access_can_roll.xml

<?xml version="1.0"?>

<scenario xmlns="http://www.github/cliffe/SecGen/scenario"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.github/cliffe/SecGen/scenario">

  <name>Access can roll</name>
  <author>Z. Cliffe Schreuders</author>
  <author>Rosie Fletcher</author>
  <description>
There are two problem solving access control challenges on the server. Look at the home directories and the .c files.

1: Use the access_my_flag program to access the two flags (hint: think about how you can use hardlink trickery to access relative paths).

2: Look at the two shell programs and how you can combine them together to get at a flag.

Your password on both systems is: tiaspbiqe2r
  </description>

  <type>ctf-lab</type>
  <!--<type>hackerbot-lab</type>-->
  <type>lab-sheet</type>
  <difficulty>intermediate</difficulty>

  <CyBOK KA="AAA" topic="Authorisation">
    <keyword>access control</keyword>
    <keyword>Elevated privileges</keyword>
    <keyword>Real and effective identity</keyword>
    <keyword>Vulnerabilities and attacks on access control misconfigurations</keyword>
  </CyBOK>
  <CyBOK KA="OSV" topic="Primitives for Isolation and Mediation">
    <keyword>Access controls and operating systems</keyword>
    <keyword>Linux security model</keyword>
    <keyword>Unix File Permissions</keyword>
    <keyword>setuid/setgid</keyword>
    <keyword>Hardlink protections</keyword>
  </CyBOK>
  <CyBOK KA="AC" topic="Public-Key Cryptography">
    <keyword>public-key signatures</keyword>
  </CyBOK>


  <system>
    <system_name>shared_desktop</system_name>
    <base distro="Debian 12" type="desktop" name="KDE"/>

    <input into_datastore="IP_addresses">
      <!-- 0 desktop -->
      <network_ip system="shared_desktop"/>
      <!-- 1 server -->
      <network_ip system="server"/>
    </input>

    <!-- generate some usernames to use -->
    <input into_datastore="usernames">
      <!-- main user -->
      <generator type="random_sanitised_word">
        <input into="wordlist">
          <value>mythical_creatures</value>
        </input>
      </generator>
      <!-- other user -->
      <generator type="random_sanitised_word">
        <input into="wordlist">
          <value>mythical_creatures</value>
        </input>
      </generator>
    </input>

    <!-- generate some passwords to use -->
    <input into_datastore="passwords">
      <generator type="medium_password_generator"/>
    </input>

    <input into_datastore="groups">
      <value>staff</value>
      <value>team_one</value>
      <value>team_two</value>
    </input>

    <!-- accounts on the desktop, with the main user as a sudoer -->
    <input into_datastore="user_accounts_desktop">
      <!-- main user, sudoer -->
      <generator type="account">
        <input into="username">
          <datastore access="0">usernames</datastore>
        </input>
        <input into="password">
          <value>tiaspbiqe2r</value>
        </input>
        <input into="leaked_filenames">
          <value>access_my_secrets.c</value>
          <value>mysecret</value>
        </input>
        <input into="strings_to_leak">
          <value>
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;sys/types.h&gt;
#include &lt;unistd.h&gt;
#include &lt;errno.h&gt;

int main()
{
  printf(&quot;        UID           GID \n&quot;
       &quot;Real    %d  Real    %d \n&quot;
       &quot;Effective %d  Effective %d \n&quot;,
       getuid (),   getgid (),
       geteuid(),   getegid());

  FILE *fp = fopen(&quot;mysecret&quot;, &quot;r&quot;);
  if (fp == NULL) {
    printf(&quot;Error: Could not open file&quot;);
    exit(EXIT_FAILURE);
  }
  char c;
  while ((c=getc(fp)) != EOF) {
    putchar(c);
  }
  putchar(&apos;\n&apos;);
  return EXIT_SUCCESS;
}
          </value>
          <generator type="random_line_generator">
            <input into="linelist">
              <value>secrets</value>
            </input>
          </generator>

        </input>
        <input into="super_user">
          <value>true</value>
        </input>
      </generator>
      <!-- other user, no flags -->
      <generator type="account">
        <input into="username">
          <datastore access="next">usernames</datastore>
        </input>
        <input into="password">
          <datastore access="0">passwords</datastore>
        </input>
      </generator>

    </input>

    <input into_datastore="desktop_root_password">
      <generator type="strong_password_generator"/>
    </input>

    <!--Create the groups-->
    <utility module_path=".*/groups">
      <input into="groups">
        <datastore>groups</datastore>
      </input>
    </utility>
    <!--Create the users-->
    <utility module_path=".*/parameterised_accounts">
      <input into="accounts">
        <datastore>user_accounts_desktop</datastore>
      </input>
    </utility>

    <utility module_path=".*/kde_minimal">
      <input into="autologin_user">
        <datastore access="0">usernames</datastore>
      </input>
      <input into="accounts">
        <datastore>user_accounts_desktop</datastore>
      </input>
      <input into="autostart_konsole">
        <value>true</value>
      </input>
    </utility>
    <utility module_path=".*/handy_cli_tools"/>
    <utility module_path=".*/gcc"/>

    <vulnerability module_path=".*/ssh_root_login">
      <input into="root_password">
        <datastore>desktop_root_password</datastore>
      </input>
    </vulnerability>

    <network type="private_network"/>
    <input into_datastore="spoiler_admin_pass">
      <generator type="strong_password_generator"/>
    </input>
    <build type="cleanup">
      <input into="root_password">
        <datastore>spoiler_admin_pass</datastore>
      </input>
    </build>
  </system>

  <system>
    <system_name>server</system_name>
    <base distro="Debian 12" type="desktop" name="KDE"/>

    <!-- user accounts on the server, with matching usernames and passwords, but with flags to find -->
    <input into_datastore="user_accounts_server">
      <!-- main user, NOT sudoer -->
      <generator type="account">
        <input into="username">
          <datastore access="0">usernames</datastore>
        </input>
        <input into="password">
          <value>tiaspbiqe2r</value>
        </input>
        <input into="super_user">
          <value>false</value>
        </input>
        <input into="groups">
          <value>staff</value>
          <value>team_one</value>
        </input>
      </generator>
      <!-- other users, with the SAME passwords -->
      <generator type="account">
        <input into="username">
          <datastore access="next">usernames</datastore>
        </input>
        <input into="password">
          <datastore access="0">passwords</datastore>
        </input>
        <input into="groups">
          <value>staff</value>
          <value>team_one</value>
          <value>team_two</value>
        </input>
      </generator>

    </input>

    <!--Create the groups-->
    <utility module_path=".*/groups">
      <input into="groups">
        <datastore>groups</datastore>
      </input>
    </utility>
    <!--Create the users-->
    <utility module_path=".*/parameterised_accounts">
      <input into="accounts">
        <datastore>user_accounts_server</datastore>
      </input>
    </utility>

    <utility module_path=".*/handy_cli_tools"/>
    <utility module_path=".*/gcc"/>

    <vulnerability module_path=".*/ssh_root_login">
      <input into="root_password">
        <datastore>desktop_root_password</datastore>
      </input>
    </vulnerability>

    <vulnerability module_path=".*/relative_path_suid_hardlinks"/>
    <vulnerability module_path=".*/two_shell_calls"/>
    <!-- <vulnerability module_path=".*/ssh_leaked_keys"/> -->


    <network type="private_network"/>
    <build type="cleanup">
      <input into="root_password">
        <datastore>spoiler_admin_pass</datastore>
      </input>
    </build>
  </system>

</scenario>