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<chapter id="protocol">

<title>Frontend/Backend Protocol</title>

For all authentication methods except GSSAPI and SSPI, there is at most

one request and one response. In some methods, no response

at all is needed from the frontend, and so no authentication request

occurs. For GSSAPI and SSPI, multipleiterations of packets may be needed to

complete the authentication.

occurs. For GSSAPI and SSPI, multipleexchanges of packets may be needed

tocomplete the authentication.

</para>

<para>

or a previous AuthenticationGSSContinue). If the GSSAPI

or SSPI data in this message

indicates more data is needed to complete the authentication,

the frontend must sendthis data as another PasswordMessage. If

GSSAPI authentication is completed by this message, the server

willalso send AuthenticationOk to indicate successful authentication

the frontend must sendthat data as another PasswordMessage. If

GSSAPIor SSPIauthentication is completed by this message, the server

willnext send AuthenticationOk to indicate successful authentication

or ErrorResponse to indicate failure.

</para>

</listitem>

</term>

<listitem>

<para>

Specifies that this message contains GSSAPI data.

Specifies that this message contains GSSAPIor SSPIdata.

</para>

</listitem>

</varlistentry>

<listitem>

<para>

Identifies the message as a password response. Note that

this is also used by GSSAPI response messages.

this is also used for GSSAPI and SSPI response messages

(which is really a design error, since the contained data

is not a null-terminated string in that case, but can be

arbitrary binary data).

</para>

</listitem>

</varlistentry>