[CentOS-docs] CentOS-docs Digest, Vol 95, Issue 2

666threesixes666

666threesixes666 at gmail.com
Fri Oct 3 04:23:57 UTC 2014


On 10/03/2014 12:11 AM, centos-docs-request at centos.org wrote:
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> Today's Topics:
>
>     1. Securing SSH --> Change ports (Theodor Sigurjon Andresson)
>     2. Re: Securing SSH --> Change ports (Karsten Wade)
>     3. Re: Securing SSH --> Change ports (Theodor Sigurjon Andresson)
>     4. Re: Securing SSH --> Change ports (PJ Welsh)
>     5. Re: Securing SSH --> Change ports (Theodor Sigurjon Andresson)
>     6. Re: Securing SSH --> Change ports (Manuel Wolfshant)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 2 Oct 2014 22:45:29 +0000
> From: Theodor Sigurjon Andresson <TheodorSiAn at kvenno.is>
> To: "centos-docs at centos.org" <centos-docs at centos.org>
> Subject: [CentOS-docs] Securing SSH --> Change ports
> Message-ID: <9C6DB64A0CF97645A5C90525A4C4C0CC0512C494 at CRONUS>
> Content-Type: text/plain; charset="us-ascii"
>
> In there you are almost telling people that security through obscurity is a good way.
> That might sometimes be true but in this case it could mean that you would be handing passwords and other data out.
>
> When you start SSH on port 22 it is done with root privileges because the root user is the only one that can use ports below 1024. Root is the only user that can listen to that port or do something with it. If you move the port to 2222 for example you move SSH to a port that can be used with out a privileged user. This would mean I could write a script that listens to port 2222 and mimics SSH to capture the passwords. Changing the port of SSH to 2222 or anything above 1024 makes SSH less secure. Pretty ironic that this is in the "Securing SSH" chapter.  This should never be done.
>
> Location: http://wiki.centos.org/HowTos/Network/SecuringSSH#head-3579222198adaf43a3ecbdc438ebce74da40d8ec
> username: TheodorAndresson
>
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 02 Oct 2014 15:49:59 -0700
> From: Karsten Wade <kwade at redhat.com>
> To: centos-docs at centos.org
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
> Message-ID: <542DD697.3000308 at redhat.com>
> Content-Type: text/plain; charset=windows-1252
>
> -----BEGIN PGP SIGNED MESSAGE-----
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> On 10/02/2014 03:45 PM, Theodor Sigurjon Andresson wrote:
>> In there you are almost telling people that security through
>> obscurity is a good way. That might sometimes be true but in this
>> case it could mean that you would be handing passwords and other
>> data out.
>>
>> When you start SSH on port 22 it is done with root privileges
>> because the root user is the only one that can use ports below
>> 1024. Root is the only user that can listen to that port or do
>> something with it. If you move the port to 2222 for example you
>> move SSH to a port that can be used with out a privileged user.
>> This would mean I could write a script that listens to port 2222
>> and mimics SSH to capture the passwords. Changing the port of SSH
>> to 2222 or anything above 1024 makes SSH less secure. Pretty ironic
>> that this is in the "Securing SSH" chapter.  This should never be
>> done.
>>
>> Location:
>> http://wiki.centos.org/HowTos/Network/SecuringSSH#head-3579222198adaf43a3ecbdc438ebce74da40d8ec
>>
>>
> username: TheodorAndresson
>> _______________________________________________ CentOS-docs mailing
>> list CentOS-docs at centos.org
>> http://lists.centos.org/mailman/listinfo/centos-docs
>>
> What do you think about using a privileged but unassigned port such as
> 101?
>
> - - Karsten
> - -- 
> Karsten 'quaid' Wade        .^\          CentOS Doer of Stuff
> http://TheOpenSourceWay.org    \  http://community.redhat.com
> @quaid (identi.ca/twitter/IRC)  \v'             gpg: AD0E0C41
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>
> ------------------------------
>
> Message: 3
> Date: Thu, 2 Oct 2014 23:47:56 +0000
> From: Theodor Sigurjon Andresson <TheodorSiAn at kvenno.is>
> To: Mail list for wiki articles <centos-docs at centos.org>
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
> Message-ID: <9C6DB64A0CF97645A5C90525A4C4C0CC0512C4BF at CRONUS>
> Content-Type: text/plain; charset="us-ascii"
>
> To change it to unassigned privileged port would be a much better idea if the user insists on changing it. I personally don't like the idea of security through obscurity at all.
> However if I remember correctly there are some programs that depend on SSH to be run on port 22. Usually easily changed but sometimes it can't be. I might be wrong though.
>
> ________________________________________
> From: centos-docs-bounces at centos.org [centos-docs-bounces at centos.org] on behalf of Karsten Wade [kwade at redhat.com]
> Sent: Thursday, October 02, 2014 22:49
> To: centos-docs at centos.org
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 10/02/2014 03:45 PM, Theodor Sigurjon Andresson wrote:
>> In there you are almost telling people that security through
>> obscurity is a good way. That might sometimes be true but in this
>> case it could mean that you would be handing passwords and other
>> data out.
>>
>> When you start SSH on port 22 it is done with root privileges
>> because the root user is the only one that can use ports below
>> 1024. Root is the only user that can listen to that port or do
>> something with it. If you move the port to 2222 for example you
>> move SSH to a port that can be used with out a privileged user.
>> This would mean I could write a script that listens to port 2222
>> and mimics SSH to capture the passwords. Changing the port of SSH
>> to 2222 or anything above 1024 makes SSH less secure. Pretty ironic
>> that this is in the "Securing SSH" chapter.  This should never be
>> done.
>>
>> Location:
>> http://wiki.centos.org/HowTos/Network/SecuringSSH#head-3579222198adaf43a3ecbdc438ebce74da40d8ec
>>
>>
> username: TheodorAndresson
>> _______________________________________________ CentOS-docs mailing
>> list CentOS-docs at centos.org
>> http://lists.centos.org/mailman/listinfo/centos-docs
>>
> What do you think about using a privileged but unassigned port such as
> 101?
>
> - - Karsten
> - --
> Karsten 'quaid' Wade        .^\          CentOS Doer of Stuff
> http://TheOpenSourceWay.org    \  http://community.redhat.com
> @quaid (identi.ca/twitter/IRC)  \v'             gpg: AD0E0C41
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> TVkAoJXSaHTe/7PmdAEhzzmSjkzL02es
> =y+y6
> -----END PGP SIGNATURE-----
> _______________________________________________
> CentOS-docs mailing list
> CentOS-docs at centos.org
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>
> ------------------------------
>
> Message: 4
> Date: Thu, 2 Oct 2014 18:49:37 -0500
> From: PJ Welsh <pjwelsh at gmail.com>
> To: Mail list for wiki articles <centos-docs at centos.org>
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
> Message-ID:
> 	<CAMGrxtEbcfRn3SiWi29OZ_nBH82y_b1_7A_QvpmHYXpER68mrw at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> The context for ssh !22 is about what others could/would do to a ssh
> daemon. This includes script kiddies or some zero day exploit trolling for
> *easy* targets. If you have someone creating a listener on the server, you
> have an entirely different issue. How often do you randomly connect to some
> system on port 2222 and provide *your* username and password? I am *not*
> saying security through obscurity = security, but many IDS/IPS/anti-port
> scanners will begin defensive actions when you plow through ports looking
> for ssh connection. So instead of being an easier 1 port script kiddie
> target you *layer* defenses (including possible STO). Basically anything to
> slow down or deter or prevent an attack is good IMHO.
>
> Just my 2cents of course.
>
> pjwelsh
>
> On Thu, Oct 2, 2014 at 5:45 PM, Theodor Sigurjon Andresson <
> TheodorSiAn at kvenno.is> wrote:
>
>> In there you are almost telling people that security through obscurity is
>> a good way.
>> That might sometimes be true but in this case it could mean that you would
>> be handing passwords and other data out.
>>
>> When you start SSH on port 22 it is done with root privileges because the
>> root user is the only one that can use ports below 1024. Root is the only
>> user that can listen to that port or do something with it. If you move the
>> port to 2222 for example you move SSH to a port that can be used with out a
>> privileged user. This would mean I could write a script that listens to
>> port 2222 and mimics SSH to capture the passwords. Changing the port of SSH
>> to 2222 or anything above 1024 makes SSH less secure. Pretty ironic that
>> this is in the "Securing SSH" chapter.  This should never be done.
>>
>> Location:
>> http://wiki.centos.org/HowTos/Network/SecuringSSH#head-3579222198adaf43a3ecbdc438ebce74da40d8ec
>> username: TheodorAndresson
>>
>> _______________________________________________
>> CentOS-docs mailing list
>> CentOS-docs at centos.org
>> http://lists.centos.org/mailman/listinfo/centos-docs
>>
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> ------------------------------
>
> Message: 5
> Date: Fri, 3 Oct 2014 01:17:09 +0000
> From: Theodor Sigurjon Andresson <TheodorSiAn at kvenno.is>
> To: Mail list for wiki articles <centos-docs at centos.org>
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
> Message-ID: <9C6DB64A0CF97645A5C90525A4C4C0CC0512C4DF at CRONUS>
> Content-Type: text/plain; charset="us-ascii"
>
> Yes, when securing your services you *layer* defenses that could include using STO. But when STO is set up in a wrong way it can lead to a security issue. It isn't good to protect your services to slow down or prevent an attack by opening up a security risk. As in this case changing the port of SSH to 2222 isn't a good way to include STO. It doesn't matter how big the risk is, you just don't want this issue to be there. If you want to include STO in your security measures then you have to do it without opening up a security risk because you might be opening up a security risk that could be dangerous. In my opinion that is the case with SSH to port 2222. Changing the port to an privileged unassigned or unused port is a better way to include STO in your security measures for SSH. That way you don't have the risk of another user listening on your SSH.
>
> ________________________________________
> From: centos-docs-bounces at centos.org [centos-docs-bounces at centos.org] on behalf of PJ Welsh [pjwelsh at gmail.com]
> Sent: Thursday, October 02, 2014 23:49
> To: Mail list for wiki articles
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
>
> The context for ssh !22 is about what others could/would do to a ssh daemon. This includes script kiddies or some zero day exploit trolling for *easy* targets. If you have someone creating a listener on the server, you have an entirely different issue. How often do you randomly connect to some system on port 2222 and provide *your* username and password? I am *not* saying security through obscurity = security, but many IDS/IPS/anti-port scanners will begin defensive actions when you plow through ports looking for ssh connection. So instead of being an easier 1 port script kiddie target you *layer* defenses (including possible STO). Basically anything to slow down or deter or prevent an attack is good IMHO.
>
> Just my 2cents of course.
>
> pjwelsh
>
> On Thu, Oct 2, 2014 at 5:45 PM, Theodor Sigurjon Andresson <TheodorSiAn at kvenno.is<mailto:TheodorSiAn at kvenno.is>> wrote:
> In there you are almost telling people that security through obscurity is a good way.
> That might sometimes be true but in this case it could mean that you would be handing passwords and other data out.
>
> When you start SSH on port 22 it is done with root privileges because the root user is the only one that can use ports below 1024. Root is the only user that can listen to that port or do something with it. If you move the port to 2222 for example you move SSH to a port that can be used with out a privileged user. This would mean I could write a script that listens to port 2222 and mimics SSH to capture the passwords. Changing the port of SSH to 2222 or anything above 1024 makes SSH less secure. Pretty ironic that this is in the "Securing SSH" chapter.  This should never be done.
>
> Location: http://wiki.centos.org/HowTos/Network/SecuringSSH#head-3579222198adaf43a3ecbdc438ebce74da40d8ec
> username: TheodorAndresson
>
> _______________________________________________
> CentOS-docs mailing list
> CentOS-docs at centos.org<mailto:CentOS-docs at centos.org>
> http://lists.centos.org/mailman/listinfo/centos-docs
>
>
>
> ------------------------------
>
> Message: 6
> Date: Fri, 03 Oct 2014 07:11:15 +0300
> From: Manuel Wolfshant <wolfy at nobugconsulting.ro>
> To: Mail list for wiki articles <centos-docs at centos.org>
> Subject: Re: [CentOS-docs] Securing SSH --> Change ports
> Message-ID: <542E21E3.1030209 at nobugconsulting.ro>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> On 10/03/2014 04:17 AM, Theodor Sigurjon Andresson wrote:
>> Yes, when securing your services you*layer*  defenses that could include using STO. But when STO is set up in a wrong way it can lead to a security issue. It isn't good to protect your services to slow down or prevent an attack by opening up a security risk. As in this case changing the port of SSH to 2222 isn't a good way to include STO. It doesn't matter how big the risk is, you just don't want this issue to be there. If you want to include STO in your security measures then you have to do it without opening up a security risk because you might be opening up a security risk that could be dangerous. In my opinion that is the case with SSH to port 2222. Changing the port to an privileged unassigned or unused port is a better way to include STO in your security measures for SSH. That way you don't have the risk of another user listening on your SSH.
> I agree with you on two things
> - changing the default port is not a security measure, it just lowers
> the noise in the logs and takes you a bit out of the path of automated
> scripts looking for easy targets.
> - changing the default port to anything above 1024 creates a greater
> risk than using one below 1024
>
> On the other hand, even if it's easier to start a rouge daemon
> impersonating sshd to listen on a higher port, if you have a malevolent
> user already sniffing on a port - any port - from my point of view you
> already have bigger issues than the potential risk you mentioned.
>
>
> Incidentally I am a fan of using iptables (recent match) to limit the
> number of admissible attempts from any given IP to connect to sshd (
> yes, I know, it has nothing to do with the initial concern you raised )
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> End of CentOS-docs Digest, Vol 95, Issue 2
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>
i think the rate limiting section sucks too...  it should instead be 
suggesting sshguard which can ban multiple failed login attempts for 
variable amounts of time.  i have mine set to ban for a week. fail2ban 
can do the same for passwords but you can stream keys to it.  
-666threesixes666
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