From owner-freebsd-bugs@FreeBSD.ORG Sat Jul 26 17:27:23 2014 Return-Path: Delivered-To: freebsd-bugs@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id ABB2C1F6 for ; Sat, 26 Jul 2014 17:27:23 +0000 (UTC) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 793D42E11 for ; Sat, 26 Jul 2014 17:27:23 +0000 (UTC) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.14.8/8.14.8) with ESMTP id s6QHRNI8098531 for ; Sat, 26 Jul 2014 17:27:23 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 192138] New: pw useradd and pw groupadd existence check races Date: Sat, 26 Jul 2014 17:27:23 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: bin X-Bugzilla-Version: 10.0-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: sheets@alum.mit.edu X-Bugzilla-Status: Needs Triage X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 26 Jul 2014 17:27:23 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=192138 Bug ID: 192138 Summary: pw useradd and pw groupadd existence check races Product: Base System Version: 10.0-STABLE Hardware: Any OS: Any Status: Needs Triage Severity: Affects Some People Priority: --- Component: bin Assignee: freebsd-bugs@FreeBSD.org Reporter: sheets@alum.mit.edu pw useradd has a race between checking if the username is already in use and updating the pw database: getpwnam check addpwent with useless return value check pw_update without check or nonzero return inside of lock pw groupadd has a race between checking if the groupname is already in use and updating the gr database: getgrnam check addgrent with useless return value check gr_update without check or nonzero return inside of lock This race is exhibited when multiple processes attempt to use the error return code of useradd/groupadd to indicate whether they have successfully created a unique user for themselves. If the race occurs, the uid/gid of the database entry may change out from under the first successful process as the second process finds an unused uid/gid and then updates the database using the same key (but the new uid/gid). I don't believe this bug is a security vulnerability except in contexts where attackers may have control over user/group creation by applications assuming that the database locks ensure non-collision. pw useradd/groupadd should either consistently let the operator overwrite existing groups/users or should consistently produce a name collision error pw groupadd/useradd sometimes exits due to a name collision and sometimes overwrites existing groups/users -- You are receiving this mail because: You are the assignee for the bug.