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Category:   Application (File Transfer/Sharing)  >   Red Hat Gluster Storage Vendors:   Red Hat
(Red Hat Issues Fix for Red Hat Gluster Storage) Samba Symlink Race Condition Lets Remote Authenticated Users View Non-Exported Files on the Target System
SecurityTracker Alert ID:  1039406
SecurityTracker URL:  http://securitytracker.com/id/1039406
CVE Reference:   CVE-2017-2619   (Links to External Site)
Date:  Sep 21 2017
Impact:   Disclosure of system information, Disclosure of user information
Fix Available:  Yes  Vendor Confirmed:  Yes  

Description:   A vulnerability was reported in Samba. A remote authenticated user can obtain files on the target system. Red Hat Gluster Storage is affected.

A remote authenticated user with write access to the exported portions of the file system on the target server via SMB1 unix extensions or NFS can rename a file on the target share and then create a symbolic link (symlink) to an arbitrary location on the target file system to potentially access the target file.

[Editor's note: The vendor indicates that the race condition is difficult to win but is theoretically possible.]

Jann Horn of Google reported this vulnerability.

Impact:   A remote authenticated user with write privileges on the target share can obtain files from non-exported directories on the target system.
Solution:   Red Hat has issued a fix for Red Hat Gluster Storage.

The Red Hat advisory is available at:

https://access.redhat.com/errata/RHSA-2017:2778

Vendor URL:  access.redhat.com/errata/RHSA-2017:2778 (Links to External Site)
Cause:   Access control error, State error
Underlying OS:  Linux (Red Hat Enterprise)

Message History:   This archive entry is a follow-up to the message listed below.
Mar 23 2017 Samba Symlink Race Condition Lets Remote Authenticated Users View Non-Exported Files on the Target System



 Source Message Contents

Subject:  [RHSA-2017:2778-01] Moderate: samba security, bug fix, and enhancement update

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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Moderate: samba security, bug fix, and enhancement update
Advisory ID:       RHSA-2017:2778-01
Product:           Red Hat Gluster Storage
Advisory URL:      https://access.redhat.com/errata/RHSA-2017:2778
Issue date:        2017-09-21
CVE Names:         CVE-2017-2619 CVE-2017-9461 
=====================================================================

1. Summary:

An update for samba is now available for Red Hat Gluster Storage 3.3 for
RHEL 6.

Red Hat Product Security has rated this update as having a security impact
of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which
gives a detailed severity rating, is available for each vulnerability from
the CVE link(s) in the References section.

2. Relevant releases/architectures:

Red Hat Gluster 3.3 Samba on RHEL-6 - noarch, x86_64

3. Description:

Samba is an open-source implementation of the Server Message Block (SMB)
protocol and the related Common Internet File System (CIFS) protocol, which
allow PC-compatible machines to share files, printers, and various
information.

Security Fix(es):

* A race condition was found in samba server. A malicious samba client
could use this flaw to access files and directories in areas of the server
file system not exported under the share definitions. (CVE-2017-2619)

* A flaw was found in the way Samba handled dangling symlinks. An
authenticated malicious Samba client could use this flaw to cause the smbd
daemon to enter an infinite loop and use an excessive amount of CPU and
memory. (CVE-2017-9461)

Red Hat would like to thank the Samba project for reporting CVE-2017-2619.
Upstream acknowledges Jann Horn (Google) as the original reporter of
CVE-2017-2619.

Bug Fix(es):

* In the samba configuration, by default the 'posix locking' is enabled and
'stat cache' is disabled. Enabling 'posix locking' sends the file lock
request to the bricks too, and disabling 'stat cache' blocks samba to cache
certain information at the samba layer. This led to decrease in performance
of SMB access of Red Hat Gluster Storage volumes  

As a fix, the following two options are included in the samba configuration
file:
posix locking = No
stat cache = Yes

Due to this, a slight improvement in the performance is observed.
(BZ#1436265)

4. Solution:

For details on how to apply this update, which includes the changes
described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing this update, the smb service will be restarted
automatically.

5. Bugs fixed (https://bugzilla.redhat.com/):

1334397 - Samba [RHEL6] : Upon smbd crash the log displays core dump path as /var/log/samba/cores/smbd but in actual the core is dumped in /var/log/cores
1426663 - [RHEL6] Samba: Yum update for Samba will fail due to higher versions in RHEL 6
1429472 - CVE-2017-2619 samba: symlink race permits opening files outside share directory
1436265 - Smb.conf options for performance improvements [RHEL6]
1444028 - [SAMBA-RHEL6]Unable to start smbd in RHEL6 as /run/smbd.pid does not exist
1459464 - CVE-2017-9461 samba: fd_open_atomic infinite loop due to wrong handling of dangling symlinks

6. Package List:

Red Hat Gluster 3.3 Samba on RHEL-6:

Source:
libldb-1.1.29-1.el6rhs.src.rpm
libtalloc-2.1.9-1.el6rhs.src.rpm
libtdb-1.3.12-1.1.el6rhs.src.rpm
libtevent-0.9.31-1.el6rhs.src.rpm
samba-4.6.3-5.el6rhs.src.rpm

noarch:
samba-common-4.6.3-5.el6rhs.noarch.rpm
samba-pidl-4.6.3-5.el6rhs.noarch.rpm

x86_64:
ctdb-4.6.3-5.el6rhs.x86_64.rpm
ctdb-tests-4.6.3-5.el6rhs.x86_64.rpm
ldb-tools-1.1.29-1.el6rhs.x86_64.rpm
libldb-1.1.29-1.el6rhs.x86_64.rpm
libldb-debuginfo-1.1.29-1.el6rhs.x86_64.rpm
libldb-devel-1.1.29-1.el6rhs.x86_64.rpm
libsmbclient-4.6.3-5.el6rhs.x86_64.rpm
libsmbclient-devel-4.6.3-5.el6rhs.x86_64.rpm
libtalloc-2.1.9-1.el6rhs.x86_64.rpm
libtalloc-debuginfo-2.1.9-1.el6rhs.x86_64.rpm
libtalloc-devel-2.1.9-1.el6rhs.x86_64.rpm
libtdb-1.3.12-1.1.el6rhs.x86_64.rpm
libtdb-debuginfo-1.3.12-1.1.el6rhs.x86_64.rpm
libtdb-devel-1.3.12-1.1.el6rhs.x86_64.rpm
libtevent-0.9.31-1.el6rhs.x86_64.rpm
libtevent-debuginfo-0.9.31-1.el6rhs.x86_64.rpm
libtevent-devel-0.9.31-1.el6rhs.x86_64.rpm
libwbclient-4.6.3-5.el6rhs.x86_64.rpm
libwbclient-devel-4.6.3-5.el6rhs.x86_64.rpm
pyldb-1.1.29-1.el6rhs.x86_64.rpm
pyldb-devel-1.1.29-1.el6rhs.x86_64.rpm
pytalloc-2.1.9-1.el6rhs.x86_64.rpm
pytalloc-devel-2.1.9-1.el6rhs.x86_64.rpm
python-tdb-1.3.12-1.1.el6rhs.x86_64.rpm
python-tevent-0.9.31-1.el6rhs.x86_64.rpm
samba-4.6.3-5.el6rhs.x86_64.rpm
samba-client-4.6.3-5.el6rhs.x86_64.rpm
samba-client-libs-4.6.3-5.el6rhs.x86_64.rpm
samba-common-libs-4.6.3-5.el6rhs.x86_64.rpm
samba-common-tools-4.6.3-5.el6rhs.x86_64.rpm
samba-dc-4.6.3-5.el6rhs.x86_64.rpm
samba-dc-libs-4.6.3-5.el6rhs.x86_64.rpm
samba-debuginfo-4.6.3-5.el6rhs.x86_64.rpm
samba-devel-4.6.3-5.el6rhs.x86_64.rpm
samba-krb5-printing-4.6.3-5.el6rhs.x86_64.rpm
samba-libs-4.6.3-5.el6rhs.x86_64.rpm
samba-python-4.6.3-5.el6rhs.x86_64.rpm
samba-test-4.6.3-5.el6rhs.x86_64.rpm
samba-test-libs-4.6.3-5.el6rhs.x86_64.rpm
samba-vfs-glusterfs-4.6.3-5.el6rhs.x86_64.rpm
samba-winbind-4.6.3-5.el6rhs.x86_64.rpm
samba-winbind-clients-4.6.3-5.el6rhs.x86_64.rpm
samba-winbind-krb5-locator-4.6.3-5.el6rhs.x86_64.rpm
samba-winbind-modules-4.6.3-5.el6rhs.x86_64.rpm
tdb-tools-1.3.12-1.1.el6rhs.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2017-2619
https://access.redhat.com/security/cve/CVE-2017-9461
https://access.redhat.com/security/updates/classification/#moderate

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2017 Red Hat, Inc.
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