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<title>Using keys manager for signatures/encryption.: XML Security Library Reference Manual</title>
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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-keys-manager-sign-enc"></a>Using keys manager for signatures/encryption.</h2></div></div></div>
<p>Instead of specifiying signature or encryption key in the
corresponding context object (<em class="structfield"><code>signKey</code></em>
member of <a class="link" href="xmlsec-xmldsig.html#xmlSecDSigCtx" title="struct xmlSecDSigCtx">xmlSecDSigCtx</a>
structure or <em class="structfield"><code>encKey</code></em> member of
<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a> structure),
the application can use keys manager to select the
signature or encryption key. This is especialy useful
when you are encrypting or signing something with a session key
which is by itself should be encrypted. The key for the
session key encryption in the
<a class="ulink" href="" target="_top"><EncryptedKey/></a>
node could be selected using
<a class="ulink" href="" target="_top"><dsig:KeyName/></a>
node in the template.
</p>
<p>
</p>
<div class="example">
<a name="id-1.2.10.4.3.1"></a><p class="title"><b>Example 17. Encrypting file using a session key and a permanent key from keys manager.</b></p>
<div class="example-contents">
<pre class="programlisting">
/**
* load_rsa_keys:
* @key_file: the key filename.
*
* Creates default keys manager and load RSA key from #key_file in it.
* The caller is responsible for destroing returned keys manager using
* @xmlSecKeysMngrDestroy.
*
* Returns the pointer to newly created keys manager or NULL if an error
* occurs.
*/
xmlSecKeysMngrPtr
load_rsa_keys(char* key_file) {
xmlSecKeysMngrPtr mngr;
xmlSecKeyPtr key;
assert(key_file);
/* create and initialize keys manager, we use a default list based
* keys manager, implement your own xmlSecKeysStore klass if you need
* something more sophisticated
*/
mngr = xmlSecKeysMngrCreate();
if(mngr == NULL) {
fprintf(stderr, "Error: failed to create keys manager.\n");
return(NULL);
}
if(xmlSecCryptoAppDefaultKeysMngrInit(mngr) < 0) {
fprintf(stderr, "Error: failed to initialize keys manager.\n");
xmlSecKeysMngrDestroy(mngr);
return(NULL);
}
/* load private RSA key */
key = xmlSecCryptoAppKeyLoad(key_file, xmlSecKeyDataFormatPem, NULL, NULL, NULL);
if(key == NULL) {
fprintf(stderr,"Error: failed to load rsa key from file \"%s\"\n", key_file);
xmlSecKeysMngrDestroy(mngr);
return(NULL);
}
/* set key name to the file name, this is just an example! */
if(xmlSecKeySetName(key, BAD_CAST key_file) < 0) {
fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
xmlSecKeyDestroy(key);
xmlSecKeysMngrDestroy(mngr);
return(NULL);
}
/* add key to keys manager, from now on keys manager is responsible
* for destroying key
*/
if(xmlSecCryptoAppDefaultKeysMngrAdoptKey(mngr, key) < 0) {
fprintf(stderr,"Error: failed to add key from \"%s\" to keys manager\n", key_file);
xmlSecKeyDestroy(key);
xmlSecKeysMngrDestroy(mngr);
return(NULL);
}
return(mngr);
}
/**
* encrypt_file:
* @mngr: the pointer to keys manager.
* @xml_file: the encryption template file name.
* @key_name: the RSA key name.
*
* Encrypts #xml_file using a dynamicaly created template, a session DES key
* and an RSA key from keys manager.
*
* Returns 0 on success or a negative value if an error occurs.
*/
int
encrypt_file(xmlSecKeysMngrPtr mngr, const char* xml_file, const char* key_name) {
xmlDocPtr doc = NULL;
xmlNodePtr encDataNode = NULL;
xmlNodePtr keyInfoNode = NULL;
xmlNodePtr encKeyNode = NULL;
xmlNodePtr keyInfoNode2 = NULL;
xmlSecEncCtxPtr encCtx = NULL;
int res = -1;
assert(mngr);
assert(xml_file);
assert(key_name);
/* load template */
doc = xmlParseFile(xml_file);
if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
goto done;
}
/* create encryption template to encrypt XML file and replace
* its content with encryption result */
encDataNode = xmlSecTmplEncDataCreate(doc, xmlSecTransformDes3CbcId,
NULL, xmlSecTypeEncElement, NULL, NULL);
if(encDataNode == NULL) {
fprintf(stderr, "Error: failed to create encryption template\n");
goto done;
}
/* we want to put encrypted data in the <enc:CipherValue/> node */
if(xmlSecTmplEncDataEnsureCipherValue(encDataNode) == NULL) {
fprintf(stderr, "Error: failed to add CipherValue node\n");
goto done;
}
/* add <dsig:KeyInfo/> */
keyInfoNode = xmlSecTmplEncDataEnsureKeyInfo(encDataNode, NULL);
if(keyInfoNode == NULL) {
fprintf(stderr, "Error: failed to add key info\n");
goto done;
}
/* add <enc:EncryptedKey/> to store the encrypted session key */
encKeyNode = xmlSecTmplKeyInfoAddEncryptedKey(keyInfoNode,
xmlSecTransformRsaOaepId,
NULL, NULL, NULL);
if(encKeyNode == NULL) {
fprintf(stderr, "Error: failed to add key info\n");
goto done;
}
/* we want to put encrypted key in the <enc:CipherValue/> node */
if(xmlSecTmplEncDataEnsureCipherValue(encKeyNode) == NULL) {
fprintf(stderr, "Error: failed to add CipherValue node\n");
goto done;
}
/* add <dsig:KeyInfo/> and <dsig:KeyName/> nodes to <enc:EncryptedKey/> */
keyInfoNode2 = xmlSecTmplEncDataEnsureKeyInfo(encKeyNode, NULL);
if(keyInfoNode2 == NULL) {
fprintf(stderr, "Error: failed to add key info\n");
goto done;
}
/* set key name so we can lookup key when needed */
if(xmlSecTmplKeyInfoAddKeyName(keyInfoNode2, key_name) == NULL) {
fprintf(stderr, "Error: failed to add key name\n");
goto done;
}
/* create encryption context */
encCtx = xmlSecEncCtxCreate(mngr);
if(encCtx == NULL) {
fprintf(stderr,"Error: failed to create encryption context\n");
goto done;
}
/* generate a Triple DES key */
encCtx->encKey = xmlSecKeyGenerate(xmlSecKeyDataDesId, 192, xmlSecKeyDataTypeSession);
if(encCtx->encKey == NULL) {
fprintf(stderr,"Error: failed to generate session des key\n");
goto done;
}
/* encrypt the data */
if(xmlSecEncCtxXmlEncrypt(encCtx, encDataNode, xmlDocGetRootElement(doc)) < 0) {
fprintf(stderr,"Error: encryption failed\n");
goto done;
}
/* we template is inserted in the doc */
encDataNode = NULL;
/* print encrypted data with document to stdout */
xmlDocDump(stdout, doc);
/* success */
res = 0;
done:
/* cleanup */
if(encCtx != NULL) {
xmlSecEncCtxDestroy(encCtx);
}
if(encDataNode != NULL) {
xmlFreeNode(encDataNode);
}
if(doc != NULL) {
xmlFreeDoc(doc);
}
return(res);
}
</pre>
<p><a class="link" href="xmlsec-encrypt-with-session-key.html#xmlsec-example-encrypt3" title="encrypt3.c">Full program listing</a></p>
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<p><br class="example-break">
</p>
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