Find all strings in list which have keywords in it from another list
Your general coding style is very readable.
You stick to PEP8 and your function and the variables are named reasonably.
You could optimize your code by using the built-in functions filter and all:

def string_search(strings, keys):
    return filter(lambda string: all(key in string for key in keys), strings)


Also do not use if var == True: but if var: instead.