Look around here at part #34607. Looks like a double aluminum(? some type of soft metal that gets used only once) crush washer for either side of the hose at the banjo bolt? Scroll down in the parts listing below the illustration then click on that for the images and Subaru part number. Once you get the hang of the part no./newer part no. updates in the small title blocks of the illustrations, this is a great way to shop for OEM Subaru parts vs. the guy at the parts counter at the dealership....at least my dealership anyway.
https://parts.subaru.com/a/Subaru_2004_WRX-205-5MT-4WD-SEDAN/_54100_6028433/POWER-STEERING-SYSTEM-HOSE--TANK-04MY-/G11-346-05.html
https://parts.subaru.com/p/Subaru_2004_WRX-205-5MT-4WD-SEDAN/Power-Steering-Hose-O-Ring/49246166/34621AC024.html