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tokencrypto.cpp
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tokencrypto.cpp
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#include <fstream>
#include "tokencrypto.h"
#include "cryptopp/hkdf.h"
#include "cryptopp/sha.h"
#include "cryptopp/osrng.h"
using namespace CryptoPP;
using namespace std;
namespace tokencrypto{
/**
* Generates a random salt of the specified lenght.
*
* @param int the number of bytes to generate
* @returns byte* the generated salt, in bytes
**/
byte* generateRandomSalt(int size=DEFAULT_SALT_SIZE){
// Get a random number from the OS
byte* random_salt;
random_salt = new byte[size];
AutoSeededRandomPool rng;
rng.GenerateBlock(random_salt, size);
byte* salt;
salt = new byte[size];
memset(salt, 0, sizeof(salt));
memcpy(salt, random_salt, size);
return salt;
}
/**
* Derivate a key using the HKDF algorithm.
*
* The underlying algorithm used is SHA256.
*
* @param byte* the adress of the input keyring material
* @param byte* the adress of the salt to use to derivate the key
* @parm int the size of the key to output
* @param byte* the adress of some additionale info to use while derivating
* the key.
* @returns byte* the derivated output keyring material
**/
byte* deriveKey(int size, byte* ikm, int ikm_size, byte* salt,
int salt_size){
byte* okm = new byte[size];
HMACKeyDerivationFunction<SHA256> hkdf;
hkdf.DeriveKey(okm, size,
ikm, ikm_size,
salt, salt_size,
NULL, 0);
return okm;
}
/**
* Reads a key from the filesystem and return it's content in bytes
*
* @param string the name of the file to read from the disk
* @returns byte* the content of the file, in bytes
**/
byte* readFile(string filename){
FILE* pFile;
long lSize;
char* buffer;
size_t result;
pFile = fopen(filename.c_str(), "r");
if (pFile == NULL) {
fputs("Unknown file", stderr); exit(1);
}
// obtain file size:
fseek(pFile, 0, SEEK_END);
lSize = ftell(pFile);
rewind(pFile);
// allocate memory to contain the whole file:
buffer = (char*) malloc(sizeof(char) * lSize);
if (buffer == NULL) {
fputs("Memory error", stderr);
exit (2);
}
// copy the file into the buffer:
result = fread(buffer, 1, lSize,pFile);
if ((long)result != lSize) {
fputs("Reading error", stderr);
exit (3);
}
// terminate
fclose (pFile);
return (byte*) buffer;
}
void writeFile(string filename, byte* content, int size){
ofstream oFile;
oFile.open(filename.c_str(), ofstream::binary);
oFile.write((char*) content, size);
oFile.close();
}
}