--- /dev/null
+/* 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 gcm_add_aad.c
+ GCM implementation, Add AAD data to the stream, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef LTC_GCM_MODE
+
+/**
+ Add AAD to the GCM state
+ @param gcm The GCM state
+ @param adata The additional authentication data to add to the GCM state
+ @param adatalen The length of the AAD data.
+ @return CRYPT_OK on success
+ */
+int gcm_add_aad(gcm_state *gcm,
+ const unsigned char *adata, unsigned long adatalen)
+{
+ unsigned long x;
+ int err;
+#ifdef LTC_FAST
+ unsigned long y;
+#endif
+
+ LTC_ARGCHK(gcm != NULL);
+ if (adatalen > 0) {
+ LTC_ARGCHK(adata != NULL);
+ }
+
+ if (gcm->buflen > 16 || gcm->buflen < 0) {
+ return CRYPT_INVALID_ARG;
+ }
+
+ if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
+ return err;
+ }
+
+ /* in IV mode? */
+ if (gcm->mode == LTC_GCM_MODE_IV) {
+ /* IV length must be > 0 */
+ if (gcm->buflen == 0 && gcm->totlen == 0) return CRYPT_ERROR;
+ /* let's process the IV */
+ if (gcm->ivmode || gcm->buflen != 12) {
+ for (x = 0; x < (unsigned long)gcm->buflen; x++) {
+ gcm->X[x] ^= gcm->buf[x];
+ }
+ if (gcm->buflen) {
+ gcm->totlen += gcm->buflen * CONST64(8);
+ gcm_mult_h(gcm, gcm->X);
+ }
+
+ /* mix in the length */
+ zeromem(gcm->buf, 8);
+ STORE64H(gcm->totlen, gcm->buf+8);
+ for (x = 0; x < 16; x++) {
+ gcm->X[x] ^= gcm->buf[x];
+ }
+ gcm_mult_h(gcm, gcm->X);
+
+ /* copy counter out */
+ XMEMCPY(gcm->Y, gcm->X, 16);
+ zeromem(gcm->X, 16);
+ } else {
+ XMEMCPY(gcm->Y, gcm->buf, 12);
+ gcm->Y[12] = 0;
+ gcm->Y[13] = 0;
+ gcm->Y[14] = 0;
+ gcm->Y[15] = 1;
+ }
+ XMEMCPY(gcm->Y_0, gcm->Y, 16);
+ zeromem(gcm->buf, 16);
+ gcm->buflen = 0;
+ gcm->totlen = 0;
+ gcm->mode = LTC_GCM_MODE_AAD;
+ }
+
+ if (gcm->mode != LTC_GCM_MODE_AAD || gcm->buflen >= 16) {
+ return CRYPT_INVALID_ARG;
+ }
+
+ x = 0;
+#ifdef LTC_FAST
+ if (gcm->buflen == 0) {
+ for (x = 0; x < (adatalen & ~15); x += 16) {
+ for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+ *(LTC_FAST_TYPE_PTR_CAST(&gcm->X[y])) ^= *(LTC_FAST_TYPE_PTR_CAST(&adata[x + y]));
+ }
+ gcm_mult_h(gcm, gcm->X);
+ gcm->totlen += 128;
+ }
+ adata += x;
+ }
+#endif
+
+
+ /* start adding AAD data to the state */
+ for (; x < adatalen; x++) {
+ gcm->X[gcm->buflen++] ^= *adata++;
+
+ if (gcm->buflen == 16) {
+ /* GF mult it */
+ gcm_mult_h(gcm, gcm->X);
+ gcm->buflen = 0;
+ gcm->totlen += 128;
+ }
+ }
+
+ return CRYPT_OK;
+}
+#endif
+
+
+/* ref: $Format:%D$ */
+/* git commit: $Format:%H$ */
+/* commit time: $Format:%ai$ */