GenerateHash.c

//written by Rick2600 rick2600s[at]gmail{dot}com
//tweaked just a little by Peter Van Eeckhoutte
//http://www.corelan.be:8800
//This script will produce a hash for a given function name
//If no arguments are given, a list with some common function
//names and their corresponding hashes will be displayed
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
long rol(long value, int n);
long ror(long value, int n);
long calculate_hash(char *function_name);
void banner();

int main(int argc, char *argv[])
{
	banner();
	if (argc < 2)
	{
		int i=0;
		char *func[] =
		{
			"FatalAppExitA",
			"LoadLibraryA",
			"GetProcAddress",
			"WriteFile",
			"CloseHandle",
			"Sleep",
			"ReadFile",
			"GetStdHandle",
			"CreatePipe",
			"SetHandleInformation",
			"WinExec",
			"ExitProcess",
			0x0
		};
		printf("HASH\t\t\tFUNCTION\n----\t\t\t--------\n");
		while ( *func )
		{
			printf("0x%X\t\t%s\n", calculate_hash(*func), *func);
			i++;
			*func = func[i];
		}
	}
	else
	{
		char *manfunc[] = {argv[1]};
		printf("HASH\t\t\tFUNCTION\n----\t\t\t--------\n");
		printf("0x%X\t\t%s\n", calculate_hash(*manfunc), *manfunc);
	}
	return 0;
}

long calculate_hash( char *function_name )
{
	int aux = 0;
	unsigned long hash = 0;
	while (*function_name)
	{
		hash = ror(hash, 13);
		hash += *function_name;
		*function_name++;
	}
	while ( hash > 0 )
	{
		aux = aux << 8;
		aux += (hash & 0x00000FF);
		hash = hash >> 8;
	}
	hash = aux;
	return hash;
}

long rol(long value, int n)
{
	__asm__ ("rol %%cl, %%eax"
		: "=a" (value)
		: "a" (value), "c" (n)
	);
	return value;
}

long ror(long value, int n)
{
	__asm__ ("ror %%cl, %%eax"
		: "=a" (value)
		: "a" (value), "c" (n)
	);
	return value;
}

void banner()
{
	printf("----------------------------------------------\n");
	printf(" --==[ GenerateHash v1.0 ]==--\n");
	printf(" written by rick2600 and Peter Van Eeckhoutte\n");
	printf(" http://www.corelan.be:8800\n");
	printf("----------------------------------------------\n");
}