Does shroud prevent a creature's controller from targeting it with their own spells?

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.'" The rule makes no distinction between you and your opponents — it blanket-prohibits everyone from targeting that object.

This means if your own creature has shroud, you cannot target it with your own pump spells, auras, or activated abilities that require a target. The creature simply cannot be a legal target for anyone, period (CR 114.9: a spell or ability requires a legal target at the time it's announced and when it resolves).

This is the key difference between shroud and hexproof. Hexproof (CR 702.11a) only prevents opponents from targeting the creature — its controller may still target it freely. Shroud offers no such exemption.

Concrete example: You control a Gladecover Scout... wait, that has hexproof. Instead, imagine your creature gains shroud from Veil of Secrecy. If you then try to cast Giant Growth targeting that creature, you cannot — it is an illegal target. You'd have to target a different creature or the spell can't be cast that way.

If you want protection that still allows you to buff your own creature, look for hexproof instead of shroud. They look similar but have this important distinction in CR 702.11a vs. 702.18a.