Thread: Credcheck- credcheck.max_auth_failure

In the use of the Credcheck suite, the parameter "credcheck.max_auth_failure = '3'" is set in the postgresql.conf file to limit users from entering incorrect passwords more than three times, after which their account will be locked.

Due to certain requirements, I would like to ask if there is a way or feature to set this parameter differently for a specific user or role, so that it does not apply to them.

On Wed, Dec 11, 2024 at 5:46 AM 張宸瑋 <kenny020307@gmail.com> wrote:

In the use of the Credcheck suite, the parameter "credcheck.max_auth_failure = '3'" is set in the postgresql.conf file to limit users from entering incorrect passwords more than three times, after which their account will be locked.

Won't that allow absolutely anyone to lock out anyone else, including admins/superusers? Sounds like a bad idea to me.

 

Due to certain requirements, I would like to ask if there is a way or feature to set this parameter differently for a specific user or role, so that it does not apply to them.

There is not, but there is always the credcheck.reset_superuser setting as an emergency measure. I'd keep the password complexity settings and not enable max_auth_failure at all, myself. Three strikes and you're out feels pretty draconian. Is there a particular threat model that is driving that?

On 2024-12-11 13:43:38 -0500, Ron Johnson wrote:
> On Wed, Dec 11, 2024 at 12:57 PM Greg Sabino Mullane <htamfids@gmail.com>
> wrote:
>
>     On Wed, Dec 11, 2024 at 5:46 AM 張宸瑋 <kenny020307@gmail.com> wrote:
>
>         In the use of the Credcheck suite, the parameter
>         "credcheck.max_auth_failure = '3'" is set in the postgresql.conf file
>         to limit users from entering incorrect passwords more than three times,
>         after which their account will be locked.
>
>
>     Won't that allow absolutely anyone to lock out anyone else, including
>     admins/superusers? Sounds like a bad idea to me.
>
>
> Isn't this a pretty common password setting?

Yes, but that doesn't mean it's a good idea.

Actually, let me tease that apart a bit.

It is very common for the setting to exist (probably just about any OS
and many applications, too), but much less common for it to be turned on.

There are good reasons for that.

Limiting the number of failed attempts makes a lot of sense for debit
cards: The PINs are short enough that a person could bruteforce all
combinations and that typos are uncommon. So multiple failed attempts
probably mean that the card was stolen. There is also no way to DOS
somebody, since you need the card before you can enter the PIN.

It may have made a bit of sense in the 1980s, when most people had short
and easily guessable passwords and hosts were typically only accessible
from directly connected terminals and not from the internet.

But it really doesn't make much sense now: Passwords should be so long
that brute-forcing them via login attempts is completely futile. Either
the attacker knows the password (then the limit doesn't help), or they
won't guess it in a million attempts (so the limit doesn't help either).
OTOH, the limit gives an attacker a very simple way to deny the service to
the legitimate used: Just enter a bogus password three times and boom -
account locked. (That threat can be mitigated by applying the limit per
IP address - but the attacker may have a botnet with a million nodes,
making the limit ineffective.)

        hp

--
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp@hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"

We have both regular accounts and system accounts. For regular accounts, we still require password complexity and the lockout functionality after multiple failed login attempts.

However, for system accounts, due to information security regulations, password complexity is also required.

The issue is that system accounts are used for system integration, and if the account gets locked, it may affect system services, which could lead to problems. To prevent this, we would like to exclude system accounts from being affected by the credcheck.max_auth_failure parameter.

On Mon, Dec 16, 2024 at 5:32 AM 張宸瑋 <kenny020307@gmail.com> wrote:

We have both regular accounts and system accounts. For regular accounts, we still require password complexity and the lockout functionality after multiple failed login attempts.

Again, what is the threat model here?

Most people have their password in a .pgpass file or similar, so it seems this only adds complexity and annoyance without any real benefit.

We have both regular accounts and system accounts. For regular accounts, we still require password complexity and the lockout functionality after multiple failed login attempts. However, for system accounts, due to information security regulations, password complexity is also required. The issue is that system accounts are used for system integration, and if the account gets locked, it may affect system services, which could lead to problems. To prevent this, we would like to exclude system accounts from being affected by the credcheck.max_auth_failure parameter.

Peter J. Holzer <hjp-pgsql@hjp.at>於 2024年12月14日 週六，上午4:24寫道：

On 2024-12-11 13:43:38 -0500, Ron Johnson wrote:
> On Wed, Dec 11, 2024 at 12:57 PM Greg Sabino Mullane <htamfids@gmail.com>
> wrote:
>
>     On Wed, Dec 11, 2024 at 5:46 AM 張宸瑋 <kenny020307@gmail.com> wrote:
>
>         In the use of the Credcheck suite, the parameter
>         "credcheck.max_auth_failure = '3'" is set in the postgresql.conf file
>         to limit users from entering incorrect passwords more than three times,
>         after which their account will be locked.
>
>
>     Won't that allow absolutely anyone to lock out anyone else, including
>     admins/superusers? Sounds like a bad idea to me.
>
>
> Isn't this a pretty common password setting?

Yes, but that doesn't mean it's a good idea.

Actually, let me tease that apart a bit.

It is very common for the setting to exist (probably just about any OS
and many applications, too), but much less common for it to be turned on.

There are good reasons for that.

Limiting the number of failed attempts makes a lot of sense for debit
cards: The PINs are short enough that a person could bruteforce all
combinations and that typos are uncommon. So multiple failed attempts
probably mean that the card was stolen. There is also no way to DOS
somebody, since you need the card before you can enter the PIN.

It may have made a bit of sense in the 1980s, when most people had short
and easily guessable passwords and hosts were typically only accessible
from directly connected terminals and not from the internet.

But it really doesn't make much sense now: Passwords should be so long
that brute-forcing them via login attempts is completely futile. Either
the attacker knows the password (then the limit doesn't help), or they
won't guess it in a million attempts (so the limit doesn't help either).
OTOH, the limit gives an attacker a very simple way to deny the service to
the legitimate used: Just enter a bogus password three times and boom -
account locked. (That threat can be mitigated by applying the limit per
IP address - but the attacker may have a botnet with a million nodes,
making the limit ineffective.)

        hp

--
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp@hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"

On 2024-12-16 09:17:25 -0500, Ron Johnson wrote:
> Local (socket-based) connections are typically peer-authenticated
> (meaning that authentication is handled by Linux pam).
                                     ^^^
Is it? I haven't checked the source code, but this doesn't seem
plausible. You can get the uid of a socket peer directly from the
kernel, which can be converted to a user name via getpwuid, and the
mapping to postgresql roles is done via pg_ident.conf. I see no role for
PAM in that path.

> Thus, if someone enters too many wrong passwords for a superuser
> account, you should still be able to locally connect to PG.

True. But the client may not be on the same machine.

        hp

--
   _  | Peter J. Holzer    | Story must make more sense than reality.
|_|_) |                    |
| |   | hjp@hjp.at         |    -- Charles Stross, "Creative writing
__/   | http://www.hjp.at/ |       challenge!"

On 2024-12-16 10:37:59 -0500, Ron Johnson wrote:
> On Mon, Dec 16, 2024 at 10:19 AM Peter J. Holzer <hjp-pgsql@hjp.at> wrote:
>
>     On 2024-12-16 09:17:25 -0500, Ron Johnson wrote:
>     > Local (socket-based) connections are typically peer-authenticated
>     > (meaning that authentication is handled by Linux pam).
>                                          ^^^
>     Is it? I haven't checked the source code, but this doesn't seem
>     plausible. You can get the uid of a socket peer directly from the
>     kernel, which can be converted to a user name via getpwuid, and the
>     mapping to postgresql roles is done via pg_ident.conf. I see no role for
>     PAM in that path.
>
>
> https://www.postgresql.org/docs/16/auth-peer.html
>
> "
> The peer authentication method works by obtaining the client's operating system
> user name from the kernel and using it as the allowed database user name (with
> optional user name mapping). This method is only supported on local
> connections.
> [snip]
> Peer authentication is only available on operating systems providing the 
> getpeereid() function, the SO_PEERCRED socket parameter, or similar mechanisms.
> Currently that includes Linux, most flavors of BSD including macOS, and Solaris
> .
> "
>
> That means pam

No, it doesn't. PAM is used to authenticate a user to the OS (plus to do
a bit of setup and teardown at the beginning and end of each session).
But here the user is already authenticated to the OS and postgresql is
using that information to authenticate the user to itself. This will use
the nsswitch mechanism on Linux (and probably something similar on the
other OSs) to do the uid->username lookup, but it will not use PAM,
since that simply isn't what PAM is for (or capable of to my knowledge).