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 initdb. It is
possible to place the authentication configuration file elsewhere,
however; see the hba_file configuration parameter.
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. 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 quoted. Records
cannot be continued across lines.
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
local database user auth-method [auth-option]
host database user CIDR-address auth-method [auth-option]
hostssl database user CIDR-address auth-method [auth-option]
hostnossl database user CIDR-address auth-method [auth-option]
host database user IP-address IP-mask auth-method [auth-option]
hostssl database user IP-address IP-mask auth-method [auth-option]
hostnossl database user IP-address IP-mask auth-method [auth-option]
The meaning of the fields is as follows:
- local
This record matches connection attempts using Unix-domain
sockets. Without a record of this type, Unix-domain socket
connections are disallowed.
- host
This record matches connection attempts made using TCP/IP.
host records match either
SSL or non-SSL connection
attempts.
Note: Remote TCP/IP connections will not be possible unless
the server is started with an appropriate value for the
listen_addresses configuration parameter,
since the default behavior is to listen for TCP/IP connections
only on the local loopback address localhost.
- hostssl
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
SSL support. Furthermore,
SSL must be enabled at server start time
by setting the ssl configuration parameter (see
Section 17.8 for more information).
- hostnossl
This record type has the opposite logic to hostssl:
it only matches connection attempts made over
TCP/IP that do not use SSL.
- database
Specifies which database names this record matches. The value
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. (samegroup is an
obsolete but still accepted spelling of samerole.)
Otherwise, this is the name of
a specific PostgreSQL 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 with @.
- user
Specifies which database user names this record
matches. The value all specifies that it
matches all users. Otherwise, this is either the name of a specific
database user, or a group name preceded by +.
(Recall 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.)
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 @.
- CIDR-address
Specifies the client machine IP address range that this record
matches. It contains an IP address in standard dotted decimal
notation and a CIDR mask length. (IP addresses can only be
specified numerically, not as domain or host names.) The mask
length indicates the number of high-order bits of the client
IP address that must match. Bits to the right of this must
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 a CIDR-address are
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.
To specify a single host, use a CIDR mask of 32 for IPv4 or
128 for IPv6. In a network address, do not omit trailing zeroes.
An IP address given in IPv4 format will match IPv6 connections that
have the corresponding address, for example 127.0.0.1
will match the IPv6 address ::ffff:127.0.0.1. 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.
This field only applies to host,
hostssl, and hostnossl records.
- IP-address
IP-mask These fields can be used as an alternative to the
CIDR-address notation. 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 host,
hostssl, and hostnossl records.
- auth-method
Specifies the authentication method to use when connecting via
this record. The possible choices are summarized here; details
are in Section 21.2.
- trust
Allow the connection unconditionally. This method
allows anyone that can connect to the
PostgreSQL database server to login as
any PostgreSQL user they like,
without the need for a password. See Section 21.2.1 for details.
- reject
Reject the connection unconditionally. This is useful for
"filtering out" certain hosts from a group.
- md5
Require the client to supply an MD5-encrypted password for
authentication.
See Section 21.2.2 for details.
- crypt
Note: This option is recommended only for communicating with pre-7.2
clients.
Require the client to supply a crypt()-encrypted
password for authentication.
md5 is now recommended over crypt.
See Section 21.2.2 for details.
- password
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.
It also does not usually work with threaded client applications.
See Section 21.2.2 for details.
- gss
Use GSSAPI to authenticate the user. This is only
available for TCP/IP connections. See Section 21.2.3 for details.
- sspi
Use SSPI to authenticate the user. This is only
available on Windows. See Section 21.2.4 for details.
- krb5
Use Kerberos V5 to authenticate the user. This is only
available for TCP/IP connections. See Section 21.2.5 for details.
- ident
Obtain the operating system user name of the client (for
TCP/IP connections by contacting the ident server on the
client, for local connections by getting it from the
operating system) and check if the user is allowed to
connect as the requested database user by consulting the map
specified after the ident key word.
See Section 21.2.6 for details.
- ldap
Authenticate using LDAP to a central server. See Section 21.2.7 for details.
- pam
Authenticate using the Pluggable Authentication Modules
(PAM) service provided by the operating system. See Section 21.2.8 for details.
- auth-option
The meaning of this optional field depends on the chosen
authentication method. Details appear below.
Files included by @ constructs 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 following @ is an absolute
path, it is taken to be relative to the directory containing the
referencing file.
Since the pg_hba.conf records 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 to use 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 addresses.
The 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 server
(using pg_ctl reload or kill -HUP) to make it
re-read the file.
Tip: To connect to a particular database, a user must not only pass the
pg_hba.conf checks, but must have the
CONNECT privilege for the database. If you wish to
restrict which users can connect to which databases, it's usually
easier to control this by granting/revoking CONNECT privilege
than to put the rules into pg_hba.conf entries.
Some examples of pg_hba.conf entries are shown in
Example 21-1. See the next section for details on the
different authentication methods.
Example 21-1. Example pg_hba.conf entries
# Allow any user on the local system to connect to any database under
# any database user name using Unix-domain sockets (the default for local
# connections).
#
# TYPE DATABASE USER CIDR-ADDRESS METHOD
local all all trust
# The same using local loopback TCP/IP connections.
#
# TYPE DATABASE USER CIDR-ADDRESS METHOD
host all all 127.0.0.1/32 trust
# The same as the last 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
# 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 Unix user name).
#
# TYPE DATABASE USER CIDR-ADDRESS METHOD
host postgres all 192.168.93.0/24 ident sameuser
# Allow a user from host 192.168.12.10 to connect to database
# "postgres" if the user's password is correctly supplied.
#
# TYPE DATABASE USER CIDR-ADDRESS METHOD
host postgres all 192.168.12.10/32 md5
# In the absence of preceding "host" lines, these two lines will
# reject all connection from 192.168.54.1 (since that entry will be
# matched first), but allow Kerberos 5 connections from anywhere else
# on the Internet. The zero mask means that no bits of the host IP
# address are considered so it matches any host.
#
# TYPE DATABASE USER CIDR-ADDRESS METHOD
host all all 192.168.54.1/32 reject
host all all 0.0.0.0/0 krb5
# 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 CIDR-ADDRESS METHOD
host all all 192.168.0.0/16 ident 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 CIDR-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
