Generate sha256 with OpenSSL and C++

Question

I'm looking to create a hash with sha256 using openssl and C++. I know there's a similar post at Generate SHA hash in C++ using OpenSSL library, but I'm looking to specifically create sha256.

UPDATE:

Seems to be a problem with the include paths. It can't find any OpenSSL functions even though I included

#include "openssl/sha.h" 

and I included the paths in my build

-I/opt/ssl/include/ -L/opt/ssl/lib/ -lcrypto  

Answer 1

Here's how I did it:

void sha256_hash_string (unsigned char hash[SHA256_DIGEST_LENGTH], char outputBuffer[65]) {     int i = 0;      for(i = 0; i < SHA256_DIGEST_LENGTH; i++)     {         sprintf(outputBuffer + (i * 2), "%02x", hash[i]);     }      outputBuffer[64] = 0; }   void sha256_string(char *string, char outputBuffer[65]) {     unsigned char hash[SHA256_DIGEST_LENGTH];     SHA256_CTX sha256;     SHA256_Init(&sha256);     SHA256_Update(&sha256, string, strlen(string));     SHA256_Final(hash, &sha256);     int i = 0;     for(i = 0; i < SHA256_DIGEST_LENGTH; i++)     {         sprintf(outputBuffer + (i * 2), "%02x", hash[i]);     }     outputBuffer[64] = 0; }  int sha256_file(char *path, char outputBuffer[65]) {     FILE *file = fopen(path, "rb");     if(!file) return -534;      unsigned char hash[SHA256_DIGEST_LENGTH];     SHA256_CTX sha256;     SHA256_Init(&sha256);     const int bufSize = 32768;     unsigned char *buffer = malloc(bufSize);     int bytesRead = 0;     if(!buffer) return ENOMEM;     while((bytesRead = fread(buffer, 1, bufSize, file)))     {         SHA256_Update(&sha256, buffer, bytesRead);     }     SHA256_Final(hash, &sha256);      sha256_hash_string(hash, outputBuffer);     fclose(file);     free(buffer);     return 0; } 

It's called like this:

static unsigned char buffer[65]; sha256("string", buffer); printf("%s\n", buffer); 

Answer 2

std based

#include <iostream> #include <iomanip> #include <sstream> #include <string>  using namespace std;  #include <openssl/sha.h> string sha256(const string str) {     unsigned char hash[SHA256_DIGEST_LENGTH];     SHA256_CTX sha256;     SHA256_Init(&sha256);     SHA256_Update(&sha256, str.c_str(), str.size());     SHA256_Final(hash, &sha256);     stringstream ss;     for(int i = 0; i < SHA256_DIGEST_LENGTH; i++)     {         ss << hex << setw(2) << setfill('0') << (int)hash[i];     }     return ss.str(); }  int main() {     cout << sha256("1234567890_1") << endl;     cout << sha256("1234567890_2") << endl;     cout << sha256("1234567890_3") << endl;     cout << sha256("1234567890_4") << endl;     return 0; }