From 41b4121253a9c0e8d82d3eebcfe728d5d43e1b51 Mon Sep 17 00:00:00 2001
From: Dmitry Belyavskiy <beldmit@gmail.com>
Date: Sun, 3 May 2020 19:42:05 +0300
Subject: Magma/Kuznyechik ASN1 parameters and functions

---
 gost_gost2015.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 gost_gost2015.c

(limited to 'gost_gost2015.c')

diff --git a/gost_gost2015.c b/gost_gost2015.c
new file mode 100644
index 0000000..6ae65d6
--- /dev/null
+++ b/gost_gost2015.c
@@ -0,0 +1,122 @@
+#include "gost_lcl.h"
+#include "gost_gost2015.h"
+#include "e_gost_err.h"
+#include <string.h>
+
+int gost2015_final_call(EVP_CIPHER_CTX *ctx, EVP_MD_CTX *omac_ctx, size_t mac_size,
+			unsigned char *encrypted_mac,
+			int (*do_cipher) (EVP_CIPHER_CTX *ctx,
+				unsigned char *out,
+				const unsigned char *in,
+				size_t inl))
+{
+	unsigned char calculated_mac[KUZNYECHIK_MAC_MAX_SIZE];
+	memset(calculated_mac, 0, KUZNYECHIK_MAC_MAX_SIZE);
+
+	if (EVP_CIPHER_CTX_encrypting(ctx)) {
+		EVP_DigestSignFinal(omac_ctx, calculated_mac, &mac_size);
+
+		if (do_cipher(ctx, encrypted_mac, calculated_mac, mac_size) <= 0) {
+			  return -1;
+		}
+	} else {
+		unsigned char expected_mac[KUZNYECHIK_MAC_MAX_SIZE];
+
+		memset(expected_mac, 0, KUZNYECHIK_MAC_MAX_SIZE);
+		EVP_DigestSignFinal(omac_ctx, calculated_mac, &mac_size);
+
+		if (do_cipher(ctx, expected_mac, encrypted_mac, mac_size) <= 0) {
+			  return -1;
+		}
+
+		if (CRYPTO_memcmp(expected_mac, calculated_mac, mac_size) != 0)
+			return -1;
+	}
+	return 0;
+}
+
+/*
+ * UKM = iv|kdf_seed
+ * */
+#define MAX_GOST2015_UKM_SIZE 16
+#define KDF_SEED_SIZE 8
+int gost2015_get_asn1_params(const ASN1_TYPE *params, size_t ukm_size,
+	unsigned char *iv, size_t ukm_offset, unsigned char *kdf_seed)
+{
+  int iv_len = 16;
+  GOST2015_CIPHER_PARAMS *gcp = NULL;
+
+  unsigned char *p = NULL;
+
+  memset(iv, 0, iv_len);
+
+  /* Проверяем тип params */
+  if (ASN1_TYPE_get(params) != V_ASN1_SEQUENCE) {
+      GOSTerr(GOST_F_GOST2015_GET_ASN1_PARAMS, GOST_R_INVALID_CIPHER_PARAMS);
+      return 0;
+  }
+
+  p = params->value.sequence->data;
+  /* Извлекаем структуру параметров */
+  gcp = d2i_GOST2015_CIPHER_PARAMS(NULL, (const unsigned char **)&p, params->value.sequence->length);
+  if (gcp == NULL) {
+      GOSTerr(GOST_F_GOST2015_GET_ASN1_PARAMS, GOST_R_INVALID_CIPHER_PARAMS);
+      return 0;
+  }
+
+  /* Проверяем длину синхропосылки */
+  if (gcp->ukm->length != (int)ukm_size) {
+      GOSTerr(GOST_F_GOST2015_GET_ASN1_PARAMS, GOST_R_INVALID_CIPHER_PARAMS);
+      GOST2015_CIPHER_PARAMS_free(gcp);
+      return 0;
+  }
+
+  memcpy(iv, gcp->ukm->data, ukm_offset);
+  memcpy(kdf_seed, gcp->ukm->data+ukm_offset, KDF_SEED_SIZE);
+
+  GOST2015_CIPHER_PARAMS_free(gcp);
+  return 1;
+}
+
+int gost2015_set_asn1_params(ASN1_TYPE *params,
+	const unsigned char *iv, size_t iv_size, const unsigned char *kdf_seed)
+{
+	GOST2015_CIPHER_PARAMS *gcp = GOST2015_CIPHER_PARAMS_new();
+	int ret = 0, len = 0;
+
+	ASN1_OCTET_STRING *os = NULL;
+	unsigned char ukm_buf[MAX_GOST2015_UKM_SIZE];
+	unsigned char *buf = NULL;
+
+	if (gcp == NULL) {
+	    GOSTerr(GOST_F_GOST2015_SET_ASN1_PARAMS, ERR_R_MALLOC_FAILURE);
+			return 0;
+	}
+
+	memcpy(ukm_buf, iv, iv_size);
+	memcpy(ukm_buf+iv_size, kdf_seed, KDF_SEED_SIZE);
+
+	if (ASN1_STRING_set(gcp->ukm, ukm_buf, iv_size + KDF_SEED_SIZE) == 0) {
+	    GOSTerr(GOST_F_GOST2015_SET_ASN1_PARAMS, ERR_R_MALLOC_FAILURE);
+			goto end;
+	}
+
+	len = i2d_GOST2015_CIPHER_PARAMS(gcp, &buf);
+
+	if (len <= 0
+	    || (os = ASN1_OCTET_STRING_new()) == NULL
+			|| ASN1_OCTET_STRING_set(os, buf, len) == 0) {
+			goto end;
+	}
+
+	ASN1_TYPE_set(params, V_ASN1_SEQUENCE, os);
+	ret = 1;
+
+end:
+	OPENSSL_free(buf);
+	if (ret <= 0 && os)
+		ASN1_OCTET_STRING_free(os);
+
+	GOST2015_CIPHER_PARAMS_free(gcp);
+	return ret;
+}
-- 
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