Re: [Qemu-block] [PATCH 05/10] block/crypto: implement the encryption key management

[Daniel P . Berrangé]

On Fri, Aug 30, 2019 at 11:56:03PM +0300, Maxim Levitsky wrote:
> This implements the encryption key management
> using the generic code in qcrypto layer
> (currently only for qemu-img amend)
> 
> This code adds another 'write_func' because the initialization
> write_func works directly on the underlying file,
> because during the creation, there is no open instance
> of the luks driver, but during regular use, we have it,
> and should use it instead.
> 
> Signed-off-by: Maxim Levitsky <address@hidden>
> ---
>  block/crypto.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 103 insertions(+), 3 deletions(-)
> 
> diff --git a/block/crypto.c b/block/crypto.c
> index a6a3e1f1d8..dbd95a99ba 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -36,6 +36,7 @@ typedef struct BlockCrypto BlockCrypto;
>  
>  struct BlockCrypto {
>      QCryptoBlock *block;
> +    bool updating_keys;
>  };
>  
>  
> @@ -70,6 +71,24 @@ static ssize_t block_crypto_read_func(QCryptoBlock *block,
>      return ret;
>  }
>  
> +static ssize_t block_crypto_write_func(QCryptoBlock *block,
> +                                      size_t offset,
> +                                      const uint8_t *buf,
> +                                      size_t buflen,
> +                                      void *opaque,
> +                                      Error **errp)

Indent off-by-1 - align with param on the first line

> +{
> +    BlockDriverState *bs = opaque;
> +    ssize_t ret;
> +
> +    ret = bdrv_pwrite(bs->file, offset, buf, buflen);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret, "Could not write encryption header");
> +        return ret;
> +    }
> +    return ret;
> +}
> +
>  
>  struct BlockCryptoCreateData {
>      BlockBackend *blk;
> @@ -647,6 +666,88 @@ block_crypto_get_specific_info_luks(BlockDriverState 
> *bs, Error **errp)
>      return spec_info;
>  }
>  
> +
> +static int
> +block_crypto_amend_options(BlockDriverState *bs,
> +                           QemuOpts *opts,
> +                           BlockDriverAmendStatusCB *status_cb,
> +                           void *cb_opaque,
> +                           bool force,
> +                           Error **errp)
> +{
> +    BlockCrypto *crypto = bs->opaque;
> +    QDict *cryptoopts = NULL;
> +    QCryptoBlockCreateOptions *amend_options = NULL;
> +    int ret;
> +
> +    assert(crypto);
> +    assert(crypto->block);
> +
> +    crypto->updating_keys = true;
> +
> +    ret = bdrv_child_refresh_perms(bs, bs->file, errp);
> +    if (ret) {

I can;'t remember - does this need to be "ret < 0" or
does refresh_perms return positive errnos ?

> +        goto cleanup;
> +    }
> +
> +    cryptoopts = qemu_opts_to_qdict_filtered(opts, NULL,
> +                                             &block_crypto_create_opts_luks,
> +                                             true);
> +
> +    qdict_put_str(cryptoopts, "format", "luks");
> +    amend_options = block_crypto_create_opts_init(cryptoopts, errp);
> +    if (!amend_options) {
> +        ret = -EINVAL;
> +        goto cleanup;
> +    }
> +
> +    ret = qcrypto_block_amend_options(crypto->block,
> +                                      block_crypto_read_func,
> +                                      block_crypto_write_func,
> +                                      bs,
> +                                      amend_options,
> +                                      force,
> +                                      errp);
> +cleanup:
> +    crypto->updating_keys = false;
> +    bdrv_child_refresh_perms(bs, bs->file, errp);
> +    qapi_free_QCryptoBlockCreateOptions(amend_options);
> +    qobject_unref(cryptoopts);
> +    return ret;
> +}
> +
> +
> +static void
> +block_crypto_child_perms(BlockDriverState *bs, BdrvChild *c,
> +                         const BdrvChildRole *role,
> +                         BlockReopenQueue *reopen_queue,
> +                         uint64_t perm, uint64_t shared,
> +                         uint64_t *nperm, uint64_t *nshared)
> +{
> +
> +    BlockCrypto *crypto = bs->opaque;
> +
> +    /*
> +     * This driver doesn't modify LUKS metadata except
> +     * when updating the encryption slots.
> +     * Allow share-rw=on as a special case.
> +     *
> +     * Encryption update will set the crypto->updating_keys
> +     * during that period and refresh permissions
> +     *
> +     * */
> +
> +    if (crypto->updating_keys) {
> +        /*need exclusive write access for header update  */
> +        perm |= BLK_PERM_WRITE;
> +        shared &= ~BLK_PERM_WRITE;
> +    }
> +
> +    bdrv_filter_default_perms(bs, c, role, reopen_queue,
> +            perm, shared, nperm, nshared);
> +}
> +
> +
>  static const char *const block_crypto_strong_runtime_opts[] = {
>      BLOCK_CRYPTO_OPT_LUKS_KEY_SECRET,
>  
> @@ -659,9 +760,7 @@ static BlockDriver bdrv_crypto_luks = {
>      .bdrv_probe         = block_crypto_probe_luks,
>      .bdrv_open          = block_crypto_open_luks,
>      .bdrv_close         = block_crypto_close,
> -    /* This driver doesn't modify LUKS metadata except when creating image.
> -     * Allow share-rw=on as a special case. */
> -    .bdrv_child_perm    = bdrv_filter_default_perms,
> +    .bdrv_child_perm    = block_crypto_child_perms,
>      .bdrv_co_create     = block_crypto_co_create_luks,
>      .bdrv_co_create_opts = block_crypto_co_create_opts_luks,
>      .bdrv_co_truncate   = block_crypto_co_truncate,
> @@ -674,6 +773,7 @@ static BlockDriver bdrv_crypto_luks = {
>      .bdrv_getlength     = block_crypto_getlength,
>      .bdrv_get_info      = block_crypto_get_info_luks,
>      .bdrv_get_specific_info = block_crypto_get_specific_info_luks,
> +    .bdrv_amend_options = block_crypto_amend_options,
>  
>      .strong_runtime_opts = block_crypto_strong_runtime_opts,
>  };
> -- 
> 2.17.2
> 

Regards,
Daniel
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