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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-decrypt"></a>Decrypting an encrypted document</h2></div></div></div>
<p>The typical decryption process includes following steps:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>
Load keys, X509 certificates, etc. in the <a class="link" href="xmlsec-keysmngr.html#xmlSecKeysMngr" title="struct xmlSecKeysMngr">keys manager</a> .
</p></li>
<li class="listitem"><p>
Create encryption context <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a>
using <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxCreate" title="xmlSecEncCtxCreate ()">xmlSecEncCtxCreate</a> or
<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxInitialize" title="xmlSecEncCtxInitialize ()">xmlSecEncCtxInitialize</a>
functions.
</p></li>
<li class="listitem"><p>
Select start decryption <enc:EncryptedData> node.
</p></li>
<li class="listitem"><p>
Decrypt by calling <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxDecrypt" title="xmlSecEncCtxDecrypt ()">xmlSecencCtxDecrypt</a>
function.
</p></li>
<li class="listitem"><p>
Check returned value and if necessary consume encrypted data.
</p></li>
<li class="listitem"><p>
Destroy encryption context <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a>
using <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxDestroy" title="xmlSecEncCtxDestroy ()">xmlSecEncCtxDestroy</a> or
<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxFinalize" title="xmlSecEncCtxFinalize ()">xmlSecEncCtxFinalize</a>
functions.
</p></li>
</ul></div>
<p>
</p>
<p>
</p>
<div class="example">
<a name="id-1.2.8.4.3.1"></a><p class="title"><b>Example 15. Decrypting a document.</b></p>
<div class="example-contents">
<pre class="programlisting">
int
decrypt_file(const char* enc_file, const char* key_file) {
xmlDocPtr doc = NULL;
xmlNodePtr node = NULL;
xmlSecEncCtxPtr encCtx = NULL;
int res = -1;
assert(enc_file);
assert(key_file);
/* load template */
doc = xmlParseFile(enc_file);
if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
fprintf(stderr, "Error: unable to parse file \"%s\"\n", enc_file);
goto done;
}
/* find start node */
node = xmlSecFindNode(xmlDocGetRootElement(doc), xmlSecNodeEncryptedData, xmlSecEncNs);
if(node == NULL) {
fprintf(stderr, "Error: start node not found in \"%s\"\n", enc_file);
goto done;
}
/* create encryption context, we don't need keys manager in this example */
encCtx = xmlSecEncCtxCreate(NULL);
if(encCtx == NULL) {
fprintf(stderr,"Error: failed to create encryption context\n");
goto done;
}
/* load DES key */
encCtx->encKey = xmlSecKeyReadBinaryFile(xmlSecKeyDataDesId, key_file);
if(encCtx->encKey == NULL) {
fprintf(stderr,"Error: failed to load des key from binary file \"%s\"\n", key_file);
goto done;
}
/* set key name to the file name, this is just an example! */
if(xmlSecKeySetName(encCtx->encKey, key_file) < 0) {
fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
goto done;
}
/* decrypt the data */
if((xmlSecEncCtxDecrypt(encCtx, node) < 0) || (encCtx->result == NULL)) {
fprintf(stderr,"Error: decryption failed\n");
goto done;
}
/* print decrypted data to stdout */
if(encCtx->resultReplaced != 0) {
fprintf(stdout, "Decrypted XML data:\n");
xmlDocDump(stdout, doc);
} else {
fprintf(stdout, "Decrypted binary data (%d bytes):\n", xmlSecBufferGetSize(encCtx->result));
if(xmlSecBufferGetData(encCtx->result) != NULL) {
fwrite(xmlSecBufferGetData(encCtx->result),
1,
xmlSecBufferGetSize(encCtx->result),
stdout);
}
}
fprintf(stdout, "\n");
/* success */
res = 0;
done:
/* cleanup */
if(encCtx != NULL) {
xmlSecEncCtxDestroy(encCtx);
}
if(doc != NULL) {
xmlFreeDoc(doc);
}
return(res);
}
</pre>
<p><a class="link" href="xmlsec-decrypt-with-signle-key.html#xmlsec-example-decrypt1" title="decrypt1.c">Full Program Listing</a></p>
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