'Finds a pointer to the stack via __environ, which is an exported
symbol in libc, which points to the environment block.'

def stack(self):

    symbols = ['environ', '_environ', '__environ']
    for symbol in symbols:
        environ = self.lookup(symbol, 'libc')
        if environ:
            break
    else:
        log.error('Could    not    find    the    stack')
    stack = self.leak.p(environ)
    self.success(('*environ:    %#x' % stack))
    return stack
