+#define GRASSHOPPER_BLOCK_MASK (GRASSHOPPER_BLOCK_SIZE - 1)
+static inline void apply_acpkm_grasshopper(gost_grasshopper_cipher_ctx_ctr *
+ ctx, unsigned int *num)
+{
+ if (!ctx->section_size || (*num < ctx->section_size))
+ return;
+ acpkm_next(&ctx->c);
+ *num &= GRASSHOPPER_BLOCK_MASK;
+}
+
+/* If meshing is not configured via ctrl (setting section_size)
+ * this function works exactly like plain ctr */
+static int gost_grasshopper_cipher_do_ctracpkm(EVP_CIPHER_CTX *ctx,
+ unsigned char *out,
+ const unsigned char *in,
+ size_t inl)
+{
+ gost_grasshopper_cipher_ctx_ctr *c = EVP_CIPHER_CTX_get_cipher_data(ctx);
+ unsigned char *iv = EVP_CIPHER_CTX_iv_noconst(ctx);
+ unsigned int num = EVP_CIPHER_CTX_num(ctx);
+ size_t blocks, i, lasted = inl;
+ grasshopper_w128_t tmp;
+
+ while ((num & GRASSHOPPER_BLOCK_MASK) && lasted) {
+ *out++ = *in++ ^ c->partial_buffer.b[num & GRASSHOPPER_BLOCK_MASK];
+ --lasted;
+ num++;
+ }
+ blocks = lasted / GRASSHOPPER_BLOCK_SIZE;
+
+ // full parts
+ for (i = 0; i < blocks; i++) {
+ apply_acpkm_grasshopper(c, &num);
+ grasshopper_encrypt_block(&c->c.encrypt_round_keys,
+ (grasshopper_w128_t *) iv,
+ (grasshopper_w128_t *) & c->partial_buffer,
+ &c->c.buffer);
+ grasshopper_plus128(&tmp, &c->partial_buffer,
+ (grasshopper_w128_t *) in);
+ grasshopper_copy128((grasshopper_w128_t *) out, &tmp);
+ ctr128_inc(iv);
+ in += GRASSHOPPER_BLOCK_SIZE;
+ out += GRASSHOPPER_BLOCK_SIZE;
+ num += GRASSHOPPER_BLOCK_SIZE;
+ lasted -= GRASSHOPPER_BLOCK_SIZE;
+ }
+
+ // last part
+ if (lasted > 0) {
+ apply_acpkm_grasshopper(c, &num);
+ grasshopper_encrypt_block(&c->c.encrypt_round_keys,
+ (grasshopper_w128_t *) iv,
+ &c->partial_buffer, &c->c.buffer);
+ for (i = 0; i < lasted; i++)
+ out[i] = c->partial_buffer.b[i] ^ in[i];
+ ctr128_inc(iv);
+ num += lasted;
+ }
+ EVP_CIPHER_CTX_set_num(ctx, num);
+
+ return inl;
+}
+
+static int gost_grasshopper_cipher_do_ctracpkm_omac(EVP_CIPHER_CTX *ctx,
+ unsigned char *out,
+ const unsigned char *in,
+ size_t inl)
+{
+ int result;
+ gost_grasshopper_cipher_ctx_ctr *c = EVP_CIPHER_CTX_get_cipher_data(ctx);
+ /* As in and out can be the same pointer, process unencrypted here */
+ if (EVP_CIPHER_CTX_encrypting(ctx))
+ EVP_DigestSignUpdate(c->omac_ctx, in, inl);
+
+ if (in == NULL && inl == 0) { /* Final call */
+ return gost2015_final_call(ctx, c->omac_ctx, KUZNYECHIK_MAC_MAX_SIZE, c->tag, gost_grasshopper_cipher_do_ctracpkm);
+ }
+
+ if (in == NULL) {
+ GOSTerr(GOST_F_GOST_GRASSHOPPER_CIPHER_DO_CTRACPKM_OMAC, ERR_R_EVP_LIB);
+ return -1;
+ }
+ result = gost_grasshopper_cipher_do_ctracpkm(ctx, out, in, inl);
+
+ /* As in and out can be the same pointer, process decrypted here */
+ if (!EVP_CIPHER_CTX_encrypting(ctx))
+ EVP_DigestSignUpdate(c->omac_ctx, out, inl);
+
+ return result;
+}