static int get_key(uint8_t key[KEYSIZE])
{
EVP_PKEY *privkey, *pubkey;
X509 *cert;
uint8_t cryptedkey[KEYSIZE], plainkey[KEYSIZE];
SSL_library_init();
ERR_load_crypto_strings();
privkey = load_privkey("keys/server.key");
if (privkey==NULL) {
perror("load_privkey()");
exit(1);
}
cert = load_x509("keys/server.crt");
if (cert==NULL) {
perror("load_x509()");
exit(1);
}
pubkey = EVP_PKEY_IN_X509(cert);
if (pubkey == NULL) {
ERR_print_errors_fp(stderr);
exit(1);
}
rand_sharedkey(key);
if (RSA_public_encrypt(KEYSIZE, key, cryptedkey, RSA_IN_EVP_PKEY(pubkey), RSA_NO_PADDING)<0) {
ERR_print_errors_fp(stderr);
exit(1);
}
if (RSA_private_decrypt(KEYSIZE, cryptedkey, plainkey, RSA_IN_EVP_PKEY(privkey), RSA_NO_PADDING)<0) {
ERR_print_errors_fp(stderr);
exit(1);
}
if (memcmp(key, plainkey, SHAREDKEY_BYTESIZE)==0) {
puts("RSA_public_encrypt/RSA_private_decrypt OK.");
} else {
puts("RSA_public_encrypt/RSA_private_decrypt FAILed.");
}
return 0;
}
unsigned char *rsa_decrypt(unsigned char *ciphertext, int *len)
{
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init(&ctx);
EVP_PKEY *pkey;
unsigned char *encrypted_key;
unsigned int encrypted_key_length;
uint32_t eklen_n;
unsigned char iv[EVP_MAX_IV_LENGTH];
pkey = load_privkey("private.pem");
encrypted_key = malloc(EVP_PKEY_size(pkey));
// plaintext will always be equal to or lesser than length of ciphertext
int plaintext_len = *len;
// the length of ciphertest is at most plaintext + ciphers block size.
int ciphertext_len = plaintext_len + EVP_CIPHER_block_size(EVP_des_ede_cbc());
unsigned char *plaintext = (unsigned char *)malloc(ciphertext_len);
/* First need to fetch the encrypted key length, encrypted key and IV */
int pos = 0;
memcpy(&eklen_n, ciphertext + pos, sizeof(eklen_n));
pos += sizeof(eklen_n);
encrypted_key_length = ntohl(eklen_n);
memcpy(encrypted_key, ciphertext + pos, encrypted_key_length);
pos += encrypted_key_length;
memcpy(iv, ciphertext + pos, EVP_CIPHER_iv_length(EVP_des_ede_cbc()));
pos += EVP_CIPHER_iv_length(EVP_des_ede_cbc());
// Now we have our encrypted_key and the iv we can decrypt the reamining
// data
if (!EVP_OpenInit(&ctx, EVP_des_ede_cbc(), encrypted_key, encrypted_key_length, iv, pkey))
{
fprintf(stderr, "EVP_OpenInit: failed.\n");
goto out_free;
}
if (!EVP_OpenUpdate(&ctx, plaintext, &plaintext_len, ciphertext + pos, ciphertext_len))
{
fprintf(stderr, "EVP_OpenUpdate: failed.\n");
goto out_free;
}
int total_len = plaintext_len;
if (!EVP_OpenFinal(&ctx, plaintext + total_len, &plaintext_len))
{
fprintf(stderr, "EVP_OpenFinal warning: failed.\n");
}
out_free:
EVP_PKEY_free(pkey);
free(encrypted_key);
EVP_CIPHER_CTX_cleanup(&ctx);
*len = plaintext_len + total_len;
return plaintext;
}
