RSAでtxtファイルを暗号化複合化したい。C言語。

OpenSSLのライブラリを使ってRSAでファイルの中身を暗号化したいのですが、エラーが出てうまくいきません。
エラーの内容は"pkcs decoding error"や"data greater than mod len"が出てきます。

C言語でvisual stdioです。
プログラミング初心者なのでなにがなんだか分かりません。
とりあえず動くようにしたいのですが、分かる方教えてください。
よろしくお願いします。

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/aes.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/bio.h>
#include <openssl/err.h>

	int padding = RSA_PKCS1_PADDING;
//	int padding = RSA_PKCS1_OAEP_PADDING;
//	int padding = RSA_NO_PADDING;

RSA * createRSA(unsigned char * key, int public)
{
	RSA *rsa = NULL;
	BIO *keybio;
	keybio = BIO_new_mem_buf(key, -1);
	if (keybio == NULL)
	{
		printf("Failed to create key BIO");
		return 0;
	}
	if (public)
	{
		rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa, NULL, NULL);
	}
	else
	{
		rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa, NULL, NULL);
	}
	if (rsa == NULL)
	{
		printf("Failed to create RSA");
	}

	return rsa;
}
int public_encrypt(unsigned char * data, int data_len, unsigned char * key, unsigned char *encrypted)
{
	RSA * rsa = createRSA(key, 1);
	int result = RSA_public_encrypt(data_len, data, encrypted, rsa, padding);
	RSA_free(rsa);
	return result;
}
int private_decrypt(unsigned char * enc_data, int data_len, unsigned char * key, unsigned char *decrypted)
{
	RSA * rsa = createRSA(key, 0);
	int  result = RSA_private_decrypt(data_len, enc_data, decrypted, rsa, padding);
	RSA_free(rsa);
	return result;
}
void printLastError(char *msg)
{
	char * err = malloc(130);;
	ERR_load_crypto_strings();
	ERR_error_string(ERR_get_error(), err);
	printf("%s ERROR: %s\n", msg, err);
	free(err);
}

void encrypt(FILE *ifp, FILE *ofp)
{

	char Plaintext[2048 / 8];	
	int i;
	fgets(Plaintext, 2048/8, ifp);
//	Plaintext[strlen(Plaintext)] = '\0';

	// Check Plain Text.
	printf("Public Encrypt Section.\n");
	printf("Check Plaintext :\n%s\n", Plaintext);
	int PlainLength = strlen(Plaintext);
	printf("Plain Text Binary :\n");
	for (i = 0; i < PlainLength; i++) {
		printf("0x%X ", Plaintext[i]);
	}
	printf("\n");

	unsigned char encrypted[4098];
	unsigned char publicKey[] = "-----BEGIN PUBLIC KEY-----\n"\
		"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAy8Dbv8prpJ/0kKhlGeJY\n"\
		"ozo2t60EG8L0561g13R29LvMR5hyvGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+\n"\
		"vw1HocOAZtWK0z3r26uA8kQYOKX9Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQAp\n"\
		"fc9jB9nTzphOgM4JiEYvlV8FLhg9yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68\n"\
		"i6T4nNq7NWC+UNVjQHxNQMQMzU6lWCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoV\n"\
		"PpY72+eVthKzpMeyHkBn7ciumk5qgLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUy\n"\
		"wQIDAQAB\n"\
		"-----END PUBLIC KEY-----\n";

	int encrypted_length = public_encrypt(Plaintext, strlen(Plaintext), publicKey, encrypted);

	if (encrypted_length == -1)
	{
		printLastError("Public Encrypt failed ");
		exit(0);
	}

	// Check Encrypted Text Binary.
	printf("Encrypted Text Binary :\n");
	for (i = 0; i < encrypted_length; i++) {
		printf("0x%X ", encrypted[i]);
	}
	printf("\n");
	printf("Encrypted Text length =%d\n\n", encrypted_length);

	fwrite(encrypted, sizeof(unsigned char), encrypted_length, ofp);
}

void decrypt(FILE *ifp, FILE *ofp)
{
	fseek(ifp, 0L, SEEK_END);
	long fsize = ftell(ifp);
	fseek(ifp, 0L, SEEK_SET);




	unsigned char CypherText[4098];
	char decrypted[4098];
	unsigned char privateKey[] = "-----BEGIN RSA PRIVATE KEY-----\n"\
		"MIIEowIBAAKCAQEAy8Dbv8prpJ/0kKhlGeJYozo2t60EG8L0561g13R29LvMR5hy\n"\
		"vGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+vw1HocOAZtWK0z3r26uA8kQYOKX9\n"\
		"Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQApfc9jB9nTzphOgM4JiEYvlV8FLhg9\n"\
		"yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68i6T4nNq7NWC+UNVjQHxNQMQMzU6l\n"\
		"WCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoVPpY72+eVthKzpMeyHkBn7ciumk5q\n"\
		"gLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUywQIDAQABAoIBADhg1u1Mv1hAAlX8\n"\
		"omz1Gn2f4AAW2aos2cM5UDCNw1SYmj+9SRIkaxjRsE/C4o9sw1oxrg1/z6kajV0e\n"\
		"N/t008FdlVKHXAIYWF93JMoVvIpMmT8jft6AN/y3NMpivgt2inmmEJZYNioFJKZG\n"\
		"X+/vKYvsVISZm2fw8NfnKvAQK55yu+GRWBZGOeS9K+LbYvOwcrjKhHz66m4bedKd\n"\
		"gVAix6NE5iwmjNXktSQlJMCjbtdNXg/xo1/G4kG2p/MO1HLcKfe1N5FgBiXj3Qjl\n"\
		"vgvjJZkh1as2KTgaPOBqZaP03738VnYg23ISyvfT/teArVGtxrmFP7939EvJFKpF\n"\
		"1wTxuDkCgYEA7t0DR37zt+dEJy+5vm7zSmN97VenwQJFWMiulkHGa0yU3lLasxxu\n"\
		"m0oUtndIjenIvSx6t3Y+agK2F3EPbb0AZ5wZ1p1IXs4vktgeQwSSBdqcM8LZFDvZ\n"\
		"uPboQnJoRdIkd62XnP5ekIEIBAfOp8v2wFpSfE7nNH2u4CpAXNSF9HsCgYEA2l8D\n"\
		"JrDE5m9Kkn+J4l+AdGfeBL1igPF3DnuPoV67BpgiaAgI4h25UJzXiDKKoa706S0D\n"\
		"4XB74zOLX11MaGPMIdhlG+SgeQfNoC5lE4ZWXNyESJH1SVgRGT9nBC2vtL6bxCVV\n"\
		"WBkTeC5D6c/QXcai6yw6OYyNNdp0uznKURe1xvMCgYBVYYcEjWqMuAvyferFGV+5\n"\
		"nWqr5gM+yJMFM2bEqupD/HHSLoeiMm2O8KIKvwSeRYzNohKTdZ7FwgZYxr8fGMoG\n"\
		"PxQ1VK9DxCvZL4tRpVaU5Rmknud9hg9DQG6xIbgIDR+f79sb8QjYWmcFGc1SyWOA\n"\
		"SkjlykZ2yt4xnqi3BfiD9QKBgGqLgRYXmXp1QoVIBRaWUi55nzHg1XbkWZqPXvz1\n"\
		"I3uMLv1jLjJlHk3euKqTPmC05HoApKwSHeA0/gOBmg404xyAYJTDcCidTg6hlF96\n"\
		"ZBja3xApZuxqM62F6dV4FQqzFX0WWhWp5n301N33r0qR6FumMKJzmVJ1TA8tmzEF\n"\
		"yINRAoGBAJqioYs8rK6eXzA8ywYLjqTLu/yQSLBn/4ta36K8DyCoLNlNxSuox+A5\n"\
		"w6z2vEfRVQDq4Hm4vBzjdi3QfYLNkTiTqLcvgWZ+eX44ogXtdTDO7c+GeMKWz4XX\n"\
		"uJSUVL5+CVjKLjZEJ6Qc2WZLl94xSwL71E41H4YciVnSCQxVc4Jw\n"\
		"-----END RSA PRIVATE KEY-----\n";

	fread(CypherText, sizeof(*CypherText), fsize, ifp);

	// Check CypherText Binary.
	int i;
	printf("Private Decrypt Section.\n");
	printf("Cypher Text Binary :\n");
	for (i = 0; i < fsize; i++) {
		printf("0x%X ", CypherText[i]);
	}
	printf("\n");




	int decrypted_length = private_decrypt(CypherText, strlen(CypherText), privateKey, decrypted);
	if (decrypted_length == -1)
	{
		printLastError("Private Decrypt failed \n");
		exit(0);
	}

	fwrite(decrypted, sizeof(*decrypted), decrypted_length, ofp);

}

int main(int argc, char *argv[])
{
	FILE *fIN;
	FILE *fOUT;
	errno_t error;
	char buf[255 + 1];

	if ((error = fopen_s(&fIN, "C://Projects/test_curl/Debug/plainRSA.txt", "r")) != 0) {
		strerror_s(buf, 255, error);
		printf("fopen_s error one \n%s\n", buf);
		return 0;
	}
	if ((error = fopen_s(&fOUT, "C://Projects/test_curl/Debug/cyphertextRSA.txt", "w+")) != 0) {
		strerror_s(buf, 255, error);
		printf("fopen_s error two \n%s\n", buf);
		return 0;
	}
	encrypt(fIN, fOUT);
	fclose(fIN);
	fclose(fOUT);

	if ((error = fopen_s(&fIN, "C://Projects/test_curl/Debug/cyphertextRSA.txt", "r+")) != 0) {
		strerror_s(buf, 255, error);
		printf("fopen_s error three \n%s\n", buf);
		return 0;
	}
	if ((error = fopen_s(&fOUT, "C://Projects/test_curl/Debug/decryptedRSA.txt", "w+")) != 0) {
		strerror_s(buf, 255, error);
		printf("fopen_s error four \n%s\n", buf);
		return 0;
	}
	decrypt(fIN, fOUT);
	fclose(fIN);
	fclose(fOUT);

	return 0;
}

行動規範の内容に同意します

回答2件

詳しく調べたわけではないのですが、以下の一文が参考になるかもしれません。

関数の返り値は,暗号化あるいは復号結果のデータサイズである. 失敗時は-1となる. 暗号化の場合は,平文データのサイズをRSA_size(rsa)にしてしまうと,暗号文がRSA_size(rsa)を越えてしまってエラーになる. よくわからないのだが順に試すと, RSA_size(rsa) - 11 だとうまくいく.

(出典: http://www.fireproject.jp/feature/c-language/openssl/rsa.html)

投稿2016/04/03 12:58