Straightforward, forthright, aboveboard when applied to persons, their actions, or their methods mean honest and open.
Something straightforward is consistently direct and free from deviations or evasiveness.
Something forthright has directness like that of a thrust, or goes straight to the point without swerving or hesitating.
Something aboveboard is free from all traces of deception or duplicity. Aboveboard is chiefly used predicatively and applies more often to actions or methods than to persons.
Straightforward , forthright , and aboveboard are also used adverbially with the same implications and connotations as their adjectival forms.