Import code from previous AssetBuilder version

thirdparty/libtomcrypt/encauth/eax/eax_decrypt.c

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+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ */
+
+/**
+    @file eax_decrypt.c
+    EAX implementation, decrypt block, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef LTC_EAX_MODE
+
+/**
+   Decrypt data with the EAX protocol
+   @param eax     The EAX state
+   @param ct      The ciphertext
+   @param pt      [out] The plaintext
+   @param length  The length (octets) of the ciphertext
+   @return CRYPT_OK if successful
+*/
+int eax_decrypt(eax_state *eax, const unsigned char *ct, unsigned char *pt,
+                unsigned long length)
+{
+   int err;
+
+   LTC_ARGCHK(eax != NULL);
+   LTC_ARGCHK(pt  != NULL);
+   LTC_ARGCHK(ct  != NULL);
+
+   /* omac ciphertext */
+   if ((err = omac_process(&eax->ctomac, ct, length)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* decrypt  */
+   return ctr_decrypt(ct, pt, length, &eax->ctr);
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */