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<br clear="all"><div class="SECT1">
<h1 class="SECT1"><a name="XMLSEC-NOTES-VERIFY">Verifying a signed document</a></h1>
<p>The typical signature verification process includes following steps:
	  </p>
<p></p>
<ul>
<li><p>		Load keys, X509 certificates, etc. in the <a href="xmlsec-keysmngr.html#XMLSECKEYSMNGR">keys manager</a> .
	    </p></li>
<li><p>		Create signature context <a href="xmlsec-xmldsig.html#XMLSECDSIGCTX">xmlSecDSigCtx</a>
		using <a href="xmlsec-xmldsig.html#XMLSECDSIGCTXCREATE">xmlSecDSigCtxCreate</a> or
		<a href="xmlsec-xmldsig.html#XMLSECDSIGCTXINITIALIZE">xmlSecDSigCtxInitialize</a>
		functions.
	    </p></li>
<li><p>		Select start verification 
    		<a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top"></a><a href="http://www.w3.org/TR/xmldsig-core/#sec-Signature" target="_top">&lt;dsig:Signature/&gt;</a>
		node in the signed XML document.
	    </p></li>
<li><p>		Verify signature by calling <a href="xmlsec-xmldsig.html#XMLSECDSIGCTXVERIFY">xmlSecDSigCtxVerify</a> 
		function.
	    </p></li>
<li><p>		Check returned value and verification status (<code class="STRUCTFIELD">status</code>
		member of <a href="xmlsec-xmldsig.html#XMLSECDSIGCTX">xmlSecDSigCtx</a> structure).
		If necessary, consume returned data from the <a href="xmlsec-xmldsig.html#XMLSECDSIGCTX">context</a>.
	    </p></li>
<li><p>		Destroy signature context <a href="xmlsec-xmldsig.html#XMLSECDSIGCTX">xmlSecDSigCtx</a>
		using <a href="xmlsec-xmldsig.html#XMLSECDSIGCTXDESTROY">xmlSecDSigCtxDestroy</a> or
		<a href="xmlsec-xmldsig.html#XMLSECDSIGCTXFINALIZE">xmlSecDSigCtxFinalize</a>
		functions.
	    </p></li>
</ul>
	<p>	     </p>
<div class="EXAMPLE">
<a name="AEN366"></a><p><b>Example 1. Verifying a document.</b></p>
<pre class="PROGRAMLISTING">/** 
 * verify_file:
 * @xml_file:		the signed XML file name.
 * @key_file:		the PEM public key file name.
 *
 * Verifies XML signature in #xml_file using public key from #key_file.
 *
 * Returns 0 on success or a negative value if an error occurs.
 */
int 
verify_file(const char* xml_file, const char* key_file) {
    xmlDocPtr doc = NULL;
    xmlNodePtr node = NULL;
    xmlSecDSigCtxPtr dsigCtx = NULL;
    int res = -1;
    
    assert(xml_file);
    assert(key_file);

    /* load file */
    doc = xmlParseFile(xml_file);
    if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
	fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
	goto done;	
    }
    
    /* find start node */
    node = xmlSecFindNode(xmlDocGetRootElement(doc), xmlSecNodeSignature, xmlSecDSigNs);
    if(node == NULL) {
	fprintf(stderr, "Error: start node not found in \"%s\"\n", xml_file);
	goto done;	
    }

    /* create signature context, we don't need keys manager in this example */
    dsigCtx = xmlSecDSigCtxCreate(NULL);
    if(dsigCtx == NULL) {
        fprintf(stderr,"Error: failed to create signature context\n");
	goto done;
    }

    /* load public key */
    dsigCtx-&gt;signKey = xmlSecCryptoAppKeyLoad(key_file,xmlSecKeyDataFormatPem, NULL, NULL, NULL);
    if(dsigCtx-&gt;signKey == NULL) {
        fprintf(stderr,"Error: failed to load public pem key from \"%s\"\n", key_file);
	goto done;
    }

    /* set key name to the file name, this is just an example! */
    if(xmlSecKeySetName(dsigCtx-&gt;signKey, key_file) &lt; 0) {
    	fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
	goto done;
    }

    /* Verify signature */
    if(xmlSecDSigCtxVerify(dsigCtx, node) &lt; 0) {
        fprintf(stderr,"Error: signature verify\n");
	goto done;
    }
        
    /* print verification result to stdout */
    if(dsigCtx-&gt;status == xmlSecDSigStatusSucceeded) {
	fprintf(stdout, "Signature is OK\n");
    } else {
	fprintf(stdout, "Signature is INVALID\n");
    }    

    /* success */
    res = 0;

done:    
    /* cleanup */
    if(dsigCtx != NULL) {
	xmlSecDSigCtxDestroy(dsigCtx);
    }
    
    if(doc != NULL) {
	xmlFreeDoc(doc); 
    }
    return(res);
}
		</pre>
<p><a href="xmlsec-verify-with-key.html#XMLSEC-EXAMPLE-VERIFY1">Full Program Listing</a></p>
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