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<li class="toctree-l2 current"><a class="reference internal" href="../../../manpages.html">Man pages</a><ul class="current">
<li class="toctree-l3 current"><a class="reference internal" href="../../../manpages.html#library-files">(3) Library Files</a><ul class="current">
<li class="toctree-l4"><a class="reference internal" href="sasl.html"><strong>SASL</strong> - SASL Authentication Library</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_authorize_t.html"><strong>sasl_authorize_t</strong> - The SASL authorization callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_auxprop.html"><strong>sasl_auxprop</strong> - How to work with SASL auxiliary properties</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_auxprop_add_plugin.html"><strong>sasl_auxprop_add_plugin</strong> - add a SASL auxiliary property plugin</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_auxprop_getctx.html"><strong>sasl_auxprop_getctx</strong> - Acquire an auxiliary property context</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_auxprop_request.html"><strong>sasl_auxprop_request</strong> - Request auxiliary properties from SASL</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_callbacks.html"><strong>sasl_callbacks</strong> - How to work with SASL callbacks</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_canon_user_t.html"><strong>sasl_canon_user_t</strong> - Application-supplied user canonicalization function</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_canonuser_add_plugin.html"><strong>sasl_canonuser_add_plugin</strong> - add a SASL user canonicalization plugin</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_chalprompt_t.html"><strong>sasl_chalprompt_t</strong> - Realm acquisition callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_checkapop.html"><strong>sasl_checkapop</strong> - Check an APOP challenge/response</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_checkpass.html"><strong>sasl_checkpass</strong> - Check a plaintext password</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_client_add_plugin.html"><strong>sasl_client_add_plugin</strong> - add a SASL client plugin</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_client_done.html"><strong>sasl_client_done</strong> - Cleanup function</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_client_init.html"><strong>sasl_client_init</strong> - SASL client authentication initialization</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_client_new.html"><strong>sasl_client_new</strong> - Create a new client authentication object</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_client_plug_init_t.html"><strong>sasl_client_plug_init_t</strong> - client plug‐in entry point</a></li>
<li class="toctree-l4 current"><a class="current reference internal" href="#"><strong>sasl_client_start</strong> - Begin an authentication negotiation</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_client_step.html"><strong>sasl_client_step</strong> - Perform a step in the authentication negotiation</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_decode.html"><strong>sasl_decode</strong> - Decode data received</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_decode64.html"><strong>sasl_decode64</strong> - Decode base64 string</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_dispose.html"><strong>sasl_dispose</strong> - Dispose of a SASL connection object</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_done.html"><strong>sasl_done</strong> - Dispose of a SASL connection object</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_encode.html"><strong>sasl_encode</strong> - Encode data for transport to authenticated host</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_encode64.html"><strong>sasl_encode64</strong> - Encode base64 string</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_encodev.html"><strong>sasl_encodev</strong> - Encode data for transport to authenticated host</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_erasebuffer.html"><strong>sasl_erasebuffer</strong> - erase buffer</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_errdetail.html"><strong>sasl_errdetail</strong> - Retrieve detailed information about an error</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_errors.html"><strong>sasl_errors</strong> - SASL error codes</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_errstring.html"><strong>sasl_errstring</strong> - Translate a SASL return code to a human-readable form</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getcallback_t.html"><strong>sasl_getcallback_t</strong> - callback function to lookup a sasl_callback_t for a connection</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getconfpath_t.html"><strong>sasl_getconfpath_t</strong> - The SASL callback to indicate location of the config files</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getopt_t.html"><strong>sasl_getopt_t</strong> - The SASL get option callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getpath_t.html"><strong>sasl_getpath_t</strong> - The SASL callback to indicate location of the mechanism drivers</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getprop.html"><strong>sasl_getprop</strong> - Get a SASL property</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getrealm_t.html"><strong>sasl_getrealm_t</strong> - Realm Acquisition Callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getsecret_t.html"><strong>sasl_getsecret_t</strong> - The SASL callback for secrets (passwords)</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_getsimple_t.html"><strong>sasl_getsimple_t</strong> - The SASL callback for username/authname/realm</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_global_listmech.html"><strong>sasl_global_listmech</strong> - Retrieve a list of the supported SASL mechanisms</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_idle.html"><strong>sasl_idle</strong> - Perform precalculations during an idle period</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_listmech.html"><strong>sasl_listmech</strong> - Retrieve a list of the supported SASL mechanisms</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_log_t.html"><strong>sasl_log_t</strong> - The SASL logging callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_add_plugin.html"><strong>sasl_server_add_plugin</strong> - add a SASL server plugin</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_done.html"><strong>sasl_server_done</strong> - Cleanup function</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_init.html"><strong>sasl_server_init</strong> - SASL server authentication initialization</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_new.html"><strong>sasl_server_new</strong> - Create a new server authentication object</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_plug_init_t.html"><strong>sasl_server_plug_init_t</strong> - server plug‐in entry point</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_start.html"><strong>sasl_server_start</strong> - Begin an authentication negotiation</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_step.html"><strong>sasl_server_step</strong> - Perform a step in the authentication negotiation</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_userdb_checkpass_t.html"><strong>sasl_server_userdb_checkpass_t</strong> - Plaintext Password Verification Callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_server_userdb_setpass_t.html"><strong>sasl_server_userdb_setpass_t</strong> - UserDB Plaintext Password Setting Callback</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_set_alloc.html"><strong>sasl_set_alloc</strong> - set the memory allocation functions used by the SASL library</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_set_mutex.html"><strong>sasl_set_mutex</strong> - set the mutex lock functions used by the SASL library</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_seterror.html"><strong>sasl_seterror</strong> - set the error string</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_setpass.html"><strong>sasl_setpass</strong> - Check a plaintext password</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_setprop.html"><strong>sasl_setprop</strong> - Set a SASL property</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_user_exists.html"><strong>sasl_user_exists</strong> - Check if a user exists on server</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_usererr.html"><strong>sasl_usererr</strong> - Remove information leak about accounts from sasl error codes</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_utf8verify.html"><strong>sasl_utf8verify</strong> - Verify a string is valid utf8</a></li>
<li class="toctree-l4"><a class="reference internal" href="sasl_verifyfile_t.html"><strong>sasl_verifyfile_t</strong> - The SASL file verification</a></li>
</ul>
</li>
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<li><strong>sasl_client_start</strong> - Begin an authentication negotiation</li>
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<div class="section" id="sasl-client-start-begin-an-authentication-negotiation">
<span id="sasl-reference-manpages-library-sasl-client-start"></span><span id="std:saslman-sasl_client_start(3)"></span><h1><strong>sasl_client_start</strong> - Begin an authentication negotiation<a class="headerlink" href="#sasl-client-start-begin-an-authentication-negotiation" title="Permalink to this headline">¶</a></h1>
<div class="section" id="synopsis">
<h2>Synopsis<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
<div class="highlight-C"><div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf"><sasl/sasl.h></span><span class="cp"></span>
<span class="kt">int</span> <span class="nf">sasl_client_start</span><span class="p">(</span><span class="n">sasl_conn_t</span> <span class="o">*</span> <span class="n">conn</span><span class="p">,</span>
<span class="k">const</span> <span class="kt">char</span> <span class="o">*</span> <span class="n">mechlist</span><span class="p">,</span>
<span class="n">sasl_interact_t</span> <span class="o">**</span> <span class="n">prompt_need</span><span class="p">,</span>
<span class="k">const</span> <span class="kt">char</span> <span class="o">**</span> <span class="n">clientout</span><span class="p">,</span>
<span class="kt">unsigned</span> <span class="o">*</span> <span class="n">clientoutlen</span><span class="p">,</span>
<span class="k">const</span> <span class="kt">char</span> <span class="o">**</span> <span class="n">mech</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<dl class="function">
<dt>
<code class="descname">int sasl_client_start(sasl_conn_t * conn,</code></dt>
<dt>
<code class="descname">const char * mechlist,</code></dt>
<dt>
<code class="descname">sasl_interact_t ** prompt_need,</code></dt>
<dt>
<code class="descname">const char ** clientout,</code></dt>
<dt>
<code class="descname">unsigned * clientoutlen,</code></dt>
<dt>
<code class="descname">const char ** mech);</code></dt>
<dd><p><strong>sasl_client_start()</strong> selects a mechanism for authentication and starts the
authentication session. The mechlist is the list of mechanisms the client
might like to use. The mech‐ anisms in the list are not necessarily supported
by the client or even valid. SASL determines which of these to use based
upon the security preferences specified earlier. The list of mechanisms is
typically a list of mechanisms the server supports acquired from a capability
request.</p>
<p>If <a class="reference internal" href="sasl_errors.html#c.SASL_INTERACT" title="SASL_INTERACT"><code class="xref c c-macro docutils literal"><span class="pre">SASL_INTERACT</span></code></a> is returned the library needs some values to be
filled in before it can proceed. The <cite>prompt_need</cite> structure will be filled in
with requests. The application should fulfill these requests and call
sasl_client_start again with identical parameters (the <cite>prompt_need</cite> parameter
will be the same pointer as before but filled in by the application).</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><strong>conn</strong> – is the SASL connection context</li>
<li><strong>mechlist</strong> – is a list of mechanisms the server has available.
Punctuation is ignored.</li>
<li><strong>prompt_need</strong> – is filled in with a list of prompts needed to
continue (if necessary).</li>
<li><strong>clientout</strong> – <p>is created. It is the initial
client response to send to the server. It is the job of
the client to send it over the network to the server. Any
protocol specific encoding (such as base64 encoding) necessary
needs to be done by the client.</p>
<p>If the protocol lacks client‐send‐first capability, then
set clientout to NULL.</p>
<p>If there is no initial client‐send, then *clientout will
be set to NULL on return.</p>
</li>
<li><strong>clientoutlen</strong> – length of <cite>clientout</cite>.</li>
<li><strong>mech</strong> – contains the name of the chosen SASL
mechanism (on success)</li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</div>
<div class="section" id="return-value">
<h2>Return Value<a class="headerlink" href="#return-value" title="Permalink to this headline">¶</a></h2>
<p>SASL callback functions should return SASL return codes.
See sasl.h for a complete list. <a class="reference internal" href="sasl_errors.html#c.SASL_CONTINUE" title="SASL_CONTINUE"><code class="xref c c-macro docutils literal"><span class="pre">SASL_CONTINUE</span></code></a> indicates success
and that there are more steps needed in the authentication.</p>
<p>Other return codes indicate errors and should either be handled or the authentication
session should be quit.</p>
</div>
<div class="section" id="see-also">
<h2>See Also<a class="headerlink" href="#see-also" title="Permalink to this headline">¶</a></h2>
<p><span class="target" id="index-0"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc4422.html"><strong>RFC 4422</strong></a>,:saslman:<cite>sasl(3)</cite>, <a class="reference internal" href="sasl_callbacks.html#std:saslman-sasl_callbacks(3)">sasl_callbacks(3)</a>,
<a class="reference internal" href="sasl_client_init.html#std:saslman-sasl_client_init(3)">sasl_client_init(3)</a>, <a class="reference internal" href="sasl_client_new.html#std:saslman-sasl_client_new(3)">sasl_client_new(3)</a>,
<a class="reference internal" href="sasl_client_step.html#std:saslman-sasl_client_step(3)">sasl_client_step(3)</a>, <a class="reference internal" href="sasl_errors.html#std:saslman-sasl_errors(3)">sasl_errors(3)</a></p>
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