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Add comprehensive tests and documentation for security enhancements
Co-authored-by: kuhyx <147418882+kuhyx@users.noreply.github.com>
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docs/PACMAN_WRAPPER_SECURITY.md
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docs/PACMAN_WRAPPER_SECURITY.md
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# Pacman Wrapper Security Enhancements
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## Overview
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This document describes the security enhancements made to the pacman wrapper to prevent circumvention, particularly for VirtualBox installations.
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## Problem Statement
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The original pacman wrapper had the following vulnerabilities:
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1. **Easy Policy Bypass**: Users could edit `pacman_greylist.txt` or `pacman_blocked_keywords.txt` to remove restrictions, then reinstall the wrapper.
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2. **VirtualBox Hosts Bypass**: VirtualBox VMs do not inherit the host machine's `/etc/hosts` file, allowing users to bypass content filtering within VMs.
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3. **No Tamper Detection**: The wrapper had no mechanism to detect if policy files had been modified.
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## Solutions Implemented
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### 1. Policy File Integrity Checks
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**File**: `scripts/digital_wellbeing/pacman/install_pacman_wrapper.sh`
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The installer now:
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- Generates SHA256 checksums of all policy files during installation
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- Stores checksums in `/var/lib/pacman-wrapper/policy.sha256`
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- Makes the integrity file immutable using `chattr +i`
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- Makes policy files (`pacman_blocked_keywords.txt`, `pacman_greylist.txt`) immutable
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**File**: `scripts/digital_wellbeing/pacman/pacman_wrapper.sh`
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The wrapper now:
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- Verifies policy file integrity on **every invocation**
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- Compares current file checksums against stored checksums
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- **Blocks all operations** if tampering is detected
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- Displays security warnings and instructs user to reinstall
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**Benefits**:
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- Cannot bypass restrictions by editing policy files
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- Tampering is immediately detected and blocked
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- Must use `chattr -i` (requires root) to modify files, making bypass harder
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### 2. Hardcoded VirtualBox Restrictions
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**File**: `scripts/digital_wellbeing/pacman/pacman_wrapper.sh`
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Added hardcoded VirtualBox detection that **cannot be bypassed** by editing policy files:
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```bash
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function is_virtualbox_package() {
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local pkg_lower="${1,,}"
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[[ $pkg_lower == *"virtualbox"* || $pkg_lower == *"vbox"* ]]
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}
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```
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This function:
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- Is compiled into the wrapper code itself
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- Cannot be disabled by editing text files
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- Catches all VirtualBox-related packages
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**Enhanced Challenge**:
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- 7-letter words (harder than greylist's 6-letter words)
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- 150 words to memorize (more than greylist's 120)
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- 120-second timeout (longer than greylist's 90s)
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- 45-second initial delay (psychological friction)
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- 30-50 second post-challenge delay
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**Warning Messages**:
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- Explicit warning about /etc/hosts bypass potential
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- Lists security measures that will be applied
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- Emphasizes that restrictions are hardcoded
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### 3. VirtualBox Hosts Enforcement
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**File**: `scripts/digital_wellbeing/virtualbox/enforce_vbox_hosts.sh`
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A new enforcement script that:
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**For Host Configuration**:
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- Configures all VMs to use host's DNS resolution (`--natdnshostresolver1 on`)
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- Enables NAT DNS proxy (`--natdnsproxy1 on`)
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- Adds `/etc` as a read-only shared folder to all VMs
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- Tracks enforcement status with marker file
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**For Guest Configuration**:
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- Generates a startup script for VMs
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- Mounts the shared `/etc` folder inside the VM
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- Syncs host's `/etc/hosts` to VM's `/etc/hosts`
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- Makes the hosts file read-only in the VM
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**Commands**:
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```bash
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# Apply enforcement to all VMs
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sudo enforce_vbox_hosts.sh enforce
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# Check enforcement status
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sudo enforce_vbox_hosts.sh status
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# Generate script for VM guests
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sudo enforce_vbox_hosts.sh generate-script
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```
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**Auto-Integration**:
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The pacman wrapper automatically:
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- Detects VirtualBox installation after any install operation
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- Locates and runs the enforcement script
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- Applies enforcement to all existing VMs
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- Creates enforcement marker to avoid repeated runs
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### 4. Installation Integration
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**File**: `scripts/digital_wellbeing/pacman/install_pacman_wrapper.sh`
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The installer now:
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- Installs VirtualBox enforcement script to `/usr/local/share/digital_wellbeing/virtualbox/`
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- Makes the enforcement script executable
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- Reports installation status to user
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## Security Guarantees
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### What's Protected
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1. **Policy files cannot be easily modified**:
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- Immutable attribute prevents casual editing
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- Requires `chattr -i` which requires root and knowledge
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- Changes are detected on next wrapper invocation
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2. **VirtualBox restrictions are hardcoded**:
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- Cannot remove by editing policy files
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- Would require modifying the wrapper code itself
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- Integrity checks would detect wrapper modification
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3. **VMs inherit host's content filtering**:
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- DNS queries use host's resolution
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- /etc/hosts is synced from host to guest
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- Read-only mounting prevents VM modification
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### What's Still Vulnerable
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1. **Root access can bypass everything**:
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- Root can `chattr -i` and modify files
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- Root can edit the wrapper script itself
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- Root can disable enforcement entirely
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- **Mitigation**: Not the goal; this is about self-discipline, not security against root
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2. **Wrapper replacement**:
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- Could replace `/usr/bin/pacman` with direct link to `/usr/bin/pacman.orig`
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- **Mitigation**: Periodic maintenance services can detect and alert
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- Reinstallation would fail integrity check if files are modified
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3. **VM Guest Additions bypass**:
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- If guest doesn't install VBox Guest Additions, shared folders won't work
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- **Mitigation**: DNS proxy still enforces host's DNS resolution
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- Manual hosts file sync would be needed
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## Testing
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Run the test suite:
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```bash
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bash tests/test_pacman_wrapper_security.sh
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```
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Tests verify:
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- Script syntax validity
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- Integrity check function exists and is called
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- Hardcoded VirtualBox check exists
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- VirtualBox challenge function exists
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- Immutable file attributes are set
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- VirtualBox enforcement integration
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## Usage
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### Installation
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```bash
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cd scripts/digital_wellbeing/pacman
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sudo ./install_pacman_wrapper.sh
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```
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This will:
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- Install the wrapper and policy files
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- Generate integrity checksums
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- Make policy files immutable
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- Install VirtualBox enforcement script
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### Updating Policy Files
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If you need to legitimately update policy files:
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```bash
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# Remove immutable attribute
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sudo chattr -i /usr/local/bin/pacman_blocked_keywords.txt
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sudo chattr -i /usr/local/bin/pacman_greylist.txt
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# Edit files as needed
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sudo nano /usr/local/bin/pacman_greylist.txt
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# Reinstall wrapper to update checksums
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cd scripts/digital_wellbeing/pacman
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sudo ./install_pacman_wrapper.sh
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# This will regenerate checksums and reapply immutable attributes
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```
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### VirtualBox Enforcement
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After installing VirtualBox, the wrapper will automatically apply enforcement. You can also manually run:
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```bash
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sudo /usr/local/share/digital_wellbeing/virtualbox/enforce_vbox_hosts.sh enforce
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```
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For VM guests, copy the generated script and add to startup:
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```bash
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# On host
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sudo /usr/local/share/digital_wellbeing/virtualbox/enforce_vbox_hosts.sh generate-script /tmp/vbox_sync.sh
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# Copy to VM and install
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sudo cp /tmp/vbox_sync.sh /usr/local/bin/
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sudo chmod +x /usr/local/bin/vbox_sync.sh
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# Add to crontab or systemd
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@reboot /usr/local/bin/vbox_sync.sh
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```
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## Design Philosophy
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These enhancements follow the principle of **defense in depth**:
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- **Layer 1**: Immutable policy files (prevents casual editing)
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- **Layer 2**: Integrity checksums (detects tampering)
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- **Layer 3**: Hardcoded restrictions (cannot bypass via files)
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- **Layer 4**: VirtualBox enforcement (prevents VM bypass)
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- **Layer 5**: Psychological friction (word challenges, delays)
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Each layer adds difficulty, making circumvention progressively harder while maintaining usability for legitimate use.
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## Future Enhancements
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Potential improvements:
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1. **Digital signatures**: Sign the wrapper script itself to detect modifications
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2. **Remote policy updates**: Fetch policy files from a trusted source
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3. **Logging**: Log all wrapper invocations and challenges to detect patterns
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4. **Time-based restrictions**: Different rules for different times/days
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5. **Multi-factor challenges**: Combine word challenges with other verification methods
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131
tests/test_pacman_wrapper_security.sh
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131
tests/test_pacman_wrapper_security.sh
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#!/bin/bash
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# Test script for pacman wrapper integrity checks and VirtualBox enforcement
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set -e
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SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
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WRAPPER_DIR="$SCRIPT_DIR/../scripts/digital_wellbeing/pacman"
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VBOX_DIR="$SCRIPT_DIR/../scripts/digital_wellbeing/virtualbox"
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echo "=== Testing Pacman Wrapper Security Enhancements ==="
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echo ""
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# Test 1: Check wrapper syntax
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echo "[TEST 1] Checking wrapper script syntax..."
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if bash -n "$WRAPPER_DIR/pacman_wrapper.sh"; then
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echo "✓ Wrapper script syntax is valid"
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else
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echo "✗ Wrapper script has syntax errors"
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exit 1
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fi
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# Test 2: Check installer syntax
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echo "[TEST 2] Checking installer script syntax..."
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if bash -n "$WRAPPER_DIR/install_pacman_wrapper.sh"; then
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echo "✓ Installer script syntax is valid"
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else
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echo "✗ Installer script has syntax errors"
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exit 1
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fi
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# Test 3: Check VirtualBox enforcement script syntax
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echo "[TEST 3] Checking VirtualBox enforcement script syntax..."
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if bash -n "$VBOX_DIR/enforce_vbox_hosts.sh"; then
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echo "✓ VirtualBox enforcement script syntax is valid"
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else
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echo "✗ VirtualBox enforcement script has syntax errors"
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exit 1
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fi
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# Test 4: Verify integrity check function exists
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echo "[TEST 4] Verifying integrity check function exists in wrapper..."
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if grep -q "verify_policy_integrity()" "$WRAPPER_DIR/pacman_wrapper.sh"; then
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echo "✓ Integrity verification function found"
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else
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echo "✗ Integrity verification function not found"
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exit 1
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fi
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# Test 5: Verify hardcoded VirtualBox check exists
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echo "[TEST 5] Verifying hardcoded VirtualBox check exists..."
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if grep -q "is_virtualbox_package()" "$WRAPPER_DIR/pacman_wrapper.sh"; then
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echo "✓ Hardcoded VirtualBox check function found"
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else
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echo "✗ Hardcoded VirtualBox check function not found"
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exit 1
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fi
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# Test 6: Verify VirtualBox challenge function exists
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echo "[TEST 6] Verifying VirtualBox challenge function exists..."
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if grep -q "prompt_for_virtualbox_challenge()" "$WRAPPER_DIR/pacman_wrapper.sh"; then
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echo "✓ VirtualBox challenge function found"
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else
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echo "✗ VirtualBox challenge function not found"
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exit 1
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fi
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# Test 7: Verify integrity check is called early in execution
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echo "[TEST 7] Verifying integrity check is called before operations..."
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if grep -B 2 -A 2 "verify_policy_integrity" "$WRAPPER_DIR/pacman_wrapper.sh" | grep -q "CRITICAL"; then
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echo "✓ Integrity check is called early in execution"
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else
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echo "✗ Integrity check not found in early execution"
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exit 1
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fi
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# Test 8: Verify installer creates integrity file
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echo "[TEST 8] Verifying installer creates integrity checksums..."
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if grep -q "INTEGRITY_FILE" "$WRAPPER_DIR/install_pacman_wrapper.sh"; then
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echo "✓ Installer references integrity file"
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else
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echo "✗ Installer does not create integrity file"
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exit 1
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fi
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# Test 9: Verify installer uses chattr to make files immutable
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echo "[TEST 9] Verifying installer makes policy files immutable..."
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if grep -q "chattr +i" "$WRAPPER_DIR/install_pacman_wrapper.sh"; then
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echo "✓ Installer sets immutable attributes"
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else
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echo "✗ Installer does not set immutable attributes"
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exit 1
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fi
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# Test 10: Verify VirtualBox enforcement is integrated
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echo "[TEST 10] Verifying VirtualBox enforcement is integrated into wrapper..."
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if grep -q "enforce_vbox_hosts_if_needed" "$WRAPPER_DIR/pacman_wrapper.sh"; then
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echo "✓ VirtualBox enforcement integration found"
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else
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echo "✗ VirtualBox enforcement integration not found"
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exit 1
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fi
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# Test 11: Verify VirtualBox script can show help
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echo "[TEST 11] Testing VirtualBox enforcement script help..."
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# Run without invoking sudo by setting EUID check (or just check for the help text in the file)
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if grep -q "VirtualBox /etc/hosts Enforcement Tool" "$VBOX_DIR/enforce_vbox_hosts.sh"; then
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echo "✓ VirtualBox enforcement script has help text"
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else
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echo "✗ VirtualBox enforcement script help text not found"
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exit 1
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fi
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# Test 12: Verify installer installs VirtualBox enforcement script
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echo "[TEST 12] Verifying installer handles VirtualBox enforcement script..."
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if grep -q "VBOX_ENFORCE" "$WRAPPER_DIR/install_pacman_wrapper.sh"; then
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echo "✓ Installer includes VirtualBox enforcement script"
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else
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echo "✗ Installer does not include VirtualBox enforcement script"
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exit 1
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fi
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echo ""
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echo "=== All Tests Passed! ==="
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echo ""
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echo "Summary of security enhancements:"
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echo " ✓ Policy files are protected with SHA256 checksums"
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echo " ✓ Integrity checks run on every wrapper invocation"
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echo " ✓ Policy files are made immutable with chattr +i"
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echo " ✓ VirtualBox has hardcoded restrictions (cannot bypass via file editing)"
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echo " ✓ VirtualBox VMs are automatically configured to use host's /etc/hosts"
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echo " ✓ Difficult word challenge for VirtualBox installation (7-letter words, 150 words, 120s)"
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