Smith and veteran Ray-Ray Armstrong both worked out for the Cowboys, with the team concerned about its depth with Leighton Vander Esch likely to miss his fifth straight game with a neck injury, rookie Luke Gifford needing surgery to repair a fractured forearm and Joe Thomas battling a knee injury.
Smith, 30, has a history with passing game coordinator Kris Richard from their time together with the Seattle Seahawks. He was MVP of Super Bowl XLVIII and has started 102 games for four teams in his career. He played in two games with the Jacksonville Jaguars this season before his release in November.
He is the second player the Cowboys have acquired in-season who had ties to Richard from Seattle. The Cowboys acquired defensive lineman Michael Bennett in a trade with the New England Patriots in October.