c - 使用带有 EVP 接口(interface)的 AES/GCM 的段错误

Question

我找到了一些演示( wiki 、 github )，但它们不起作用。运行我编写的代码(引用上面链接中的代码)得到段错误(核心转储)

int main(int argc, char *argv[]){
    char *ciphertext;
    char *key;
    char *iv;
    char *plaintext;

     key = "AES256-GCM-KEY-1234567890abcdefg";
     iv = "8a9cef0205a3";
     ciphertext = "uatBMo8k7EAnDQuNK4CHASJerQZpCWv86PGditzdYnQV9uqotQ==";
     plaintext = "";

    decrypt(ciphertext, NULL, 0, NULL, key, iv, plaintext);
    return 0;
}

int decrypt(unsigned char *ciphertext, unsigned char *aad, int aad_len, unsigned char *tag, unsigned char *key, unsigned char *iv, unsigned char *plaintext){
    EVP_CIPHER_CTX *ctx;
    int len, ret;
    ctx = EVP_CIPHER_CTX_new();
    EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN,strlen(iv),NULL);
    EVP_DecryptInit_ex(ctx, NULL, NULL, key, iv);
    EVP_DecryptUpdate(ctx,plaintext, &len, ciphertext, strlen(ciphertext));//"segmentation fault"
    ret = EVP_DecryptFinal_ex(ctx, plaintext, &len);
    EVP_CIPHER_CTX_free(ctx);
    printf(ret > 0 ? "success!\n" : "failed!\n");
    return 0;
}

我很困惑，如何使用这个api在不验证的情况下解密？

Answer 1

您需要为指针分配内存(全部)

key = malloc(sizeof(*key) * strlen("AES256-GCM-KEY-1234567890abcdefg") + 1);

你应该使用这些标志编译你的main(如果gcc是编译器):-W -Wall -Wextra它会告诉你你的指针尚未初始化