getting nested values from a decoded SAMLresponse XML with rapidxml

Question

I have been trying to get the values of the decoded XML, all 3 of them.

The XML file is as follows (it has way more nodes but this is just a testing preview)

<Response ID="number" Version="2.0">
    <Issuer xmlns=":assertion">
        check1
    </Issuer>
    <Status>
        <StatusCode Value="Success" />
        checkcheck2
    </Status>
    <Assertion ID="somenumber" IssueInstant="datestamp" Version="2.0"
        xmlns="urn:oasis:names:tc:SAML:2.0:assertion">
        <Issuer>
            checkcheckcheck3
        </Issuer>
    </Assertion>
</Response>

I tried to get the value out off the "Status" node in the following way (don't mind the includes I don't need I have been trying a lot of things and just keep them for now incase I need them, will remove them when it is working):

#include <iostream>
#include <sstream>
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
#include <vector>
#include "rapidxml.hpp"
#include "rapidxml_print.hpp"
#include "base64.hpp"

using namespace std;
    int main()
    {
        rapidxml::xml_node<> *root_node;
        rapidxml::xml_node<> *second_node;
        
                
        //costum base64 encoder and decoder this works as it should
        help::base64_decode;
    
        string xmlFile;
    
        // Base64 response from form data contains xml
        xmlFile = help::base64_decode("the base64 encoded SAMLResponse");
    
        //put the b64 decoded xml in a string
        stringstream decodedXml(xmlFile);
        rapidxml::xml_document<> doc;
    
        // test the decoded b64
        cout << xmlFile << endl;
    
        // Read file into vector<char>
        vector<char> buffer((istreambuf_iterator<char>(decodedXml)), istreambuf_iterator<char>());
    
        buffer.push_back('\0');
    
        doc.parse<0>(&buffer[0]);
    
        root_node = doc.first_node("Response");
    
    // this returs Issuer 
        cout << root_node->first_node()->name() << endl;
    
    // go to next sibling of the root node ?? (that should be Status)
        second_node = root_node->next_sibling(); 
    
    // gives me a exited with code=3221225477 in 0.485 seconds on compiling 
        cout << second_node->first_node()->name() << endl;

What am I doing wrong, or rather. What part of the next_sibling() function am I misunderstanding. As far as I know the next_sibling() would go to the next node that is on the same level as the one declared as root_node (which is Issuer in this case).

score 0 · Answer 1 · answered Sep 29 '22 at 12:05

0

The root node -- by definition -- cannot have a sibling. Instead, you either want ->first_node()->next_sibling and co, or better: search for child nodes by name:

doc.parse<rapidxml::parse_trim_whitespace>(&buffer[0]);

auto root_node = doc.first_node("Response");
auto issuer_node = root_node->first_node("Issuer");
auto status_node = root_node->first_node("Status");
auto assertion_issuer_node = root_node->first_node("Assertion")->first_node("Issuer");

cout << "Issuer: " << issuer_node->value() << endl;
cout << "StatusCode: " << status_node->value() << endl;
cout << "Assertion.Issuer: " << assertion_issuer_node->value() << endl;

Note the use of parse_trim_whitespace, without it your value() functions will contain lots of whitespace.

answered Sep 29 '22 at 12:05

Botje

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That makes sense.. i should have figured that root meant the first and final node. Searching for the child nodes by name would be great since i am adding costum values to the samlresponse. I'l try to implement it later tonight. Thanks in advance!! – kees prince Sep 29 '22 at 12:34
While trying this out, only with the assertion_issuer_node. It throws the same error. The whitespace parsing fixes the printing of the whitespaces wich is nice! And the first_node()->next_sibling() also works to print out checkcheck2 as a value from the next node. however that stil is doing it manually and not searching by name as you suggested. – kees prince Sep 29 '22 at 23:01
I took the exact XML snippet you put in your question (without the base64 fluff around it). Perhaps your input is different? – Botje Sep 30 '22 at 07:27
I went about it in a way that i am now while looping trough values in a certain node, and taking the values of the sibling nodes until a sibling is no longer present. Should someone arise that wants to do the same thing i'll put up some code. – kees prince Oct 03 '22 at 17:07

kees prince · Accepted Answer · 2022-12-02T15:25:33.747

In case anyone is wondering what i did to fix not being able to search nodes by string input.

i wrote a function that searches for sibling nodes.

  
//gets the coun of child nodes present in current node
int getChildCount(rapidxml::xml_node<> *n)
    {
        int c = 0;
        for (rapidxml::xml_node<> *child = n; child != NULL; child = child->next_sibling())
        {
            c++;
        }
        return c;
    }
    

static rapidxml::xml_node<> *find_sibling(rapidxml::xml_node<> *in, const std::string &s)
    {
        rapidxml::xml_document<> doc_error;
        rapidxml::xml_node<> *err = doc_error.allocate_node(rapidxml::node_element, "error");
        doc_error.append_node(err);

        std::string node_name;

        int childs = getChildCount(in);
        int count = 1;

        while (in != NULL)
        {

            in = in->next_sibling();
            count++;

            node_name = in->name();

            if (node_name == s)
            {
                return in;
            }
            if (count == childs)
            {
                return err;
            }
        }
        return err;
    }

This now allows me to search with;

rapidxml::xml_node<> *issuer_node = find_sibling(issuer_node->first_node(), "Assertion"); This wil go through the function to try and find Assertion node. And if it can not be found it within the sibling nodes instead of just crashing, it returns a xml doc with .

getting nested values from a decoded SAMLresponse XML with rapidxml

2 Answers2