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thirdparty/libtomcrypt/encauth/ocb3/ocb3_init.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 ocb3_init.c
+   OCB implementation, initialize state, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef LTC_OCB3_MODE
+
+static void _ocb3_int_calc_offset_zero(ocb3_state *ocb, const unsigned char *nonce, unsigned long noncelen, unsigned long taglen)
+{
+   int x, y, bottom;
+   int idx, shift;
+   unsigned char iNonce[MAXBLOCKSIZE];
+   unsigned char iKtop[MAXBLOCKSIZE];
+   unsigned char iStretch[MAXBLOCKSIZE+8];
+
+   /* Nonce = zeros(127-bitlen(N)) || 1 || N          */
+   zeromem(iNonce, sizeof(iNonce));
+   for (x = ocb->block_len-1, y=0; y<(int)noncelen; x--, y++) {
+     iNonce[x] = nonce[noncelen-y-1];
+   }
+   iNonce[x] = 0x01;
+   iNonce[0] |= ((taglen*8) % 128) << 1;
+
+   /* bottom = str2num(Nonce[123..128])               */
+   bottom = iNonce[ocb->block_len-1] & 0x3F;
+
+   /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6))   */
+   iNonce[ocb->block_len-1] = iNonce[ocb->block_len-1] & 0xC0;
+   if ((cipher_descriptor[ocb->cipher].ecb_encrypt(iNonce, iKtop, &ocb->key)) != CRYPT_OK) {
+      zeromem(ocb->Offset_current, ocb->block_len);
+      return;
+   }
+
+   /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
+   for (x = 0; x < ocb->block_len; x++) {
+     iStretch[x] = iKtop[x];
+   }
+   for (y = 0; y < 8; y++) {
+     iStretch[x+y] = iKtop[y] ^ iKtop[y+1];
+   }
+
+   /* Offset_0 = Stretch[1+bottom..128+bottom]        */
+   idx = bottom / 8;
+   shift = (bottom % 8);
+   for (x = 0; x < ocb->block_len; x++) {
+      ocb->Offset_current[x] = iStretch[idx+x] << shift;
+      if (shift > 0) {
+        ocb->Offset_current[x] |= iStretch[idx+x+1] >> (8-shift);
+      }
+   }
+}
+
+static const struct {
+    int           len;
+    unsigned char poly_mul[MAXBLOCKSIZE];
+} polys[] = {
+{
+    8,
+    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1B }
+}, {
+    16,
+    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 }
+}
+};
+
+/**
+   Initialize an OCB context
+   @param ocb       [out] The destination of the OCB state
+   @param cipher    The index of the desired cipher
+   @param key       The secret key
+   @param keylen    The length of the secret key (octets)
+   @param nonce     The session nonce
+   @param noncelen  The length of the session nonce (octets, up to 15)
+   @param taglen    The length of the tag (octets, up to 16)
+   @return CRYPT_OK if successful
+*/
+int ocb3_init(ocb3_state *ocb, int cipher,
+             const unsigned char *key, unsigned long keylen,
+             const unsigned char *nonce, unsigned long noncelen,
+             unsigned long taglen)
+{
+   int poly, x, y, m, err;
+   unsigned char *previous, *current;
+
+   LTC_ARGCHK(ocb   != NULL);
+   LTC_ARGCHK(key   != NULL);
+   LTC_ARGCHK(nonce != NULL);
+
+   /* valid cipher? */
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+   ocb->cipher = cipher;
+
+   /* Valid Nonce?
+    * As of RFC7253: "string of no more than 120 bits" */
+   if (noncelen > (120/8)) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* The blockcipher must have a 128-bit blocksize */
+   if (cipher_descriptor[cipher].block_length != 16) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* The TAGLEN may be any value up to 128 (bits) */
+   if (taglen > 16) {
+      return CRYPT_INVALID_ARG;
+   }
+   ocb->tag_len = taglen;
+
+   /* determine which polys to use */
+   ocb->block_len = cipher_descriptor[cipher].block_length;
+   x = (int)(sizeof(polys)/sizeof(polys[0]));
+   for (poly = 0; poly < x; poly++) {
+       if (polys[poly].len == ocb->block_len) {
+          break;
+       }
+   }
+   if (poly == x) {
+      return CRYPT_INVALID_ARG; /* block_len not found in polys */
+   }
+   if (polys[poly].len != ocb->block_len) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* schedule the key */
+   if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ocb->key)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* L_* = ENCIPHER(K, zeros(128)) */
+   zeromem(ocb->L_star, ocb->block_len);
+   if ((err = cipher_descriptor[cipher].ecb_encrypt(ocb->L_star, ocb->L_star, &ocb->key)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* compute L_$, L_0, L_1, ... */
+   for (x = -1; x < 32; x++) {
+      if (x == -1) {                /* gonna compute: L_$ = double(L_*) */
+         current  = ocb->L_dollar;
+         previous = ocb->L_star;
+      }
+      else if (x == 0) {            /* gonna compute: L_0 = double(L_$) */
+         current  = ocb->L_[0];
+         previous = ocb->L_dollar;
+      }
+      else {                        /* gonna compute: L_i = double(L_{i-1}) for every integer i > 0 */
+         current  = ocb->L_[x];
+         previous = ocb->L_[x-1];
+      }
+      m = previous[0] >> 7;
+      for (y = 0; y < ocb->block_len-1; y++) {
+         current[y] = ((previous[y] << 1) | (previous[y+1] >> 7)) & 255;
+      }
+      current[ocb->block_len-1] = (previous[ocb->block_len-1] << 1) & 255;
+      if (m == 1) {
+         /* current[] = current[] XOR polys[poly].poly_mul[]*/
+         ocb3_int_xor_blocks(current, current, polys[poly].poly_mul, ocb->block_len);
+      }
+   }
+
+   /* initialize ocb->Offset_current = Offset_0 */
+   _ocb3_int_calc_offset_zero(ocb, nonce, noncelen, taglen);
+
+   /* initialize checksum to all zeros */
+   zeromem(ocb->checksum, ocb->block_len);
+
+   /* set block index */
+   ocb->block_index = 1;
+
+   /* initialize AAD related stuff */
+   ocb->ablock_index = 1;
+   ocb->adata_buffer_bytes = 0;
+   zeromem(ocb->aOffset_current, ocb->block_len);
+   zeromem(ocb->aSum_current, ocb->block_len);
+
+   return CRYPT_OK;
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */