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

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

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.

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 98edb0ff44..6650c72348 100755
--- a/configure
+++ b/configure
@@ -471,6 +471,7 @@ gtk_gl="no"
 tls_priority="NORMAL"
 gnutls=""
 nettle=""
+nettle_xts="no"
 gcrypt=""
 gcrypt_hmac="no"
 gcrypt_xts="no"
@@ -2862,6 +2863,19 @@ 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
@@ -6337,6 +6351,10 @@ 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..08794a9b10 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_encrypt_native,
+                            ctx->alg_decrypt_native,
+                            ctx->iv, len, out, in);
+#endif
         break;
     case QCRYPTO_CIPHER_MODE_CTR:
         ctr_crypt(ctx->ctx, ctx->alg_encrypt_native,
-- 
2.21.0