Bug 1305970

Summary:	--disable-epsv option ignored for IPv6 hosts
Product:	Red Hat Enterprise Linux 6	Reporter:	Martin Frodl <mfrodl>
Component:	curl	Assignee:	Kamil Dudka <kdudka>
Status:	CLOSED WONTFIX	QA Contact:	BaseOS QE Security Team <qe-baseos-security>
Severity:	low	Docs Contact:
Priority:	low
Version:	6.8	CC:	emrakova, kdudka
Target Milestone:	rc	Keywords:	ManPageChange
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:
Clones:	1305974 (view as bug list)		Environment:
Last Closed:	2016-07-13 14:09:09 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1305974
Bug Blocks:

Description Martin Frodl 2016-02-09 17:21:11 UTC

Description of problem:

With --disable-epsv, curl should not attempt to use EPSV mode no matter what. When the host name in URL is 'localhost' or 'localhost.localdomain', EPSV is not disabled. On the other hand, when 127.0.0.1 is used instead, --disable-epsv is respected.

Version-Release number of selected component (if applicable):
curl-7.19.7-51.el6.x86_64

Steps to reproduce:
# yum -y install vsftpd
# echo OK > /var/ftp/pub/test
# service vsftpd start
# curl -v --disable-epsv ftp://localhost/pub/test

Actual results:
> EPSV
* Connect data stream passively
< 229 Entering Extended Passive Mode (|||20246|).
*   Trying 127.0.0.1... connected

Expected results:
> PASV
* Connect data stream passively
< 227 Entering Passive Mode (127,0,0,1,251,224).
*   Trying 127.0.0.1... connected

Comment 2 Eva Mrakova 2016-02-10 07:48:48 UTC

Hi,

according to several resources curl option --disable-epsv has no effect for 
IPv6 hosts.
For curl-7.19.7-51.el6 it works OK for localhost4 and also for localhost
together with curl --ipv4 option.

See e.g.
https://curl.haxx.se/libcurl/c/CURLOPT_FTP_USE_EPSV.html
...
If the server is an IPv6 host, this option will have no effect as of 7.12.3
...

Comment 3 Martin Frodl 2016-02-10 08:51:01 UTC

Thanks for the explanation. Still, I think this peculiarity should be documented right in curl man page shipped in RHEL at the very least.

Comment 4 Kamil Dudka 2016-02-10 11:52:33 UTC

Eva, thank you for replying on this!

I believe the behavior is already documented in the RHEL-6 man page.

$ rpm -q libcurl-devel
libcurl-devel-7.19.7-46.el6.i686

$ man curl_easy_setopt | grep -A8 CURLOPT_FTP_USE_EPSV
       CURLOPT_FTP_USE_EPSV
              Pass  a  long.  If the value is 1, it tells curl to use the EPSV
              command when doing passive FTP downloads (which it  always  does
              by  default). Using EPSV means that it will first attempt to use
              EPSV before using PASV, but if you pass zero to this option,  it
              will not try using EPSV, only plain PASV.

              If  the  server is an IPv6 host, this option will have no effect
              as of 7.12.3.

See also: https://github.com/curl/curl/commit/0966ddaf

Comment 5 Martin Frodl 2016-02-10 12:16:54 UTC

I would still argue that a man page provided by a devel subpackage is not the most fortunate place to provide this information. Not for a user who does not give a tinker's cuss about the internal affairs of curl and only cares about the command-line interface and the man page shipped with it.

Obviously, this is a not a high priority bug which ought to be fixed on a short notice. Nonetheless, I believe adding that one sentence to curl man page still does make sense.

Comment 6 Kamil Dudka 2016-02-12 17:52:46 UTC

upstream commit:

https://github.com/curl/curl/commit/curl-7_47_1-30-g4ef6b2d

Comment 7 Kamil Dudka 2016-07-13 14:09:09 UTC

RHEL-6 is in Production Phase 2, which means that only critical and security bugs are fixed.  The current documentation is technically correct.  Additional documentation improvements on this topic will be included in RHEL-7.