Giant-killers Oldham will face Super League leaders Warrington Wolves in the sixth round of the Challenge Cup.
The Roughyeds, who beat last season's finalists Hull KR in round five, are ninth in the Championship.
The lowest-ranked team in the draw, French side Toulouse, who are fourth in League 1, go to Wakefield.
Holders Leeds Rhinos travel to Super League's bottom side Huddersfield, while Championship club Dewsbury host 19-time winners Wigan.
Catalans Dragons, who are second in the top flight, also face Championship opposition with a trip to Batley Bulldogs.
The sixth round draw, which took place on BBC Radio 4's Today programme, sees the top eight sides from last season's Super League enter the competition.
All ties will be played on 6-8 May and BBC Sport will televise two of the matches live.
Castleford v Salford
Oldham v Warrington
Dewsbury v Wigan
Batley v Catalans
Halifax v Widnes
St Helens v Hull FC
Huddersfield v Leeds
Wakefield v Toulouse