1 files changed, 92 insertions, 0 deletions
diff --git a/libtomcrypt/src/encauth/ocb3/ocb3_done.c b/libtomcrypt/src/encauth/ocb3/ocb3_done.c
new file mode 100644
index 0000000..b913d3a
--- /dev/null
+++ b/libtomcrypt/src/encauth/ocb3/ocb3_done.c
@@ -0,0 +1,92 @@
+/* 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_done.c
+   OCB implementation, INTERNAL ONLY helper, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef LTC_OCB3_MODE
+
+/**
+   Finish OCB processing and compute the tag
+   @param ocb     The OCB state
+   @param tag     [out] The destination for the authentication tag
+   @param taglen  [in/out] The max size and resulting size of the authentication tag
+   @return CRYPT_OK if successful
+*/
+int ocb3_done(ocb3_state *ocb, unsigned char *tag, unsigned long *taglen)
+{
+   unsigned char tmp[MAXBLOCKSIZE];
+   int err, x;
+
+   LTC_ARGCHK(ocb    != NULL);
+   LTC_ARGCHK(tag    != NULL);
+   LTC_ARGCHK(taglen != NULL);
+   if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
+      goto LBL_ERR;
+   }
+
+   /* check taglen */
+   if ((int)*taglen < ocb->tag_len) {
+      *taglen = (unsigned long)ocb->tag_len;
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   /* finalize AAD processing */
+
+   if (ocb->adata_buffer_bytes>0) {
+     /* Offset_* = Offset_m xor L_* */
+     ocb3_int_xor_blocks(ocb->aOffset_current, ocb->aOffset_current, ocb->L_star, ocb->block_len);
+
+     /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
+     ocb3_int_xor_blocks(tmp, ocb->adata_buffer, ocb->aOffset_current, ocb->adata_buffer_bytes);
+     for(x=ocb->adata_buffer_bytes; x<ocb->block_len; x++) {
+       if (x == ocb->adata_buffer_bytes) {
+         tmp[x] = 0x80 ^ ocb->aOffset_current[x];
+       }
+       else {
+         tmp[x] = 0x00 ^ ocb->aOffset_current[x];
+       }
+     }
+
+     /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
+     if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(tmp, tmp, &ocb->key)) != CRYPT_OK) {
+       goto LBL_ERR;
+     }
+     ocb3_int_xor_blocks(ocb->aSum_current, ocb->aSum_current, tmp, ocb->block_len);
+   }
+
+   /* finalize TAG computing */
+
+   /* at this point ocb->aSum_current = HASH(K, A) */
+   /* tag = tag ^ HASH(K, A) */
+   ocb3_int_xor_blocks(tmp, ocb->tag_part, ocb->aSum_current, ocb->block_len);
+
+   /* copy tag bytes */
+   for(x = 0; x < ocb->tag_len; x++) tag[x] = tmp[x];
+   *taglen = (unsigned long)ocb->tag_len;
+
+   err = CRYPT_OK;
+
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+   zeromem(tmp, MAXBLOCKSIZE);
+   zeromem(ocb, sizeof(*ocb));
+#endif
+
+   return err;
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */