Client authentication is controlled by a configuration file,
which traditionally is named
pg_hba.conf and is stored in the database
cluster's data directory. (HBA
stands for host-based authentication.) A default
pg_hba.conf file is installed when the data
directory is initialized by
It is possible to place the authentication configuration file
elsewhere, however; see the hba_file
The general format of the
pg_hba.conf file is a set of records, one per
line. Blank lines are ignored, as is any text after the
# comment character. Records cannot
be continued across lines. A record is made up of a number of
fields which are separated by spaces and/or tabs. Fields can
contain white space if the field value is double-quoted. Quoting
one of the keywords in a database, user, or address field (e.g.,
replication) makes the word lose its special
meaning, and just match a database, user, or host with that
Each record specifies a connection type, a client IP address range (if relevant for the connection type), a database name, a user name, and the authentication method to be used for connections matching these parameters. The first record with a matching connection type, client address, requested database, and user name is used to perform authentication. There is no “fall-through” or “backup”: if one record is chosen and the authentication fails, subsequent records are not considered. If no record matches, access is denied.
A record can have one of the seven formats
The meaning of the fields is as follows:
This record matches connection attempts using Unix-domain sockets. Without a record of this type, Unix-domain socket connections are disallowed.
This record matches connection attempts made using
host records match
either SSL or
Remote TCP/IP connections will not be possible unless
the server is started with an appropriate value for the
configuration parameter, since the default behavior is to
listen for TCP/IP connections only on the local loopback
This record matches connection attempts made using TCP/IP, but only when the connection is made with SSL encryption.
To make use of this option the server must be built with
Furthermore, SSL must be
enabled by setting the ssl
configuration parameter (see Section 18.9
for more information). Otherwise, the
hostssl record is ignored except for
logging a warning that it cannot match any connections.
This record type has the opposite behavior of
hostssl; it only matches
connection attempts made over TCP/IP that do not use
Specifies which database name(s) this record matches.
all specifies that
it matches all databases. The value
sameuser specifies that the record matches
if the requested database has the same name as the
requested user. The value
samerole specifies that the requested user
must be a member of the role with the same name as the
requested database. (
is an obsolete but still accepted spelling of
samerole.) Superusers are not considered
to be members of a role for the purposes of
samerole unless they are explicitly
members of the role, directly or indirectly, and not just
by virtue of being a superuser. The value
replication specifies that the record
matches if a physical replication connection is requested
(note that replication connections do not specify any
particular database). Otherwise, this is the name of a
database. Multiple database names can be supplied by
separating them with commas. A separate file containing
database names can be specified by preceding the file name
Specifies which database user name(s) this record
matches. The value
specifies that it matches all users. Otherwise, this is
either the name of a specific database user, or a group
name preceded by
that there is no real distinction between users and groups
in PostgreSQL; a
+ mark really means
“match any of the
roles that are directly or indirectly members of this
role”, while a name without a
+ mark matches only that specific role.)
For this purpose, a superuser is only considered to be a
member of a role if they are explicitly a member of the
role, directly or indirectly, and not just by virtue of
being a superuser. Multiple user names can be supplied by
separating them with commas. A separate file containing
user names can be specified by preceding the file name with
Specifies the client machine address(es) that this record matches. This field can contain either a host name, an IP address range, or one of the special key words mentioned below.
An IP address range is specified using standard numeric
notation for the range's starting address, then a slash
/) and a CIDR mask length. The mask length
indicates the number of high-order bits of the client IP
address that must match. Bits to the right of this should
be zero in the given IP address. There must not be any
white space between the IP address, the
/, and the CIDR mask length.
Typical examples of an IPv4 address range specified this
172.20.143.89/32 for a
single host, or
172.20.143.0/24 for a small network, or
10.6.0.0/16 for a larger one.
An IPv6 address range might look like
::1/128 for a single host (in this case
the IPv6 loopback address) or
fe80::7a31:c1ff:0000:0000/96 for a small
all IPv4 addresses, and
represents all IPv6 addresses. To specify a single host,
use a mask length of 32 for IPv4 or 128 for IPv6. In a
network address, do not omit trailing zeroes.
An entry given in IPv4 format will match only IPv4 connections, and an entry given in IPv6 format will match only IPv6 connections, even if the represented address is in the IPv4-in-IPv6 range. Note that entries in IPv6 format will be rejected if the system's C library does not have support for IPv6 addresses.
You can also write
match any IP address,
to match any of the server's own IP addresses, or
samenet to match any address
in any subnet that the server is directly connected to.
If a host name is specified (anything that is not an IP
address range or a special key word is treated as a host
name), that name is compared with the result of a reverse
name resolution of the client's IP address (e.g., reverse
DNS lookup, if DNS is used). Host name comparisons are case
insensitive. If there is a match, then a forward name
resolution (e.g., forward DNS lookup) is performed on the
host name to check whether any of the addresses it resolves
to are equal to the client's IP address. If both directions
match, then the entry is considered to match. (The host
name that is used in
pg_hba.conf should be the one that
address-to-name resolution of the client's IP address
returns, otherwise the line won't be matched. Some host
name databases allow associating an IP address with
multiple host names, but the operating system will only
return one host name when asked to resolve an IP
A host name specification that starts with a dot
.) matches a suffix of the
actual host name. So
.example.com would match
foo.example.com (but not just
When host names are specified in
pg_hba.conf, you should make sure that
name resolution is reasonably fast. It can be of advantage
to set up a local name resolution cache such as
nscd. Also, you may wish to
enable the configuration parameter
log_hostname to see the client's host name
instead of the IP address in the log.
This field only applies to
Users sometimes wonder why host names are handled in
this seemingly complicated way, with two name resolutions
including a reverse lookup of the client's IP address.
This complicates use of the feature in case the client's
reverse DNS entry is not set up or yields some
undesirable host name. It is done primarily for
efficiency: this way, a connection attempt requires at
most two resolver lookups, one reverse and one forward.
If there is a resolver problem with some address, it
becomes only that client's problem. A hypothetical
alternative implementation that only did forward lookups
would have to resolve every host name mentioned in
pg_hba.conf during every
connection attempt. That could be quite slow if many
names are listed. And if there is a resolver problem with
one of the host names, it becomes everyone's problem.
Also, a reverse lookup is necessary to implement the suffix matching feature, because the actual client host name needs to be known in order to match it against the pattern.
Note that this behavior is consistent with other popular implementations of host name-based access control, such as the Apache HTTP Server and TCP Wrappers.
These two fields can be used as an alternative to the
Instead of specifying the mask length, the actual mask is
specified in a separate column. For example,
255.0.0.0 represents an IPv4 CIDR mask
length of 8, and
255.255.255.255 represents a CIDR mask
length of 32.
These fields only apply to
Specifies the authentication method to use when a connection matches this record. The possible choices are summarized here; details are in Section 20.3.
Allow the connection unconditionally. This method allows anyone that can connect to the PostgreSQL database server to login as any PostgreSQL user they wish, without the need for a password or any other authentication. See Section 20.4 for details.
Reject the connection unconditionally. This is
useful for “filtering out” certain hosts
from a group, for example a
reject line could block a specific
host from connecting, while a later line allows the
remaining hosts in a specific network to connect.
Perform SCRAM-SHA-256 authentication to verify the user's password. See Section 20.5 for details.
Perform SCRAM-SHA-256 or MD5 authentication to verify the user's password. See Section 20.5 for details.
Require the client to supply an unencrypted password for authentication. Since the password is sent in clear text over the network, this should not be used on untrusted networks. See Section 20.5 for details.
Use GSSAPI to authenticate the user. This is only available for TCP/IP connections. See Section 20.6 for details.
Use SSPI to authenticate the user. This is only available on Windows. See Section 20.7 for details.
Obtain the operating system user name of the client by contacting the ident server on the client and check if it matches the requested database user name. Ident authentication can only be used on TCP/IP connections. When specified for local connections, peer authentication will be used instead. See Section 20.8 for details.
Obtain the client's operating system user name from the operating system and check if it matches the requested database user name. This is only available for local connections. See Section 20.9 for details.
Authenticate using an LDAP server. See Section 20.10 for details.
Authenticate using a RADIUS server. See Section 20.11 for details.
Authenticate using SSL client certificates. See Section 20.12 for details.
Authenticate using the Pluggable Authentication Modules (PAM) service provided by the operating system. See Section 20.13 for details.
Authenticate using the BSD Authentication service provided by the operating system. See Section 20.14 for details.
auth-method field, there
can be field(s) of the form
value that specify options
for the authentication method. Details about which options
are available for which authentication methods appear
In addition to the method-specific options listed below,
there is one method-independent authentication option
clientcert, which can be
specified in any
record. When set to
option requires the client to present a valid (trusted) SSL
certificate, in addition to the other requirements of the
Files included by
are read as lists of names, which can be separated by either
whitespace or commas. Comments are introduced by
#, just as in
pg_hba.conf, and nested
@ constructs are allowed. Unless the file name
@ is an absolute path, it
is taken to be relative to the directory containing the
are examined sequentially for each connection attempt, the order
of the records is significant. Typically, earlier records will
have tight connection match parameters and weaker authentication
methods, while later records will have looser match parameters
and stronger authentication methods. For example, one might wish
trust authentication for
local TCP/IP connections but require a password for remote TCP/IP
connections. In this case a record specifying
trust authentication for connections from
127.0.0.1 would appear before a record specifying password
authentication for a wider range of allowed client IP
pg_hba.conf file is read on
start-up and when the main server process receives a SIGHUP signal. If you edit the file on an active
system, you will need to signal the postmaster (using
pg_ctl reload or
kill -HUP) to make it re-read the file.
The preceding statement is not true on Microsoft Windows:
there, any changes in the
pg_hba.conf file are immediately applied by
subsequent new connections.
The system view
pg_hba_file_rules can be helpful for
pre-testing changes to the
pg_hba.conf file, or for diagnosing problems if
loading of the file did not have the desired effects. Rows in the
view with non-null
indicate problems in the corresponding lines of the file.
To connect to a particular database, a user must not only
pg_hba.conf checks, but
must have the
for the database. If you wish to restrict which users can
connect to which databases, it's usually easier to control this
privilege than to put the rules in
Some examples of
entries are shown in Example 20.1.
See the next section for details on the different authentication
Example 20.1. Example
# Allow any user on the local system to connect to any database with # any database user name using Unix-domain sockets (the default for local # connections). # # TYPE DATABASE USER ADDRESS METHOD local all all trust # The same using local loopback TCP/IP connections. # # TYPE DATABASE USER ADDRESS METHOD host all all 127.0.0.1/32 trust # The same as the previous line, but using a separate netmask column # # TYPE DATABASE USER IP-ADDRESS IP-MASK METHOD host all all 127.0.0.1 255.255.255.255 trust # The same over IPv6. # # TYPE DATABASE USER ADDRESS METHOD host all all ::1/128 trust # The same using a host name (would typically cover both IPv4 and IPv6). # # TYPE DATABASE USER ADDRESS METHOD host all all localhost trust # Allow any user from any host with IP address 192.168.93.x to connect # to database "postgres" as the same user name that ident reports for # the connection (typically the operating system user name). # # TYPE DATABASE USER ADDRESS METHOD host postgres all 192.168.93.0/24 ident # Allow any user from host 192.168.12.10 to connect to database # "postgres" if the user's password is correctly supplied. # # TYPE DATABASE USER ADDRESS METHOD host postgres all 192.168.12.10/32 scram-sha-256 # Allow any user from hosts in the example.com domain to connect to # any database if the user's password is correctly supplied. # # Require SCRAM authentication for most users, but make an exception # for user 'mike', who uses an older client that doesn't support SCRAM # authentication. # # TYPE DATABASE USER ADDRESS METHOD host all mike .example.com md5 host all all .example.com scram-sha-256 # In the absence of preceding "host" lines, these two lines will # reject all connections from 192.168.54.1 (since that entry will be # matched first), but allow GSSAPI connections from anywhere else # on the Internet. The zero mask causes no bits of the host IP # address to be considered, so it matches any host. # # TYPE DATABASE USER ADDRESS METHOD host all all 192.168.54.1/32 reject host all all 0.0.0.0/0 gss # Allow users from 192.168.x.x hosts to connect to any database, if # they pass the ident check. If, for example, ident says the user is # "bryanh" and he requests to connect as PostgreSQL user "guest1", the # connection is allowed if there is an entry in pg_ident.conf for map # "omicron" that says "bryanh" is allowed to connect as "guest1". # # TYPE DATABASE USER ADDRESS METHOD host all all 192.168.0.0/16 ident map=omicron # If these are the only three lines for local connections, they will # allow local users to connect only to their own databases (databases # with the same name as their database user name) except for administrators # and members of role "support", who can connect to all databases. The file # $PGDATA/admins contains a list of names of administrators. Passwords # are required in all cases. # # TYPE DATABASE USER ADDRESS METHOD local sameuser all md5 local all @admins md5 local all +support md5 # The last two lines above can be combined into a single line: local all @admins,+support md5 # The database column can also use lists and file names: local db1,db2,@demodbs all md5
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