siv: add support for AES-128-GCM-SIV in Nettle

This is a newer nonce misuse-resistant cipher specified in RFC 8452,
which is now supported in the development code of the Nettle library.

The advantages over AES-SIV-CMAC-256 are shorter keys and better
performance.

configure

@@ -979,15 +979,22 @@ if [ $feat_ntp = "1" ] && [ $feat_nts = "1" ] && [ $try_gnutls = "1" ]; then
         gnutls_priority_init2((void *)1, "", NULL, GNUTLS_PRIORITY_INIT_DEF_APPEND) +
         gnutls_prf_rfc5705((void *)1, 0, "", 0, "", 16, (void *)2);'
   then
-    if test_code 'SIV in nettle' \
+    if test_code 'AES-SIV-CMAC in nettle' \
       'nettle/siv-cmac.h' "" "$LIBS" \
       'siv_cmac_aes128_set_key((void *)1, (void *)2);'
     then
       EXTRA_OBJECTS="$EXTRA_OBJECTS siv_nettle.o"
       add_def HAVE_SIV
       add_def HAVE_NETTLE_SIV_CMAC
+      if test_code 'AES-GCM-SIV in nettle' \
+        'nettle/siv-gcm.h' "" "$LIBS" \
+        'siv_gcm_aes128_encrypt_message((void *)1, 0, NULL, 0, (void *)2, 16, (void *)3,
+                                        (void *)4);'
+      then
+        add_def HAVE_NETTLE_SIV_GCM
+      fi
     else
-      if test_code 'SIV in gnutls' 'gnutls/crypto.h' \
+      if test_code 'AES-SIV-CMAC in gnutls' 'gnutls/crypto.h' \
         "$test_cflags" "$test_link $LIBS" '
           return gnutls_aead_cipher_init((void *)1, GNUTLS_CIPHER_AES_128_SIV, (void *)2);'
       then

siv_nettle.c

@@ -34,12 +34,25 @@
 #include "siv_nettle_int.c"
 #endif
 
+#ifdef HAVE_NETTLE_SIV_GCM
+#include <nettle/siv-gcm.h>
+#endif
+
 #include "memory.h"
 #include "siv.h"
 
 struct SIV_Instance_Record {
-  struct siv_cmac_aes128_ctx siv;
+  SIV_Algorithm algorithm;
   int key_set;
+  int min_nonce_length;
+  int max_nonce_length;
+  int tag_length;
+  union {
+    struct siv_cmac_aes128_ctx cmac_aes128;
+#ifdef HAVE_NETTLE_SIV_GCM
+    struct aes128_ctx aes128;
+#endif
+  } ctx;
 };
 
 /* ================================================== */
@@ -49,12 +62,30 @@ SIV_CreateInstance(SIV_Algorithm algorithm)
 {
   SIV_Instance instance;
 
-  if (algorithm != AEAD_AES_SIV_CMAC_256)
+  if (SIV_GetKeyLength(algorithm) <= 0)
     return NULL;
 
   instance = MallocNew(struct SIV_Instance_Record);
+  instance->algorithm = algorithm;
   instance->key_set = 0;
 
+  switch (algorithm) {
+    case AEAD_AES_SIV_CMAC_256:
+      instance->min_nonce_length = SIV_MIN_NONCE_SIZE;
+      instance->max_nonce_length = INT_MAX;
+      instance->tag_length = SIV_DIGEST_SIZE;
+      break;
+#ifdef HAVE_NETTLE_SIV_GCM
+    case AEAD_AES_128_GCM_SIV:
+      instance->min_nonce_length = SIV_GCM_NONCE_SIZE;
+      instance->max_nonce_length = SIV_GCM_NONCE_SIZE;
+      instance->tag_length = SIV_GCM_DIGEST_SIZE;
+      break;
+#endif
+    default:
+      assert(0);
+  }
+
   return instance;
 }
 
@@ -71,11 +102,18 @@ SIV_DestroyInstance(SIV_Instance instance)
 int
 SIV_GetKeyLength(SIV_Algorithm algorithm)
 {
-  assert(32 <= SIV_MAX_KEY_LENGTH);
+  assert(2 * AES128_KEY_SIZE <= SIV_MAX_KEY_LENGTH);
 
-  if (algorithm == AEAD_AES_SIV_CMAC_256)
+  switch (algorithm) {
-    return 32;
+    case AEAD_AES_SIV_CMAC_256:
+      return 2 * AES128_KEY_SIZE;
+#ifdef HAVE_NETTLE_SIV_GCM
+    case AEAD_AES_128_GCM_SIV:
+      return AES128_KEY_SIZE;
+#endif
+    default:
       return 0;
+  }
 }
 
 /* ================================================== */
@@ -83,10 +121,21 @@ SIV_GetKeyLength(SIV_Algorithm algorithm)
 int
 SIV_SetKey(SIV_Instance instance, const unsigned char *key, int length)
 {
-  if (length != 32)
+  if (length != SIV_GetKeyLength(instance->algorithm))
     return 0;
 
-  siv_cmac_aes128_set_key(&instance->siv, key);
+  switch (instance->algorithm) {
+    case AEAD_AES_SIV_CMAC_256:
+      siv_cmac_aes128_set_key(&instance->ctx.cmac_aes128, key);
+      break;
+#ifdef HAVE_NETTLE_SIV_GCM
+    case AEAD_AES_128_GCM_SIV:
+      aes128_set_encrypt_key(&instance->ctx.aes128, key);
+      break;
+#endif
+    default:
+      assert(0);
+  }
 
   instance->key_set = 1;
 
@@ -98,9 +147,9 @@ SIV_SetKey(SIV_Instance instance, const unsigned char *key, int length)
 int
 SIV_GetTagLength(SIV_Instance instance)
 {
-  assert(SIV_DIGEST_SIZE <= SIV_MAX_TAG_LENGTH);
+  if (instance->tag_length < 1 || instance->tag_length > SIV_MAX_TAG_LENGTH)
-
+    assert(0);
-  return SIV_DIGEST_SIZE;
+  return instance->tag_length;
 }
 
 /* ================================================== */
@@ -115,16 +164,31 @@ SIV_Encrypt(SIV_Instance instance,
   if (!instance->key_set)
     return 0;
 
-  if (nonce_length < SIV_MIN_NONCE_SIZE || assoc_length < 0 ||
+  if (nonce_length < instance->min_nonce_length ||
+      nonce_length > instance->max_nonce_length || assoc_length < 0 ||
       plaintext_length < 0 || plaintext_length > ciphertext_length ||
-      plaintext_length + SIV_DIGEST_SIZE != ciphertext_length)
+      plaintext_length + SIV_GetTagLength(instance) != ciphertext_length)
     return 0;
 
   assert(assoc && plaintext);
 
-  siv_cmac_aes128_encrypt_message(&instance->siv, nonce_length, nonce,
+  switch (instance->algorithm) {
-                                  assoc_length, assoc,
+    case AEAD_AES_SIV_CMAC_256:
+      siv_cmac_aes128_encrypt_message(&instance->ctx.cmac_aes128,
+                                      nonce_length, nonce, assoc_length, assoc,
                                       ciphertext_length, ciphertext, plaintext);
+      break;
+#ifdef HAVE_NETTLE_SIV_GCM
+    case AEAD_AES_128_GCM_SIV:
+      siv_gcm_aes128_encrypt_message(&instance->ctx.aes128,
+                                     nonce_length, nonce, assoc_length, assoc,
+                                     ciphertext_length, ciphertext, plaintext);
+      break;
+#endif
+    default:
+      assert(0);
+  }
+
   return 1;
 }
 
@@ -140,17 +204,32 @@ SIV_Decrypt(SIV_Instance instance,
   if (!instance->key_set)
     return 0;
 
-  if (nonce_length < SIV_MIN_NONCE_SIZE || assoc_length < 0 ||
+  if (nonce_length < instance->min_nonce_length ||
+      nonce_length > instance->max_nonce_length || assoc_length < 0 ||
       plaintext_length < 0 || plaintext_length > ciphertext_length ||
-      plaintext_length + SIV_DIGEST_SIZE != ciphertext_length)
+      plaintext_length + SIV_GetTagLength(instance) != ciphertext_length)
     return 0;
 
   assert(assoc && plaintext);
 
-  if (!siv_cmac_aes128_decrypt_message(&instance->siv, nonce_length, nonce,
+  switch (instance->algorithm) {
-                                       assoc_length, assoc,
+    case AEAD_AES_SIV_CMAC_256:
+      if (!siv_cmac_aes128_decrypt_message(&instance->ctx.cmac_aes128,
+                                           nonce_length, nonce, assoc_length, assoc,
                                            plaintext_length, plaintext, ciphertext))
         return 0;
+      break;
+#ifdef HAVE_NETTLE_SIV_GCM
+    case AEAD_AES_128_GCM_SIV:
+      if (!siv_gcm_aes128_decrypt_message(&instance->ctx.aes128,
+                                          nonce_length, nonce, assoc_length, assoc,
+                                          plaintext_length, plaintext, ciphertext))
+        return 0;
+      break;
+#endif
+    default:
+      assert(0);
+  }
 
   return 1;
 }

test/unit/siv.c

@@ -125,15 +125,94 @@ test_unit(void)
       "\x8d\x49\x2f\x14\x62\xa4\x7c\x2a\x57\x38\x87\xce\xc6\x72\xd3\x5c"
       "\xa1", 97
     },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b", 12,
+      "", 0,
+      "", 0,
+      "\xba\x05\x1c\x40\xeb\x7e\x5f\xa2\x3f\x6c\xe5\xbe\xfe\x5b\x04\xad", 16
+    },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b", 12,
+      "\x4c\x9d\x4f\xca\xed\x8a\xe2\xba\xad\x3f\x3e\xa6\xe9\x3c\x8c\x8b", 16,
+      "", 0,
+      "\x8f\x47\xfe\x1f\x26\x4e\xe2\x99\x5f\x35\x3d\x26\x74\x14\xd4\x3b", 16
+    },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b", 12,
+      "", 0,
+      "\xba\x05\x1c\x40\xeb\x7e\x5f\xa2\x3f\x6c\xe5\xbe\xfe\x5b\x04\xad", 16,
+      "\xa1\xc6\x1b\xf7\x32\x39\x93\x0e\x10\xf8\xa6\x21\x6c\x6e\x26\x83"
+      "\x5c\xa9\xb0\xdd\x91\x0f\x81\xa6\xf0\x3b\x45\xda\xa6\x9a\x2b\x24", 32,
+    },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b", 12,
+      "\x4c\x9d\x4f\xca\xed\x8a\xe2\xba\xad\x3f\x3e\xa6\xe9\x3c\x8c", 15,
+      "\xba\x99\x79\x31\x23\x7e\x3c\x53\x58\x7e\xd4\x93\x02\xab\xe4", 15,
+      "\x7a\x23\xa7\x35\x8d\x34\x5b\xf6\x0d\xa7\x6d\x3b\x58\x8c\x4c\x65"
+      "\xd9\x85\x4e\x17\xb7\x52\x48\xf7\x91\xb4\xdd\xd6\x8b\xec\x02", 31
+    },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b", 12,
+      "\x4c\x9d\x4f\xca\xed\x8a\xe2\xba\xad\x3f\x3e\xa6\xe9\x3c\x8c\x8b", 16,
+      "\xba\x99\x79\x31\x23\x7e\x3c\x53\x58\x7e\xd4\x93\x02\xab\xe4\xa7", 16,
+      "\xa3\x10\xae\x5f\x26\xd9\x90\xfa\xab\x30\x29\x80\x7f\x93\x62\x23"
+      "\x83\x8f\xc9\x57\x90\xbb\x05\x87\x02\x11\x57\xd6\x13\x9b\x82\x4d", 32
+    },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b", 12,
+      "\x4c\x9d\x4f\xca\xed\x8a\xe2\xba\xad\x3f\x3e\xa6\xe9\x3c\x8c\x8b"
+      "\xa0", 17,
+      "\xba\x99\x79\x31\x23\x7e\x3c\x53\x58\x7e\xd4\x93\x02\xab\xe4\xa7"
+      "\x08", 17,
+      "\x4c\x48\x67\x48\xce\x8b\x14\x7b\x70\xac\x71\xe8\x7b\x4e\x4a\x6a"
+      "\xb4\x3d\xb5\x8e\x58\x81\xfc\x3e\x97\xcd\xdf\xef\x67\x1e\xf4\x4f"
+      "\x0d", 33
+    },
+    { AEAD_AES_128_GCM_SIV,
+      "\x01\x23\x45\x67\x89\xab\xcd\xef\xf0\x12\x34\x56\x78\x9a\xbc\xde", 16,
+      "\xb0\x5a\x1b\xc7\x56\xe7\xb6\x2c\xb4\x85\xe5\x56", 12,
+      "\xe5\x8b\xd2\x6a\x30\xc5\xc5\x61\xcc\xbd\x7c\x27\xbf\xfe\xf9\x06"
+      "\x00\x5b\xd7\xfc\x11\x0b\xcf\x16\x61\xef\xac\x05\xa7\xaf\xec\x27"
+      "\x41\xc8\x5e\x9e\x0d\xf9\x2f\xaf\x20\x79\x17\xe5\x17\x91\x2a\x27"
+      "\x34\x1c\xbc\xaf\xeb\xef\x7f\x52\xe7\x1e\x4c\x2a\xca\xbd\x2b\xbe"
+      "\x34\xd6\xfb\x69\xd3\x3e\x49\x59\x60\xb4\x26\xc9\xb8\xce\xba", 79,
+      "\x6c\xe7\xcf\x7e\xab\x7b\xa0\xe1\xa7\x22\xcb\x88\xde\x5e\x42\xd2"
+      "\xec\x79\xe0\xa2\xcf\x5f\x0f\x6f\x6b\x89\x57\xcd\xae\x17\xd4\xc2"
+      "\xf3\x1b\xa2\xa8\x13\x78\x23\x2f\x83\xa8\xd4\x0c\xc0\xd2\xf3\x99"
+      "\xae\x81\xa1\xca\x5b\x5f\x45\xa6\x6f\x0c\x8a\xf3\xd4\x67\x40\x81"
+      "\x26\xe2\x01\x86\xe8\x5a\xd5\xf8\x58\x80\x9f\x56\xaa\x76\x96\xbf"
+      "\x31", 81,
+      "\xf6\xa0\x1a\xf3\x4f\xe9\x36\xde\x5c\xbd\xb6\x0a\x26\x9d\x60\x1d"
+      "\xe6\xc9\x6d\xb8\xf2\x5f\xcd\xce\x26\xf4\x0d\x86\xec\xdd\x84\x25"
+      "\xaf\xec\x72\x10\x2d\x74\x2d\xde\x95\x84\xac\xce\xbf\x8a\x52\x9f"
+      "\x10\x6f\xc2\xa8\x1f\xed\x47\xff\xeb\x28\x57\x54\xb3\x45\x45\x56"
+      "\xbb\xcf\x7d\x9b\x99\x68\xbd\x36\x75\xe3\xf7\x8c\x09\x25\x01\xbe"
+      "\xe1\xe2\x3d\x19\x4f\x15\x64\x12\x6e\xea\x67\x6c\x42\x2f\xc1\x91"
+      "\xff", 97
+    },
     { 0, "", 0 }
   };
 
   unsigned char plaintext[sizeof (((struct siv_test *)NULL)->plaintext)];
   unsigned char ciphertext[sizeof (((struct siv_test *)NULL)->ciphertext)];
   SIV_Instance siv;
-  int i, j, r;
+  int i, j, r, fixed_nonce_length;
 
-  TEST_CHECK(SIV_CreateInstance(0) == NULL);
+  for (i = 0; i < AEAD_AES_256_GCM_SIV + 10; i++) {
+    switch (i) {
+      case AEAD_AES_SIV_CMAC_256:
+      case AEAD_AES_128_GCM_SIV:
+        continue;
+    }
+    TEST_CHECK(SIV_GetKeyLength(i) == 0);
+    TEST_CHECK(SIV_CreateInstance(i) == NULL);
+  }
 
   for (i = 0; tests[i].algorithm != 0; i++) {
     DEBUG_LOG("testing %d (%d)", (int)tests[i].algorithm, i);
@@ -145,7 +224,24 @@ test_unit(void)
     assert(tests[i].ciphertext_length <= sizeof (tests[i].ciphertext));
 
     siv = SIV_CreateInstance(tests[i].algorithm);
+
+    switch (tests[i].algorithm) {
+      case AEAD_AES_SIV_CMAC_256:
         TEST_CHECK(siv != NULL);
+        fixed_nonce_length = 0;
+        break;
+      case AEAD_AES_128_GCM_SIV:
+        fixed_nonce_length = 1;
+        break;
+      default:
+        assert(0);
+    }
+
+    if (!siv) {
+      DEBUG_LOG("missing %d support", (int)tests[i].algorithm);
+      TEST_CHECK(SIV_GetKeyLength(tests[i].algorithm) == 0);
+      continue;
+    }
 
     TEST_CHECK(SIV_GetKeyLength(tests[i].algorithm) == tests[i].key_length);
 
@@ -188,7 +284,7 @@ test_unit(void)
                       tests[i].assoc, tests[i].assoc_length,
                       tests[i].plaintext, tests[i].plaintext_length,
                       ciphertext, tests[i].ciphertext_length);
-      if (j > 0) {
+      if (j > 0 && (j == tests[i].nonce_length || !fixed_nonce_length)) {
         TEST_CHECK(r);
         TEST_CHECK(memcmp(ciphertext, tests[i].ciphertext, tests[i].ciphertext_length) != 0);
       } else {