crypto: fix build with nettle >= 3.0.0

In nettle 3, cbc_encrypt() accepts 'nettle_cipher_func' instead of
'nettle_crypt_func' and these two differ in 'const' qualifier of the
first argument.  The build fails with:

  In file included from crypto/cipher.c:71:0:
  ./crypto/cipher-nettle.c: In function ‘qcrypto_cipher_encrypt’:
  ./crypto/cipher-nettle.c:154:38: error: passing argument 2 of
  ‘nettle_cbc_encrypt’ from incompatible pointer type
           cbc_encrypt(ctx->ctx_encrypt, ctx->alg_encrypt,
                                               ^
  In file included from ./crypto/cipher-nettle.c:24:0,
                   from crypto/cipher.c:71:
  /usr/include/nettle/cbc.h:48:1: note: expected
  ‘void (*)(const void *, size_t, uint8_t *, const uint8_t *)
  but argument is of type
  ‘void (*)(      void *, size_t, uint8_t *, const uint8_t *)

To allow both versions, we switch to the new definition and #if typedef
it for old versions.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Message-Id: <1436548682-9315-2-git-send-email-rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -2183,6 +2183,7 @@ if test "$gnutls_nettle" != "no"; then
     if $pkg_config --exists "nettle"; then
         nettle_cflags=`$pkg_config --cflags nettle`
         nettle_libs=`$pkg_config --libs nettle`
+        nettle_version=`$pkg_config --modversion nettle`
         libs_softmmu="$nettle_libs $libs_softmmu"
         libs_tools="$nettle_libs $libs_tools"
         QEMU_CFLAGS="$QEMU_CFLAGS $nettle_cflags"
@@ -4490,7 +4491,7 @@ echo "GTK support       $gtk"
 echo "GNUTLS support    $gnutls"
 echo "GNUTLS hash       $gnutls_hash"
 echo "GNUTLS gcrypt     $gnutls_gcrypt"
-echo "GNUTLS nettle     $gnutls_nettle"
+echo "GNUTLS nettle     $gnutls_nettle ${gnutls_nettle+($nettle_version)}"
 echo "VTE support       $vte"
 echo "curses support    $curses"
 echo "curl support      $curl"
@@ -4858,6 +4859,7 @@ if test "$gnutls_gcrypt" = "yes" ; then
 fi
 if test "$gnutls_nettle" = "yes" ; then
   echo "CONFIG_GNUTLS_NETTLE=y" >> $config_host_mak
+  echo "CONFIG_NETTLE_VERSION_MAJOR=${nettle_version%%.*}" >> $config_host_mak
 fi
 if test "$vte" = "yes" ; then
   echo "CONFIG_VTE=y" >> $config_host_mak

crypto/cipher-nettle.c

@@ -23,12 +23,16 @@
 #include <nettle/des.h>
 #include <nettle/cbc.h>
 
+#if CONFIG_NETTLE_VERSION_MAJOR < 3
+typedef nettle_crypt_func nettle_cipher_func;
+#endif
+
 typedef struct QCryptoCipherNettle QCryptoCipherNettle;
 struct QCryptoCipherNettle {
     void *ctx_encrypt;
     void *ctx_decrypt;
-    nettle_crypt_func *alg_encrypt;
+    nettle_cipher_func *alg_encrypt;
-    nettle_crypt_func *alg_decrypt;
+    nettle_cipher_func *alg_decrypt;
     uint8_t *iv;
     size_t niv;
 };
@@ -83,8 +87,8 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
         des_set_key(ctx->ctx_encrypt, rfbkey);
         g_free(rfbkey);
 
-        ctx->alg_encrypt = (nettle_crypt_func *)des_encrypt;
+        ctx->alg_encrypt = (nettle_cipher_func *)des_encrypt;
-        ctx->alg_decrypt = (nettle_crypt_func *)des_decrypt;
+        ctx->alg_decrypt = (nettle_cipher_func *)des_decrypt;
 
         ctx->niv = DES_BLOCK_SIZE;
         break;
@@ -98,8 +102,8 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
         aes_set_encrypt_key(ctx->ctx_encrypt, nkey, key);
         aes_set_decrypt_key(ctx->ctx_decrypt, nkey, key);
 
-        ctx->alg_encrypt = (nettle_crypt_func *)aes_encrypt;
+        ctx->alg_encrypt = (nettle_cipher_func *)aes_encrypt;
-        ctx->alg_decrypt = (nettle_crypt_func *)aes_decrypt;
+        ctx->alg_decrypt = (nettle_cipher_func *)aes_decrypt;
 
         ctx->niv = AES_BLOCK_SIZE;
         break;