Adding salt to sha256 openssl?

Question

This simple code take an user input and print to stdout the sha256 of the given string.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/sha.h>

int main()
{
 SHA256_CTX context;
 unsigned char md[SHA256_DIGEST_LENGTH];
 char *input;
 printf("Watta hash: ");
 scanf("%m[^\n]%*c", &input);
 size_t length = strlen((const char*)input);
 int i;
 SHA256_Init(&context);
 SHA256_Update(&context, (unsigned char*)input, length);
 SHA256_Final(md, &context);
 for(i=0; i<SHA256_DIGEST_LENGTH; i++){
   printf("%02x", md[i]);
 }
 printf("\n");
 free(input);
 return 0;
}

My question is: how to add a salt to this hash?

Answer 1

添加第二次调用SHA256_Update() ，其中数据是所需的盐。