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diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml new file mode 100644 index 0000000..4337599 --- /dev/null +++ b/doc/src/sgml/client-auth.sgml @@ -0,0 +1,2244 @@ +<!-- doc/src/sgml/client-auth.sgml --> + +<chapter id="client-authentication"> + <title>Client Authentication</title> + + <indexterm zone="client-authentication"> + <primary>client authentication</primary> + </indexterm> + + <para> + When a client application connects to the database server, it + specifies which <productname>PostgreSQL</productname> database user name it + wants to connect as, much the same way one logs into a Unix computer + as a particular user. Within the SQL environment the active database + user name determines access privileges to database objects — see + <xref linkend="user-manag"/> for more information. Therefore, it is + essential to restrict which database users can connect. + </para> + + <note> + <para> + As explained in <xref linkend="user-manag"/>, + <productname>PostgreSQL</productname> actually does privilege + management in terms of <quote>roles</quote>. In this chapter, we + consistently use <firstterm>database user</firstterm> to mean <quote>role with the + <literal>LOGIN</literal> privilege</quote>. + </para> + </note> + + <para> + <firstterm>Authentication</firstterm> is the process by which the + database server establishes the identity of the client, and by + extension determines whether the client application (or the user + who runs the client application) is permitted to connect with the + database user name that was requested. + </para> + + <para> + <productname>PostgreSQL</productname> offers a number of different + client authentication methods. The method used to authenticate a + particular client connection can be selected on the basis of + (client) host address, database, and user. + </para> + + <para> + <productname>PostgreSQL</productname> database user names are logically + separate from user names of the operating system in which the server + runs. If all the users of a particular server also have accounts on + the server's machine, it makes sense to assign database user names + that match their operating system user names. However, a server that + accepts remote connections might have many database users who have no local + operating system + account, and in such cases there need be no connection between + database user names and OS user names. + </para> + + <sect1 id="auth-pg-hba-conf"> + <title>The <filename>pg_hba.conf</filename> File</title> + + <indexterm zone="auth-pg-hba-conf"> + <primary>pg_hba.conf</primary> + </indexterm> + + <para> + Client authentication is controlled by a configuration file, + which traditionally is named + <filename>pg_hba.conf</filename> and is stored in the database + cluster's data directory. + (<acronym>HBA</acronym> stands for host-based authentication.) A default + <filename>pg_hba.conf</filename> file is installed when the data + directory is initialized by <xref linkend="app-initdb"/>. It is + possible to place the authentication configuration file elsewhere, + however; see the <xref linkend="guc-hba-file"/> configuration parameter. + </para> + + <para> + The general format of the <filename>pg_hba.conf</filename> file is + a set of records, one per line. Blank lines are ignored, as is any + text after the <literal>#</literal> comment character. + A record can be continued onto the next line by ending the line with + a backslash. (Backslashes are not special except at the end of a line.) + 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., + <literal>all</literal> or <literal>replication</literal>) makes the word lose its special + meaning, and just match a database, user, or host with that name. + Backslash line continuation applies even within quoted text or comments. + </para> + + <para> + 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 <quote>fall-through</quote> or + <quote>backup</quote>: if one record is chosen and the authentication + fails, subsequent records are not considered. If no record matches, + access is denied. + </para> + + <para> + A record can have several formats: +<synopsis> +local <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +host <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>address</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostssl <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>address</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostnossl <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>address</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostgssenc <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>address</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostnogssenc <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>address</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +host <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>IP-address</replaceable> <replaceable>IP-mask</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostssl <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>IP-address</replaceable> <replaceable>IP-mask</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostnossl <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>IP-address</replaceable> <replaceable>IP-mask</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostgssenc <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>IP-address</replaceable> <replaceable>IP-mask</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +hostnogssenc <replaceable>database</replaceable> <replaceable>user</replaceable> <replaceable>IP-address</replaceable> <replaceable>IP-mask</replaceable> <replaceable>auth-method</replaceable> <optional><replaceable>auth-options</replaceable></optional> +</synopsis> + The meaning of the fields is as follows: + + <variablelist> + <varlistentry> + <term><literal>local</literal></term> + <listitem> + <para> + This record matches connection attempts using Unix-domain + sockets. Without a record of this type, Unix-domain socket + connections are disallowed. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>host</literal></term> + <listitem> + <para> + This record matches connection attempts made using TCP/IP. + <literal>host</literal> records match + <acronym>SSL</acronym> or non-<acronym>SSL</acronym> connection + attempts as well as <acronym>GSSAPI</acronym> encrypted or + non-<acronym>GSSAPI</acronym> encrypted connection attempts. + </para> + <note> + <para> + Remote TCP/IP connections will not be possible unless + the server is started with an appropriate value for the + <xref linkend="guc-listen-addresses"/> configuration parameter, + since the default behavior is to listen for TCP/IP connections + only on the local loopback address <literal>localhost</literal>. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>hostssl</literal></term> + <listitem> + <para> + This record matches connection attempts made using TCP/IP, + but only when the connection is made with <acronym>SSL</acronym> + encryption. + </para> + + <para> + To make use of this option the server must be built with + <acronym>SSL</acronym> support. Furthermore, + <acronym>SSL</acronym> must be enabled + by setting the <xref linkend="guc-ssl"/> configuration parameter (see + <xref linkend="ssl-tcp"/> for more information). + Otherwise, the <literal>hostssl</literal> record is ignored except for + logging a warning that it cannot match any connections. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>hostnossl</literal></term> + <listitem> + <para> + This record type has the opposite behavior of <literal>hostssl</literal>; + it only matches connection attempts made over + TCP/IP that do not use <acronym>SSL</acronym>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>hostgssenc</literal></term> + <listitem> + <para> + This record matches connection attempts made using TCP/IP, + but only when the connection is made with <acronym>GSSAPI</acronym> + encryption. + </para> + + <para> + To make use of this option the server must be built with + <acronym>GSSAPI</acronym> support. Otherwise, + the <literal>hostgssenc</literal> record is ignored except for logging + a warning that it cannot match any connections. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>hostnogssenc</literal></term> + <listitem> + <para> + This record type has the opposite behavior of <literal>hostgssenc</literal>; + it only matches connection attempts made over + TCP/IP that do not use <acronym>GSSAPI</acronym> encryption. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>database</replaceable></term> + <listitem> + <para> + Specifies which database name(s) this record matches. The value + <literal>all</literal> specifies that it matches all databases. + The value <literal>sameuser</literal> specifies that the record + matches if the requested database has the same name as the + requested user. The value <literal>samerole</literal> specifies that + the requested user must be a member of the role with the same + name as the requested database. (<literal>samegroup</literal> is an + obsolete but still accepted spelling of <literal>samerole</literal>.) + Superusers are not considered to be members of a role for the + purposes of <literal>samerole</literal> unless they are explicitly + members of the role, directly or indirectly, and not just by + virtue of being a superuser. + The value <literal>replication</literal> specifies that the record + matches if a physical replication connection is requested, however, it + doesn't match with logical replication connections. Note that physical + replication connections do not specify any particular database whereas + logical replication connections do specify it. + Otherwise, this is the name of + a specific <productname>PostgreSQL</productname> 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 <literal>@</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>user</replaceable></term> + <listitem> + <para> + Specifies which database user name(s) this record + matches. The value <literal>all</literal> specifies that it + matches all users. Otherwise, this is either the name of a specific + database user, or a group name preceded by <literal>+</literal>. + (Recall that there is no real distinction between users and groups + in <productname>PostgreSQL</productname>; a <literal>+</literal> mark really means + <quote>match any of the roles that are directly or indirectly members + of this role</quote>, while a name without a <literal>+</literal> 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 <literal>@</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>address</replaceable></term> + <listitem> + <para> + 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. + </para> + + <para> + An IP address range is specified using standard numeric notation + for the range's starting address, then a slash (<literal>/</literal>) + and a <acronym>CIDR</acronym> 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 + <literal>/</literal>, and the CIDR mask length. + </para> + + <para> + Typical examples of an IPv4 address range specified this way are + <literal>172.20.143.89/32</literal> for a single host, or + <literal>172.20.143.0/24</literal> for a small network, or + <literal>10.6.0.0/16</literal> for a larger one. + An IPv6 address range might look like <literal>::1/128</literal> + for a single host (in this case the IPv6 loopback address) or + <literal>fe80::7a31:c1ff:0000:0000/96</literal> for a small + network. + <literal>0.0.0.0/0</literal> represents all + IPv4 addresses, and <literal>::0/0</literal> 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. + </para> + + <para> + 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. + </para> + + <para> + You can also write <literal>all</literal> to match any IP address, + <literal>samehost</literal> to match any of the server's own IP + addresses, or <literal>samenet</literal> to match any address in any + subnet that the server is directly connected to. + </para> + + <para> + 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 <filename>pg_hba.conf</filename> 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 address.) + </para> + + <para> + A host name specification that starts with a dot + (<literal>.</literal>) matches a suffix of the actual host + name. So <literal>.example.com</literal> would match + <literal>foo.example.com</literal> (but not just + <literal>example.com</literal>). + </para> + + <para> + When host names are specified + in <filename>pg_hba.conf</filename>, 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 <command>nscd</command>. Also, you may wish to enable the + configuration parameter <varname>log_hostname</varname> to see + the client's host name instead of the IP address in the log. + </para> + + <para> + These fields do not apply to <literal>local</literal> records. + </para> + + <note> + <para> + 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 + <filename>pg_hba.conf</filename> 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. + </para> + + <para> + 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. + </para> + + <para> + 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. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>IP-address</replaceable></term> + <term><replaceable>IP-mask</replaceable></term> + <listitem> + <para> + These two fields can be used as an alternative to the + <replaceable>IP-address</replaceable><literal>/</literal><replaceable>mask-length</replaceable> + notation. Instead of + specifying the mask length, the actual mask is specified in a + separate column. For example, <literal>255.0.0.0</literal> represents an IPv4 + CIDR mask length of 8, and <literal>255.255.255.255</literal> represents a + CIDR mask length of 32. + </para> + + <para> + These fields do not apply to <literal>local</literal> records. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>auth-method</replaceable></term> + <listitem> + <para> + Specifies the authentication method to use when a connection matches + this record. The possible choices are summarized here; details + are in <xref linkend="auth-methods"/>. All the options + are lower case and treated case sensitively, so even acronyms like + <literal>ldap</literal> must be specified as lower case. + + <variablelist> + <varlistentry> + <term><literal>trust</literal></term> + <listitem> + <para> + Allow the connection unconditionally. This method + allows anyone that can connect to the + <productname>PostgreSQL</productname> database server to login as + any <productname>PostgreSQL</productname> user they wish, + without the need for a password or any other authentication. See <xref + linkend="auth-trust"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>reject</literal></term> + <listitem> + <para> + Reject the connection unconditionally. This is useful for + <quote>filtering out</quote> certain hosts from a group, for example a + <literal>reject</literal> line could block a specific host from connecting, + while a later line allows the remaining hosts in a specific + network to connect. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>scram-sha-256</literal></term> + <listitem> + <para> + Perform SCRAM-SHA-256 authentication to verify the user's + password. See <xref linkend="auth-password"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>md5</literal></term> + <listitem> + <para> + Perform SCRAM-SHA-256 or MD5 authentication to verify the + user's password. See <xref linkend="auth-password"/> + for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>password</literal></term> + <listitem> + <para> + 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 <xref linkend="auth-password"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>gss</literal></term> + <listitem> + <para> + Use GSSAPI to authenticate the user. This is only + available for TCP/IP connections. See <xref + linkend="gssapi-auth"/> for details. It can be used in conjunction + with GSSAPI encryption. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>sspi</literal></term> + <listitem> + <para> + Use SSPI to authenticate the user. This is only + available on Windows. See <xref + linkend="sspi-auth"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>ident</literal></term> + <listitem> + <para> + 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 <xref linkend="auth-ident"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>peer</literal></term> + <listitem> + <para> + 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 <xref linkend="auth-peer"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>ldap</literal></term> + <listitem> + <para> + Authenticate using an <acronym>LDAP</acronym> server. See <xref + linkend="auth-ldap"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>radius</literal></term> + <listitem> + <para> + Authenticate using a RADIUS server. See <xref + linkend="auth-radius"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>cert</literal></term> + <listitem> + <para> + Authenticate using SSL client certificates. See + <xref linkend="auth-cert"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>pam</literal></term> + <listitem> + <para> + Authenticate using the Pluggable Authentication Modules + (PAM) service provided by the operating system. See <xref + linkend="auth-pam"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>bsd</literal></term> + <listitem> + <para> + Authenticate using the BSD Authentication service provided by the + operating system. See <xref linkend="auth-bsd"/> for details. + </para> + </listitem> + </varlistentry> + </variablelist> + + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>auth-options</replaceable></term> + <listitem> + <para> + After the <replaceable>auth-method</replaceable> field, there can be field(s) of + the form <replaceable>name</replaceable><literal>=</literal><replaceable>value</replaceable> that + specify options for the authentication method. Details about which + options are available for which authentication methods appear below. + </para> + + <para> + In addition to the method-specific options listed below, there is a + method-independent authentication option <literal>clientcert</literal>, which + can be specified in any <literal>hostssl</literal> record. + This option can be set to <literal>verify-ca</literal> or + <literal>verify-full</literal>. Both options require the client + to present a valid (trusted) SSL certificate, while + <literal>verify-full</literal> additionally enforces that the + <literal>cn</literal> (Common Name) in the certificate matches + the username or an applicable mapping. + This behavior is similar to the <literal>cert</literal> authentication + method (see <xref linkend="auth-cert"/>) but enables pairing + the verification of client certificates with any authentication + method that supports <literal>hostssl</literal> entries. + </para> + <para> + On any record using client certificate authentication (i.e. one + using the <literal>cert</literal> authentication method or one + using the <literal>clientcert</literal> option), you can specify + which part of the client certificate credentials to match using + the <literal>clientname</literal> option. This option can have one + of two values. If you specify <literal>clientname=CN</literal>, which + is the default, the username is matched against the certificate's + <literal>Common Name (CN)</literal>. If instead you specify + <literal>clientname=DN</literal> the username is matched against the + entire <literal>Distinguished Name (DN)</literal> of the certificate. + This option is probably best used in conjunction with a username map. + The comparison is done with the <literal>DN</literal> in + <ulink url="https://tools.ietf.org/html/rfc2253">RFC 2253</ulink> + format. To see the <literal>DN</literal> of a client certificate + in this format, do +<programlisting> +openssl x509 -in myclient.crt -noout --subject -nameopt RFC2253 | sed "s/^subject=//" +</programlisting> + Care needs to be taken when using this option, especially when using + regular expression matching against the <literal>DN</literal>. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + Files included by <literal>@</literal> constructs are read as lists of names, + which can be separated by either whitespace or commas. Comments are + introduced by <literal>#</literal>, just as in + <filename>pg_hba.conf</filename>, and nested <literal>@</literal> constructs are + allowed. Unless the file name following <literal>@</literal> is an absolute + path, it is taken to be relative to the directory containing the + referencing file. + </para> + + <para> + Since the <filename>pg_hba.conf</filename> 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 <literal>trust</literal> + authentication for local TCP/IP connections but require a password for + remote TCP/IP connections. In this case a record specifying + <literal>trust</literal> 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. + </para> + + <para> + The <filename>pg_hba.conf</filename> file is read on start-up and when + the main server process receives a + <systemitem>SIGHUP</systemitem><indexterm><primary>SIGHUP</primary></indexterm> + signal. If you edit the file on an + active system, you will need to signal the postmaster + (using <literal>pg_ctl reload</literal>, calling the SQL function + <function>pg_reload_conf()</function>, or using <literal>kill + -HUP</literal>) to make it re-read the file. + </para> + + <note> + <para> + The preceding statement is not true on Microsoft Windows: there, any + changes in the <filename>pg_hba.conf</filename> file are immediately + applied by subsequent new connections. + </para> + </note> + + <para> + The system view + <link linkend="view-pg-hba-file-rules"><structname>pg_hba_file_rules</structname></link> + can be helpful for pre-testing changes to the <filename>pg_hba.conf</filename> + file, or for diagnosing problems if loading of the file did not have the + desired effects. Rows in the view with + non-null <structfield>error</structfield> fields indicate problems in the + corresponding lines of the file. + </para> + + <tip> + <para> + To connect to a particular database, a user must not only pass the + <filename>pg_hba.conf</filename> checks, but must have the + <literal>CONNECT</literal> 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 <literal>CONNECT</literal> privilege + than to put the rules in <filename>pg_hba.conf</filename> entries. + </para> + </tip> + + <para> + Some examples of <filename>pg_hba.conf</filename> entries are shown in + <xref linkend="example-pg-hba.conf"/>. See the next section for details on the + different authentication methods. + </para> + + <example id="example-pg-hba.conf"> + <title>Example <filename>pg_hba.conf</filename> Entries</title> +<programlisting> +# 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 three lines will +# reject all connections from 192.168.54.1 (since that entry will be +# matched first), but allow GSSAPI-encrypted 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. Unencrypted GSSAPI connections +# (which "fall through" to the third line since "hostgssenc" only matches +# encrypted GSSAPI connections) are allowed, but only from 192.168.12.10. +# +# TYPE DATABASE USER ADDRESS METHOD +host all all 192.168.54.1/32 reject +hostgssenc all all 0.0.0.0/0 gss +host all all 192.168.12.10/32 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 +</programlisting> + </example> + </sect1> + + <sect1 id="auth-username-maps"> + <title>User Name Maps</title> + + <indexterm zone="auth-username-maps"> + <primary>User name maps</primary> + </indexterm> + + <para> + When using an external authentication system such as Ident or GSSAPI, + the name of the operating system user that initiated the connection + might not be the same as the database user (role) that is to be used. + In this case, a user name map can be applied to map the operating system + user name to a database user. To use user name mapping, specify + <literal>map</literal>=<replaceable>map-name</replaceable> + in the options field in <filename>pg_hba.conf</filename>. This option is + supported for all authentication methods that receive external user names. + Since different mappings might be needed for different connections, + the name of the map to be used is specified in the + <replaceable>map-name</replaceable> parameter in <filename>pg_hba.conf</filename> + to indicate which map to use for each individual connection. + </para> + + <para> + User name maps are defined in the ident map file, which by default is named + <filename>pg_ident.conf</filename><indexterm><primary>pg_ident.conf</primary></indexterm> + and is stored in the + cluster's data directory. (It is possible to place the map file + elsewhere, however; see the <xref linkend="guc-ident-file"/> + configuration parameter.) + The ident map file contains lines of the general form: +<synopsis> +<replaceable>map-name</replaceable> <replaceable>system-username</replaceable> <replaceable>database-username</replaceable> +</synopsis> + Comments, whitespace and line continuations are handled in the same way as in + <filename>pg_hba.conf</filename>. The + <replaceable>map-name</replaceable> is an arbitrary name that will be used to + refer to this mapping in <filename>pg_hba.conf</filename>. The other + two fields specify an operating system user name and a matching + database user name. The same <replaceable>map-name</replaceable> can be + used repeatedly to specify multiple user-mappings within a single map. + </para> + <para> + There is no restriction regarding how many database users a given + operating system user can correspond to, nor vice versa. Thus, entries + in a map should be thought of as meaning <quote>this operating system + user is allowed to connect as this database user</quote>, rather than + implying that they are equivalent. The connection will be allowed if + there is any map entry that pairs the user name obtained from the + external authentication system with the database user name that the + user has requested to connect as. + </para> + <para> + If the <replaceable>system-username</replaceable> field starts with a slash (<literal>/</literal>), + the remainder of the field is treated as a regular expression. + (See <xref linkend="posix-syntax-details"/> for details of + <productname>PostgreSQL</productname>'s regular expression syntax.) The regular + expression can include a single capture, or parenthesized subexpression, + which can then be referenced in the <replaceable>database-username</replaceable> + field as <literal>\1</literal> (backslash-one). This allows the mapping of + multiple user names in a single line, which is particularly useful for + simple syntax substitutions. For example, these entries +<programlisting> +mymap /^(.*)@mydomain\.com$ \1 +mymap /^(.*)@otherdomain\.com$ guest +</programlisting> + will remove the domain part for users with system user names that end with + <literal>@mydomain.com</literal>, and allow any user whose system name ends with + <literal>@otherdomain.com</literal> to log in as <literal>guest</literal>. + </para> + + <tip> + <para> + Keep in mind that by default, a regular expression can match just part of + a string. It's usually wise to use <literal>^</literal> and <literal>$</literal>, as + shown in the above example, to force the match to be to the entire + system user name. + </para> + </tip> + + <para> + The <filename>pg_ident.conf</filename> file is read on start-up and + when the main server process receives a + <systemitem>SIGHUP</systemitem><indexterm><primary>SIGHUP</primary></indexterm> + signal. If you edit the file on an + active system, you will need to signal the postmaster + (using <literal>pg_ctl reload</literal>, calling the SQL function + <function>pg_reload_conf()</function>, or using <literal>kill + -HUP</literal>) to make it re-read the file. + </para> + + <para> + The system view + <link linkend="view-pg-ident-file-mappings"><structname>pg_ident_file_mappings</structname></link> + can be helpful for pre-testing changes to the + <filename>pg_ident.conf</filename> file, or for diagnosing problems if + loading of the file did not have the desired effects. Rows in the view with + non-null <structfield>error</structfield> fields indicate problems in the + corresponding lines of the file. + </para> + + <para> + A <filename>pg_ident.conf</filename> file that could be used in + conjunction with the <filename>pg_hba.conf</filename> file in <xref + linkend="example-pg-hba.conf"/> is shown in <xref + linkend="example-pg-ident.conf"/>. In this example, anyone + logged in to a machine on the 192.168 network that does not have the + operating system user name <literal>bryanh</literal>, <literal>ann</literal>, or + <literal>robert</literal> would not be granted access. Unix user + <literal>robert</literal> would only be allowed access when he tries to + connect as <productname>PostgreSQL</productname> user <literal>bob</literal>, not + as <literal>robert</literal> or anyone else. <literal>ann</literal> would + only be allowed to connect as <literal>ann</literal>. User + <literal>bryanh</literal> would be allowed to connect as either + <literal>bryanh</literal> or as <literal>guest1</literal>. + </para> + + <example id="example-pg-ident.conf"> + <title>An Example <filename>pg_ident.conf</filename> File</title> +<programlisting> +# MAPNAME SYSTEM-USERNAME PG-USERNAME + +omicron bryanh bryanh +omicron ann ann +# bob has user name robert on these machines +omicron robert bob +# bryanh can also connect as guest1 +omicron bryanh guest1 +</programlisting> + </example> + </sect1> + + <sect1 id="auth-methods"> + <title>Authentication Methods</title> + + <para> + <productname>PostgreSQL</productname> provides various methods for + authenticating users: + + <itemizedlist> + <listitem> + <para> + <link linkend="auth-trust">Trust authentication</link>, which + simply trusts that users are who they say they are. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-password">Password authentication</link>, which + requires that users send a password. + </para> + </listitem> + <listitem> + <para> + <link linkend="gssapi-auth">GSSAPI authentication</link>, which + relies on a GSSAPI-compatible security library. Typically this is + used to access an authentication server such as a Kerberos or + Microsoft Active Directory server. + </para> + </listitem> + <listitem> + <para> + <link linkend="sspi-auth">SSPI authentication</link>, which + uses a Windows-specific protocol similar to GSSAPI. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-ident">Ident authentication</link>, which + relies on an <quote>Identification Protocol</quote> + (<ulink url="https://tools.ietf.org/html/rfc1413">RFC 1413</ulink>) + service on the client's machine. (On local Unix-socket connections, + this is treated as peer authentication.) + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-peer">Peer authentication</link>, which + relies on operating system facilities to identify the process at the + other end of a local connection. This is not supported for remote + connections. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-ldap">LDAP authentication</link>, which + relies on an LDAP authentication server. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-radius">RADIUS authentication</link>, which + relies on a RADIUS authentication server. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-cert">Certificate authentication</link>, which + requires an SSL connection and authenticates users by checking the + SSL certificate they send. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-pam">PAM authentication</link>, which + relies on a PAM (Pluggable Authentication Modules) library. + </para> + </listitem> + <listitem> + <para> + <link linkend="auth-bsd">BSD authentication</link>, which + relies on the BSD Authentication framework (currently available + only on OpenBSD). + </para> + </listitem> + </itemizedlist> + </para> + + <para> + Peer authentication is usually recommendable for local connections, + though trust authentication might be sufficient in some circumstances. + Password authentication is the easiest choice for remote connections. + All the other options require some kind of external security + infrastructure (usually an authentication server or a certificate + authority for issuing SSL certificates), or are platform-specific. + </para> + + <para> + The following sections describe each of these authentication methods + in more detail. + </para> + </sect1> + + <sect1 id="auth-trust"> + <title>Trust Authentication</title> + + <para> + When <literal>trust</literal> authentication is specified, + <productname>PostgreSQL</productname> assumes that anyone who can + connect to the server is authorized to access the database with + whatever database user name they specify (even superuser names). + Of course, restrictions made in the <literal>database</literal> and + <literal>user</literal> columns still apply. + This method should only be used when there is adequate + operating-system-level protection on connections to the server. + </para> + + <para> + <literal>trust</literal> authentication is appropriate and very + convenient for local connections on a single-user workstation. It + is usually <emphasis>not</emphasis> appropriate by itself on a multiuser + machine. However, you might be able to use <literal>trust</literal> even + on a multiuser machine, if you restrict access to the server's + Unix-domain socket file using file-system permissions. To do this, set the + <varname>unix_socket_permissions</varname> (and possibly + <varname>unix_socket_group</varname>) configuration parameters as + described in <xref linkend="runtime-config-connection"/>. Or you + could set the <varname>unix_socket_directories</varname> + configuration parameter to place the socket file in a suitably + restricted directory. + </para> + + <para> + Setting file-system permissions only helps for Unix-socket connections. + Local TCP/IP connections are not restricted by file-system permissions. + Therefore, if you want to use file-system permissions for local security, + remove the <literal>host ... 127.0.0.1 ...</literal> line from + <filename>pg_hba.conf</filename>, or change it to a + non-<literal>trust</literal> authentication method. + </para> + + <para> + <literal>trust</literal> authentication is only suitable for TCP/IP connections + if you trust every user on every machine that is allowed to connect + to the server by the <filename>pg_hba.conf</filename> lines that specify + <literal>trust</literal>. It is seldom reasonable to use <literal>trust</literal> + for any TCP/IP connections other than those from <systemitem>localhost</systemitem> (127.0.0.1). + </para> + + </sect1> + + <sect1 id="auth-password"> + <title>Password Authentication</title> + + <indexterm> + <primary>MD5</primary> + </indexterm> + <indexterm> + <primary>SCRAM</primary> + </indexterm> + <indexterm> + <primary>password</primary> + <secondary>authentication</secondary> + </indexterm> + + <para> + There are several password-based authentication methods. These methods + operate similarly but differ in how the users' passwords are stored on the + server and how the password provided by a client is sent across the + connection. + </para> + + <variablelist> + <varlistentry> + <term><literal>scram-sha-256</literal></term> + <listitem> + <para> + The method <literal>scram-sha-256</literal> performs SCRAM-SHA-256 + authentication, as described in + <ulink url="https://tools.ietf.org/html/rfc7677">RFC 7677</ulink>. It + is a challenge-response scheme that prevents password sniffing on + untrusted connections and supports storing passwords on the server in a + cryptographically hashed form that is thought to be secure. + </para> + + <para> + This is the most secure of the currently provided methods, but it is + not supported by older client libraries. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>md5</literal></term> + <listitem> + <para> + The method <literal>md5</literal> 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. + </para> + + <para> + The <literal>md5</literal> method cannot be used with + the <xref linkend="guc-db-user-namespace"/> feature. + </para> + + <para> + To ease transition from the <literal>md5</literal> method to the newer + SCRAM method, if <literal>md5</literal> is specified as a method + in <filename>pg_hba.conf</filename> but the user's password on the + server is encrypted for SCRAM (see below), then SCRAM-based + authentication will automatically be chosen instead. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>password</literal></term> + <listitem> + <para> + The method <literal>password</literal> sends the password in clear-text and is + therefore vulnerable to password <quote>sniffing</quote> attacks. It should + always be avoided if possible. If the connection is protected by SSL + encryption then <literal>password</literal> can be used safely, though. + (Though SSL certificate authentication might be a better choice if one + is depending on using SSL). + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + <productname>PostgreSQL</productname> database passwords are + separate from operating system user passwords. The password for + each database user is stored in the <literal>pg_authid</literal> system + catalog. Passwords can be managed with the SQL commands + <xref linkend="sql-createrole"/> and + <xref linkend="sql-alterrole"/>, + e.g., <userinput>CREATE ROLE foo WITH LOGIN PASSWORD 'secret'</userinput>, + or the <application>psql</application> + command <literal>\password</literal>. + If no password has been set up for a user, the stored password + is null and password authentication will always fail for that user. + </para> + + <para> + The availability of the different password-based authentication methods + depends on how a user's password on the server is encrypted (or hashed, + more accurately). This is controlled by the configuration + parameter <xref linkend="guc-password-encryption"/> at the time the + password is set. If a password was encrypted using + the <literal>scram-sha-256</literal> setting, then it can be used for the + authentication methods <literal>scram-sha-256</literal> + and <literal>password</literal> (but password transmission will be in + plain text in the latter case). The authentication method + specification <literal>md5</literal> will automatically switch to using + the <literal>scram-sha-256</literal> method in this case, as explained + above, so it will also work. If a password was encrypted using + the <literal>md5</literal> setting, then it can be used only for + the <literal>md5</literal> and <literal>password</literal> authentication + method specifications (again, with the password transmitted in plain text + in the latter case). (Previous PostgreSQL releases supported storing the + password on the server in plain text. This is no longer possible.) To + check the currently stored password hashes, see the system + catalog <literal>pg_authid</literal>. + </para> + + <para> + To upgrade an existing installation from <literal>md5</literal> + to <literal>scram-sha-256</literal>, after having ensured that all client + libraries in use are new enough to support SCRAM, + set <literal>password_encryption = 'scram-sha-256'</literal> + in <filename>postgresql.conf</filename>, make all users set new passwords, + and change the authentication method specifications + in <filename>pg_hba.conf</filename> to <literal>scram-sha-256</literal>. + </para> + </sect1> + + <sect1 id="gssapi-auth"> + <title>GSSAPI Authentication</title> + + <indexterm zone="gssapi-auth"> + <primary>GSSAPI</primary> + </indexterm> + + <para> + <productname>GSSAPI</productname> is an industry-standard protocol + for secure authentication defined in + <ulink url="https://tools.ietf.org/html/rfc2743">RFC 2743</ulink>. + <productname>PostgreSQL</productname> + supports <productname>GSSAPI</productname> for authentication, + communications encryption, or both. + <productname>GSSAPI</productname> provides automatic authentication + (single sign-on) for systems that support it. The authentication itself is + secure. If <productname>GSSAPI</productname> encryption + or <acronym>SSL</acronym> encryption is + used, the data sent along the database connection will be encrypted; + otherwise, it will not. + </para> + + <para> + GSSAPI support has to be enabled when <productname>PostgreSQL</productname> is built; + see <xref linkend="installation"/> for more information. + </para> + + <para> + When <productname>GSSAPI</productname> uses + <productname>Kerberos</productname>, it uses a standard service + principal (authentication identity) name in the format + <literal><replaceable>servicename</replaceable>/<replaceable>hostname</replaceable>@<replaceable>realm</replaceable></literal>. + The principal name used by a particular installation is not encoded in + the <productname>PostgreSQL</productname> server in any way; rather it + is specified in the <firstterm>keytab</firstterm> file that the server + reads to determine its identity. If multiple principals are listed in + the keytab file, the server will accept any one of them. + The server's realm name is the preferred realm specified in the Kerberos + configuration file(s) accessible to the server. + </para> + + <para> + When connecting, the client must know the principal name of the server + it intends to connect to. The <replaceable>servicename</replaceable> + part of the principal is ordinarily <literal>postgres</literal>, + but another value can be selected via <application>libpq</application>'s + <xref linkend="libpq-connect-krbsrvname"/> connection parameter. + The <replaceable>hostname</replaceable> part is the fully qualified + host name that <application>libpq</application> is told to connect to. + The realm name is the preferred realm specified in the Kerberos + configuration file(s) accessible to the client. + </para> + + <para> + The client will also have a principal name for its own identity + (and it must have a valid ticket for this principal). To + use <productname>GSSAPI</productname> for authentication, the client + principal must be associated with + a <productname>PostgreSQL</productname> database user name. + The <filename>pg_ident.conf</filename> configuration file can be used + to map principals to user names; for example, + <literal>pgusername@realm</literal> could be mapped to just <literal>pgusername</literal>. + Alternatively, you can use the full <literal>username@realm</literal> principal as + the role name in <productname>PostgreSQL</productname> without any mapping. + </para> + + <para> + <productname>PostgreSQL</productname> also supports mapping + client principals to user names by just stripping the realm from + the principal. This method is supported for backwards compatibility and is + strongly discouraged as it is then impossible to distinguish different users + with the same user name but coming from different realms. To enable this, + set <literal>include_realm</literal> to 0. For simple single-realm + installations, doing that combined with setting the + <literal>krb_realm</literal> parameter (which checks that the principal's realm + matches exactly what is in the <literal>krb_realm</literal> parameter) + is still secure; but this is a + less capable approach compared to specifying an explicit mapping in + <filename>pg_ident.conf</filename>. + </para> + + <para> + The location of the server's keytab file is specified by the <xref + linkend="guc-krb-server-keyfile"/> configuration parameter. + For security reasons, it is recommended to use a separate keytab + just for the <productname>PostgreSQL</productname> server rather + than allowing the server to read the system keytab file. + Make sure that your server keytab file is readable (and preferably + only readable, not writable) by the <productname>PostgreSQL</productname> + server account. (See also <xref linkend="postgres-user"/>.) + </para> + + <para> + The keytab file is generated using the Kerberos software; see the + Kerberos documentation for details. The following example shows + doing this using the <application>kadmin</application> tool of + MIT-compatible Kerberos 5 implementations: +<screen> +<prompt>kadmin% </prompt><userinput>addprinc -randkey postgres/server.my.domain.org</userinput> +<prompt>kadmin% </prompt><userinput>ktadd -k krb5.keytab postgres/server.my.domain.org</userinput> +</screen> + </para> + + <para> + The following authentication options are supported for + the <productname>GSSAPI</productname> authentication method: + <variablelist> + <varlistentry> + <term><literal>include_realm</literal></term> + <listitem> + <para> + If set to 0, the realm name from the authenticated user principal is + stripped off before being passed through the user name mapping + (<xref linkend="auth-username-maps"/>). This is discouraged and is + primarily available for backwards compatibility, as it is not secure + in multi-realm environments unless <literal>krb_realm</literal> is + also used. It is recommended to + leave <literal>include_realm</literal> set to the default (1) and to + provide an explicit mapping in <filename>pg_ident.conf</filename> to convert + principal names to <productname>PostgreSQL</productname> user names. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>map</literal></term> + <listitem> + <para> + Allows mapping from client principals to database user names. See + <xref linkend="auth-username-maps"/> for details. For a GSSAPI/Kerberos + principal, such as <literal>username@EXAMPLE.COM</literal> (or, less + commonly, <literal>username/hostbased@EXAMPLE.COM</literal>), the + user name used for mapping is + <literal>username@EXAMPLE.COM</literal> (or + <literal>username/hostbased@EXAMPLE.COM</literal>, respectively), + unless <literal>include_realm</literal> has been set to 0, in which case + <literal>username</literal> (or <literal>username/hostbased</literal>) + is what is seen as the system user name when mapping. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>krb_realm</literal></term> + <listitem> + <para> + Sets the realm to match user principal names against. If this parameter + is set, only users of that realm will be accepted. If it is not set, + users of any realm can connect, subject to whatever user name mapping + is done. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + In addition to these settings, which can be different for + different <filename>pg_hba.conf</filename> entries, there is the + server-wide <xref linkend="guc-krb-caseins-users"/> configuration + parameter. If that is set to true, client principals are matched to + user map entries case-insensitively. <literal>krb_realm</literal>, if + set, is also matched case-insensitively. + </para> + </sect1> + + <sect1 id="sspi-auth"> + <title>SSPI Authentication</title> + + <indexterm zone="sspi-auth"> + <primary>SSPI</primary> + </indexterm> + + <para> + <productname>SSPI</productname> is a <productname>Windows</productname> + technology for secure authentication with single sign-on. + <productname>PostgreSQL</productname> will use SSPI in + <literal>negotiate</literal> mode, which will use + <productname>Kerberos</productname> when possible and automatically + fall back to <productname>NTLM</productname> in other cases. + <productname>SSPI</productname> authentication only works when both + server and client are running <productname>Windows</productname>, + or, on non-Windows platforms, when <productname>GSSAPI</productname> + is available. + </para> + + <para> + When using <productname>Kerberos</productname> authentication, + <productname>SSPI</productname> works the same way + <productname>GSSAPI</productname> does; see <xref linkend="gssapi-auth"/> + for details. + </para> + + <para> + The following configuration options are supported for <productname>SSPI</productname>: + <variablelist> + + <varlistentry> + <term><literal>include_realm</literal></term> + <listitem> + <para> + If set to 0, the realm name from the authenticated user principal is + stripped off before being passed through the user name mapping + (<xref linkend="auth-username-maps"/>). This is discouraged and is + primarily available for backwards compatibility, as it is not secure + in multi-realm environments unless <literal>krb_realm</literal> is + also used. It is recommended to + leave <literal>include_realm</literal> set to the default (1) and to + provide an explicit mapping in <filename>pg_ident.conf</filename> to convert + principal names to <productname>PostgreSQL</productname> user names. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>compat_realm</literal></term> + <listitem> + <para> + If set to 1, the domain's SAM-compatible name (also known as the + NetBIOS name) is used for the <literal>include_realm</literal> + option. This is the default. If set to 0, the true realm name from + the Kerberos user principal name is used. + </para> + <para> + Do not disable this option unless your server runs under a domain + account (this includes virtual service accounts on a domain member + system) and all clients authenticating through SSPI are also using + domain accounts, or authentication will fail. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>upn_username</literal></term> + <listitem> + <para> + If this option is enabled along with <literal>compat_realm</literal>, + the user name from the Kerberos UPN is used for authentication. If + it is disabled (the default), the SAM-compatible user name is used. + By default, these two names are identical for new user accounts. + </para> + <para> + Note that <application>libpq</application> uses the SAM-compatible name if no + explicit user name is specified. If you use + <application>libpq</application> or a driver based on it, you should + leave this option disabled or explicitly specify user name in the + connection string. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>map</literal></term> + <listitem> + <para> + Allows for mapping between system and database user names. See + <xref linkend="auth-username-maps"/> for details. For an SSPI/Kerberos + principal, such as <literal>username@EXAMPLE.COM</literal> (or, less + commonly, <literal>username/hostbased@EXAMPLE.COM</literal>), the + user name used for mapping is + <literal>username@EXAMPLE.COM</literal> (or + <literal>username/hostbased@EXAMPLE.COM</literal>, respectively), + unless <literal>include_realm</literal> has been set to 0, in which case + <literal>username</literal> (or <literal>username/hostbased</literal>) + is what is seen as the system user name when mapping. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>krb_realm</literal></term> + <listitem> + <para> + Sets the realm to match user principal names against. If this parameter + is set, only users of that realm will be accepted. If it is not set, + users of any realm can connect, subject to whatever user name mapping + is done. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + </sect1> + + <sect1 id="auth-ident"> + <title>Ident Authentication</title> + + <indexterm> + <primary>ident</primary> + </indexterm> + + <para> + The ident authentication method works by obtaining the client's + operating system user name from an ident server and using it as + the allowed database user name (with an optional user name mapping). + This is only supported on TCP/IP connections. + </para> + + <note> + <para> + When ident is specified for a local (non-TCP/IP) connection, + peer authentication (see <xref linkend="auth-peer"/>) will be + used instead. + </para> + </note> + + <para> + The following configuration options are supported for <literal>ident</literal>: + <variablelist> + <varlistentry> + <term><literal>map</literal></term> + <listitem> + <para> + Allows for mapping between system and database user names. See + <xref linkend="auth-username-maps"/> for details. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + The <quote>Identification Protocol</quote> is described in + <ulink url="https://tools.ietf.org/html/rfc1413">RFC 1413</ulink>. + Virtually every Unix-like + operating system ships with an ident server that listens on TCP + port 113 by default. The basic functionality of an ident server + is to answer questions like <quote>What user initiated the + connection that goes out of your port <replaceable>X</replaceable> + and connects to my port <replaceable>Y</replaceable>?</quote>. + Since <productname>PostgreSQL</productname> knows both <replaceable>X</replaceable> and + <replaceable>Y</replaceable> when a physical connection is established, it + can interrogate the ident server on the host of the connecting + client and can theoretically determine the operating system user + for any given connection. + </para> + + <para> + The drawback of this procedure is that it depends on the integrity + of the client: if the client machine is untrusted or compromised, + an attacker could run just about any program on port 113 and + return any user name they choose. This authentication method is + therefore only appropriate for closed networks where each client + machine is under tight control and where the database and system + administrators operate in close contact. In other words, you must + trust the machine running the ident server. + Heed the warning: + <blockquote> + <attribution>RFC 1413</attribution> + <para> + The Identification Protocol is not intended as an authorization + or access control protocol. + </para> + </blockquote> + </para> + + <para> + Some ident servers have a nonstandard option that causes the returned + user name to be encrypted, using a key that only the originating + machine's administrator knows. This option <emphasis>must not</emphasis> be + used when using the ident server with <productname>PostgreSQL</productname>, + since <productname>PostgreSQL</productname> does not have any way to decrypt the + returned string to determine the actual user name. + </para> + </sect1> + + <sect1 id="auth-peer"> + <title>Peer Authentication</title> + + <indexterm> + <primary>peer</primary> + </indexterm> + + <para> + 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. + </para> + + <para> + The following configuration options are supported for <literal>peer</literal>: + <variablelist> + <varlistentry> + <term><literal>map</literal></term> + <listitem> + <para> + Allows for mapping between system and database user names. See + <xref linkend="auth-username-maps"/> for details. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + Peer authentication is only available on operating systems providing + the <function>getpeereid()</function> function, the <symbol>SO_PEERCRED</symbol> + socket parameter, or similar mechanisms. Currently that includes + <systemitem class="osname">Linux</systemitem>, + most flavors of <systemitem class="osname">BSD</systemitem> including + <systemitem class="osname">macOS</systemitem>, + and <systemitem class="osname">Solaris</systemitem>. + </para> + + </sect1> + + <sect1 id="auth-ldap"> + <title>LDAP Authentication</title> + + <indexterm zone="auth-ldap"> + <primary>LDAP</primary> + </indexterm> + + <para> + This authentication method operates similarly to + <literal>password</literal> except that it uses LDAP + as the password verification method. LDAP is used only to validate + the user name/password pairs. Therefore the user must already + exist in the database before LDAP can be used for + authentication. + </para> + + <para> + LDAP authentication can operate in two modes. In the first mode, + which we will call the simple bind mode, + the server will bind to the distinguished name constructed as + <replaceable>prefix</replaceable> <replaceable>username</replaceable> <replaceable>suffix</replaceable>. + Typically, the <replaceable>prefix</replaceable> parameter is used to specify + <literal>cn=</literal>, or <replaceable>DOMAIN</replaceable><literal>\</literal> in an Active + Directory environment. <replaceable>suffix</replaceable> is used to specify the + remaining part of the DN in a non-Active Directory environment. + </para> + + <para> + In the second mode, which we will call the search+bind mode, + the server first binds to the LDAP directory with + a fixed user name and password, specified with <replaceable>ldapbinddn</replaceable> + and <replaceable>ldapbindpasswd</replaceable>, and performs a search for the user trying + to log in to the database. If no user and password is configured, an + anonymous bind will be attempted to the directory. The search will be + performed over the subtree at <replaceable>ldapbasedn</replaceable>, and will try to + do an exact match of the attribute specified in + <replaceable>ldapsearchattribute</replaceable>. + Once the user has been found in + this search, the server disconnects and re-binds to the directory as + this user, using the password specified by the client, to verify that the + login is correct. This mode is the same as that used by LDAP authentication + schemes in other software, such as Apache <literal>mod_authnz_ldap</literal> and <literal>pam_ldap</literal>. + This method allows for significantly more flexibility + in where the user objects are located in the directory, but will cause + two separate connections to the LDAP server to be made. + </para> + + <para> + The following configuration options are used in both modes: + <variablelist> + <varlistentry> + <term><literal>ldapserver</literal></term> + <listitem> + <para> + Names or IP addresses of LDAP servers to connect to. Multiple + servers may be specified, separated by spaces. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapport</literal></term> + <listitem> + <para> + Port number on LDAP server to connect to. If no port is specified, + the LDAP library's default port setting will be used. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapscheme</literal></term> + <listitem> + <para> + Set to <literal>ldaps</literal> to use LDAPS. This is a non-standard + way of using LDAP over SSL, supported by some LDAP server + implementations. See also the <literal>ldaptls</literal> option for + an alternative. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldaptls</literal></term> + <listitem> + <para> + Set to 1 to make the connection between PostgreSQL and the LDAP server + use TLS encryption. This uses the <literal>StartTLS</literal> + operation per <ulink url="https://tools.ietf.org/html/rfc4513">RFC 4513</ulink>. + See also the <literal>ldapscheme</literal> option for an alternative. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + Note that using <literal>ldapscheme</literal> or + <literal>ldaptls</literal> only encrypts the traffic between the + PostgreSQL server and the LDAP server. The connection between the + PostgreSQL server and the PostgreSQL client will still be unencrypted + unless SSL is used there as well. + </para> + + <para> + The following options are used in simple bind mode only: + <variablelist> + <varlistentry> + <term><literal>ldapprefix</literal></term> + <listitem> + <para> + String to prepend to the user name when forming the DN to bind as, + when doing simple bind authentication. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapsuffix</literal></term> + <listitem> + <para> + String to append to the user name when forming the DN to bind as, + when doing simple bind authentication. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + The following options are used in search+bind mode only: + <variablelist> + <varlistentry> + <term><literal>ldapbasedn</literal></term> + <listitem> + <para> + Root DN to begin the search for the user in, when doing search+bind + authentication. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapbinddn</literal></term> + <listitem> + <para> + DN of user to bind to the directory with to perform the search when + doing search+bind authentication. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapbindpasswd</literal></term> + <listitem> + <para> + Password for user to bind to the directory with to perform the search + when doing search+bind authentication. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapsearchattribute</literal></term> + <listitem> + <para> + Attribute to match against the user name in the search when doing + search+bind authentication. If no attribute is specified, the + <literal>uid</literal> attribute will be used. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapsearchfilter</literal></term> + <listitem> + <para> + The search filter to use when doing search+bind authentication. + Occurrences of <literal>$username</literal> will be replaced with the + user name. This allows for more flexible search filters than + <literal>ldapsearchattribute</literal>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>ldapurl</literal></term> + <listitem> + <para> + An <ulink url="https://tools.ietf.org/html/rfc4516">RFC 4516</ulink> + LDAP URL. This is an alternative way to write some of the + other LDAP options in a more compact and standard form. The format is +<synopsis> +ldap[s]://<replaceable>host</replaceable>[:<replaceable>port</replaceable>]/<replaceable>basedn</replaceable>[?[<replaceable>attribute</replaceable>][?[<replaceable>scope</replaceable>][?[<replaceable>filter</replaceable>]]]] +</synopsis> + <replaceable>scope</replaceable> must be one + of <literal>base</literal>, <literal>one</literal>, <literal>sub</literal>, + typically the last. (The default is <literal>base</literal>, which + is normally not useful in this application.) <replaceable>attribute</replaceable> can + nominate a single attribute, in which case it is used as a value for + <literal>ldapsearchattribute</literal>. If + <replaceable>attribute</replaceable> is empty then + <replaceable>filter</replaceable> can be used as a value for + <literal>ldapsearchfilter</literal>. + </para> + + <para> + The URL scheme <literal>ldaps</literal> chooses the LDAPS method for + making LDAP connections over SSL, equivalent to using + <literal>ldapscheme=ldaps</literal>. To use encrypted LDAP + connections using the <literal>StartTLS</literal> operation, use the + normal URL scheme <literal>ldap</literal> and specify the + <literal>ldaptls</literal> option in addition to + <literal>ldapurl</literal>. + </para> + + <para> + For non-anonymous binds, <literal>ldapbinddn</literal> + and <literal>ldapbindpasswd</literal> must be specified as separate + options. + </para> + + <para> + LDAP URLs are currently only supported with + <productname>OpenLDAP</productname>, not on Windows. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + It is an error to mix configuration options for simple bind with options + for search+bind. + </para> + + <para> + When using search+bind mode, the search can be performed using a single + attribute specified with <literal>ldapsearchattribute</literal>, or using + a custom search filter specified with + <literal>ldapsearchfilter</literal>. + Specifying <literal>ldapsearchattribute=foo</literal> is equivalent to + specifying <literal>ldapsearchfilter="(foo=$username)"</literal>. If neither + option is specified the default is + <literal>ldapsearchattribute=uid</literal>. + </para> + + <para> + If <productname>PostgreSQL</productname> was compiled with + <productname>OpenLDAP</productname> as the LDAP client library, the + <literal>ldapserver</literal> setting may be omitted. In that case, a + list of host names and ports is looked up via + <ulink url="https://tools.ietf.org/html/rfc2782">RFC 2782</ulink> DNS SRV records. + The name <literal>_ldap._tcp.DOMAIN</literal> is looked up, where + <literal>DOMAIN</literal> is extracted from <literal>ldapbasedn</literal>. + </para> + + <para> + Here is an example for a simple-bind LDAP configuration: +<programlisting> +host ... ldap ldapserver=ldap.example.net ldapprefix="cn=" ldapsuffix=", dc=example, dc=net" +</programlisting> + When a connection to the database server as database + user <literal>someuser</literal> is requested, PostgreSQL will attempt to + bind to the LDAP server using the DN <literal>cn=someuser, dc=example, + dc=net</literal> and the password provided by the client. If that connection + succeeds, the database access is granted. + </para> + + <para> + Here is an example for a search+bind configuration: +<programlisting> +host ... ldap ldapserver=ldap.example.net ldapbasedn="dc=example, dc=net" ldapsearchattribute=uid +</programlisting> + When a connection to the database server as database + user <literal>someuser</literal> is requested, PostgreSQL will attempt to + bind anonymously (since <literal>ldapbinddn</literal> was not specified) to + the LDAP server, perform a search for <literal>(uid=someuser)</literal> + under the specified base DN. If an entry is found, it will then attempt to + bind using that found information and the password supplied by the client. + If that second connection succeeds, the database access is granted. + </para> + + <para> + Here is the same search+bind configuration written as a URL: +<programlisting> +host ... ldap ldapurl="ldap://ldap.example.net/dc=example,dc=net?uid?sub" +</programlisting> + Some other software that supports authentication against LDAP uses the + same URL format, so it will be easier to share the configuration. + </para> + + <para> + Here is an example for a search+bind configuration that uses + <literal>ldapsearchfilter</literal> instead of + <literal>ldapsearchattribute</literal> to allow authentication by + user ID or email address: +<programlisting> +host ... ldap ldapserver=ldap.example.net ldapbasedn="dc=example, dc=net" ldapsearchfilter="(|(uid=$username)(mail=$username))" +</programlisting> + </para> + + <para> + Here is an example for a search+bind configuration that uses DNS SRV + discovery to find the host name(s) and port(s) for the LDAP service for the + domain name <literal>example.net</literal>: +<programlisting> +host ... ldap ldapbasedn="dc=example,dc=net" +</programlisting> + </para> + + <tip> + <para> + Since LDAP often uses commas and spaces to separate the different + parts of a DN, it is often necessary to use double-quoted parameter + values when configuring LDAP options, as shown in the examples. + </para> + </tip> + + </sect1> + + <sect1 id="auth-radius"> + <title>RADIUS Authentication</title> + + <indexterm zone="auth-radius"> + <primary>RADIUS</primary> + </indexterm> + + <para> + This authentication method operates similarly to + <literal>password</literal> except that it uses RADIUS + as the password verification method. RADIUS is used only to validate + the user name/password pairs. Therefore the user must already + exist in the database before RADIUS can be used for + authentication. + </para> + + <para> + When using RADIUS authentication, an Access Request message will be sent + to the configured RADIUS server. This request will be of type + <literal>Authenticate Only</literal>, and include parameters for + <literal>user name</literal>, <literal>password</literal> (encrypted) and + <literal>NAS Identifier</literal>. The request will be encrypted using + a secret shared with the server. The RADIUS server will respond to + this request with either <literal>Access Accept</literal> or + <literal>Access Reject</literal>. There is no support for RADIUS accounting. + </para> + + <para> + Multiple RADIUS servers can be specified, in which case they will + be tried sequentially. If a negative response is received from + a server, the authentication will fail. If no response is received, + the next server in the list will be tried. To specify multiple + servers, separate the server names with commas and surround the list + with double quotes. If multiple servers are specified, the other + RADIUS options can also be given as comma-separated lists, to provide + individual values for each server. They can also be specified as + a single value, in which case that value will apply to all servers. + </para> + + <para> + The following configuration options are supported for RADIUS: + <variablelist> + <varlistentry> + <term><literal>radiusservers</literal></term> + <listitem> + <para> + The DNS names or IP addresses of the RADIUS servers to connect to. + This parameter is required. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>radiussecrets</literal></term> + <listitem> + <para> + The shared secrets used when talking securely to the RADIUS + servers. This must have exactly the same value on the PostgreSQL + and RADIUS servers. It is recommended that this be a string of + at least 16 characters. This parameter is required. + <note> + <para> + The encryption vector used will only be cryptographically + strong if <productname>PostgreSQL</productname> is built with support for + <productname>OpenSSL</productname>. In other cases, the transmission to the + RADIUS server should only be considered obfuscated, not secured, and + external security measures should be applied if necessary. + </para> + </note> + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>radiusports</literal></term> + <listitem> + <para> + The port numbers to connect to on the RADIUS servers. If no port + is specified, the default RADIUS port (<literal>1812</literal>) + will be used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>radiusidentifiers</literal></term> + <listitem> + <para> + The strings to be used as <literal>NAS Identifier</literal> in the + RADIUS requests. This parameter can be used, for example, to + identify which database cluster the user is attempting to connect + to, which can be useful for policy matching on + the RADIUS server. If no identifier is specified, the default + <literal>postgresql</literal> will be used. + </para> + </listitem> + </varlistentry> + + </variablelist> + </para> + + <para> + If it is necessary to have a comma or whitespace in a RADIUS parameter + value, that can be done by putting double quotes around the value, but + it is tedious because two layers of double-quoting are now required. + An example of putting whitespace into RADIUS secret strings is: +<programlisting> +host ... radius radiusservers="server1,server2" radiussecrets="""secret one"",""secret two""" +</programlisting> + </para> + </sect1> + + <sect1 id="auth-cert"> + <title>Certificate Authentication</title> + + <indexterm zone="auth-cert"> + <primary>Certificate</primary> + </indexterm> + + <para> + This authentication method uses SSL client certificates to perform + authentication. It is therefore only available for SSL connections. + When using this authentication method, the server will require that + the client provide a valid, trusted certificate. No password prompt + will be sent to the client. The <literal>cn</literal> (Common Name) + attribute of the certificate + will be compared to the requested database user name, and if they match + the login will be allowed. User name mapping can be used to allow + <literal>cn</literal> to be different from the database user name. + </para> + + <para> + The following configuration options are supported for SSL certificate + authentication: + <variablelist> + <varlistentry> + <term><literal>map</literal></term> + <listitem> + <para> + Allows for mapping between system and database user names. See + <xref linkend="auth-username-maps"/> for details. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + It is redundant to use the <literal>clientcert</literal> option with + <literal>cert</literal> authentication because <literal>cert</literal> + authentication is effectively <literal>trust</literal> authentication + with <literal>clientcert=verify-full</literal>. + </para> + </sect1> + + <sect1 id="auth-pam"> + <title>PAM Authentication</title> + + <indexterm zone="auth-pam"> + <primary>PAM</primary> + </indexterm> + + <para> + This authentication method operates similarly to + <literal>password</literal> except that it uses PAM (Pluggable + Authentication Modules) as the authentication mechanism. The + default PAM service name is <literal>postgresql</literal>. + PAM is used only to validate user name/password pairs and optionally the + connected remote host name or IP address. Therefore the user must already + exist in the database before PAM can be used for authentication. For more + information about PAM, please read the + <ulink url="https://www.kernel.org/pub/linux/libs/pam/"> + <productname>Linux-PAM</productname> Page</ulink>. + </para> + + <para> + The following configuration options are supported for PAM: + <variablelist> + <varlistentry> + <term><literal>pamservice</literal></term> + <listitem> + <para> + PAM service name. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>pam_use_hostname</literal></term> + <listitem> + <para> + Determines whether the remote IP address or the host name is provided + to PAM modules through the <symbol>PAM_RHOST</symbol> item. By + default, the IP address is used. Set this option to 1 to use the + resolved host name instead. Host name resolution can lead to login + delays. (Most PAM configurations don't use this information, so it is + only necessary to consider this setting if a PAM configuration was + specifically created to make use of it.) + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <note> + <para> + If PAM is set up to read <filename>/etc/shadow</filename>, authentication + will fail because the PostgreSQL server is started by a non-root + user. However, this is not an issue when PAM is configured to use + LDAP or other authentication methods. + </para> + </note> + </sect1> + + <sect1 id="auth-bsd"> + <title>BSD Authentication</title> + + <indexterm zone="auth-bsd"> + <primary>BSD Authentication</primary> + </indexterm> + + <para> + This authentication method operates similarly to + <literal>password</literal> except that it uses BSD Authentication + to verify the password. BSD Authentication is used only + to validate user name/password pairs. Therefore the user's role must + already exist in the database before BSD Authentication can be used + for authentication. The BSD Authentication framework is currently + only available on OpenBSD. + </para> + + <para> + BSD Authentication in <productname>PostgreSQL</productname> uses + the <literal>auth-postgresql</literal> login type and authenticates with + the <literal>postgresql</literal> login class if that's defined + in <filename>login.conf</filename>. By default that login class does not + exist, and <productname>PostgreSQL</productname> will use the default login class. + </para> + + <note> + <para> + To use BSD Authentication, the PostgreSQL user account (that is, the + operating system user running the server) must first be added to + the <literal>auth</literal> group. The <literal>auth</literal> group + exists by default on OpenBSD systems. + </para> + </note> + </sect1> + + <sect1 id="client-authentication-problems"> + <title>Authentication Problems</title> + + <para> + Authentication failures and related problems generally + manifest themselves through error messages like the following: + </para> + + <para> +<programlisting> +FATAL: no pg_hba.conf entry for host "123.123.123.123", user "andym", database "testdb" +</programlisting> + This is what you are most likely to get if you succeed in contacting + the server, but it does not want to talk to you. As the message + suggests, the server refused the connection request because it found + no matching entry in its <filename>pg_hba.conf</filename> + configuration file. + </para> + + <para> +<programlisting> +FATAL: password authentication failed for user "andym" +</programlisting> + Messages like this indicate that you contacted the server, and it is + willing to talk to you, but not until you pass the authorization + method specified in the <filename>pg_hba.conf</filename> file. Check + the password you are providing, or check your Kerberos or ident + software if the complaint mentions one of those authentication + types. + </para> + + <para> +<programlisting> +FATAL: user "andym" does not exist +</programlisting> + The indicated database user name was not found. + </para> + + <para> +<programlisting> +FATAL: database "testdb" does not exist +</programlisting> + The database you are trying to connect to does not exist. Note that + if you do not specify a database name, it defaults to the database + user name, which might or might not be the right thing. + </para> + + <tip> + <para> + The server log might contain more information about an + authentication failure than is reported to the client. If you are + confused about the reason for a failure, check the server log. + </para> + </tip> + </sect1> + + </chapter> |