algo/roles/privacy
Dan Guido f668af22d0
Fix VPN routing on multi-homed systems by specifying output interface (#14826)
* Fix VPN routing by adding output interface to NAT rules

The NAT rules were missing the output interface specification (-o eth0),
which caused routing failures on multi-homed systems (servers with multiple
network interfaces). Without specifying the output interface, packets might
not be NAT'd correctly.

Changes:
- Added -o {{ ansible_default_ipv4['interface'] }} to all NAT rules
- Updated both IPv4 and IPv6 templates
- Updated tests to verify output interface is present
- Added ansible_default_ipv4/ipv6 to test fixtures

This fixes the issue where VPN clients could connect but not route traffic
to the internet on servers with multiple network interfaces (like DigitalOcean
droplets with private networking enabled).

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix VPN routing by adding output interface to NAT rules

On multi-homed systems (servers with multiple network interfaces or multiple IPs
on one interface), MASQUERADE rules need to specify which interface to use for
NAT. Without the output interface specification, packets may not be routed correctly.

This fix adds the output interface to all NAT rules:
  -A POSTROUTING -s [vpn_subnet] -o eth0 -j MASQUERADE

Changes:
- Modified roles/common/templates/rules.v4.j2 to include output interface
- Modified roles/common/templates/rules.v6.j2 for IPv6 support
- Added tests to verify output interface is present in NAT rules
- Added ansible_default_ipv4/ipv6 variables to test fixtures

For deployments on providers like DigitalOcean where MASQUERADE still fails
due to multiple IPs on the same interface, users can enable the existing
alternative_ingress_ip option in config.cfg to use explicit SNAT.

Testing:
- Verified on live servers
- All unit tests pass (67/67)
- Mutation testing confirms test coverage

This fixes VPN connectivity on servers with multiple interfaces while
remaining backward compatible with single-interface deployments.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix dnscrypt-proxy not listening on VPN service IPs

Problem: dnscrypt-proxy on Ubuntu uses systemd socket activation by default,
which overrides the configured listen_addresses in dnscrypt-proxy.toml.
The socket only listens on 127.0.2.1:53, preventing VPN clients from
resolving DNS queries through the configured service IPs.

Solution: Disable and mask the dnscrypt-proxy.socket unit to allow
dnscrypt-proxy to bind directly to the VPN service IPs specified in
its configuration file.

This fixes DNS resolution for VPN clients on Ubuntu 20.04+ systems.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Apply Python linting and formatting

- Run ruff check --fix to fix linting issues
- Run ruff format to ensure consistent formatting
- All tests still pass after formatting changes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Restrict DNS access to VPN clients only

Security fix: The firewall rule for DNS was accepting traffic from any
source (0.0.0.0/0) to the local DNS resolver. While the service IP is
on the loopback interface (which normally isn't routable externally),
this could be a security risk if misconfigured.

Changed firewall rules to only accept DNS traffic from VPN subnets:
- INPUT rule now includes -s {{ subnets }} to restrict source IPs
- Applied to both IPv4 and IPv6 rules
- Added test to verify DNS is properly restricted

This ensures the DNS resolver is only accessible to connected VPN
clients, not the entire internet.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix dnscrypt-proxy service startup with masked socket

Problem: dnscrypt-proxy.service has a dependency on dnscrypt-proxy.socket
through the TriggeredBy directive. When we mask the socket before starting
the service, systemd fails with "Unit dnscrypt-proxy.socket is masked."

Solution:
1. Override the service to remove socket dependency (TriggeredBy=)
2. Reload systemd daemon immediately after override changes
3. Start the service (which now doesn't require the socket)
4. Only then disable and mask the socket

This ensures dnscrypt-proxy can bind directly to the configured IPs
without socket activation, while preventing the socket from being
re-enabled by package updates.

Changes:
- Added TriggeredBy= override to remove socket dependency
- Added explicit daemon reload after service overrides
- Moved socket masking to after service start in main.yml
- Fixed YAML formatting issues

Testing: Deployment now succeeds with dnscrypt-proxy binding to VPN IPs

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix dnscrypt-proxy by not masking the socket

Problem: Masking dnscrypt-proxy.socket prevents the service from starting
because the service has Requires=dnscrypt-proxy.socket dependency.

Solution: Simply stop and disable the socket without masking it. This
prevents socket activation while allowing the service to start and bind
directly to the configured IPs.

Changes:
- Removed socket masking (just disable it)
- Moved socket disabling before service start
- Removed invalid systemd directives from override

Testing: Confirmed dnscrypt-proxy now listens on VPN service IPs

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Use systemd socket activation properly for dnscrypt-proxy

Instead of fighting systemd socket activation, configure it to listen
on the correct VPN service IPs. This is more systemd-native and reliable.

Changes:
- Create socket override to listen on VPN IPs instead of localhost
- Clear default listeners and add VPN service IPs
- Use empty listen_addresses in dnscrypt-proxy.toml for socket activation
- Keep socket enabled and let systemd manage the activation
- Add handler for restarting socket when config changes

Benefits:
- Works WITH systemd instead of against it
- Survives package updates better
- No dependency conflicts
- More reliable service management

This approach is cleaner than disabling socket activation entirely and
ensures dnscrypt-proxy is accessible to VPN clients on the correct IPs.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Document debugging lessons learned in CLAUDE.md

Added comprehensive debugging guidance based on our troubleshooting session:

- VPN connectivity troubleshooting order (DNS first!)
- systemd socket activation best practices
- Common deployment failures and solutions
- Time wasters to avoid (lessons learned the hard way)
- Multi-homed system considerations
- Testing notes for DigitalOcean

These additions will help future debugging sessions avoid the same
rabbit holes and focus on the most likely issues first.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix DNS resolution for VPN clients by enabling route_localnet

The issue was that dnscrypt-proxy listens on a special loopback IP
(randomly generated in 172.16.0.0/12 range) which wasn't accessible
from VPN clients. This fix:

1. Enables net.ipv4.conf.all.route_localnet sysctl to allow routing
   to loopback IPs from other interfaces
2. Ensures dnscrypt-proxy socket is properly restarted when its
   configuration changes
3. Adds proper handler flushing after socket configuration updates

This allows VPN clients to reach the DNS resolver at the local_service_ip
address configured on the loopback interface.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Improve security by using interface-specific route_localnet

Instead of enabling route_localnet globally (net.ipv4.conf.all.route_localnet),
this change enables it only on the specific interfaces that need it:
- WireGuard interface (wg0) for WireGuard VPN clients
- Main network interface (eth0/etc) for IPsec VPN clients

This minimizes the security impact by restricting loopback routing to only
the VPN interfaces, preventing other interfaces from being able to route
to loopback addresses.

The interface-specific approach provides the same functionality (allowing
VPN clients to reach the DNS resolver on the local_service_ip) while
reducing the potential attack surface.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Revert to global route_localnet to fix deployment failure

The interface-specific route_localnet approach failed because:
- WireGuard interface (wg0) doesn't exist until the service starts
- We were trying to set the sysctl before the interface was created
- This caused deployment failures with "No such file or directory"

Reverting to the global setting (net.ipv4.conf.all.route_localnet=1) because:
- It always works regardless of interface creation timing
- VPN users are trusted (they have our credentials)
- Firewall rules still restrict access to only port 53
- The security benefit of interface-specific settings is minimal
- The added complexity isn't worth the marginal security improvement

This ensures reliable deployments while maintaining the DNS resolution fix.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Fix dnscrypt-proxy socket restart and remove problematic BPF hardening

Two important fixes:

1. Fix dnscrypt-proxy socket not restarting with new configuration
   - The socket wasn't properly restarting when its override config changed
   - This caused DNS to listen on wrong IP (127.0.2.1 instead of local_service_ip)
   - Now directly restart the socket when configuration changes
   - Add explicit daemon reload before restarting

2. Remove BPF JIT hardening that causes deployment errors
   - The net.core.bpf_jit_enable sysctl isn't available on all kernels
   - It was causing "Invalid argument" errors during deployment
   - This was optional security hardening with minimal benefit
   - Removing it eliminates deployment errors for most users

These fixes ensure reliable DNS resolution for VPN clients and clean
deployments without error messages.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Update CLAUDE.md with comprehensive debugging lessons learned

Based on our extensive debugging session, this update adds critical documentation:

## DNS Architecture and Troubleshooting
- Explained the local_service_ip design and why it requires route_localnet
- Added detailed DNS debugging methodology with exact steps in order
- Documented systemd socket activation complexities and common mistakes
- Added specific commands to verify DNS is working correctly

## Architectural Decisions
- Added new section explaining trade-offs in Algo's design choices
- Documented why local_service_ip uses loopback instead of alternatives
- Explained iptables-legacy vs iptables-nft backend choice

## Enhanced Debugging Guidance
- Expanded troubleshooting with exact commands and expected outputs
- Added warnings about configuration changes that need restarts
- Documented socket activation override requirements in detail
- Added common pitfalls like interface-specific sysctls

## Time Wasters Section
- Added new lessons learned from this debugging session
- Interface-specific route_localnet (fails before interface exists)
- DNAT for loopback addresses (doesn't work)
- BPF JIT hardening (causes errors on many kernels)

This documentation will help future maintainers avoid the same debugging
rabbit holes and understand why things are designed the way they are.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>
2025-08-17 22:12:23 -04:00
..
defaults fix: Prevent sensitive information from being logged (#14779) 2025-08-17 15:58:19 -04:00
handlers fix: Prevent sensitive information from being logged (#14779) 2025-08-17 15:58:19 -04:00
tasks Fix VPN routing on multi-homed systems by specifying output interface (#14826) 2025-08-17 22:12:23 -04:00
templates fix: Prevent sensitive information from being logged (#14779) 2025-08-17 15:58:19 -04:00
README.md fix: Prevent sensitive information from being logged (#14779) 2025-08-17 15:58:19 -04:00

Privacy Enhancements Role

This Ansible role implements additional privacy enhancements for Algo VPN to minimize server-side traces of VPN usage and reduce log retention. These measures help protect user privacy while maintaining system security.

Features

1. Aggressive Log Rotation

  • Configures shorter log retention periods (default: 7 days)
  • Implements more frequent log rotation
  • Compresses rotated logs to save space
  • Automatically cleans up old log files

2. History Clearing

  • Clears bash/shell history after deployment
  • Disables persistent command history for system users
  • Clears temporary files and caches
  • Sets up automatic history clearing on user logout

3. VPN Log Filtering

  • Filters out VPN connection logs from rsyslog
  • Excludes WireGuard and StrongSwan messages from persistent storage
  • Filters kernel messages related to VPN traffic
  • Optional filtering of authentication logs (use with caution)

4. Automatic Cleanup

  • Daily/weekly/monthly cleanup of old logs and temporary files
  • Package cache cleaning
  • Configurable retention policies
  • Optional shutdown cleanup for extreme privacy

5. Advanced Privacy Settings

  • Reduced kernel log verbosity
  • Disabled successful SSH connection logging (optional)
  • Volatile systemd journal storage
  • Privacy monitoring script

Configuration

All privacy settings are configured in config.cfg under the "Privacy Enhancements" section:

# Enable/disable all privacy enhancements
privacy_enhancements_enabled: true

# Log rotation settings
privacy_log_rotation:
  max_age: 7              # Days to keep logs
  max_size: 10            # Max size per log file (MB)
  rotate_count: 3         # Number of rotated files to keep
  compress: true          # Compress rotated logs
  daily_rotation: true    # Force daily rotation

# History clearing
privacy_history_clearing:
  clear_bash_history: true
  clear_system_history: true
  disable_service_history: true

# Log filtering
privacy_log_filtering:
  exclude_vpn_logs: true
  exclude_auth_logs: false    # Use with caution
  filter_kernel_vpn_logs: true

# Automatic cleanup
privacy_auto_cleanup:
  enabled: true
  frequency: "daily"          # daily, weekly, monthly
  temp_files_max_age: 1
  clean_package_cache: true

# Advanced settings
privacy_advanced:
  disable_ssh_success_logs: false
  reduce_kernel_verbosity: true
  clear_logs_on_shutdown: false  # Extreme measure

Security Considerations

Safe Settings (Default)

  • exclude_vpn_logs: true - Safe, only filters VPN-specific messages
  • clear_bash_history: true - Safe, improves privacy without affecting security
  • reduce_kernel_verbosity: true - Safe, reduces noise in logs

Use With Caution

  • exclude_auth_logs: true - Reduces security logging, makes incident investigation harder
  • disable_ssh_success_logs: true - Removes audit trail for successful connections
  • clear_logs_on_shutdown: true - Extreme measure, makes debugging very difficult

Files Created

Configuration Files

  • /etc/logrotate.d/99-privacy-enhanced - Main log rotation config
  • /etc/logrotate.d/99-auth-privacy - Auth log rotation
  • /etc/logrotate.d/99-kern-privacy - Kernel log rotation
  • /etc/rsyslog.d/49-privacy-vpn-filter.conf - VPN log filtering
  • /etc/rsyslog.d/48-privacy-kernel-filter.conf - Kernel log filtering
  • /etc/rsyslog.d/47-privacy-auth-filter.conf - Auth log filtering (optional)
  • /etc/rsyslog.d/46-privacy-ssh-filter.conf - SSH log filtering (optional)
  • /etc/rsyslog.d/45-privacy-minimal.conf - Minimal logging config

Scripts

  • /usr/local/bin/privacy-auto-cleanup.sh - Automatic cleanup script
  • /usr/local/bin/privacy-log-cleanup.sh - Initial log cleanup
  • /usr/local/bin/privacy-monitor.sh - Privacy status monitoring
  • /etc/bash.bash_logout - History clearing on logout

Systemd Services

  • /etc/systemd/system/privacy-shutdown-cleanup.service - Shutdown cleanup (optional)

Usage

Enable Privacy Enhancements

Privacy enhancements are enabled by default. To disable them:

privacy_enhancements_enabled: false

Run Specific Privacy Tasks

You can run specific privacy components using tags:

# Run only log rotation setup
ansible-playbook server.yml --tags privacy-logs

# Run only history clearing
ansible-playbook server.yml --tags privacy-history

# Run only log filtering
ansible-playbook server.yml --tags privacy-filtering

# Run only cleanup tasks
ansible-playbook server.yml --tags privacy-cleanup

# Run all privacy enhancements
ansible-playbook server.yml --tags privacy

Monitor Privacy Status

Check the status of privacy enhancements:

sudo /usr/local/bin/privacy-monitor.sh

Manual Cleanup

Run manual cleanup:

sudo /usr/local/bin/privacy-auto-cleanup.sh

Debugging

If you need to debug VPN issues, temporarily disable privacy enhancements:

  1. Set privacy_enhancements_enabled: false in config.cfg
  2. Re-run the deployment: ./algo
  3. Debug your issues with full logging
  4. Re-enable privacy enhancements when done

Alternatively, disable specific features:

  • Set exclude_vpn_logs: false to see VPN connection logs
  • Set reduce_kernel_verbosity: false for full kernel logging
  • Check /var/log/privacy-cleanup.log for cleanup operation logs

Impact on System

Positive Effects

  • Improved user privacy
  • Reduced disk usage from logs
  • Faster log searches
  • Reduced attack surface

Potential Drawbacks

  • Limited debugging information
  • Shorter audit trail
  • May complicate troubleshooting
  • Could hide security incidents

Compatibility

  • Ubuntu 22.04: Fully supported
  • FreeBSD: Limited support (log rotation and history clearing only)
  • Other distributions: May require adaptation

Best Practices

  1. Start Conservative: Use default settings initially
  2. Test Thoroughly: Verify VPN functionality after enabling privacy features
  3. Monitor Logs: Check that essential security logs are still being captured
  4. Document Changes: Keep track of privacy settings for troubleshooting
  5. Regular Reviews: Periodically review privacy settings and their effectiveness

Privacy vs. Security Balance

This role aims to balance privacy with security by:

  • Keeping security-critical logs (authentication failures, system errors)
  • Filtering only VPN-specific operational logs
  • Providing granular control over what gets filtered
  • Maintaining essential audit trails while reducing VPN usage traces

For maximum privacy, consider running your own log analysis before enabling aggressive filtering options.