No, there is no rule that you always have to use the passive form.
However, I realized that a Japanese sentence often omits the subject, often implying the subject is the speaker without other context, and that this style makes the sentence in the passive form.
He told me what I needed to know.
can be translated to
This Japanese sentence is correct. In fact, if this was an exam of translation, I would answer in this way because there would be no way to mark it as a mistake or blame for missing information. On the other hand, it is not colloquial (or naturally composed Japanese) because it is explicitly stating the subjects (action taker) "彼は" and "私が".
This translation can be modified to
by omitting "私が". There is almost no worry about misunderstanding about 'who needed to know it'. Japanese speakers assume the subject is "私が" by default.
The same sentence can be translated to
These Japanese sentences correspond more to
I was told by him what I needed to know.
and omit the subject "I" at both of the two occurrences. [Version (b) emphasizes 'by him' more than version (b').] The forms (b) and (b') sound more natural than (a). [I am not sure if (b) and (b') are more natural than (a').]
Even more colloquial form will be
This corresponds more to
I heard necessary things from him.
The words are changed, and the sentence might be a little strange as English. However, as a Japanese sentence, version (c) is concise but clear enough that it is delivering the same information as (a), and it is suitable for conversation.