Bug 82041

Summary: ignores wide links, serving files which shouldn't be served
Product: [Retired] Red Hat Linux Reporter: Chris Ricker <chris.ricker>
Component: sambaAssignee: Jay Fenlason <fenlason>
Status: CLOSED ERRATA QA Contact: David Lawrence <dkl>
Severity: medium Docs Contact:
Priority: medium    
Version: 8.0CC: dkelson, jfeeney, kmaraas
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2003-04-08 07:00:50 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Chris Ricker 2003-01-16 18:05:35 UTC
Samba has two options which control Samba's behavior when a Samba client
requests a file which is a symbolic link.

follow symlinks = yes

instructs Samba to give the requesting client the target of the symlink

If follow symlinks = yes, then a second option enters in:

wide links = yes

instructs Samba to serve the target of the symlink, even if the target is
outside the directory space being shared

wide links = no

instructs Samba to serve the target of the symlink only when the target is
within the directory space being shared

This behavior is documented in the Samba documentation


However, on Red Hat 8 (samba-2.2.5-10) this option does not work. Whether wide
links = yes or wide links = no, targets of symlinks outside shared space are
always served if follow symlinks = yes.

This has the usual obvious security implications....

To reproduce this easily, on one machine use a trivial smb.conf file

# cat /etc/samba/smb.conf
workgroup = EXAMPLE
netbios name = station1
follow symlinks = yes

path = /tmp
writeable = yes
guest ok = yes
wide links = no

Then on that machine

# cd /tmp
# ln -s /etc/passwd .

Connect from another machine (guest access is fine) and download passwd. Your
download will succeed, even though it shouldn't

Comment 1 Jay Fenlason 2003-01-31 22:52:43 UTC
This only occurs on symlinks to files, rather than symlinks to directories.  I
get the same behavior with samba-2.2.7a on an OpenBSD-2.1 system, so this is
either a generic Samba bug or an undocumented feature.  I've opened a bug report
upstream, so we'll see what they say.

Note that this does not allow reading of files that the user cannot usually
read: a symlink to /etc/shadow correctly returns "Access Denied" when a Windows
client attempts to read it.  Also note that any user that can create a symlink
to /etc/passwd can also do "cp /etc/passwd resume.txt", so the actual security
enhancement in blocking symlinks to files is minimal.

Comment 2 Jay Fenlason 2003-03-06 20:28:38 UTC
This is fixed in samba-2.2.8pre1 and later.  I'll probably make errata after
2.2.8 is released.

Comment 3 Kjartan Maraas 2003-04-03 19:42:20 UTC
These were included in the current errata, right? Close this then?

Comment 4 Mark J. Cox 2003-04-08 07:00:50 UTC
An errata has been issued which should help the problem described in this bug report. 
This report is therefore being closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files, please follow the link below. You may reopen 
this bug report if the solution does not work for you.