Thread: strange behavior of pg_hba.conf file

Am 22.11.23 um 17:21 schrieb Atul Kumar:
>
>
> Since then I have started getting the below error:
>
> no pg_hba.conf entry for host "::1", user "postgres", database "postgres
>
>
>
>
> What I am missing here, please suggest.
>
>

that's sounds like an issue with IPv6. Do you use it? Disable it or add 
an entry for it.


Regards, Andreas

-- 
Andreas Kretschmer - currently still (garden leave)
Technical Account Manager (TAM)
www.enterprisedb.com

On 11/22/23 08:21, Atul Kumar wrote:
> Hi,
> 
> I have postgres 12 running in centos 7, recently I changed the 
> authentication of entries of pg_hba.conf to scram-sh-256 for localhost.
> 
> Since then I have started getting the below error:
> 
> no pg_hba.conf entry for host "::1", user "postgres", database "postgres

The host is ::1 which IPv6 and your pg_hba.conf entry below is for IPv4. 
You need to add IPv6 line.

> 
> 
> 
> 
> The entry of pg_hba.conf is like below:
> 
> # TYPE  DATABASE USER ADDRESS METHOD
> 
> # "local" is for Unix domain socket connections only
> 
> local all all                                          scram-sha-256
> 
> # IPv4 local connections:
> 
> host all postgres 127.0.0.1/32 <http://127.0.0.1/32> scram-sha-256
> 
> 
> 
> What I am missing here, please suggest.
> 
> 
> 
> 
> Regards,
> 
> Atul
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

On 11/22/23 09:03, Atul Kumar wrote:
> The entries that I changed were to replace the md5 with scram-sha-256 
> and remove unnecessary remote IPs.

FYI from:

https://www.postgresql.org/docs/current/auth-password.html

md5

     The method md5 uses a custom less secure challenge-response 
mechanism. It prevents password sniffing and avoids storing passwords on 
the server in plain text but provides no protection if an attacker 
manages to steal the password hash from the server. Also, the MD5 hash 
algorithm is nowadays no longer considered secure against determined 
attacks.

     The md5 method cannot be used with the db_user_namespace feature.

     To ease transition from the md5 method to the newer SCRAM method, 
if md5 is specified as a method in pg_hba.conf but the user's password 
on the server is encrypted for SCRAM (see below), then SCRAM-based 
authentication will automatically be chosen instead.

> 
> But it has nothing to do with connecting the server locally with "psql 
> -d postgres -U postgres -h localhost"

The error:

no pg_hba.conf entry for host "::1", user "postgres", database "postgres


says it does and the error is correct as you do not have an IPv6 entry 
for localhost in pg_hba.conf. At least in the snippet you showed us.


> 
> But when I try to connect it locally I get this error. So it is related 

When you say connect locally do you mean to localhost or to local(socket)?

> to local connections only and when I pass the hostname or ip of the 
> server it works fine without any issue.
> 
> 
> Regards.
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com

Am 22.11.23 um 18:44 schrieb Atul Kumar:
> I am giving this command
> psql -d postgres -U postgres -p 5432 -h localhost
> Then only I get that error.

so localhost resolved to an IPv6 - address ...

>
> but when I  pass ip or hostname of the local server then I don't get 
> such error message
> 1. psql -d postgres -U postgres -p 5432 -h <ip of local server>
> 2. psql -d postgres -U postgres -p 5432 -h <hostname of local server>

resolves to an IPv4 - address. you can see the difference?

localhost != iv4-address != hostname with ipv4 address

Andreas

>
>
> I don;t get that error while using the above two commands.
>
>
> Regards.
>
>
> On Wed, Nov 22, 2023 at 10:45 PM Adrian Klaver 
> <adrian.klaver@aklaver.com> wrote:
>
>     On 11/22/23 09:03, Atul Kumar wrote:
>     > The entries that I changed were to replace the md5 with
>     scram-sha-256
>     > and remove unnecessary remote IPs.
>
>     FYI from:
>
>     https://www.postgresql.org/docs/current/auth-password.html
>
>     md5
>
>          The method md5 uses a custom less secure challenge-response
>     mechanism. It prevents password sniffing and avoids storing
>     passwords on
>     the server in plain text but provides no protection if an attacker
>     manages to steal the password hash from the server. Also, the MD5
>     hash
>     algorithm is nowadays no longer considered secure against determined
>     attacks.
>
>          The md5 method cannot be used with the db_user_namespace feature.
>
>          To ease transition from the md5 method to the newer SCRAM
>     method,
>     if md5 is specified as a method in pg_hba.conf but the user's
>     password
>     on the server is encrypted for SCRAM (see below), then SCRAM-based
>     authentication will automatically be chosen instead.
>
>     >
>     > But it has nothing to do with connecting the server locally with
>     "psql
>     > -d postgres -U postgres -h localhost"
>
>     The error:
>
>     no pg_hba.conf entry for host "::1", user "postgres", database
>     "postgres
>
>
>     says it does and the error is correct as you do not have an IPv6
>     entry
>     for localhost in pg_hba.conf. At least in the snippet you showed us.
>
>
>     >
>     > But when I try to connect it locally I get this error. So it is
>     related
>
>     When you say connect locally do you mean to localhost or to
>     local(socket)?
>
>     > to local connections only and when I pass the hostname or ip of the
>     > server it works fine without any issue.
>     >
>     >
>     > Regards.
>     >
>
>     -- 
>     Adrian Klaver
>     adrian.klaver@aklaver.com
>

-- 
Andreas Kretschmer - currently still (garden leave)
Technical Account Manager (TAM)
www.enterprisedb.com

Am 22.11.23 um 18:44 schrieb Atul Kumar:

I am giving this command
psql -d postgres -U postgres -p 5432 -h localhost
Then only I get that error.

so localhost resolved to an IPv6 - address ...

Yeah, you should take a look at:

/etc/hosts

In meantime include a  line for IPv6 in pg_hba.conf. where the address would be:

::1/128 

Please can you share any command  for due diligence whether ip is resolved to ipv6 ?.

This:

psql -d postgres -U postgres -p 5432 -h localhost

where pretty sure

/etc/hosts

is resolving localhost --> ::1

On Wed, Nov 22, 2023 at 11:25 PM Andreas Kretschmer <andreas@a-kretschmer.de> wrote:

Am 22.11.23 um 18:44 schrieb Atul Kumar:
> I am giving this command
> psql -d postgres -U postgres -p 5432 -h localhost
> Then only I get that error.

so localhost resolved to an IPv6 - address ...

>
> but when I  pass ip or hostname of the local server then I don't get
> such error message
> 1. psql -d postgres -U postgres -p 5432 -h <ip of local server>
> 2. psql -d postgres -U postgres -p 5432 -h <hostname of local server>

resolves to an IPv4 - address. you can see the difference?

localhost != iv4-address != hostname with ipv4 address

Andreas

>
>
> I don;t get that error while using the above two commands.
>
>
> Regards.
>
>
> On Wed, Nov 22, 2023 at 10:45 PM Adrian Klaver
> <adrian.klaver@aklaver.com> wrote:
>
>     On 11/22/23 09:03, Atul Kumar wrote:
>     > The entries that I changed were to replace the md5 with
>     scram-sha-256
>     > and remove unnecessary remote IPs.
>
>     FYI from:
>
>     https://www.postgresql.org/docs/current/auth-password.html
>
>     md5
>
>          The method md5 uses a custom less secure challenge-response
>     mechanism. It prevents password sniffing and avoids storing
>     passwords on
>     the server in plain text but provides no protection if an attacker
>     manages to steal the password hash from the server. Also, the MD5
>     hash
>     algorithm is nowadays no longer considered secure against determined
>     attacks.
>
>          The md5 method cannot be used with the db_user_namespace feature.
>
>          To ease transition from the md5 method to the newer SCRAM
>     method,
>     if md5 is specified as a method in pg_hba.conf but the user's
>     password
>     on the server is encrypted for SCRAM (see below), then SCRAM-based
>     authentication will automatically be chosen instead.
>
>     >
>     > But it has nothing to do with connecting the server locally with
>     "psql
>     > -d postgres -U postgres -h localhost"
>
>     The error:
>
>     no pg_hba.conf entry for host "::1", user "postgres", database
>     "postgres
>
>
>     says it does and the error is correct as you do not have an IPv6
>     entry
>     for localhost in pg_hba.conf. At least in the snippet you showed us.
>
>
>     >
>     > But when I try to connect it locally I get this error. So it is
>     related
>
>     When you say connect locally do you mean to localhost or to
>     local(socket)?
>
>     > to local connections only and when I pass the hostname or ip of the
>     > server it works fine without any issue.
>     >
>     >
>     > Regards.
>     >
>
>     --
>     Adrian Klaver
>     adrian.klaver@aklaver.com
>

--
Andreas Kretschmer - currently still (garden leave)
Technical Account Manager (TAM)
www.enterprisedb.com

On 11/22/23 9:55 AM, Andreas Kretschmer wrote:

Am 22.11.23 um 18:44 schrieb Atul Kumar:

I am giving this command
psql -d postgres -U postgres -p 5432 -h localhost
Then only I get that error.

so localhost resolved to an IPv6 - address ...

Yeah, you should take a look at:

/etc/hosts

In meantime include a  line for IPv6 in pg_hba.conf. where the address would be:

::1/128 

Or you could change

host all postgres 127.0.0.1/32 scram-sha-256

to

host all postgres localhost scram-sha-256

On Wed, 2023-11-22 at 23:33 +0530, Atul Kumar wrote:
> Please can you share any command  for due diligence whether ip is resolved to ipv6 ?.

Not a lot of diligence is due to figure out that you can use

  ping localhost

Yours,
Laurenz Albe