C: 无法解密消息 Openssl

Question

我是密码学的新手，所以我决定创建一个简单的程序来打开一个文件加密数据，将其放入 etest.txt，然后打开该文件解密并将其放入 detest.txt.我知道这听起来很奇怪，但它是出于教育目的。所以这是我的代码。

#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <stdio.h>
#include <string.h>

int main(void) {
size_t pri_len;            // Length of private key
size_t pub_len;            // Length of public key
char   *pri_key;           // Private key
char   *pub_key;           // Public key
char   *msg = malloc(256);  // Message to encrypt
char   *encrypt = NULL;    // Encrypted message
char   *decrypt = NULL;    // Decrypted message
char   *err;               // Buffer for any error messages

// Generate key pair
RSA *keypair = RSA_generate_key(2048, 3, NULL, NULL);
 FILE *in   = fopen("test.txt", "rb");
 FILE *out  = fopen("etest.txt", "wb");

 if(in == NULL)
 {
    printf("in Error is %d (%s).\n", errno, strerror(errno));
 }
 if(out == NULL)
 {
    printf("out Error is %d (%s).\n", errno, strerror(errno));
 }

encrypt = malloc(RSA_size(keypair));
for(;;)
{
    //213 because of padding
    memset(msg, '[=10=]', 256);
    memset(encrypt, '[=10=]', 256);
    fread(msg, 213, 1, in);

    if((RSA_public_encrypt(strlen(msg), (unsigned char*)msg, (unsigned char*)encrypt,
                                         keypair, RSA_PKCS1_OAEP_PADDING)) == -1) {
        ERR_load_crypto_strings();
        ERR_error_string(ERR_get_error(), err);
        fprintf(stderr, "Error encrypting message: %s\n", err);           
    }

     if(fwrite(encrypt, 256, 1, out) != 1)
     {
       printf("fwrite Error is %d (%s).\n", errno, strerror(errno));
     }

    if(feof(in))
    {
        break;
    }      
}

fclose(in);
fclose(out);

in   = fopen("etest.txt", "rb");
out  = fopen("dtest.txt", "wb");

 if(in == NULL)
 {
    printf("in Error is %d (%s).\n", errno, strerror(errno));
 }
 if(out == NULL)
 {
    printf("out Error is %d (%s).\n", errno, strerror(errno));
 }

decrypt = malloc(RSA_size(keypair));

for(;;)
{
     //I use malloc because if i didnt it would from file and if it filled the msg and if this function would execute second time it would not overwrite the whole buffer and would cause problem
     memset(decrypt, '[=10=]', 256);
     memset(msg, '[=10=]', 256);

     fread(msg, 256, 1, in);


     if(RSA_private_decrypt(256, (unsigned char*)msg, (unsigned char*)decrypt,
                           keypair, RSA_PKCS1_OAEP_PADDING) == -1) {
        ERR_load_crypto_strings();
        ERR_error_string(ERR_get_error(), err);
        fprintf(stderr, "Error decrypting message: %s\n", err);
    }

    fwrite(decrypt, 256, 1, out);

    if(feof(in))
    {
      break;
    }
}

fclose(in);
fclose(out);
RSA_free(keypair);
return 0;

}

当我运行编码时，它返回错误消息：Error decrypting message: error:0407A079:rsa routines:RSA_padding_check_PKCS1_OAEP:oaep decoding error 但是如果我删除这段代码 memset(msg, '[=14=]', 256); 它表明一切正常，但它会导致问题，因为 msg 缓冲区是用第二个 fread() 函数覆盖的前几个字节覆盖。对不起，如果我的问题听起来很愚蠢。希望你能帮忙。谢谢。

Answer 1

您使用的 fwrite(decrypt, 256, 1, out); 是错误的。size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream) 第二个参数是要读取的每个元素的字节大小第三个是元素的数量，每个元素的大小为大小字节。

C: 无法解密消息 Openssl

C: Can not decrypt message Openssl

c

encryption

file-io

openssl

rsa