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postgresql9.6-docs-9.6.22-1.mga7.noarch.rpm

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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="SSL-TCP"
>18.9. 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 16</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 20.1</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
>.
  </P
><P
>   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
>.  Alternatively, the file can be
   owned by root and have group read access (that is, <TT
CLASS="LITERAL"
>0640</TT
>
   permissions).  That setup is intended for installations where certificate
   and key files are managed by the operating system.  The user under which
   the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server runs should then be made a
   member of the group that has access to those certificate and key files.
  </P
><P
>   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
>   The first certificate in <TT
CLASS="FILENAME"
>server.crt</TT
> must be the
   server's certificate because it must match the server's private key.
   The certificates of <SPAN
CLASS="QUOTE"
>"intermediate"</SPAN
> certificate authorities
   can also be appended to the file.  Doing this avoids the necessity of
   storing intermediate certificates on clients, assuming the root and
   intermediate certificates were created with <TT
CLASS="LITERAL"
>v3_ca </TT
>
   extensions.  (This sets the certificate's basic constraint of
   <TT
CLASS="LITERAL"
>CA</TT
> to <TT
CLASS="LITERAL"
>true</TT
>.)
   This allows easier expiration of intermediate certificates.
  </P
><P
>   It is not necessary to add the root certificate to
   <TT
CLASS="FILENAME"
>server.crt</TT
>.  Instead, clients must have the root
   certificate of the server's certificate chain.
  </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SSL-CLIENT-CERTIFICATES"
>18.9.1. Using Client Certificates</A
></H2
><P
>   To require the client to supply a trusted certificate,
   place certificates of the root certificate authorities
   (<ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
>s) you trust in a file 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 the new file name, and add the
   authentication option <TT
CLASS="LITERAL"
>clientcert=1</TT
> to 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 32.18</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.
  </P
><P
>   Intermediate certificates that chain up to existing root certificates
   can also appear in the file <TT
CLASS="FILENAME"
>root.crt</TT
> if
   you wish to avoid storing them on clients (assuming the root and
   intermediate certificates were created with <TT
CLASS="LITERAL"
>v3_ca</TT
>
   extensions).  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.
  </P
><P
>   The <TT
CLASS="LITERAL"
>clientcert</TT
> authentication option is available for
   all authentication methods, but only in <TT
CLASS="FILENAME"
>pg_hba.conf</TT
> lines
   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 any presented
   client certificates against its CA file, if one is configured &mdash; but
   it will not insist that a client certificate be presented.
  </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 20.3.9</A
> for details.  (It is not necessary to
   specify <TT
CLASS="LITERAL"
>clientcert=1</TT
> explicitly when using
   the <TT
CLASS="LITERAL"
>cert</TT
> authentication method.)
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SSL-SERVER-FILES"
>18.9.2. SSL Server File Usage</A
></H2
><P
>    <A
HREF="ssl-tcp.html#SSL-FILE-USAGE"
>Table 18-2</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 18-2. 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"
>18.9.3. Creating Certificates</A
></H2
><P
>     To create a simple self-signed certificate for the server, valid for 365
     days, use the following <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
> command,
     replacing <TT
CLASS="REPLACEABLE"
><I
>dbhost.yourdomain.com</I
></TT
> with the
     server's host name:
</P><PRE
CLASS="PROGRAMLISTING"
>openssl req -new -x509 -days 365 -nodes -text -out server.crt \
  -keyout server.key -subj "/CN=<TT
CLASS="REPLACEABLE"
><I
>dbhost.yourdomain.com</I
></TT
>"</PRE
><P>
    Then 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
>    While a self-signed certificate can be used for testing, a certificate
    signed by a certificate authority (<ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
>) (usually an
    enterprise-wide root <ACRONYM
CLASS="ACRONYM"
>CA</ACRONYM
>) should be used in production.
   </P
><P
>    To create a server certificate whose identity can be validated
    by clients, first create a certificate signing request
    (<ACRONYM
CLASS="ACRONYM"
>CSR</ACRONYM
>) and a public/private key file:
</P><PRE
CLASS="PROGRAMLISTING"
>openssl req -new -nodes -text -out root.csr \
  -keyout root.key -subj "/CN=<TT
CLASS="REPLACEABLE"
><I
>root.yourdomain.com</I
></TT
>"
chmod og-rwx root.key</PRE
><P>
    Then, sign the request with the key to create a root certificate
    authority (using the default <SPAN
CLASS="PRODUCTNAME"
>OpenSSL</SPAN
>
    configuration file location on <SPAN
CLASS="PRODUCTNAME"
>Linux</SPAN
>):
</P><PRE
CLASS="PROGRAMLISTING"
>openssl x509 -req -in root.csr -text -days 3650 \
  -extfile /etc/ssl/openssl.cnf -extensions v3_ca \
  -signkey root.key -out root.crt</PRE
><P>
    Finally, create a server certificate signed by the new root certificate
    authority:
</P><PRE
CLASS="PROGRAMLISTING"
>openssl req -new -nodes -text -out server.csr \
  -keyout server.key -subj "/CN=<TT
CLASS="REPLACEABLE"
><I
>dbhost.yourdomain.com</I
></TT
>"
chmod og-rwx server.key

openssl x509 -req -in server.csr -text -days 365 \
  -CA root.crt -CAkey root.key -CAcreateserial \
  -out server.crt</PRE
><P>
    <TT
CLASS="FILENAME"
>server.crt</TT
> and <TT
CLASS="FILENAME"
>server.key</TT
>
    should be stored on the server, and <TT
CLASS="FILENAME"
>root.crt</TT
> should
    be stored on the client so the client can verify that the server's leaf
    certificate was signed by its trusted root certificate. 
    <TT
CLASS="FILENAME"
>root.key</TT
> should be stored offline for use in
    creating future certificates.
   </P
><P
>    It is also possible to create a chain of trust that includes
    intermediate certificates:
</P><PRE
CLASS="PROGRAMLISTING"
># root
openssl req -new -nodes -text -out root.csr \
  -keyout root.key -subj "/CN=<TT
CLASS="REPLACEABLE"
><I
>root.yourdomain.com</I
></TT
>"
chmod og-rwx root.key
openssl x509 -req -in root.csr -text -days 3650 \
  -extfile /etc/ssl/openssl.cnf -extensions v3_ca \
  -signkey root.key -out root.crt

# intermediate
openssl req -new -nodes -text -out intermediate.csr \
  -keyout intermediate.key -subj "/CN=<TT
CLASS="REPLACEABLE"
><I
>intermediate.yourdomain.com</I
></TT
>"
chmod og-rwx intermediate.key
openssl x509 -req -in intermediate.csr -text -days 1825 \
  -extfile /etc/ssl/openssl.cnf -extensions v3_ca \
  -CA root.crt -CAkey root.key -CAcreateserial \
  -out intermediate.crt

# leaf
openssl req -new -nodes -text -out server.csr \
  -keyout server.key -subj "/CN=<TT
CLASS="REPLACEABLE"
><I
>dbhost.yourdomain.com</I
></TT
>"
chmod og-rwx server.key
openssl x509 -req -in server.csr -text -days 365 \
  -CA intermediate.crt -CAkey intermediate.key -CAcreateserial \
  -out server.crt</PRE
><P>
    <TT
CLASS="FILENAME"
>server.crt</TT
> and
    <TT
CLASS="FILENAME"
>intermediate.crt</TT
> should be concatenated
    into a certificate file bundle and stored on the server.
    <TT
CLASS="FILENAME"
>server.key</TT
> should also be stored on the server.
    <TT
CLASS="FILENAME"
>root.crt</TT
> should be stored on the client so
    the client can verify that the server's leaf certificate was signed
    by a chain of certificates linked to its trusted root certificate.
    <TT
CLASS="FILENAME"
>root.key</TT
> and <TT
CLASS="FILENAME"
>intermediate.key</TT
>
    should be stored offline for use in creating future certificates.
   </P
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