--- /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_process.c
+ GCM implementation, process message data, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef LTC_GCM_MODE
+
+/**
+ Process plaintext/ciphertext through GCM
+ @param gcm The GCM state
+ @param pt The plaintext
+ @param ptlen The plaintext length (ciphertext length is the same)
+ @param ct The ciphertext
+ @param direction Encrypt or Decrypt mode (GCM_ENCRYPT or GCM_DECRYPT)
+ @return CRYPT_OK on success
+ */
+int gcm_process(gcm_state *gcm,
+ unsigned char *pt, unsigned long ptlen,
+ unsigned char *ct,
+ int direction)
+{
+ unsigned long x;
+ int y, err;
+ unsigned char b;
+
+ LTC_ARGCHK(gcm != NULL);
+ if (ptlen > 0) {
+ LTC_ARGCHK(pt != NULL);
+ LTC_ARGCHK(ct != NULL);
+ }
+
+ if (gcm->buflen > 16 || gcm->buflen < 0) {
+ return CRYPT_INVALID_ARG;
+ }
+
+ if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
+ return err;
+ }
+
+ /* 0xFFFFFFFE0 = ((2^39)-256)/8 */
+ if (gcm->pttotlen / 8 + (ulong64)gcm->buflen + (ulong64)ptlen >= CONST64(0xFFFFFFFE0)) {
+ return CRYPT_INVALID_ARG;
+ }
+
+ if (gcm->mode == LTC_GCM_MODE_IV) {
+ /* let's process the IV */
+ if ((err = gcm_add_aad(gcm, NULL, 0)) != CRYPT_OK) return err;
+ }
+
+ /* in AAD mode? */
+ if (gcm->mode == LTC_GCM_MODE_AAD) {
+ /* let's process the AAD */
+ if (gcm->buflen) {
+ gcm->totlen += gcm->buflen * CONST64(8);
+ gcm_mult_h(gcm, gcm->X);
+ }
+
+ /* increment counter */
+ for (y = 15; y >= 12; y--) {
+ if (++gcm->Y[y] & 255) { break; }
+ }
+ /* encrypt the counter */
+ if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+ return err;
+ }
+
+ gcm->buflen = 0;
+ gcm->mode = LTC_GCM_MODE_TEXT;
+ }
+
+ if (gcm->mode != LTC_GCM_MODE_TEXT) {
+ return CRYPT_INVALID_ARG;
+ }
+
+ x = 0;
+#ifdef LTC_FAST
+ if (gcm->buflen == 0) {
+ if (direction == GCM_ENCRYPT) {
+ for (x = 0; x < (ptlen & ~15); x += 16) {
+ /* ctr encrypt */
+ for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+ *(LTC_FAST_TYPE_PTR_CAST(&ct[x + y])) = *(LTC_FAST_TYPE_PTR_CAST(&pt[x+y])) ^ *(LTC_FAST_TYPE_PTR_CAST(&gcm->buf[y]));
+ *(LTC_FAST_TYPE_PTR_CAST(&gcm->X[y])) ^= *(LTC_FAST_TYPE_PTR_CAST(&ct[x+y]));
+ }
+ /* GMAC it */
+ gcm->pttotlen += 128;
+ gcm_mult_h(gcm, gcm->X);
+ /* increment counter */
+ for (y = 15; y >= 12; y--) {
+ if (++gcm->Y[y] & 255) { break; }
+ }
+ if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+ return err;
+ }
+ }
+ } else {
+ for (x = 0; x < (ptlen & ~15); x += 16) {
+ /* ctr encrypt */
+ for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+ *(LTC_FAST_TYPE_PTR_CAST(&gcm->X[y])) ^= *(LTC_FAST_TYPE_PTR_CAST(&ct[x+y]));
+ *(LTC_FAST_TYPE_PTR_CAST(&pt[x + y])) = *(LTC_FAST_TYPE_PTR_CAST(&ct[x+y])) ^ *(LTC_FAST_TYPE_PTR_CAST(&gcm->buf[y]));
+ }
+ /* GMAC it */
+ gcm->pttotlen += 128;
+ gcm_mult_h(gcm, gcm->X);
+ /* increment counter */
+ for (y = 15; y >= 12; y--) {
+ if (++gcm->Y[y] & 255) { break; }
+ }
+ if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+ return err;
+ }
+ }
+ }
+ }
+#endif
+
+ /* process text */
+ for (; x < ptlen; x++) {
+ if (gcm->buflen == 16) {
+ gcm->pttotlen += 128;
+ gcm_mult_h(gcm, gcm->X);
+
+ /* increment counter */
+ for (y = 15; y >= 12; y--) {
+ if (++gcm->Y[y] & 255) { break; }
+ }
+ if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+ return err;
+ }
+ gcm->buflen = 0;
+ }
+
+ if (direction == GCM_ENCRYPT) {
+ b = ct[x] = pt[x] ^ gcm->buf[gcm->buflen];
+ } else {
+ b = ct[x];
+ pt[x] = ct[x] ^ gcm->buf[gcm->buflen];
+ }
+ gcm->X[gcm->buflen++] ^= b;
+ }
+
+ return CRYPT_OK;
+}
+
+#endif
+
+/* ref: $Format:%D$ */
+/* git commit: $Format:%H$ */
+/* commit time: $Format:%ai$ */