Import code from previous AssetBuilder version

thirdparty/libtomcrypt/modes/cfb/cfb_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.
+ */
+#include "tomcrypt.h"
+
+/**
+  @file cfb_decrypt.c
+  CFB implementation, decrypt data, Tom St Denis
+*/
+
+#ifdef LTC_CFB_MODE
+
+/**
+   CFB decrypt
+   @param ct      Ciphertext
+   @param pt      [out] Plaintext
+   @param len     Length of ciphertext (octets)
+   @param cfb     CFB state
+   @return CRYPT_OK if successful
+*/
+int cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb)
+{
+   int err;
+
+   LTC_ARGCHK(pt != NULL);
+   LTC_ARGCHK(ct != NULL);
+   LTC_ARGCHK(cfb != NULL);
+
+   if ((err = cipher_is_valid(cfb->cipher)) != CRYPT_OK) {
+       return err;
+   }
+
+   /* is blocklen/padlen valid? */
+   if (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) ||
+       cfb->padlen   < 0 || cfb->padlen   > (int)sizeof(cfb->pad)) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   while (len-- > 0) {
+       if (cfb->padlen == cfb->blocklen) {
+          if ((err = cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key)) != CRYPT_OK) {
+             return err;
+          }
+          cfb->padlen = 0;
+       }
+       cfb->pad[cfb->padlen] = *ct;
+       *pt = *ct ^ cfb->IV[cfb->padlen];
+       ++pt;
+       ++ct;
+       ++(cfb->padlen);
+   }
+   return CRYPT_OK;
+}
+
+#endif
+
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */