According to Space Exploration and Humanity: A Historical Encyclopedia:
During Vostok, Voskhod, and Soyuz flights, urine and feces were entrained in an air stream and collected for disposal at the end of the mission
Spaceflight Life Support and Biospherics makes the same claim.
This suggests, remarkably, that there was a form of space toilet aboard or at the least a pneumatic collection hose. No other details seem to appear in those books, unfortunately, and I'm a little skeptical of the claim.
Soyuz: A Universal Spacecraft is scant on details regarding the Soyuz waste facilities, and of course they've probably evolved from those on Vostok.