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The typical decryption process includes following steps:
Load keys, X509 certificates, etc. in the keys manager .
Create encryption context xmlSecEncCtx using xmlSecEncCtxCreate or xmlSecEncCtxInitialize functions.
Select start decryption <enc:EncryptedData> node.
Decrypt by calling xmlSecencCtxDecrypt function.
Check returned value and if necessary consume encrypted data.
Destroy encryption context xmlSecEncCtx using xmlSecEncCtxDestroy or xmlSecEncCtxFinalize functions.
Example 15. Decrypting a document.
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);
}