Bug 1662705 (CVE-2018-20483)

Summary: CVE-2018-20483 wget: Information exposure in set_file_metadata function in xattr.c
Product: [Other] Security Response Reporter: Pedro Sampaio <psampaio>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abhgupta, dbaker, huzaifas, john.j5live, jokerman, kdudka, paul, sthangav, thozza, trankin
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: wget 1.20.1 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2019-11-06 00:51:34 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 1662833, 1662834, 1662851, 1662852    
Bug Blocks: 1662706    

Description Pedro Sampaio 2018-12-31 21:09:50 UTC
set_file_metadata in xattr.c in GNU Wget before 1.20.1 stores a file's origin URL in the user.xdg.origin.url metadata attribute of the extended attributes of the downloaded file, which allows local users to obtain sensitive information (e.g., credentials contained in the URL) by reading this attribute, as demonstrated by getfattr. This also applies to Referer information in the user.xdg.referrer.url metadata attribute. According to 2016-07-22 in the Wget ChangeLog, user.xdg.origin.url was partially based on the behavior of fwrite_xattr in tool_xattr.c in curl.

References:

http://git.savannah.gnu.org/cgit/wget.git/tree/NEWS

Upstream patches:

http://git.savannah.gnu.org/cgit/wget.git/commit/?id=c125d24762962d91050d925fbbd9e6f30b2302f8
http://git.savannah.gnu.org/cgit/wget.git/commit/?id=3cdfb594cf75f11cdbb9702ac5e856c332ccacfa

Comment 3 Huzaifa S. Sidhpurwala 2019-01-02 06:26:55 UTC
Analysis notes:

The security flaw exists in the way wget caches credentials passed as a part of the URL, in the extended attributes of the downloaded file. For example:

$ wget https://user1:redhat@localhost
[..] 
Saving to: ‘index.html’
index.html                          [ <=>                                                   ]       0  --.-KB/s    in 0s      

$ getfattr -n user.xdg.origin.url index.html 
# file: index.html
user.xdg.origin.url="https://user1:redhat@localhost/"

However credentials passed to wget using the "--user"/"--password" command line parameters are not cached. Similarly when "--user"/"--ask-password" is used which prompts the user to enter password on the command line (hereby preventing the password appearing in the command line history), the credentials will not be cached.

Further to this wget already has a command line flags called "--no-xattr" which when used will turn off storage of metadata in extended file attributes.

The patch applied by upstream ensures that:
1. --no-xattr is the default behaviour and storing of extended attributes can be turned on by the user using the new --xattr flag.
2. By default no username/passwords are not saved in the file extended attributes.

Comment 4 Huzaifa S. Sidhpurwala 2019-01-02 06:28:48 UTC
External References:

http://git.savannah.gnu.org/cgit/wget.git/tree/NEWS

Comment 6 Huzaifa S. Sidhpurwala 2019-01-02 06:46:16 UTC
Support for storing extended attribute information was added to wget in version 1.19 using the following commit:
http://git.savannah.gnu.org/cgit/wget.git/commit/?id=a933bdd31eee9c956a3b5cc142f004ef1fa94cb3

Therefore this issue does not affect the version of wget shipped with Red Hat Enterprise Linux 5, 6 and 7.

Comment 7 Huzaifa S. Sidhpurwala 2019-01-02 06:46:26 UTC
Created wget tracking bugs for this issue:

Affects: fedora-all [bug 1662833]

Comment 9 Huzaifa S. Sidhpurwala 2019-01-02 06:54:04 UTC
curl seems to have a similar issue, filed an upstream bug at:
https://github.com/curl/curl/issues/3423

except that in curl storage of extended attributes is disabled by default and needs to be explicitly enabled by passing the --xattr command line argument.

Comment 10 Huzaifa S. Sidhpurwala 2019-01-02 08:22:36 UTC
Mitigation:

wget users should pass credentials using the "--user/password" or the "--user/--ask-password" command line argument to wget or use --no-xattr to turn off saving extended attribute information. In curl downloading extended attributes is disabled by default.

Comment 12 Huzaifa S. Sidhpurwala 2019-01-02 08:24:07 UTC
Created curl tracking bugs for this issue:

Affects: fedora-all [bug 1662852]

Comment 15 Kamil Dudka 2019-01-03 10:39:15 UTC
(In reply to Huzaifa S. Sidhpurwala from comment #9)
> curl seems to have a similar issue, filed an upstream bug at:
> https://github.com/curl/curl/issues/3423

... and here is the corresponding pull request at curl upstream:

https://github.com/curl/curl/pull/3433

Comment 19 errata-xmlrpc 2019-11-05 22:06:04 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2019:3701 https://access.redhat.com/errata/RHSA-2019:3701

Comment 20 Product Security DevOps Team 2019-11-06 00:51:34 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2018-20483