Import code from previous AssetBuilder version

thirdparty/libtomcrypt/stream/chacha/chacha_crypt.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.
+ */
+
+/* The implementation is based on:
+ * chacha-ref.c version 20080118
+ * Public domain from D. J. Bernstein
+ */
+
+#include "tomcrypt.h"
+
+#ifdef LTC_CHACHA
+
+#define QUARTERROUND(a,b,c,d) \
+  x[a] += x[b]; x[d] = ROL(x[d] ^ x[a], 16); \
+  x[c] += x[d]; x[b] = ROL(x[b] ^ x[c], 12); \
+  x[a] += x[b]; x[d] = ROL(x[d] ^ x[a],  8); \
+  x[c] += x[d]; x[b] = ROL(x[b] ^ x[c],  7);
+
+static void _chacha_block(unsigned char *output, const ulong32 *input, int rounds)
+{
+   ulong32 x[16];
+   int i;
+   XMEMCPY(x, input, sizeof(x));
+   for (i = rounds; i > 0; i -= 2) {
+      QUARTERROUND(0, 4, 8,12)
+      QUARTERROUND(1, 5, 9,13)
+      QUARTERROUND(2, 6,10,14)
+      QUARTERROUND(3, 7,11,15)
+      QUARTERROUND(0, 5,10,15)
+      QUARTERROUND(1, 6,11,12)
+      QUARTERROUND(2, 7, 8,13)
+      QUARTERROUND(3, 4, 9,14)
+   }
+   for (i = 0; i < 16; ++i) {
+     x[i] += input[i];
+     STORE32L(x[i], output + 4 * i);
+   }
+}
+
+/**
+   Encrypt (or decrypt) bytes of ciphertext (or plaintext) with ChaCha
+   @param st      The ChaCha state
+   @param in      The plaintext (or ciphertext)
+   @param inlen   The length of the input (octets)
+   @param out     [out] The ciphertext (or plaintext), length inlen
+   @return CRYPT_OK if successful
+*/
+int chacha_crypt(chacha_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out)
+{
+   unsigned char buf[64];
+   unsigned long i, j;
+
+   if (inlen == 0) return CRYPT_OK; /* nothing to do */
+
+   LTC_ARGCHK(st        != NULL);
+   LTC_ARGCHK(in        != NULL);
+   LTC_ARGCHK(out       != NULL);
+   LTC_ARGCHK(st->ivlen != 0);
+
+   if (st->ksleft > 0) {
+      j = MIN(st->ksleft, inlen);
+      for (i = 0; i < j; ++i, st->ksleft--) out[i] = in[i] ^ st->kstream[64 - st->ksleft];
+      inlen -= j;
+      if (inlen == 0) return CRYPT_OK;
+      out += j;
+      in  += j;
+   }
+   for (;;) {
+     _chacha_block(buf, st->input, st->rounds);
+     if (st->ivlen == 8) {
+       /* IV-64bit, increment 64bit counter */
+       if (0 == ++st->input[12] && 0 == ++st->input[13]) return CRYPT_OVERFLOW;
+     }
+     else {
+       /* IV-96bit, increment 32bit counter */
+       if (0 == ++st->input[12]) return CRYPT_OVERFLOW;
+     }
+     if (inlen <= 64) {
+       for (i = 0; i < inlen; ++i) out[i] = in[i] ^ buf[i];
+       st->ksleft = 64 - inlen;
+       for (i = inlen; i < 64; ++i) st->kstream[i] = buf[i];
+       return CRYPT_OK;
+     }
+     for (i = 0; i < 64; ++i) out[i] = in[i] ^ buf[i];
+     inlen -= 64;
+     out += 64;
+     in  += 64;
+   }
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */