在evp_encrypt不会工作在C循环 [英] evp_encrypt wont work in a for loop in c

问题描述

我是新来的，所以请原谅，如果我做错了什么。

I'm new here so please excuse if I'm doing something wrong.

我试图让使用加密的字符串数组，我使用该加密的EVP API。这工作得很好，但是当我尝试使用加密功能，在福尔环控制台给我什么。

I attempt to make an array with encrypted strings, I'm using the EVP API for the encryption. This works fine, but wHen I try to use the encrypt function in a foor loop the console gives me nothing.

下面是我的加密功能：

char *encrypt(char *key, char *iv, char * source){

    //char *target;
    int in_len, out_len;
    EVP_CIPHER_CTX ctx;
    in_len=strlen((const char *)source);
    unsigned char *target = (unsigned char *) malloc(in_len);
        //printf("This is the text before ciphering: %s\n",source);
        //printf("The length of the string is: %d\n",in_len);
        //starting the encryption process
        EVP_CIPHER_CTX_init(&ctx);
        EVP_EncryptInit_ex(&ctx,EVP_aes_128_cbc(),NULL,(unsigned char*) key,(unsigned char*)iv);
        EVP_EncryptUpdate(&ctx,target,&out_len,(unsigned char*)source,in_len);
        EVP_EncryptFinal_ex(&ctx,target,&out_len);
        target[out_len] = '\0';

        //EVP_CIPHER_CTX_cleanup(&ctx);


        return ((char *)target);
}

和主循环：

int main(){
    char source[17]="Shahababamamaaaa";
    char key[17]="ahardtobreakkey1";
    char iv[17] = "veryinterestingv";
     int rows = 1280;
     int cols = (3*800)/16;
        char *encrypted=encrypt(key, iv, source);
        printf("encrypted: %s\n", encrypted);
        char *encrypted2;
        encrypted2=encrypt(key, iv, encrypted);
        printf("encrypted2: %s\n", encrypted2);
        char *mx[rows];
        char *in, *temp;
        in = (char *) malloc ( cols * sizeof(char) );
        temp =(char *) malloc ( strlen(encrypted) );
        int i, j;

        for (i=0; i<5; i++){
            strcpy(in,encrypted);
            for(j=0;j<3;j++){
                    printf("in: %s\n", in);
                    strcpy(temp, encrypted2);
                    printf("temp: %s\n", temp);
                    memset(encrypted2,0x00, strlen(encrypted));
                    encrypted2=encrypt(key, iv,temp);
                    printf("encrypted2 nach j=%d : %s\n",j, encrypted2);

                    mx[i]=in;
            }

        }
        printf("Stele 0 Inhalt %s\n",mx[0]);
        printf("Laenge von 1 %d\n", strlen(mx[0]));

        //system ("PAUSE");
        free(in);
        return 0;

     }

我在想什么？它是IMPOSIBLE再次使用encrypt2？
非常感谢你。

What am I missing? Is it imposible to use encrypt2 again? Thank you very much.

推荐答案

正如你所说的，主要的问题是在你的加密（）函数，还你怎么称呼它。您正在使用malloc（）来分配自己的函数中的内存，从不释放它，这是一个内存泄漏（和malloc的是一个没有没有在C ++中是这样）。您还没有运行您的CTX的清理功能。和你的encrypt_final被覆盖的输出缓冲器的第一部分。所以，这里的清理加密（），和匹配解密（）：

As you said, the main problem is in your encrypt() function, but also how you call it. You are using malloc() to allocate memory inside your function, and never freeing it, which is a memory leak (and malloc is a no-no in c++ anyway). You are also not running the cleanup function for your ctx. And your encrypt_final is overwriting the first part of your output buffer. So, here's a cleaned up encrypt(), and a matching decrypt():

int encrypt(unsigned char *key, 
        unsigned char *iv, 
        unsigned char * source, 
        unsigned char* target, 
        int in_len) // Need an in length.  Not all input is going to be
                    // zero-terminated, for example if we're reading from a file

{

    int out_len; // Return the output length.  Because it also won't be null
                 // terminated, and may contain null characters inline

    int final_out_len; // So that we don't overwrite out_len with the final call
    EVP_CIPHER_CTX ctx;

    EVP_CIPHER_CTX_init(&ctx);
    EVP_EncryptInit_ex(&ctx,EVP_aes_128_cbc(),NULL,key,iv);
    EVP_EncryptUpdate(&ctx,target,&out_len,source,in_len);
    EVP_EncryptFinal_ex(&ctx,target+out_len,&final_out_len);
    EVP_CIPHER_CTX_cleanup(&ctx);
    return out_len+final_out_len; // need to sum these together, because both
                                  // encrypt calls wrote data
}

和解密：

int decrypt(unsigned char *key, 
        unsigned char *iv, 
        unsigned char * source, 
        unsigned char* target, 
        int in_len)
{

    int out_len=0,final_out_len=0;
    EVP_CIPHER_CTX ctx;
    EVP_CIPHER_CTX_init(&ctx);
    EVP_DecryptInit_ex(&ctx,EVP_aes_128_cbc(),NULL,key,iv);
    EVP_DecryptUpdate(&ctx,target,&out_len,source,in_len);
    EVP_DecryptFinal_ex(&ctx,target+out_len,&final_out_len);
    EVP_CIPHER_CTX_cleanup(&ctx);
    //Just to be nice, we'll add a zero at the end of the decrypted string
    target[out_len+final_out_len] = 0;
    return out_len+final_out_len;
}

拉​​在一起（在一个循环，来证明你的概念）：

Pulling it all together (in a loop, to prove your concept):

int _tmain(int argc, _TCHAR* argv[])
{
    unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
    unsigned char ivec[] = {1,2,3,4,5,6,7,8};
    char *raw_buffer = "This is a test string";
    int raw_count = strlen(raw_buffer);
    for (int i=0; i<5; i++){
        unsigned char *decrypted_buffer = new unsigned char[raw_count+64];
        unsigned char *encrypted_buffer = new unsigned char[raw_count+64];
        int final_len = encrypt(key,ivec,(unsigned char*)raw_buffer,(unsigned char*)encrypted_buffer,raw_count);
        int dec_len = decrypt(key,ivec,(unsigned char*)encrypted_buffer,(unsigned char*)decrypted_buffer,final_len);
        printf("raw_count: %i\nfinal_len: %i\ndec_len: %i\n",raw_count,final_len,dec_len);
        printf("Original str: \n%s\n",raw_buffer);
        printf("Encrypted: \n%s\n", encrypted_buffer);
        printf("Decrypted:\n%s\n\n\n", decrypted_buffer);
        delete[] decrypted_buffer;
        delete[] encrypted_buffer;
    }
    char c;
    c=getchar();
    return 0;
}

这篇关于在evp_encrypt不会工作在C循环的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！