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thirdparty/libtomcrypt/encauth/ccm/ccm_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.
+ */
+#include "tomcrypt.h"
+
+#ifdef LTC_CCM_MODE
+
+/**
+  Initialize a CCM state
+  @param ccm     The CCM state to initialize
+  @param cipher  The index of the cipher to use
+  @param key     The secret key
+  @param keylen  The length of the secret key
+  @param ptlen   The length of the plain/cipher text that will be processed
+  @param taglen  The max length of the MAC tag
+  @param aadlen  The length of the AAD
+
+  @return CRYPT_OK on success
+ */
+int ccm_init(ccm_state *ccm, int cipher,
+             const unsigned char *key, int keylen, int ptlen, int taglen, int aadlen)
+{
+   int            err;
+
+   LTC_ARGCHK(ccm    != NULL);
+   LTC_ARGCHK(key    != NULL);
+   LTC_ARGCHK(taglen != 0);
+
+   XMEMSET(ccm, 0, sizeof(ccm_state));
+
+   /* check cipher input */
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+   if (cipher_descriptor[cipher].block_length != 16) {
+      return CRYPT_INVALID_CIPHER;
+   }
+
+   /* make sure the taglen is even and <= 16 */
+   ccm->taglen = taglen;
+   ccm->taglen &= ~1;
+   if (ccm->taglen > 16) {
+      ccm->taglen = 16;
+   }
+
+   /* can't use < 4 */
+   if (ccm->taglen < 4) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* schedule key */
+   if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ccm->K)) != CRYPT_OK) {
+      return err;
+   }
+   ccm->cipher = cipher;
+
+   /* let's get the L value */
+   ccm->ptlen = ptlen;
+   ccm->L   = 0;
+   while (ptlen) {
+      ++ccm->L;
+      ptlen >>= 8;
+   }
+   if (ccm->L <= 1) {
+      ccm->L = 2;
+   }
+
+   ccm->aadlen = aadlen;
+   return CRYPT_OK;
+}
+
+#endif
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */