
+     * not have effect.
+     */
     options = qdict_new();
     qdict_put_str(options, "driver", "qcow2");
     blk = blk_new_open(filename, NULL, options,
-                       BDRV_O_RDWR | BDRV_O_NO_BACKING, &local_err);
+                       BDRV_O_RDWR | BDRV_O_NO_BACKING | BDRV_O_NO_IO,
+                       &local_err);
     if (blk == NULL) {
         error_propagate(errp, local_err);
         ret = -EIO;
@@ -3226,9 +3304,9 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
             backing_format = qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT);
         } else if (!strcmp(desc->name, BLOCK_OPT_ENCRYPT)) {
             encrypt = qemu_opt_get_bool(opts, BLOCK_OPT_ENCRYPT,
-                                        !!s->cipher);
+                                        !!s->crypto);
 
-            if (encrypt != !!s->cipher) {
+            if (encrypt != !!s->crypto) {
                 error_report("Changing the encryption flag is not supported");
                 return -ENOTSUP;
             }
@@ -3454,6 +3532,7 @@ static QemuOptsList qcow2_create_opts = {
             .type = QEMU_OPT_STRING,
             .help = "Encrypt the image, format choices: 'aes'",
         },
+        BLOCK_CRYPTO_OPT_DEF_QCOW_KEY_SECRET("encrypt."),
         {
             .name = BLOCK_OPT_CLUSTER_SIZE,
             .type = QEMU_OPT_SIZE,
@@ -3496,7 +3575,6 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_create        = qcow2_create,
     .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_get_block_status = qcow2_co_get_block_status,
-    .bdrv_set_key       = qcow2_set_key,
 
     .bdrv_co_preadv         = qcow2_co_preadv,
     .bdrv_co_pwritev        = qcow2_co_pwritev,