NetBSD Problem Report #50823

From www@NetBSD.org  Wed Feb 17 12:07:02 2016
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Date: Wed, 17 Feb 2016 12:07:01 +0000 (UTC)
From: dcb314@hotmail.com
Reply-To: dcb314@hotmail.com
To: gnats-bugs@NetBSD.org
Subject: src/lib/libwrap/hosts_access.c:317: huge input data problem ?
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>Number:         50823
>Category:       lib
>Synopsis:       src/lib/libwrap/hosts_access.c:317: huge input data problem ?
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    lib-bug-people
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 17 12:10:00 +0000 2016
>Closed-Date:    Wed Feb 17 19:58:03 +0000 2016
>Last-Modified:  Mon Feb 22 18:40:00 +0000 2016
>Originator:     David Binderman
>Release:        cvs dated 20160216
>Organization:
>Environment:
>Description:

[src/lib/libwrap/hosts_access.c:317]: (warning) scanf without field width limits can crash with huge input data.

Source code is

    while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host)))
         /* void */ ;

but

    char    tok[BUFSIZ];

so the code assumes all lines in the file are shorter than BUFSIZ
and will smash the stack if they aren't. This might be a security issue.

>How-To-Repeat:

>Fix:

>Release-Note:

>Audit-Trail:
From: "Christos Zoulas" <christos@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/50823 CVS commit: src/lib/libwrap
Date: Wed, 17 Feb 2016 14:52:20 -0500

 Module Name:	src
 Committed By:	christos
 Date:		Wed Feb 17 19:52:20 UTC 2016

 Modified Files:
 	src/lib/libwrap: hosts_access.c

 Log Message:
 PR/50823: David Binderman: Limit scanf width


 To generate a diff of this commit:
 cvs rdiff -u -r1.20 -r1.21 src/lib/libwrap/hosts_access.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: wiz@NetBSD.org
State-Changed-When: Wed, 17 Feb 2016 19:58:03 +0000
State-Changed-Why:
Fixed by christos, thanks.


From: "Jeremy C. Reed" <reed@reedmedia.net>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: lib/50823: src/lib/libwrap/hosts_access.c:317: huge input data
 problem ?
Date: Mon, 22 Feb 2016 12:39:28 -0600 (CST)

 On Wed, 17 Feb 2016, dcb314@hotmail.com wrote:

 > This might be a security issue.

 Thanks again for reporting this. For the record, I received this from 
 one of the security officers: "This is not a security issue (unless 
 users other than root have write access to the /etc/hosts.{allow,deny} 
 files and the files that are referred from them, which is a security 
 issue itself), since the files parsed are under root control."

>Unformatted:

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