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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Secure TCP/IP Connections with SSL</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Server Setup and Operation" HREF="runtime.html"><LINK REL="PREVIOUS" TITLE="Encryption Options" HREF="encryption-options.html"><LINK REL="NEXT" TITLE="Secure TCP/IP Connections with SSH Tunnels" HREF="ssh-tunnels.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Encryption Options" HREF="encryption-options.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="runtime.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 17. Server Setup and Operation</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Secure TCP/IP Connections with SSH Tunnels" HREF="ssh-tunnels.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="SSL-TCP" >17.9. Secure TCP/IP Connections with SSL</A ></H1 ><P > <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > has native support for using <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM > connections to encrypt client/server communications for increased security. This requires that <SPAN CLASS="PRODUCTNAME" >OpenSSL</SPAN > is installed on both client and server systems and that support in <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > is enabled at build time (see <A HREF="installation.html" >Chapter 15</A >). </P ><P > With <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM > support compiled in, the <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > server can be started with <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM > enabled by setting the parameter <A HREF="runtime-config-connection.html#GUC-SSL" >ssl</A > to <TT CLASS="LITERAL" >on</TT > in <TT CLASS="FILENAME" >postgresql.conf</TT >. The server will listen for both normal and <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM > connections on the same TCP port, and will negotiate with any connecting client on whether to use <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM >. By default, this is at the client's option; see <A HREF="auth-pg-hba-conf.html" >Section 19.1</A > about how to set up the server to require use of <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM > for some or all connections. </P ><P > <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > reads the system-wide <SPAN CLASS="PRODUCTNAME" >OpenSSL</SPAN > configuration file. By default, this file is named <TT CLASS="FILENAME" >openssl.cnf</TT > and is located in the directory reported by <TT CLASS="LITERAL" >openssl version -d</TT >. This default can be overridden by setting environment variable <TT CLASS="ENVAR" >OPENSSL_CONF</TT > to the name of the desired configuration file. </P ><P > <SPAN CLASS="PRODUCTNAME" >OpenSSL</SPAN > supports a wide range of ciphers and authentication algorithms, of varying strength. While a list of ciphers can be specified in the <SPAN CLASS="PRODUCTNAME" >OpenSSL</SPAN > configuration file, you can specify ciphers specifically for use by the database server by modifying <A HREF="runtime-config-connection.html#GUC-SSL-CIPHERS" >ssl_ciphers</A > in <TT CLASS="FILENAME" >postgresql.conf</TT >. </P ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B > It is possible to have authentication without encryption overhead by using <TT CLASS="LITERAL" >NULL-SHA</TT > or <TT CLASS="LITERAL" >NULL-MD5</TT > ciphers. However, a man-in-the-middle could read and pass communications between client and server. Also, encryption overhead is minimal compared to the overhead of authentication. For these reasons NULL ciphers are not recommended. </P ></BLOCKQUOTE ></DIV ><P > To start in <ACRONYM CLASS="ACRONYM" >SSL</ACRONYM > mode, files containing the server certificate and private key must exist. By default, these files are expected to be named <TT CLASS="FILENAME" >server.crt</TT > and <TT CLASS="FILENAME" >server.key</TT >, respectively, in the server's data directory, but other names and locations can be specified using the configuration parameters <A HREF="runtime-config-connection.html#GUC-SSL-CERT-FILE" >ssl_cert_file</A > and <A HREF="runtime-config-connection.html#GUC-SSL-KEY-FILE" >ssl_key_file</A >. On Unix systems, the permissions on <TT CLASS="FILENAME" >server.key</TT > must disallow any access to world or group; achieve this by the command <TT CLASS="COMMAND" >chmod 0600 server.key</TT >. If the private key is protected with a passphrase, the server will prompt for the passphrase and will not start until it has been entered. </P ><P > In some cases, the server certificate might be signed by an <SPAN CLASS="QUOTE" >"intermediate"</SPAN > certificate authority, rather than one that is directly trusted by clients. To use such a certificate, append the certificate of the signing authority to the <TT CLASS="FILENAME" >server.crt</TT > file, then its parent authority's certificate, and so on up to a <SPAN CLASS="QUOTE" >"root"</SPAN > authority that is trusted by the clients. The root certificate should be included in every case where <TT CLASS="FILENAME" >server.crt</TT > contains more than one certificate. </P ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="SSL-CLIENT-CERTIFICATES" >17.9.1. Using Client Certificates</A ></H2 ><P > To require the client to supply a trusted certificate, place certificates of the certificate authorities (<ACRONYM CLASS="ACRONYM" >CA</ACRONYM >s) you trust in the file <TT CLASS="FILENAME" >root.crt</TT > in the data directory, set the parameter <A HREF="runtime-config-connection.html#GUC-SSL-CA-FILE" >ssl_ca_file</A > in <TT CLASS="FILENAME" >postgresql.conf</TT > to <TT CLASS="LITERAL" >root.crt</TT >, and set the <TT CLASS="LITERAL" >clientcert</TT > parameter to 1 on the appropriate <TT CLASS="LITERAL" >hostssl</TT > line(s) in <TT CLASS="FILENAME" >pg_hba.conf</TT >. A certificate will then be requested from the client during SSL connection startup. (See <A HREF="libpq-ssl.html" >Section 31.18</A > for a description of how to set up certificates on the client.) The server will verify that the client's certificate is signed by one of the trusted certificate authorities. Certificate Revocation List (CRL) entries are also checked if the parameter <A HREF="runtime-config-connection.html#GUC-SSL-CRL-FILE" >ssl_crl_file</A > is set. (See <A HREF="http://h71000.www7.hp.com/doc/83final/ba554_90007/ch04s02.html" TARGET="_top" >http://h71000.www7.hp.com/doc/83final/ba554_90007/ch04s02.html</A > for diagrams showing SSL certificate usage.) </P ><P > The <TT CLASS="LITERAL" >clientcert</TT > option in <TT CLASS="FILENAME" >pg_hba.conf</TT > is available for all authentication methods, but only for rows specified as <TT CLASS="LITERAL" >hostssl</TT >. When <TT CLASS="LITERAL" >clientcert</TT > is not specified or is set to 0, the server will still verify presented client certificates against its CA list, if one is configured, — but it will not insist that a client certificate be presented. </P ><P > Note that <TT CLASS="FILENAME" >root.crt</TT > lists the top-level CAs that are considered trusted for signing client certificates. In principle it need not list the CA that signed the server's certificate, though in most cases that CA would also be trusted for client certificates. </P ><P > If you are setting up client certificates, you may wish to use the <TT CLASS="LITERAL" >cert</TT > authentication method, so that the certificates control user authentication as well as providing connection security. See <A HREF="auth-methods.html#AUTH-CERT" >Section 19.3.10</A > for details. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="SSL-SERVER-FILES" >17.9.2. SSL Server File Usage</A ></H2 ><P > <A HREF="ssl-tcp.html#SSL-FILE-USAGE" >Table 17-3</A > summarizes the files that are relevant to the SSL setup on the server. (The shown file names are default or typical names. The locally configured names could be different.) </P ><DIV CLASS="TABLE" ><A NAME="SSL-FILE-USAGE" ></A ><P ><B >Table 17-3. SSL Server File Usage</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >File</TH ><TH >Contents</TH ><TH >Effect</TH ></TR ></THEAD ><TBODY ><TR ><TD ><A HREF="runtime-config-connection.html#GUC-SSL-CERT-FILE" >ssl_cert_file</A > (<TT CLASS="FILENAME" >$PGDATA/server.crt</TT >)</TD ><TD >server certificate</TD ><TD >sent to client to indicate server's identity</TD ></TR ><TR ><TD ><A HREF="runtime-config-connection.html#GUC-SSL-KEY-FILE" >ssl_key_file</A > (<TT CLASS="FILENAME" >$PGDATA/server.key</TT >)</TD ><TD >server private key</TD ><TD >proves server certificate was sent by the owner; does not indicate certificate owner is trustworthy</TD ></TR ><TR ><TD ><A HREF="runtime-config-connection.html#GUC-SSL-CA-FILE" >ssl_ca_file</A > (<TT CLASS="FILENAME" >$PGDATA/root.crt</TT >)</TD ><TD >trusted certificate authorities</TD ><TD >checks that client certificate is signed by a trusted certificate authority</TD ></TR ><TR ><TD ><A HREF="runtime-config-connection.html#GUC-SSL-CRL-FILE" >ssl_crl_file</A > (<TT CLASS="FILENAME" >$PGDATA/root.crl</TT >)</TD ><TD >certificates revoked by certificate authorities</TD ><TD >client certificate must not be on this list</TD ></TR ></TBODY ></TABLE ></DIV ><P > The files <TT CLASS="FILENAME" >server.key</TT >, <TT CLASS="FILENAME" >server.crt</TT >, <TT CLASS="FILENAME" >root.crt</TT >, and <TT CLASS="FILENAME" >root.crl</TT > (or their configured alternative names) are only examined during server start; so you must restart the server for changes in them to take effect. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="SSL-CERTIFICATE-CREATION" >17.9.3. Creating a Self-signed Certificate</A ></H2 ><P > To create a quick self-signed certificate for the server, use the following <SPAN CLASS="PRODUCTNAME" >OpenSSL</SPAN > command: </P><PRE CLASS="PROGRAMLISTING" >openssl req -new -text -out server.req</PRE ><P> Fill out the information that <SPAN CLASS="APPLICATION" >openssl</SPAN > asks for. Make sure you enter the local host name as <SPAN CLASS="QUOTE" >"Common Name"</SPAN >; the challenge password can be left blank. The program will generate a key that is passphrase protected; it will not accept a passphrase that is less than four characters long. To remove the passphrase (as you must if you want automatic start-up of the server), run the commands: </P><PRE CLASS="PROGRAMLISTING" >openssl rsa -in privkey.pem -out server.key rm privkey.pem</PRE ><P> Enter the old passphrase to unlock the existing key. Now do: </P><PRE CLASS="PROGRAMLISTING" >openssl req -x509 -in server.req -text -key server.key -out server.crt</PRE ><P> to turn the certificate into a self-signed certificate and to copy the key and certificate to where the server will look for them. Finally do: </P><PRE CLASS="PROGRAMLISTING" >chmod og-rwx server.key</PRE ><P> because the server will reject the file if its permissions are more liberal than this. For more details on how to create your server private key and certificate, refer to the <SPAN CLASS="PRODUCTNAME" >OpenSSL</SPAN > documentation. </P ><P > A self-signed certificate can be used for testing, but a certificate signed by a certificate authority (<ACRONYM CLASS="ACRONYM" >CA</ACRONYM >) (either one of the global <ACRONYM CLASS="ACRONYM" >CAs</ACRONYM > or a local one) should be used in production so that clients can verify the server's identity. If all the clients are local to the organization, using a local <ACRONYM CLASS="ACRONYM" >CA</ACRONYM > is recommended. </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="encryption-options.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="ssh-tunnels.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Encryption Options</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="runtime.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Secure TCP/IP Connections with <SPAN CLASS="APPLICATION" >SSH</SPAN > Tunnels</TD ></TR ></TABLE ></DIV ></BODY ></HTML >