diff --git a/cmac_nettle.c b/cmac_nettle.c
new file mode 100644
index 0000000..46aadce
--- /dev/null
+++ b/cmac_nettle.c
@@ -0,0 +1,115 @@
+/*
+  chronyd/chronyc - Programs for keeping computer clocks accurate.
+
+ **********************************************************************
+ * Copyright (C) Miroslav Lichvar  2019
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ * 
+ **********************************************************************
+
+  =======================================================================
+
+  Support for AES128 and AES256 CMAC in Nettle.
+
+  */
+
+#include "config.h"
+
+#include "sysincl.h"
+
+#include <nettle/cmac.h>
+
+#include "cmac.h"
+#include "memory.h"
+
+struct CMC_Instance_Record {
+  int key_length;
+  union {
+    struct cmac_aes128_ctx aes128;
+    struct cmac_aes256_ctx aes256;
+  } context;
+};
+
+/* ================================================== */
+
+unsigned int
+CMC_GetKeyLength(const char *cipher)
+{
+  if (strcmp(cipher, "AES128") == 0)
+    return AES128_KEY_SIZE;
+  else if (strcmp(cipher, "AES256") == 0)
+    return AES256_KEY_SIZE;
+  return 0;
+}
+
+/* ================================================== */
+
+CMC_Instance
+CMC_CreateInstance(const char *cipher, const unsigned char *key, unsigned int length)
+{
+  CMC_Instance inst;
+
+  if (length == 0 || length != CMC_GetKeyLength(cipher))
+    return NULL;
+
+  inst = MallocNew(struct CMC_Instance_Record);
+  inst->key_length = length;
+
+  switch (length) {
+    case AES128_KEY_SIZE:
+      cmac_aes128_set_key(&inst->context.aes128, key);
+      break;
+    case AES256_KEY_SIZE:
+      cmac_aes256_set_key(&inst->context.aes256, key);
+      break;
+    default:
+      assert(0);
+  }
+
+  return inst;
+}
+
+/* ================================================== */
+
+unsigned int
+CMC_Hash(CMC_Instance inst, const unsigned char *in, unsigned int in_len,
+         unsigned char *out, unsigned int out_len)
+{
+  if (out_len > CMAC128_DIGEST_SIZE)
+    out_len = CMAC128_DIGEST_SIZE;
+
+  switch (inst->key_length) {
+    case AES128_KEY_SIZE:
+      cmac_aes128_update(&inst->context.aes128, in_len, in);
+      cmac_aes128_digest(&inst->context.aes128, out_len, out);
+      break;
+    case AES256_KEY_SIZE:
+      cmac_aes256_update(&inst->context.aes256, in_len, in);
+      cmac_aes256_digest(&inst->context.aes256, out_len, out);
+      break;
+    default:
+      assert(0);
+  }
+
+  return out_len;
+}
+
+/* ================================================== */
+
+void
+CMC_DestroyInstance(CMC_Instance inst)
+{
+  Free(inst);
+}
diff --git a/configure b/configure
index 93a7ce5..8dbbc93 100755
--- a/configure
+++ b/configure
@@ -880,6 +880,13 @@ if [ $feat_sechash = "1" ] && [ "x$HASH_LINK" = "x" ]  && [ $try_nettle = "1" ];
     HASH_LINK="$test_link"
     MYCPPFLAGS="$MYCPPFLAGS $test_cflags"
     add_def FEAT_SECHASH
+
+    if test_code 'CMAC in nettle' 'nettle/cmac.h' "$test_cflags" "$test_link" \
+      'cmac128_update(NULL, NULL, NULL, 0, NULL);'
+    then
+      add_def HAVE_CMAC
+      EXTRA_OBJECTS="$EXTRA_OBJECTS cmac_nettle.o"
+    fi
   fi
 fi