Re: [PULL 4/4] crypto: add support for nettle's native XTS impl

["Alex Bennée" <alex.bennee@linaro.org>]

Daniel P. Berrangé <berrange@redhat.com> writes:

> Nettle 3.5.0 will add support for the XTS mode. Use this because long
> term we wish to delete QEMU's XTS impl to avoid carrying private crypto
> algorithm impls.
>
> Unfortunately this degrades nettle performance from 612 MB/s to 568 MB/s
> as nettle's XTS impl isn't so well optimized yet.

Unfortunately this has broken some of the Travis tests, specifically:

  # QEMU configure log Wed 30 Oct 14:16:57 GMT 2019
  # Configured with: '../../configure' '--disable-tools' '--disable-docs' '--static' '--disable-system'

> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  configure              | 18 ++++++++++++++++++
>  crypto/cipher-nettle.c | 18 ++++++++++++++++++
>  2 files changed, 36 insertions(+)
>
> diff --git a/configure b/configure
> index d1e9e457ce..452c2dfe4e 100755
> --- a/configure
> +++ b/configure
> @@ -472,6 +472,7 @@ gtk_gl="no"
>  tls_priority="NORMAL"
>  gnutls=""
>  nettle=""
> +nettle_xts="no"
>  gcrypt=""
>  gcrypt_hmac="no"
>  gcrypt_xts="no"
> @@ -2871,6 +2872,19 @@ if test "$nettle" != "no"; then
>              pass="yes"
>          fi
>      fi
> +    if test "$pass" = "yes"
> +    then
> +        cat > $TMPC << EOF
> +#include <nettle/xts.h>
> +int main(void) {
> +  return 0;
> +}
> +EOF
> +        if compile_prog "$nettle_cflags" "$nettle_libs" ; then
> +            nettle_xts=yes
> +            qemu_private_xts=no
> +        fi
> +    fi
>      if test "$pass" = "no" && test "$nettle" = "yes"; then
>          feature_not_found "nettle" "Install nettle devel >= 2.7.1"
>      else
> @@ -6346,6 +6360,10 @@ then
>     echo "  XTS             $gcrypt_xts"
>  fi
>  echo "nettle            $nettle $(echo_version $nettle $nettle_version)"
> +if test "$nettle" = "yes"
> +then
> +   echo "  XTS             $nettle_xts"
> +fi
>  echo "libtasn1          $tasn1"
>  echo "PAM               $auth_pam"
>  echo "iconv support     $iconv"
> diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c
> index d7411bb8ff..7e9a4cc199 100644
> --- a/crypto/cipher-nettle.c
> +++ b/crypto/cipher-nettle.c
> @@ -19,7 +19,9 @@
>   */
>
>  #include "qemu/osdep.h"
> +#ifdef CONFIG_QEMU_PRIVATE_XTS
>  #include "crypto/xts.h"
> +#endif
>  #include "cipherpriv.h"
>
>  #include <nettle/nettle-types.h>
> @@ -30,6 +32,9 @@
>  #include <nettle/serpent.h>
>  #include <nettle/twofish.h>
>  #include <nettle/ctr.h>
> +#ifndef CONFIG_QEMU_PRIVATE_XTS
> +#include <nettle/xts.h>
> +#endif
>
>  typedef void (*QCryptoCipherNettleFuncWrapper)(const void *ctx,
>                                                 size_t length,
> @@ -626,9 +631,15 @@ qcrypto_nettle_cipher_encrypt(QCryptoCipher *cipher,
>          break;
>
>      case QCRYPTO_CIPHER_MODE_XTS:
> +#ifdef CONFIG_QEMU_PRIVATE_XTS
>          xts_encrypt(ctx->ctx, ctx->ctx_tweak,
>                      ctx->alg_encrypt_wrapper, ctx->alg_encrypt_wrapper,
>                      ctx->iv, len, out, in);
> +#else
> +        xts_encrypt_message(ctx->ctx, ctx->ctx_tweak,
> +                            ctx->alg_encrypt_native,
> +                            ctx->iv, len, out, in);
> +#endif
>          break;
>
>      case QCRYPTO_CIPHER_MODE_CTR:
> @@ -673,9 +684,16 @@ qcrypto_nettle_cipher_decrypt(QCryptoCipher *cipher,
>          break;
>
>      case QCRYPTO_CIPHER_MODE_XTS:
> +#ifdef CONFIG_QEMU_PRIVATE_XTS
>          xts_decrypt(ctx->ctx, ctx->ctx_tweak,
>                      ctx->alg_encrypt_wrapper, ctx->alg_decrypt_wrapper,
>                      ctx->iv, len, out, in);
> +#else
> +        xts_decrypt_message(ctx->ctx, ctx->ctx_tweak,
> +                            ctx->alg_decrypt_native,
> +                            ctx->alg_encrypt_native,
> +                            ctx->iv, len, out, in);
> +#endif
>          break;
>      case QCRYPTO_CIPHER_MODE_CTR:
>          ctr_crypt(ctx->ctx, ctx->alg_encrypt_native,


--
Alex Bennée