- 1 year ago
How to use bcrypt_gensalt with /dev/urandom on Windows?
On Windows, you can use the bcrypt_gensalt
function from the bcrypt library to generate a salt for password hashing. However, since Windows doesn't have a /dev/urandom
device like Unix-based systems, you need to find an alternative way to obtain cryptographically secure random bytes.
One common approach is to use the Windows Cryptographic API (CryptoAPI) to generate random bytes. Here's a step-by-step guide on how to use bcrypt with the Windows Cryptographic API to generate a secure salt:
Step 1: Include Necessary Headers
c#include <bcrypt.h>
#pragma comment(lib, "bcrypt.lib")
Step 2: Generate Salt
c#define SALT_LENGTH 16 // Adjust the length of the salt as needed (16 bytes is recommended)
// Function to generate a secure random salt using the Windows Cryptographic API
BOOL GenerateSecureSalt(PUCHAR salt, ULONG saltLength)
{
BCRYPT_ALG_HANDLE hProvider;
if (BCryptOpenAlgorithmProvider(&hProvider, BCRYPT_RNG_ALGORITHM, NULL, 0) != STATUS_SUCCESS)
{
return FALSE;
}
if (BCryptGenRandom(hProvider, salt, saltLength, BCRYPT_USE_SYSTEM_PREFERRED_RNG) != STATUS_SUCCESS)
{
BCryptCloseAlgorithmProvider(hProvider, 0);
return FALSE;
}
BCryptCloseAlgorithmProvider(hProvider, 0);
return TRUE;
}
// Usage:
int main()
{
UCHAR salt[SALT_LENGTH];
if (GenerateSecureSalt(salt, SALT_LENGTH))
{
// Now you have a secure random salt in the 'salt' buffer.
// You can use it with bcrypt_gensalt function to generate the hashed password.
// ...
}
else
{
// Failed to generate a secure random salt.
// Handle the error.
}
return 0;
}
In the code above, we first define the length of the salt we want to generate (SALT_LENGTH). Then, we create a function GenerateSecureSalt
that uses the BCryptGenRandom
function from the Windows Cryptographic API to generate cryptographically secure random bytes.
Remember to adjust the length of the salt according to your specific needs. A common recommendation is to use a salt length of 16 bytes (128 bits) for bcrypt.