+++ /dev/null
-/**
- * @file /cryptron/ecies.c
- *
- * @brief ECIES encryption/decryption functions.
- *
- * $Author: Ladar Levison $
- * $Website: http://lavabit.com $
- *
- */
-
-#include "ies.h"
-#include <iostream>
-#include <vector>
-
-#define SET_ERROR(string) \
- sprintf(error, "%s %s:%d", (string), __FILE__, __LINE__)
-#define SET_OSSL_ERROR(string) \
- sprintf(error, "%s {error = %s} %s:%d", (string), ERR_error_string(ERR_get_error(), NULL), __FILE__, __LINE__)
-
-/* Copyright (c) 1998-2011 The OpenSSL Project. All rights reserved.
- * Taken from openssl/crypto/ecdh/ech_kdf.c in github:openssl/openssl
- * ffa08b3242e0f10f1fef3c93ef3f0b51de8c27a9 */
-
-/* Key derivation function from X9.62/SECG */
-/* Way more than we will ever need */
-#define ECDH_KDF_MAX (1 << 30)
-int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,
- const unsigned char *Z, size_t Zlen,
- const unsigned char *sinfo, size_t sinfolen,
- const EVP_MD *md)
-{
- EVP_MD_CTX mctx;
- int rv = 0;
- unsigned int i;
- size_t mdlen;
- unsigned char ctr[4];
- if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX || Zlen > ECDH_KDF_MAX)
- return 0;
- mdlen = EVP_MD_size(md);
- EVP_MD_CTX_init(&mctx);
- for (i = 1;;i++)
- {
- unsigned char mtmp[EVP_MAX_MD_SIZE];
- EVP_DigestInit_ex(&mctx, md, NULL);
- ctr[3] = i & 0xFF;
- ctr[2] = (i >> 8) & 0xFF;
- ctr[1] = (i >> 16) & 0xFF;
- ctr[0] = (i >> 24) & 0xFF;
- if (!EVP_DigestUpdate(&mctx, Z, Zlen))
- goto err;
- if (!EVP_DigestUpdate(&mctx, ctr, sizeof(ctr)))
- goto err;
- if (!EVP_DigestUpdate(&mctx, sinfo, sinfolen))
- goto err;
- if (outlen >= mdlen)
- {
- if (!EVP_DigestFinal(&mctx, out, NULL))
- goto err;
- outlen -= mdlen;
- if (outlen == 0)
- break;
- out += mdlen;
- }
- else
- {
- if (!EVP_DigestFinal(&mctx, mtmp, NULL))
- goto err;
- memcpy(out, mtmp, outlen);
- OPENSSL_cleanse(mtmp, mdlen);
- break;
- }
- }
- rv = 1;
- err:
- EVP_MD_CTX_cleanup(&mctx);
- return rv;
-}
-
-static size_t envelope_key_len(const ies_ctx_t *ctx)
-{
- return EVP_CIPHER_key_length(ctx->cipher) + EVP_MD_size(ctx->md);
-}
-
-static EC_KEY * ecies_key_create(const EC_KEY *user, char *error) {
-
- const EC_GROUP *group;
- EC_KEY *key = NULL;
-
- if (!(key = EC_KEY_new())) {
- SET_OSSL_ERROR("EC_KEY_new failed");
- return NULL;
- }
-
- if (!(group = EC_KEY_get0_group(user))) {
- SET_ERROR("The user key does not have group");
- EC_KEY_free(key);
- return NULL;
- }
-
- if (EC_KEY_set_group(key, group) != 1) {
- SET_OSSL_ERROR("EC_KEY_set_group failed");
- EC_KEY_free(key);
- return NULL;
- }
-
- if (EC_KEY_generate_key(key) != 1) {
- SET_OSSL_ERROR("EC_KEY_generate_key failed");
- EC_KEY_free(key);
- return NULL;
- }
-
- return key;
-}
-
-static unsigned char *prepare_envelope_key(const ies_ctx_t *ctx, cryptogram_t *cryptogram, char *error)
-{
-
- const size_t key_buf_len = envelope_key_len(ctx);
- const size_t ecdh_key_len = (EC_GROUP_get_degree(EC_KEY_get0_group(ctx->user_key)) + 7) / 8;
- unsigned char *envelope_key = NULL, *ktmp = NULL;
- EC_KEY *ephemeral = NULL;
- size_t written_length;
-
- /* High-level ECDH via EVP does not allow use of arbitrary KDF function.
- * We should use low-level API for KDF2
- * c.f. openssl/crypto/ec/ec_pmeth.c */
- if ((envelope_key = (unsigned char *) OPENSSL_malloc(key_buf_len)) == NULL) {
- SET_ERROR("Failed to allocate memory for envelope_key");
- goto err;
- }
-
- if (!(ephemeral = ecies_key_create(ctx->user_key, error))) {
- goto err;
- }
-
- /* key agreement and KDF
- * reference: openssl/crypto/ec/ec_pmeth.c */
- ktmp = (unsigned char *) OPENSSL_malloc(ecdh_key_len);
- if (ktmp == NULL) {
- SET_ERROR("No memory for ECDH temporary key");
- goto err;
- }
-
- if (ECDH_compute_key(ktmp, ecdh_key_len, EC_KEY_get0_public_key(ctx->user_key), ephemeral, NULL)
- != (int)ecdh_key_len) {
- SET_OSSL_ERROR("An error occurred while ECDH_compute_key");
- goto err;
- }
-
- /* equals to ISO 18033-2 KDF2 */
- if (!ECDH_KDF_X9_62(envelope_key, key_buf_len, ktmp, ecdh_key_len, 0, 0, ctx->kdf_md)) {
- SET_OSSL_ERROR("Failed to stretch with KDF2");
- goto err;
- }
-
- /* Store the public key portion of the ephemeral key. */
- written_length = EC_POINT_point2oct(
- EC_KEY_get0_group(ephemeral),
- EC_KEY_get0_public_key(ephemeral),
- POINT_CONVERSION_COMPRESSED,
- cryptogram_key_data(cryptogram),
- ctx->stored_key_length,
- NULL);
- if (written_length == 0) {
- SET_OSSL_ERROR("Error while recording the public portion of the envelope key");
- goto err;
- }
- if (written_length != ctx->stored_key_length) {
- SET_ERROR("Written envelope key length does not match with expected");
- goto err;
- }
-
- EC_KEY_free(ephemeral);
- OPENSSL_cleanse(ktmp, ecdh_key_len);
- OPENSSL_free(ktmp);
-
- return envelope_key;
-
- err:
- if (ephemeral)
- EC_KEY_free(ephemeral);
- if (envelope_key) {
- OPENSSL_cleanse(envelope_key, key_buf_len);
- OPENSSL_free(envelope_key);
- }
- if (ktmp) {
- OPENSSL_cleanse(ktmp, ecdh_key_len);
- OPENSSL_free(ktmp);
- }
- return NULL;
-}
-
-static int store_cipher_body(
- const ies_ctx_t *ctx,
- const unsigned char *envelope_key,
- const unsigned char *data,
- size_t length,
- cryptogram_t *cryptogram,
- char *error)
-{
- int out_len, len_sum = 0;
- size_t expected_len = cryptogram_body_length(cryptogram);
- unsigned char iv[EVP_MAX_IV_LENGTH];
- EVP_CIPHER_CTX cipher;
- unsigned char *body;
-
- /* For now we use an empty initialization vector. */
- memset(iv, 0, EVP_MAX_IV_LENGTH);
-
- EVP_CIPHER_CTX_init(&cipher);
- body = cryptogram_body_data(cryptogram);
-
- if (EVP_EncryptInit_ex(&cipher, ctx->cipher, NULL, envelope_key, iv) != 1
- || EVP_EncryptUpdate(&cipher, body, &out_len, data, length) != 1) {
- SET_OSSL_ERROR("Error while trying to secure the data using the symmetric cipher");
- EVP_CIPHER_CTX_cleanup(&cipher);
- return 0;
- }
-
- if (expected_len < (size_t)out_len) {
- SET_ERROR("The symmetric cipher overflowed");
- EVP_CIPHER_CTX_cleanup(&cipher);
- return 0;
- }
-
- body += out_len;
- len_sum += out_len;
- if (EVP_EncryptFinal_ex(&cipher, body, &out_len) != 1) {
- SET_OSSL_ERROR("Error while finalizing the data using the symmetric cipher");
- EVP_CIPHER_CTX_cleanup(&cipher);
- cryptogram_free(cryptogram);
- return 0;
- }
-
- EVP_CIPHER_CTX_cleanup(&cipher);
-
- if (expected_len < (size_t)len_sum) {
- SET_ERROR("The symmetric cipher overflowed");
- return 0;
- }
-
- return 1;
-}
-
-static int store_mac_tag(const ies_ctx_t *ctx, const unsigned char *envelope_key, cryptogram_t *cryptogram, char *error) {
- const size_t key_offset = EVP_CIPHER_key_length(ctx->cipher);
- const size_t key_length = EVP_MD_size(ctx->md);
- const size_t mac_length = cryptogram_mac_length(cryptogram);
- unsigned int out_len;
- HMAC_CTX hmac;
-
- HMAC_CTX_init(&hmac);
-
- /* Generate hash tag using encrypted data */
- if (HMAC_Init_ex(&hmac, envelope_key + key_offset, key_length, ctx->md, NULL) != 1
- || HMAC_Update(&hmac, cryptogram_body_data(cryptogram), cryptogram_body_length(cryptogram)) != 1
- || HMAC_Final(&hmac, cryptogram_mac_data(cryptogram), &out_len) != 1) {
- SET_OSSL_ERROR("Unable to generate tag");
- HMAC_CTX_cleanup(&hmac);
- return 0;
- }
-
- HMAC_CTX_cleanup(&hmac);
-
- if (out_len != mac_length) {
- SET_ERROR("MAC length expectation does not meet");
- return 0;
- }
-
- return 1;
-}
-
-cryptogram_t * ecies_encrypt(const ies_ctx_t *ctx, const unsigned char *data, size_t length, char *error) {
-
- if (!ctx || !data || !length) {
- SET_ERROR("Invalid arguments");
- return NULL;
- }
-
- const size_t block_length = EVP_CIPHER_block_size(ctx->cipher);
- const size_t mac_length = EVP_MD_size(ctx->md);
- cryptogram_t *cryptogram = NULL;
- unsigned char *envelope_key = NULL;
-
- if (block_length == 0 || block_length > EVP_MAX_BLOCK_LENGTH) {
- SET_ERROR("Derived block size is incorrect");
- return NULL;
- }
-
- cryptogram = cryptogram_alloc(ctx->stored_key_length,
- mac_length,
- length + (length % block_length ? (block_length - (length % block_length)) : 0));
- if (!cryptogram) {
- SET_ERROR("Unable to allocate a cryptogram_t buffer to hold the encrypted result.");
- goto err;
- }
-
- if ((envelope_key = prepare_envelope_key(ctx, cryptogram, error)) == NULL) {
- goto err;
- }
-
- if (!store_cipher_body(ctx, envelope_key, data, length, cryptogram, error)) {
- goto err;
- }
-
- if (!store_mac_tag(ctx, envelope_key, cryptogram, error)) {
- goto err;
- }
-
- OPENSSL_cleanse(envelope_key, envelope_key_len(ctx));
- OPENSSL_free(envelope_key);
-
- return cryptogram;
-
- err:
- if (cryptogram)
- cryptogram_free(cryptogram);
- if (envelope_key) {
- OPENSSL_cleanse(envelope_key, envelope_key_len(ctx));
- OPENSSL_free(envelope_key);
- }
- return NULL;
-}
-
-static EC_KEY *ecies_key_create_public_octets(EC_KEY *user, unsigned char *octets, size_t length, char *error) {
-
- EC_KEY *key = NULL;
- EC_POINT *point = NULL;
- const EC_GROUP *group = NULL;
-
- if (!(key = EC_KEY_new())) {
- SET_OSSL_ERROR("Cannot create instance for ephemeral key");
- return NULL;
- }
-
- if (!(group = EC_KEY_get0_group(user))) {
- SET_ERROR("Cannot get group from user key");
- EC_KEY_free(key);
- return NULL;
- }
-
- if (EC_KEY_set_group(key, group) != 1) {
- SET_OSSL_ERROR("EC_KEY_set_group failed");
- EC_KEY_free(key);
- return NULL;
- }
-
- if (!(point = EC_POINT_new(group))) {
- SET_OSSL_ERROR("EC_POINT_new failed");
- EC_KEY_free(key);
- return NULL;
- }
-
- if (EC_POINT_oct2point(group, point, octets, length, NULL) != 1) {
- SET_OSSL_ERROR("EC_POINT_oct2point failed");
- EC_KEY_free(key);
- return NULL;
- }
-
- if (EC_KEY_set_public_key(key, point) != 1) {
- SET_OSSL_ERROR("EC_KEY_set_public_key failed");
- EC_POINT_free(point);
- EC_KEY_free(key);
- return NULL;
- }
-
- EC_POINT_free(point);
-
- if (EC_KEY_check_key(key) != 1) {
- SET_OSSL_ERROR("EC_KEY_check_key failed");
- EC_KEY_free(key);
- return NULL;
- }
-
- return key;
-}
-
-unsigned char *restore_envelope_key(const ies_ctx_t *ctx, const cryptogram_t *cryptogram, char *error)
-{
-
- const size_t key_buf_len = envelope_key_len(ctx);
- const size_t ecdh_key_len = (EC_GROUP_get_degree(EC_KEY_get0_group(ctx->user_key)) + 7) / 8;
- EC_KEY *ephemeral = NULL, *user_copy = NULL;
- unsigned char *envelope_key = NULL, *ktmp = NULL;
-
- if ((envelope_key = (unsigned char *) OPENSSL_malloc(key_buf_len)) == NULL) {
- SET_ERROR("Failed to allocate memory for envelope_key");
- goto err;
- }
-
- if (!(user_copy = EC_KEY_new())) {
- SET_OSSL_ERROR("Failed to create instance for user key copy");
- goto err;
- }
-
- if (!(EC_KEY_copy(user_copy, ctx->user_key))) {
- SET_OSSL_ERROR("Failed to copy user key");
- goto err;
- }
-
- if (!(ephemeral = ecies_key_create_public_octets(user_copy, cryptogram_key_data(cryptogram), cryptogram_key_length(cryptogram), error))) {
- goto err;
- }
-
- /* key agreement and KDF
- * reference: openssl/crypto/ec/ec_pmeth.c */
- ktmp = (unsigned char *) OPENSSL_malloc(ecdh_key_len);
- if (ktmp == NULL) {
- SET_ERROR("No memory for ECDH temporary key");
- goto err;
- }
-
- if (ECDH_compute_key(ktmp, ecdh_key_len, EC_KEY_get0_public_key(ephemeral), user_copy, NULL)
- != (int)ecdh_key_len) {
- SET_OSSL_ERROR("An error occurred while ECDH_compute_key");
- goto err;
- }
-
- /* equals to ISO 18033-2 KDF2 */
- if (!ECDH_KDF_X9_62(envelope_key, key_buf_len, ktmp, ecdh_key_len, 0, 0, ctx->kdf_md)) {
- SET_OSSL_ERROR("Failed to stretch with KDF2");
- goto err;
- }
-
- EC_KEY_free(user_copy);
- EC_KEY_free(ephemeral);
- OPENSSL_cleanse(ktmp, ecdh_key_len);
- OPENSSL_free(ktmp);
-
- return envelope_key;
-
- err:
- if (ephemeral)
- EC_KEY_free(ephemeral);
- if (user_copy)
- EC_KEY_free(user_copy);
- if (envelope_key) {
- OPENSSL_cleanse(envelope_key, key_buf_len);
- OPENSSL_free(envelope_key);
- }
- if (ktmp) {
- OPENSSL_cleanse(ktmp, ecdh_key_len);
- OPENSSL_free(ktmp);
- }
- return NULL;
-}
-
-static int verify_mac(const ies_ctx_t *ctx, const cryptogram_t *cryptogram, const unsigned char * envelope_key, char *error)
-{
- const size_t key_offset = EVP_CIPHER_key_length(ctx->cipher);
- const size_t key_length = EVP_MD_size(ctx->md);
- const size_t mac_length = cryptogram_mac_length(cryptogram);
- unsigned int out_len;
- HMAC_CTX hmac;
- unsigned char md[EVP_MAX_MD_SIZE];
-
- HMAC_CTX_init(&hmac);
-
- /* Generate hash tag using encrypted data */
- if (HMAC_Init_ex(&hmac, envelope_key + key_offset, key_length, ctx->md, NULL) != 1
- || HMAC_Update(&hmac, cryptogram_body_data(cryptogram), cryptogram_body_length(cryptogram)) != 1
- || HMAC_Final(&hmac, md, &out_len) != 1) {
- SET_OSSL_ERROR("Unable to generate tag");
- HMAC_CTX_cleanup(&hmac);
- return 0;
- }
-
- HMAC_CTX_cleanup(&hmac);
-
- if (out_len != mac_length) {
- SET_ERROR("MAC length expectation does not meet");
- return 0;
- }
-
- if (memcmp(md, cryptogram_mac_data(cryptogram), mac_length) != 0) {
- SET_ERROR("MAC tag verification failed");
- return 0;
- }
-
- return 1;
-}
-
-unsigned char *decrypt_body(const ies_ctx_t *ctx, const cryptogram_t *cryptogram, const unsigned char *envelope_key, size_t *length, char *error)
-{
- int out_len;
- size_t output_sum;
- const size_t body_length = cryptogram_body_length(cryptogram);
- unsigned char iv[EVP_MAX_IV_LENGTH], *block, *output;
- EVP_CIPHER_CTX cipher;
-
- if (!(output = (unsigned char*)malloc(body_length + 1))) {
- SET_ERROR("Failed to allocate memory for clear text");
- return NULL;
- }
-
- /* For now we use an empty initialization vector */
- memset(iv, 0, EVP_MAX_IV_LENGTH);
- memset(output, 0, body_length + 1);
-
- EVP_CIPHER_CTX_init(&cipher);
-
- block = output;
- if (EVP_DecryptInit_ex(&cipher, ctx->cipher, NULL, envelope_key, iv) != 1
- || EVP_DecryptUpdate(&cipher, block, &out_len, cryptogram_body_data(cryptogram), body_length) != 1) {
- SET_OSSL_ERROR("Unable to decrypt");
- EVP_CIPHER_CTX_cleanup(&cipher);
- free(output);
- return NULL;
- }
- output_sum = out_len;
-
- block += output_sum;
- if (EVP_DecryptFinal_ex(&cipher, block, &out_len) != 1) {
- printf("Unable to decrypt the data using the chosen symmetric cipher. {error = %s}\n", ERR_error_string(ERR_get_error(), NULL));
- EVP_CIPHER_CTX_cleanup(&cipher);
- free(output);
- return NULL;
- }
- output_sum += out_len;
-
- EVP_CIPHER_CTX_cleanup(&cipher);
-
- *length = output_sum;
-
- return output;
-}
-
-unsigned char * ecies_decrypt(const ies_ctx_t *ctx, const cryptogram_t *cryptogram, size_t *length, char *error)
-{
- unsigned char *envelope_key = NULL, *output = NULL;
-
- if (!ctx || !cryptogram || !length || !error) {
- SET_ERROR("Invalid argument");
- goto err;
- }
-
- envelope_key = restore_envelope_key(ctx, cryptogram, error);
- if (envelope_key == NULL) {
- goto err;
- }
-
- if (!verify_mac(ctx, cryptogram, envelope_key, error)) {
- goto err;
- }
-
- if ((output = decrypt_body(ctx, cryptogram, envelope_key, length, error)) == NULL) {
- goto err;
- }
-
- err:
- OPENSSL_cleanse(envelope_key, envelope_key_len(ctx));
- OPENSSL_free(envelope_key);
-
- return output;
-}
-
-ies_ctx_t *create_context(EC_KEY *user_key)
-{
- try {
- ies_ctx_t* ctx = new ies_ctx_t;
- ctx->cipher = EVP_aes_128_cbc();
- ctx->md = EVP_sha1();
- ctx->kdf_md = EVP_sha1();
- ctx->stored_key_length = 33;
- ctx->user_key = user_key;
- return ctx;
- }
- catch (const std::bad_alloc& e) {
- printf("Error: %s in %s:%d\n", e.what(), __FILE__, __LINE__);
- return NULL;
- }
-}
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