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CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="SSL-TCP"
>17.8. Secure TCP/IP Connections with SSL</A
></H1
><A
NAME="AEN22382"
></A
><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 standard
   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 21.1</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, the files <TT
CLASS="FILENAME"
>server.crt</TT
>
   and <TT
CLASS="FILENAME"
>server.key</TT
> must exist in the server's data directory.
   These files should contain the server certificate and private key,
   respectively. 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
>   To require the client to supply a trusted certificate, place
   certificates of the certificate authorities (<ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
>)
   you trust in the file <TT
CLASS="FILENAME"
>root.crt</TT
> in the data
   directory.  A certificate will then be requested from the client during
   SSL connection startup.  (See <A
HREF="libpq-ssl.html"
>Section 30.16</A
> for a
   description of how to set up client certificates.)  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 file <TT
CLASS="FILENAME"
>root.crl</TT
> exists.
   
   (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
>   If the <TT
CLASS="FILENAME"
>root.crt</TT
> file is not present, client
   certificates will not be requested or checked.  In this mode, SSL
   provides encrypted communication but not authentication.
  </P
><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
>
   are only examined during server start; so you must restart 
   the server for changes in them to take effect.
  </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
><TT
CLASS="FILENAME"
>server.crt</TT
></TD
><TD
>server certificate</TD
><TD
>requested by client</TD
></TR
><TR
><TD
><TT
CLASS="FILENAME"
>server.key</TT
></TD
><TD
>server private key</TD
><TD
>proves server certificate sent by owner; does not indicate
      certificate owner is trustworthy</TD
></TR
><TR
><TD
><TT
CLASS="FILENAME"
>root.crt</TT
></TD
><TD
>trusted certificate authorities</TD
><TD
>requests client certificate; checks certificate is
      signed by a trusted certificate authority</TD
></TR
><TR
><TD
><TT
CLASS="FILENAME"
>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
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SSL-CERTIFICATE-CREATION"
>17.8.1. 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
chmod og-rwx server.key</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.
    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 the client can verify the server's identity.
   </P
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