There's another part to this story; however, it only references the Dolphins and their draft options. This is the only Cowboys info found in this particular rumor.
http://insider.espn.go.com/nfl/features/rumors
Trading partners for No. 12 pick
Philadelphia Eagles: They want to grab one of the elite safeties, and have lots of trade ammo, including two second-rounders.
Green Bay Packers: Mentioned by ESPN Insider Adam Schefter as a team looking to move up.
Dallas Cowboys: Do the 'Boys need to move up this badly? Probably not, but we're still waiting for Jerry Jones to make his first offseason splash.
San Diego Chargers: This depends on how badly they feel that they want Dan Williams and/or C.J. Spiller.
New England Patriots: This is based largely upon their cache of picks (including three second-rounders). Any other season, an intra-division trade wouldn't happen. This year? All bets are off.
Source: Dave Hyde, South Florida Sun-Sentinel