Does shroud prevent your own spells from targeting your permanents?

Shroud is a static ability defined in CR 702.18a: "Shroud means 'This permanent or player can't be the target of spells or abilities.'" Critically, this protection is absolute — it does not distinguish between friendly and enemy sources.

CR 114.9 states that if a spell or ability requires a target, the chosen target must be legal at the time it's chosen. A permanent with shroud simply cannot be chosen as a target by any spell or ability, regardless of who controls that spell or ability or who controls the shroud permanent.

This is one key difference between shroud and hexproof. Hexproof (CR 702.11a) only prevents targeting by opponents, so you can still target your own hexproof permanents with your own spells. Shroud, by contrast, locks out everyone — including yourself.

Concrete example: You control a Troll Ascetic (which has shroud). You want to enchant it with Rancor. Even though you control both permanents, you cannot cast Rancor targeting Troll Ascetic — shroud makes it an illegal target for your own Aura spell as well.

So if you want a creature that you can still buff yourself while protecting it from opponents, look for hexproof rather than shroud.