pgsql-ulogd2

pgsql-ulogd2

[Mr Dash Four]

I just came across the pgsql script for the ulogd2 daemon supplied with the latest sources and since I intend to deploy it (upgrading my system from syslog-ng) I thought to ask about a couple of ideas I have.

As I see it, the script does not have any security/permission policies created or implemented. Is such feature planned? 

If not, I think I have enough PostgreSQL experience and could alter that script to include such implementation, though I might need help with the NFLOG/ULOGD2 part as I am fairly new to this.

The idea I have is that the ulogd2 daemon should only be allowed INSERT permissions (nothing else) to the log tables, so that even if someone is able to hijack the ulogd2 connection to PostgreSQL somehow, they won't be able to see what has been logged, let alone alter it or delete it.

For certain views, I am sure there is a need for SELECT permission and for others there would even be a need for USAGE or REFERENCES privileges.

I tried to email the author of that script (Pierre - chifflier@inl.fr), but my emails are not getting through for some reason. Thanks!

Re: pgsql-ulogd2

[Eric Leblond]

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Hello,

Le vendredi 13 juillet 2012 à 15:13 +0100, Mr Dash Four a écrit :
> I just came across the pgsql script for the ulogd2 daemon supplied with the latest sources and since I intend to deploy it (upgrading my system from syslog-ng) I thought to ask about a couple of ideas I have.
> 
> As I see it, the script does not have any security/permission policies created or implemented. Is such feature planned? 

No work is planned on that but it is a good idea.

> 
> If not, I think I have enough PostgreSQL experience and could alter that script to include such implementation, though I might need help with the NFLOG/ULOGD2 part as I am fairly new to this.

I'm here to help ;)

> The idea I have is that the ulogd2 daemon should only be allowed INSERT permissions (nothing else) to the log tables, so that even if someone is able to hijack the ulogd2 connection to PostgreSQL somehow, they won't be able to see what has been logged, let alone alter it or delete it.

That's a sane setup.

> 
> For certain views, I am sure there is a need for SELECT permission and for others there would even be a need for USAGE or REFERENCES privileges.
> 
> I tried to email the author of that script (Pierre - chifflier@inl.fr), but my emails are not getting through for some reason. Thanks!

INL company is dead but I'm sure that Pierre is still reading this ML
from another mail ;)

BR,
-- 
Eric Leblond 
Blog: http://home.regit.org/ - Portfolio: http://regit.500px.com/

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Re: pgsql-ulogd2

[Mr Dash Four]

> No work is planned on that but it is a good idea.
>   
Yeah, I thought as much.

>> If not, I think I have enough PostgreSQL experience and could alter that script to include such implementation, though I might need help with the NFLOG/ULOGD2 part as I am fairly new to this.
>>     
>
> I'm here to help ;)
>   
OK, for now I have some general queries with regards to ulogd2. When I 
gain more knowledge (and experience) my queries will become more 
specific. For now though I have to sort out the following:

In the manual there is a very good example on how to use NFLOG (as a 
iptables target), but I have no idea how to apply and select NFACCT and 
NFCT. How do I use this?

OK, I defined 2 stacks which use both NFCT and NFACCT, but how do I tell 
iptables how to use them? I presume this is in a similar way to NFLOG 
(with a target), but in that manual there are no examples (or even 
hints) given on how to use that.

Also, there are quite a few plugins which I have just a vague idea what 
they do (they are not documented in the manual - I presume because they 
were recently introduced) - GPRINT springs to mind, NACCT is the other. 
Is there a description on the purpose of these and their configuration 
parameters, if any?

Probably my last 2 queries for now: when I define a stack, I use a 
series of plugins to define a chain - from the source of where the 
packet originates, to a cascade of "filters" and then the output plugin.

Does the order of "filter" plugins matters (in other words, are they 
traversed from left-to-right in the order they are specified in the 
"stack" statement in ulogd.conf) or is this order irrelevant?

And the second query: usually every plugin, when defined in a stack 
statement has its own section when the various plugin parameters are 
defined. Say, "emu1" has its own "[emu1]" section in ulogd.conf and 
there I could define various parameters related to the LOGEMU plug in.

There are some plugins though, which do not have such section, which 
follows me to conclude that either defining that section is not 
mandatory (in which case I presume the plugin "assumes" default values) 
or, the plugin in question does not have any values to be specified, so 
no such section is needed. Am I correct in this assumption?

>> The idea I have is that the ulogd2 daemon should only be allowed INSERT permissions (nothing else) to the log tables, so that even if someone is able to hijack the ulogd2 connection to PostgreSQL somehow, they won't be able to see what has been logged, let alone alter it or delete it.
>>     
>
> That's a sane setup.
>   
I will dig much more deeper into this once I know how ulogd works as my 
knowledge of ulogd2 is not that great (yet!). My initial instinct is 
that I may have to alter this script slightly, because from what I 
gather ulogd2 is "sensing" the structure of the logging table by reading 
the "description" of it in PostgreSQL. That particular operation usually 
requires higher-than-needed privileges and in order to avoid that I 
might need to find other ways to impose the "insert-only" restriction, 
which, lets be clear, is what ulogd needs. Again, I might be wrong with 
this, but that is what my initial observations with the script and ulogd 
suggest.

> INL company is dead but I'm sure that Pierre is still reading this ML
> from another mail ;)
>   
Ah, that explains it! Well, if he reads this thread, I would love to get 
some feedback when I am confident enough to start digging into that 
script. ;-)

Re: pgsql-ulogd2

[Eric Leblond]

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Hello,

Le samedi 14 juillet 2012 à 14:00 +0100, Mr Dash Four a écrit :
> > No work is planned on that but it is a good idea.
> >   
> Yeah, I thought as much.
> 
> >> If not, I think I have enough PostgreSQL experience and could alter that script to include such implementation, though I might need help with the NFLOG/ULOGD2 part as I am fairly new to this.
> >>     
> >
> > I'm here to help ;)
> >   
> OK, for now I have some general queries with regards to ulogd2. When I 
> gain more knowledge (and experience) my queries will become more 
> specific. For now though I have to sort out the following:
> 
> In the manual there is a very good example on how to use NFLOG (as a 
> iptables target), but I have no idea how to apply and select NFACCT and 
> NFCT. How do I use this?

For NFCT, you simply need to have nfnetlink_conntrack loaded.

Things are more complicated for NFACCT and I've just wrote a page
dedicated to this point:
https://home.regit.org/2012/07/flow-accounting-with-netfilter-and-ulogd2/


> 
> OK, I defined 2 stacks which use both NFCT and NFACCT, but how do I tell 
> iptables how to use them? I presume this is in a similar way to NFLOG 
> (with a target), but in that manual there are no examples (or even 
> hints) given on how to use that.
> 
> Also, there are quite a few plugins which I have just a vague idea what 
> they do (they are not documented in the manual - I presume because they 
> were recently introduced) - GPRINT springs to mind, NACCT is the other. 

GPRINT is a one line per item textual log. NACCT is an tab separated
output format dedicated to NFACCT data and that can be used to import
data in other tools (Astaro does so).

> Is there a description on the purpose of these and their configuration 
> parameters, if any?

To now which keys are used and whch config var are available, you can
use the -i option of ulogd:

ulogd -i libexec/ulogd/ulogd_filter_MARK.so 
Name: MARK
Config options:
        Var: mark (Integer, Default: 0)
        Var: mask (Integer, Default: -1)
Input keys:
        Key: ct.mark (unsigned int 32, optional)
        Key: oob.mark (unsigned int 32, optional)
Output keys:
        No statically defined keys


> Probably my last 2 queries for now: when I define a stack, I use a 
> series of plugins to define a chain - from the source of where the 
> packet originates, to a cascade of "filters" and then the output plugin.
> 
> Does the order of "filter" plugins matters (in other words, are they 
> traversed from left-to-right in the order they are specified in the 
> "stack" statement in ulogd.conf) or is this order irrelevant?

This is read from end to start. All that matter is that for a plugin the
needed keys are exported by another plugin on the left.
 
> And the second query: usually every plugin, when defined in a stack 
> statement has its own section when the various plugin parameters are 
> defined. Say, "emu1" has its own "[emu1]" section in ulogd.conf and 
> there I could define various parameters related to the LOGEMU plug in.
> 
> There are some plugins though, which do not have such section, which 
> follows me to conclude that either defining that section is not 
> mandatory (in which case I presume the plugin "assumes" default values) 
> or, the plugin in question does not have any values to be specified, so 
> no such section is needed. Am I correct in this assumption?

Yes, there is default value. But for at least INPUT plugins, you need to
specify a section. I really don't remember why but this is the case.

> 
> >> The idea I have is that the ulogd2 daemon should only be allowed INSERT permissions (nothing else) to the log tables, so that even if someone is able to hijack the ulogd2 connection to PostgreSQL somehow, they won't be able to see what has been logged, let alone alter it or delete it.
> >>     
> >
> > That's a sane setup.
> >   
> I will dig much more deeper into this once I know how ulogd works as my 
> knowledge of ulogd2 is not that great (yet!). My initial instinct is 
> that I may have to alter this script slightly, because from what I 
> gather ulogd2 is "sensing" the structure of the logging table by reading 
> the "description" of it in PostgreSQL. That particular operation usually 
> requires higher-than-needed privileges and in order to avoid that I 
> might need to find other ways to impose the "insert-only" restriction, 
> which, lets be clear, is what ulogd needs. Again, I might be wrong with 
> this, but that is what my initial observations with the script and ulogd 
> suggest.

Yes, there's a discovery system that may require some tuning. But it can
be made on a separate table use for the only purpose of describing the
variables.

> > INL company is dead but I'm sure that Pierre is still reading this ML
> > from another mail ;)
> >   
> Ah, that explains it! Well, if he reads this thread, I would love to get 
> some feedback when I am confident enough to start digging into that 
> script. ;-)
> 

BR,
-- 
Eric Leblond 
Blog: http://home.regit.org/ - Portfolio: http://regit.500px.com/


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Re: pgsql-ulogd2

[Mr Dash Four]

> For NFCT, you simply need to have nfnetlink_conntrack loaded.
>   
I did, but I also made the mistake of including a few filters in that 
stack, which were incompatible and that was the reason I did not get any 
NFCT logs. Once that was corrected I started seeing connection tracking 
logged.

I have another question with regards to this: Is it possible to limit 
(by a separate filter or otherwise) the reporting and restrict it, to 
say, a specific set of interfaces or specific source/destination IP 
addresses/subnets?

Currently, NFCT reports absolutely everything, which is not what I 
really want as I have to sift through thousands of logs, not to mention 
that by reporting everything the system load is much higher.

So, is there a way for me to do that, somehow?

> Things are more complicated for NFACCT and I've just wrote a page
> dedicated to this point:
> https://home.regit.org/2012/07/flow-accounting-with-netfilter-and-ulogd2/
>   
Very helpful, thanks! I don't see it as complicated at all, certainly no 
more complicated than the existing accounting techniques.

>> Is there a description on the purpose of these and their configuration 
>> parameters, if any?
>>     
>
> To now which keys are used and whch config var are available, you can
> use the -i option of ulogd:
>
> ulogd -i libexec/ulogd/ulogd_filter_MARK.so 
> Name: MARK
> Config options:
>         Var: mark (Integer, Default: 0)
>         Var: mask (Integer, Default: -1)
> Input keys:
>         Key: ct.mark (unsigned int 32, optional)
>         Key: oob.mark (unsigned int 32, optional)
> Output keys:
>         No statically defined keys
>   
Or look at the source code, which is what I did at the end.

>> I will dig much more deeper into this once I know how ulogd works as my 
>> knowledge of ulogd2 is not that great (yet!). My initial instinct is 
>> that I may have to alter this script slightly, because from what I 
>> gather ulogd2 is "sensing" the structure of the logging table by reading 
>> the "description" of it in PostgreSQL. That particular operation usually 
>> requires higher-than-needed privileges and in order to avoid that I 
>> might need to find other ways to impose the "insert-only" restriction, 
>> which, lets be clear, is what ulogd needs. Again, I might be wrong with 
>> this, but that is what my initial observations with the script and ulogd 
>> suggest.
>>     
>
> Yes, there's a discovery system that may require some tuning. But it can
> be made on a separate table use for the only purpose of describing the
> variables.
>   
Yep, the pgsql plugin makes extensive use of pg_namespace, pg_class and 
pg_attribute which are system tables. These contain definitions of every 
single object registered on that database server and is a major security 
risk (as I pointed out, if that ulogd connection to the database server 
is hijacked, then the attacker could find out what is on that database 
without any problems, which is not good).

I had in mind exactly what you've suggested above - use a separate, 
manually-registered table containing the table columns and their mapping 
to ulogd2 parameters - much less risk and everything is configurable, 
though the downside is that the two tables need to be synchronised if 
the structure of the main ulogd table changes (columns renamed or added).

Re: pgsql-ulogd2

[Mr Dash Four]

> Yep, the pgsql plugin makes extensive use of pg_namespace, pg_class 
> and pg_attribute which are system tables. These contain definitions of 
> every single object registered on that database server and is a major 
> security risk (as I pointed out, if that ulogd connection to the 
> database server is hijacked, then the attacker could find out what is 
> on that database without any problems, which is not good).
>
> I had in mind exactly what you've suggested above - use a separate, 
> manually-registered table containing the table columns and their 
> mapping to ulogd2 parameters - much less risk and everything is 
> configurable, though the downside is that the two tables need to be 
> synchronised if the structure of the main ulogd table changes (columns 
> renamed or added).
One other thing which I forgot to ask: currently, the pgsql plugin uses 
an unencrypted connection to the database server. I haven't studied the 
underlying source code which handles pgsql-specific functions, but in 
principle it is possible to use encrypted (SSL) connections to the 
server by using client/server certificates. Has this been attempted and 
considered to be included as an option to that particular plugin?

If not, would there be any objections if such feature is implemented 
(obviously, there will be a need to add additional parameters to that 
plugin to configure the type of connection, client/server/ca 
certificates etc)?

Re: pgsql-ulogd2

[Eric Leblond]

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Hello,

Le dimanche 15 juillet 2012 à 13:24 +0100, Mr Dash Four a écrit :
> > For NFCT, you simply need to have nfnetlink_conntrack loaded.
> >   
> I did, but I also made the mistake of including a few filters in that 
> stack, which were incompatible and that was the reason I did not get any 
> NFCT logs. Once that was corrected I started seeing connection tracking 
> logged.
> 
> I have another question with regards to this: Is it possible to limit 
> (by a separate filter or otherwise) the reporting and restrict it, to 
> say, a specific set of interfaces or specific source/destination IP 
> addresses/subnets?
> 
> Currently, NFCT reports absolutely everything, which is not what I 
> really want as I have to sift through thousands of logs, not to mention 
> that by reporting everything the system load is much higher.
> 
> So, is there a way for me to do that, somehow?

Not now but I'm working on it: Pablo has made a filter system in
libnetfilter_conntrack. I will used it to filter.
> 
> > Things are more complicated for NFACCT and I've just wrote a page
> > dedicated to this point:
> > https://home.regit.org/2012/07/flow-accounting-with-netfilter-and-ulogd2/
> >   
> Very helpful, thanks! I don't see it as complicated at all, certainly no 
> more complicated than the existing accounting techniques.

Yes, not that complicated, documentation was just lacking.

> 
> >> Is there a description on the purpose of these and their configuration 
> >> parameters, if any?
> >>     
> >
> > To now which keys are used and whch config var are available, you can
> > use the -i option of ulogd:
> >
> > ulogd -i libexec/ulogd/ulogd_filter_MARK.so 
> > Name: MARK
> > Config options:
> >         Var: mark (Integer, Default: 0)
> >         Var: mask (Integer, Default: -1)
> > Input keys:
> >         Key: ct.mark (unsigned int 32, optional)
> >         Key: oob.mark (unsigned int 32, optional)
> > Output keys:
> >         No statically defined keys
> >   
> Or look at the source code, which is what I did at the end.

:)

> 
> >> I will dig much more deeper into this once I know how ulogd works as my 
> >> knowledge of ulogd2 is not that great (yet!). My initial instinct is 
> >> that I may have to alter this script slightly, because from what I 
> >> gather ulogd2 is "sensing" the structure of the logging table by reading 
> >> the "description" of it in PostgreSQL. That particular operation usually 
> >> requires higher-than-needed privileges and in order to avoid that I 
> >> might need to find other ways to impose the "insert-only" restriction, 
> >> which, lets be clear, is what ulogd needs. Again, I might be wrong with 
> >> this, but that is what my initial observations with the script and ulogd 
> >> suggest.
> >>     
> >
> > Yes, there's a discovery system that may require some tuning. But it can
> > be made on a separate table use for the only purpose of describing the
> > variables.
> >   
> Yep, the pgsql plugin makes extensive use of pg_namespace, pg_class and 
> pg_attribute which are system tables. These contain definitions of every 
> single object registered on that database server and is a major security 
> risk (as I pointed out, if that ulogd connection to the database server 
> is hijacked, then the attacker could find out what is on that database 
> without any problems, which is not good).

You're right.

> I had in mind exactly what you've suggested above - use a separate, 
> manually-registered table containing the table columns and their mapping 
> to ulogd2 parameters - much less risk and everything is configurable, 
> though the downside is that the two tables need to be synchronised if 
> the structure of the main ulogd table changes (columns renamed or added).

It seems the safest way.

BR,
-- 
Eric Leblond 
Blog: http://home.regit.org/ - Portfolio: http://regit.500px.com/

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Re: pgsql-ulogd2

[Mr Dash Four]

>> Currently, NFCT reports absolutely everything, which is not what I 
>> really want as I have to sift through thousands of logs, not to mention 
>> that by reporting everything the system load is much higher.
>>
>> So, is there a way for me to do that, somehow?
>>     
>
> Not now but I'm working on it: Pablo has made a filter system in
> libnetfilter_conntrack. I will used it to filter.
>   
This would be some awesome feature. I think this new filter which 
implements "custom" restrictions should not be for a particular input 
filter, but rather be universal. In other words, to be able to 
customise, say, certain IP addresses/subnets, certain ethernet 
interfaces etc, and then used anywhere in stack statements - NFCT, NFLOG 
and so on.

If this is implemented, it will certainly make ulogd2 very powerful and 
flexible at the same time - a bit like what syslog-ng is to the old 
syslog ;-)

The specific reason I raised this issue is because on the main firewall 
we have here, if I deploy ulogd2 and use NFCT at its present form, I 
will get the logs from all 7 interfaces, and it would make it an 
absolutely huge task to sift through all these logs and "match" the 
various entries (OK, doing it through the database will help up a bit, 
but not a lot).

If I am able to place a "custom" filter with different "filter" values 
in each separate stack, redirecting input to different places, then I 
would be able to track down what I want quite easily.

>> I had in mind exactly what you've suggested above - use a separate, 
>> manually-registered table containing the table columns and their mapping 
>> to ulogd2 parameters - much less risk and everything is configurable, 
>> though the downside is that the two tables need to be synchronised if 
>> the structure of the main ulogd table changes (columns renamed or added).
>>     
>
> It seems the safest way.
>   
It looks that way, doesn't it? In the coming days I'll look at the PGSQL 
implementation code to see whether SSL connection to the database server 
is a possibility with this plug in - it will be another good security 
feature if that is possible to be implemented.

Re: pgsql-ulogd2

[Eric Leblond]

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Hello,

Le dimanche 15 juillet 2012 à 23:36 +0100, Mr Dash Four a écrit :
> >> Currently, NFCT reports absolutely everything, which is not what I 
> >> really want as I have to sift through thousands of logs, not to mention 
> >> that by reporting everything the system load is much higher.
> >>
> >> So, is there a way for me to do that, somehow?
> >>     
> >
> > Not now but I'm working on it: Pablo has made a filter system in
> > libnetfilter_conntrack. I will used it to filter.
> >   
> This would be some awesome feature. I think this new filter which 
> implements "custom" restrictions should not be for a particular input 
> filter, but rather be universal.

Yes and no ;) (maybe maybe)

>  In other words, to be able to 
> customise, say, certain IP addresses/subnets, certain ethernet 
> interfaces etc, and then used anywhere in stack statements - NFCT, NFLOG 
> and so on.

If this universal filter is an excellent idea, it will suffer from some
performance issue. The NFCT filter I'm currently implementing does the
filtering inside the kernel which is really efficient. For NFLOG, kernel
filtering can be done via iptables.
Implementing a userpsace filter is indeed a good idea but I don't think
it is possible to do a kernel filtering ulogd module. The ulogd
architecture will hardly deal with that because you will not be able to
access to the constructor (in the input plugin) from the filter module.


> 
> If this is implemented, it will certainly make ulogd2 very powerful and 
> flexible at the same time - a bit like what syslog-ng is to the old 
> syslog ;-)

lol, the stack system is already a really big improvment.

> 
> The specific reason I raised this issue is because on the main firewall 
> we have here, if I deploy ulogd2 and use NFCT at its present form, I 
> will get the logs from all 7 interfaces, and it would make it an 
> absolutely huge task to sift through all these logs and "match" the 
> various entries (OK, doing it through the database will help up a bit, 
> but not a lot).
> 
> If I am able to place a "custom" filter with different "filter" values 
> in each separate stack, redirecting input to different places, then I 
> would be able to track down what I want quite easily.

You should be able to do a per-network filtering with my current work. I
should have a patch ready today.

> 
> >> I had in mind exactly what you've suggested above - use a separate, 
> >> manually-registered table containing the table columns and their mapping 
> >> to ulogd2 parameters - much less risk and everything is configurable, 
> >> though the downside is that the two tables need to be synchronised if 
> >> the structure of the main ulogd table changes (columns renamed or added).
> >>     
> >
> > It seems the safest way.
> >   
> It looks that way, doesn't it? In the coming days I'll look at the PGSQL 
> implementation code to see whether SSL connection to the database server 
> is a possibility with this plug in - it will be another good security 
> feature if that is possible to be implemented.

Fine!

BR,
-- 
Eric Leblond 
Blog: http://home.regit.org/ - Portfolio: http://regit.500px.com/

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Re: pgsql-ulogd2

[Mr Dash Four]

>>  In other words, to be able to 
>> customise, say, certain IP addresses/subnets, certain ethernet 
>> interfaces etc, and then used anywhere in stack statements - NFCT, NFLOG 
>> and so on.
>>     
>
> If this universal filter is an excellent idea, it will suffer from some
> performance issue. The NFCT filter I'm currently implementing does the
> filtering inside the kernel which is really efficient. For NFLOG, kernel
> filtering can be done via iptables.
>   
Yeah, sorry, I've got carried away a bit there. :-) 

Of course, with NFLOG things are much more easier.

>> If I am able to place a "custom" filter with different "filter" values 
>> in each separate stack, redirecting input to different places, then I 
>> would be able to track down what I want quite easily.
>>     
>
> You should be able to do a per-network filtering with my current work. I
> should have a patch ready today.
>   
Looking forward to it.

>> In the coming days I'll look at the PGSQL 
>> implementation code to see whether SSL connection to the database server 
>> is a possibility with this plug in - it will be another good security 
>> feature if that is possible to be implemented.
>>     
>
> Fine!
>   
I managed to get some preliminary code working yesterday and later today 
when I get home I'll get the chance to test it with the real plug in to 
see whether SSL works. If it does, I'll propose some changes to include 
SSL capability to the PGSQL plugin.

Re: pgsql-ulogd2

[Mr Dash Four]

> I managed to get some preliminary code working yesterday and later 
> today when I get home I'll get the chance to test it with the real 
> plug in to see whether SSL works. If it does, I'll propose some 
> changes to include SSL capability to the PGSQL plugin.
OK, I've just done some testing using the PGSQL plugin with hard-coded 
values to create a secure (SSL) connection and verify how that plugin 
works. In short - it is absolutely flawless!

I am able to establish 4 types of SSL connections between ulogd and my 
PostgreSQL database server and conducted tests on various (known) 
attacks to see how it behaves - it passes with flying colours!

In the mean time, I found a bug and a "maybe" bug:

1. pgsql-ulogd2 script:

CREATE TABLE ulog2 (
  [...]
timestamp timestamp NOT NULL default 'now'

The above will insert a string, equivalent to the current timestamp when 
the table was created as a default value (which PostgreSQL will 
automatically convert to timestamp) and *not* when a record is inserted 
into the table. The correct syntax is:

"timestamp" timestamp NOT NULL default now()


2. When I start using NFCT and it does the logging to the database, I am 
getting endless sequences of the following statement in the main 
ulogd.log file:

<5> ulogd_inpflow_NFCT.c:697 unsupported message type

I don't know whether there is something I am doing wrong or whether 
there is a message which ulogd cannot interpret. Maybe a bug, maybe not, 
I don't know.

So, for SSL implementation in the PGSQL plugin, this is how I see it: 
PostgreSQL (the server) allows for 6 different types of SSL connections 
to be established between it and a client [1]:

Option          Description
~~~~~~        ~~~~~~~~~~~
disable          only try a non-SSL connection
allow          first try a non-SSL connection; if that fails, try an SSL 
connection
prefer        (default) first try an SSL connection; if that fails, try 
a non-SSL connection
require          only try an SSL connection
verify-ca     only try an SSL connection, and verify that the server 
certificate is issued by a trusted CA
verify-full   only try an SSL connection, verify that the server 
certificate is issued by a trusted CA and that the server host name 
matches that in the certificate

The above option is configured with the "sslmode" connection option 
("sslmode=verfify-full" for example). In earlier PostgreSQL versions 
(below 8, I think), there was only one possible option and that was 
"requiressl" ("requiressl=1" is equivalent to "sslmode=require" above, 
while "requiressl=0" is the equivalent to "sslmode=prefer").

As far as verification goes, there is one additional parameter which 
could also be deployed on the PostgreSQL server to check request and 
check the client certificate as well. So verification and checking could 
be a dual process on both the client and the server.

In addition to the above parameter, 4 other connection options can be 
specified:

sslcert - This parameter specifies the file name of the client SSL 
certificate, replacing the default ‘~/.postgresql/postgresql.crt’. This 
parameter is ignored if an SSL connection is not made.

sslkey - This parameter specifies the location for the secret key used 
for the client certificate. It can either specify a file name that will 
be used instead of the default ‘~/.postgresql/postgresql.key’, or it can 
specify a key obtained from an external “engine” (engines are OpenSSL 
loadable modules). An external engine specification should consist of a 
colon-separated engine name and an engine-specific key identifier. This 
parameter is ignored if an SSL connection is not made. If this key is 
protected with a password, this will be asked when the connection is 
made. On the server side, it is stored internally and asked once when 
the server starts up. on the client side it is asked every time an 
attempt for a connection is made.

sslrootcert - This parameter specifies the name of a file containing SSL 
certificate authority (CA) certificate(s). If the file exists, the 
server's certificate will be verified to be signed by one of these 
authorities. The default is ‘~/.postgresql/root.crt’.

sslcrl - This parameter specifies the file name of the SSL certificate 
revocation list (CRL). Certificates listed in this file, if it exists, 
will be rejected while attempting to authenticate the server's 
certificate. The default is ‘~/.postgresql/root.crl’.

So, the way I see it, we can mirror all of the above 5 options, 
including their default values quite easily and let PGconn do the rest 
(please note that the PG .so object library takes care of opening the 
certificate files as well as checking and validating the various 
certificates contained within - this is done transparently to the client 
- PGSQL plugin in this case). The modifications to the PGSQL plugin 
would be minimal and will consists of little more than adding the above 
parameters and then passing their values as connection options to PGconn.

As far as hardening the access to the system tables goes, the way I see 
it there are 2 possible options:

1. Change the meaning of the "table" plugin parameter to point to a 
user-defined table, which contains a single row where all column names 
of the main ulogd table are stored. This option *will* brake backward 
compatibility!

2. Keep the existing "table" option and add a separate parameter 
(probably called "columns" or "table_columns" or something like that), 
which will contain a single row with the description of all usable 
columns in the "table" table where the main ulogd logging will take place.

I think option 2 is better, though at the expense of adding an extra 
configuration parameter, in addition to the 5 new ones for SSL support I 
listed above.

A few other observations and a query: Currently, there isn't a 
"user-friendly" NCFT view implemented in the PGSQL plugin, similar to 
the one designed for NFLOG (the one implemented for NFLOG is called 
ulog, I think) where the various numeric and raw values are "deciphered" 
for the end user and presented in a nice format to be understood more 
easily.

All NFCT logs are currently dumped, quite literally, in the ulogd2_ct 
table. Such a view would be very easy to create - I could do it and 
submit it together with the above changes if there is interest.

One last question - is there a way where I could get *all* possible 
values which a given filter plugin interprets, like source/destination 
IP address/subnet, interface names etc?

The reason I am asking this is because if I could use or implement a 
command line parameter (similar to "ulogd -i"), which asks every filter 
plugin to list the names of the parameters it processes from the input 
plugin, then I could build a reliable set of parameters which are then 
used to build a complete database script to be used in the creating the 
database schema which is then used by ulogd2.

Currently, I am only guessing what each plugin processes - it is like a 
black box, which isn't good-enough for me.


[1] - PostgreSQL v9.0 Programmer's Manual - 
http://www.network-theory.co.uk/docs/postgresql9/vol2/DatabaseConnectionControlFunctions.html
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Re: pgsql-ulogd2

[Florian Westphal]

Mr Dash Four <mr.dash.four@googlemail.com> wrote:
> The specific reason I raised this issue is because on the main
> firewall we have here, if I deploy ulogd2 and use NFCT at its
> present form, I will get the logs from all 7 interfaces, and it
> would make it an absolutely huge task to sift through all these logs
> and "match" the various entries (OK, doing it through the database
> will help up a bit, but not a lot).

Try something like
iptables -t raw -A PREROUTING (thingsyoudontwant) -j CT --ctevents related

(i don't think its possible to disable event delivery completely
 at the moment without disabling conntrack ).

Re: pgsql-ulogd2

[Pablo Neira Ayuso]

On Mon, Jul 16, 2012 at 10:00:13AM +0200, Florian Westphal wrote:
> Mr Dash Four <mr.dash.four@googlemail.com> wrote:
> > The specific reason I raised this issue is because on the main
> > firewall we have here, if I deploy ulogd2 and use NFCT at its
> > present form, I will get the logs from all 7 interfaces, and it
> > would make it an absolutely huge task to sift through all these logs
> > and "match" the various entries (OK, doing it through the database
> > will help up a bit, but not a lot).
> 
> Try something like
> iptables -t raw -A PREROUTING (thingsyoudontwant) -j CT --ctevents related
> 
> (i don't think its possible to disable event delivery completely
>  at the moment without disabling conntrack ).

You can do it via:

/proc/sys/net/netfilter/nf_conntrack_events

Re: pgsql-ulogd2

[Mr Dash Four]

>> The specific reason I raised this issue is because on the main
>> firewall we have here, if I deploy ulogd2 and use NFCT at its
>> present form, I will get the logs from all 7 interfaces, and it
>> would make it an absolutely huge task to sift through all these logs
>> and "match" the various entries (OK, doing it through the database
>> will help up a bit, but not a lot).
>>     
>
> Try something like
> iptables -t raw -A PREROUTING (thingsyoudontwant) -j CT --ctevents related
>   
What do you mean by "(thingsyoudontwant)"? How would that affect 
tracking (sorry, I probably need to brush-up on the CT a bit)?

Re: pgsql-ulogd2

[Florian Westphal]

Mr Dash Four <mr.dash.four@googlemail.com> wrote:
> 
> >>The specific reason I raised this issue is because on the main
> >>firewall we have here, if I deploy ulogd2 and use NFCT at its
> >>present form, I will get the logs from all 7 interfaces, and it
> >>would make it an absolutely huge task to sift through all these logs
> >>and "match" the various entries (OK, doing it through the database
> >>will help up a bit, but not a lot).
> >
> >Try something like
> >iptables -t raw -A PREROUTING (thingsyoudontwant) -j CT --ctevents related
> What do you mean by "(thingsyoudontwant)"? How would that affect
> tracking (sorry, I probably need to brush-up on the CT a bit)?

It specifies what events to generate; Events that aren't generated can't be
seen by NFCT.  Tracking itself is not influenced.

As Pablo pointed out, you could also try disabling event reporting
completely via sysctl and only enable events for those networks/services
you're interested in.

So e.g. if you are only interested in logging the start and end
of connections coming from 192.168.1/24 on eth0 and going out
via eth7 you could try

echo 0 > /proc/sys/net/netfilter/nf_conntrack_events

iptables -t raw -A PREROUTING -i eth0 -o eth7 \
	 -s 192.168.1.0/24 -j CT --ctevents new,related,destroy

Re: pgsql-ulogd2

[Pablo Neira Ayuso]

On Mon, Jul 16, 2012 at 03:27:59PM +0200, Florian Westphal wrote:
> Mr Dash Four <mr.dash.four@googlemail.com> wrote:
> > 
> > >>The specific reason I raised this issue is because on the main
> > >>firewall we have here, if I deploy ulogd2 and use NFCT at its
> > >>present form, I will get the logs from all 7 interfaces, and it
> > >>would make it an absolutely huge task to sift through all these logs
> > >>and "match" the various entries (OK, doing it through the database
> > >>will help up a bit, but not a lot).
> > >
> > >Try something like
> > >iptables -t raw -A PREROUTING (thingsyoudontwant) -j CT --ctevents related
> > What do you mean by "(thingsyoudontwant)"? How would that affect
> > tracking (sorry, I probably need to brush-up on the CT a bit)?
> 
> It specifies what events to generate; Events that aren't generated can't be
> seen by NFCT.  Tracking itself is not influenced.
> 
> As Pablo pointed out, you could also try disabling event reporting
> completely via sysctl and only enable events for those networks/services
> you're interested in.
> 
> So e.g. if you are only interested in logging the start and end
> of connections coming from 192.168.1/24 on eth0 and going out
> via eth7 you could try
> 
> echo 0 > /proc/sys/net/netfilter/nf_conntrack_events

oops, sorry, this is not what I meant to say. This line above
*completely* disables events. Thus, the line below does not have effect
anymore.

> iptables -t raw -A PREROUTING -i eth0 -o eth7 \
> 	 -s 192.168.1.0/24 -j CT --ctevents new,related,destroy

It should be hard to add some "none" for --ctevents so you can add to
the following rules below:

iptables -t raw -A PREROUTING -i eth0 -o eth7 \
	 -s 192.168.1.0/24 -j CT --ctevents new,related,destroy
iptables -t raw -A PREROUTING -i eth0 -o eth7 \
	 ! -s 192.168.1.0/24 -j CT --ctevents none

Not to report events for others. Note that the "none" is missing now
in iptables.

Thus, we will only get events coming from 192.168.1.0/24.

Still, for better per-process (not global) filtering some ulogd2
filter that uses the libnetfilter_conntrack filtering based on
Berkeley Socket Filters can help.

I remember that I posted some patches long time ago to add
unicast-based ctevent. These days that could be easier by reusing the
user-space cthelper infrastructure that went into the kernel for
3.7.

Re: pgsql-ulogd2

[Mr Dash Four]

>> iptables -t raw -A PREROUTING -i eth0 -o eth7 \
>> 	 -s 192.168.1.0/24 -j CT --ctevents new,related,destroy
>>     
>
> It should be hard to add some "none" for --ctevents so you can add to
> the following rules below:
>
> iptables -t raw -A PREROUTING -i eth0 -o eth7 \
> 	 -s 192.168.1.0/24 -j CT --ctevents new,related,destroy
> iptables -t raw -A PREROUTING -i eth0 -o eth7 \
> 	 ! -s 192.168.1.0/24 -j CT --ctevents none
>
> Not to report events for others. Note that the "none" is missing now
> in iptables.
>
> Thus, we will only get events coming from 192.168.1.0/24.
>   
I am not entirely certain whether I could do more damage to my setup if 
I do the above. Let me explain:

On all interfaces, with the exception of one, I have a limited set of 
rules, which are traversed only when a new connection is established 
(i.e. the state is NEW). In all other cases, I have -j ACCEPT when the 
state is RELATED or ESTABLISHED. This was done primarily to lower the 
load on the firewall machine and also to save me from writing iptables 
rules for both sides of a connection.

I am not sure if I apply the above, how would that affect the setup I 
just described and I am not sure whether it would make things worse. 
Again, my aim is to be able to configure full logging of particular type 
of connections via NFCT (from their inception to their closure), 
depending on the interface and source/destiantion IP address/subnet, 
possibly without affecting the above setup too much.

I know how to do that with packets via NFLOG - that is easy enough for 
me, but I am struggling with NFCT, unfortunately.

Re: pgsql-ulogd2

[Pablo Neira Ayuso]

On Sun, Jul 15, 2012 at 10:52:08PM +0200, Eric Leblond wrote:
> Hello,
> 
> Le dimanche 15 juillet 2012 à 13:24 +0100, Mr Dash Four a écrit :
> > > For NFCT, you simply need to have nfnetlink_conntrack loaded.
> > >   
> > I did, but I also made the mistake of including a few filters in that 
> > stack, which were incompatible and that was the reason I did not get any 
> > NFCT logs. Once that was corrected I started seeing connection tracking 
> > logged.
> > 
> > I have another question with regards to this: Is it possible to limit 
> > (by a separate filter or otherwise) the reporting and restrict it, to 
> > say, a specific set of interfaces or specific source/destination IP 
> > addresses/subnets?
> > 
> > Currently, NFCT reports absolutely everything, which is not what I 
> > really want as I have to sift through thousands of logs, not to mention 
> > that by reporting everything the system load is much higher.
> > 
> > So, is there a way for me to do that, somehow?
> 
> Not now but I'm working on it: Pablo has made a filter system in
> libnetfilter_conntrack. I will used it to filter.

You can also use the CT target to filter conntrack events. It's a
global configurable parameter though, but it's easy.
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