ProxmoxVED/docs/TECHNICAL_REFERENCE.md

Technical Reference: Configuration System Architecture

For Developers and Advanced Users

Deep dive into how the defaults and configuration system works

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Table of Contents

1. System Architecture
2. File Format Specifications
3. Function Reference
4. Variable Precedence
5. Data Flow Diagrams
6. Security Model
7. Implementation Details

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System Architecture

Component Overview

┌─────────────────────────────────────────────────────────────┐
│                    Installation Script                       │
│  (pihole-install.sh, docker-install.sh, etc.)              │
└────────────────────┬────────────────────────────────────────┘
                     │
                     v
┌─────────────────────────────────────────────────────────────┐
│                   build.func Library                         │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  variables()                                         │   │
│  │  - Initialize NSAPP, var_install, etc.             │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  install_script()                                    │   │
│  │  - Display mode menu                                │   │
│  │  - Route to appropriate workflow                    │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  base_settings()                                     │   │
│  │  - Apply built-in defaults                          │   │
│  │  - Read environment variables (var_*)               │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  load_vars_file()                                    │   │
│  │  - Safe file parsing (NO source/eval)              │   │
│  │  - Whitelist validation                             │   │
│  │  - Value sanitization                               │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  default_var_settings()                              │   │
│  │  - Load user defaults                               │   │
│  │  - Display summary                                  │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  maybe_offer_save_app_defaults()                     │   │
│  │  - Offer to save current settings                   │   │
│  │  - Handle updates vs. new saves                     │   │
│  └──────────────────────────────────────────────────────┘   │
└─────────────────────────────────────────────────────────────┘
                     │
                     v
┌─────────────────────────────────────────────────────────────┐
│           Configuration Files (on Disk)                      │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  /usr/local/community-scripts/default.vars          │   │
│  │  (User global defaults)                             │   │
│  └──────────────────────────────────────────────────────┘   │
│  ┌──────────────────────────────────────────────────────┐   │
│  │  /usr/local/community-scripts/defaults/*.vars       │   │
│  │  (App-specific defaults)                            │   │
│  └──────────────────────────────────────────────────────┘   │
└─────────────────────────────────────────────────────────────┘

---

File Format Specifications

User Defaults: default.vars

Location: /usr/local/community-scripts/default.vars

MIME Type: text/plain

Encoding: UTF-8 (no BOM)

Format Specification:

# File Format: Simple key=value pairs
# Purpose: Store global user defaults
# Security: Sanitized values, whitelist validation

# Comments and blank lines are ignored
# Line format: var_name=value
# No spaces around the equals sign
# String values do not need quoting (but may be quoted)

[CONTENT]
var_cpu=4
var_ram=2048
var_disk=20
var_hostname=mydefault
var_brg=vmbr0
var_gateway=192.168.1.1

Formal Grammar:

FILE       := (BLANK_LINE | COMMENT_LINE | VAR_LINE)*
BLANK_LINE := \n
COMMENT_LINE := '#' [^\n]* \n
VAR_LINE   := VAR_NAME '=' VAR_VALUE \n
VAR_NAME   := 'var_' [a-z_]+
VAR_VALUE  := [^\n]*  # Any printable characters except newline

Constraints:

Constraint	Value
Max file size	64 KB
Max line length	1024 bytes
Max variables	100
Allowed var names	var_[a-z_]+
Value validation	Whitelist + Sanitization

Example Valid File:

# Global User Defaults
# Created: 2024-11-28

# Resource defaults
var_cpu=4
var_ram=2048
var_disk=20

# Network defaults
var_brg=vmbr0
var_gateway=192.168.1.1
var_mtu=1500
var_vlan=100

# System defaults
var_timezone=Europe/Berlin
var_hostname=default-container

# Storage
var_container_storage=local
var_template_storage=local

# Security
var_ssh=yes
var_protection=0
var_unprivileged=1

App Defaults: <app>.vars

Location: /usr/local/community-scripts/defaults/<appname>.vars

Format: Identical to default.vars

Naming Convention: <nsapp>.vars

• nsapp = lowercase app name with spaces removed
• Examples:
  • pihole → pihole.vars
  • opnsense → opnsense.vars
  • docker compose → dockercompose.vars

Example App Defaults:

# App-specific defaults for PiHole (pihole)
# Generated on 2024-11-28T15:32:00Z
# These override user defaults when installing pihole

var_unprivileged=1
var_cpu=2
var_ram=1024
var_disk=10
var_brg=vmbr0
var_net=veth
var_gateway=192.168.1.1
var_hostname=pihole
var_timezone=Europe/Berlin
var_container_storage=local
var_template_storage=local
var_tags=dns,pihole

---

Function Reference

load_vars_file()

Purpose: Safely load variables from .vars files without using source or eval

Signature:

load_vars_file(filepath)

Parameters:

Param	Type	Required	Example
filepath	String	Yes	/usr/local/community-scripts/default.vars

Returns:

• 0 on success
• 1 on error (file missing, parse error, etc.)

Environment Side Effects:

• Sets all parsed var_* variables as shell variables
• Does NOT unset variables if file missing (safe)
• Does NOT affect other variables

Implementation Pattern:

load_vars_file() {
  local file="$1"
  
  # File must exist
  [ -f "$file" ] || return 0
  
  # Parse line by line (not with source/eval)
  local line key val
  while IFS='=' read -r key val || [ -n "$key" ]; do
    # Skip comments and empty lines
    [[ "$key" =~ ^[[:space:]]*# ]] && continue
    [[ -z "$key" ]] && continue
    
    # Validate key is in whitelist
    _is_whitelisted_key "$key" || continue
    
    # Sanitize and export value
    val="$(_sanitize_value "$val")"
    [ $? -eq 0 ] && export "$key=$val"
  done < "$file"
  
  return 0
}

Usage Examples:

# Load user defaults
load_vars_file "/usr/local/community-scripts/default.vars"

# Load app-specific defaults
load_vars_file "$(get_app_defaults_path)"

# Check if successful
if load_vars_file "$vars_path"; then
  echo "Settings loaded successfully"
else
  echo "Failed to load settings"
fi

# Values are now available as variables
echo "Using $var_cpu cores"
echo "Allocating ${var_ram} MB RAM"

---

get_app_defaults_path()

Purpose: Get the full path for app-specific defaults file

Signature:

get_app_defaults_path()

Parameters: None

Returns:

• String: Full path to app defaults file

Implementation:

get_app_defaults_path() {
  local n="${NSAPP:-${APP,,}}"
  echo "/usr/local/community-scripts/defaults/${n}.vars"
}

Usage Examples:

# Get app defaults path
app_defaults="$(get_app_defaults_path)"
echo "App defaults at: $app_defaults"

# Check if app defaults exist
if [ -f "$(get_app_defaults_path)" ]; then
  echo "App defaults available"
fi

# Load app defaults
load_vars_file "$(get_app_defaults_path)"

---

default_var_settings()

Purpose: Load and display user global defaults

Signature:

default_var_settings()

Parameters: None

Returns:

• 0 on success
• 1 on error

Workflow:

1. Find default.vars location
   (usually /usr/local/community-scripts/default.vars)
   
2. Create if missing
   
3. Load variables from file
   
4. Map var_verbose → VERBOSE variable
   
5. Call base_settings (apply to container config)
   
6. Call echo_default (display summary)

Implementation Pattern:

default_var_settings() {
  local VAR_WHITELIST=(
    var_apt_cacher var_apt_cacher_ip var_brg var_cpu var_disk var_fuse
    var_gateway var_hostname var_ipv6_method var_mac var_mtu
    var_net var_ns var_pw var_ram var_tags var_tun var_unprivileged
    var_verbose var_vlan var_ssh var_ssh_authorized_key
    var_container_storage var_template_storage
  )
  
  # Ensure file exists
  _ensure_default_vars
  
  # Find and load
  local dv="$(_find_default_vars)"
  load_vars_file "$dv"
  
  # Map verbose flag
  if [[ -n "${var_verbose:-}" ]]; then
    case "${var_verbose,,}" in
      1 | yes | true | on) VERBOSE="yes" ;;
      *) VERBOSE="${var_verbose}" ;;
    esac
  fi
  
  # Apply and display
  base_settings "$VERBOSE"
  echo_default
}

---

maybe_offer_save_app_defaults()

Purpose: Offer to save current settings as app-specific defaults

Signature:

maybe_offer_save_app_defaults()

Parameters: None

Returns: None (side effects only)

Behavior:

1. After advanced installation completes
2. Offers user: "Save as App Defaults for ?"
3. If yes:
   • Saves to /usr/local/community-scripts/defaults/<app>.vars
   • Only whitelisted variables included
   • Previous defaults backed up (if exists)
4. If no:
   • No action taken

Flow:

maybe_offer_save_app_defaults() {
  local app_vars_path="$(get_app_defaults_path)"
  
  # Build current settings from memory
  local new_tmp="$(_build_current_app_vars_tmp)"
  
  # Check if already exists
  if [ -f "$app_vars_path" ]; then
    # Show diff and ask: Update? Keep? View Diff?
    _show_app_defaults_diff_menu "$new_tmp" "$app_vars_path"
  else
    # New defaults - just save
    if whiptail --yesno "Save as App Defaults for $APP?" 10 60; then
      mv "$new_tmp" "$app_vars_path"
      chmod 644 "$app_vars_path"
    fi
  fi
}

---

_sanitize_value()

Purpose: Remove dangerous characters/patterns from configuration values

Signature:

_sanitize_value(value)

Parameters:

Param	Type	Required
value	String	Yes

Returns:

• 0 (success) + sanitized value on stdout
• 1 (failure) + nothing if dangerous

Dangerous Patterns:

Pattern	Threat	Example
$(...)	Command substitution	$(rm -rf /)
` `	Command substitution	`whoami`
;	Command separator	value; rm -rf /
&	Background execution	value & malicious
<(	Process substitution	<(cat /etc/passwd)

Implementation:

_sanitize_value() {
  case "$1" in
  *'$('* | *'`'* | *';'* | *'&'* | *'<('*)
    echo ""
    return 1  # Reject dangerous value
    ;;
  esac
  echo "$1"
  return 0
}

Usage Examples:

# Safe value
_sanitize_value "192.168.1.1"  # Returns: 192.168.1.1 (status: 0)

# Dangerous value
_sanitize_value "$(whoami)"     # Returns: (empty) (status: 1)

# Usage in code
if val="$(_sanitize_value "$user_input")"; then
  export var_hostname="$val"
else
  msg_error "Invalid value: contains dangerous characters"
fi

---

_is_whitelisted_key()

Purpose: Check if variable name is in allowed whitelist

Signature:

_is_whitelisted_key(key)

Parameters:

Param	Type	Required	Example
key	String	Yes	var_cpu

Returns:

• 0 if key is whitelisted
• 1 if key is NOT whitelisted

Implementation:

_is_whitelisted_key() {
  local k="$1"
  local w
  for w in "${VAR_WHITELIST[@]}"; do
    [ "$k" = "$w" ] && return 0
  done
  return 1
}

Usage Examples:

# Check if variable can be saved
if _is_whitelisted_key "var_cpu"; then
  echo "var_cpu can be saved"
fi

# Reject unknown variables
if ! _is_whitelisted_key "var_custom"; then
  msg_error "var_custom is not supported"
fi

---

Variable Precedence

Loading Order

When a container is being created, variables are resolved in this order:

Step 1: Read ENVIRONMENT VARIABLES
   ├─ Check if var_cpu is already set in shell environment
   ├─ Check if var_ram is already set
   └─ ...all var_* variables

Step 2: Load APP-SPECIFIC DEFAULTS
   ├─ Check if /usr/local/community-scripts/defaults/pihole.vars exists
   ├─ Load all var_* from that file
   └─ These override built-ins but NOT environment variables

Step 3: Load USER GLOBAL DEFAULTS
   ├─ Check if /usr/local/community-scripts/default.vars exists
   ├─ Load all var_* from that file
   └─ These override built-ins but NOT app-specific

Step 4: Use BUILT-IN DEFAULTS
   └─ Hardcoded in script (lowest priority)

Precedence Examples

Example 1: Environment Variable Wins

# Shell environment has highest priority
$ export var_cpu=16
$ bash pihole-install.sh

# Result: Container gets 16 cores
# (ignores app defaults, user defaults, built-ins)

Example 2: App Defaults Override User Defaults

# User Defaults: var_cpu=4
# App Defaults: var_cpu=2
$ bash pihole-install.sh

# Result: Container gets 2 cores
# (app-specific setting takes precedence)

Example 3: All Defaults Missing (Built-ins Used)

# No environment variables set
# No app defaults file
# No user defaults file
$ bash pihole-install.sh

# Result: Uses built-in defaults
# (var_cpu might be 2 by default)

Implementation in Code

# Typical pattern in build.func

base_settings() {
  # Priority 1: Environment variables (already set if export used)
  CT_TYPE=${var_unprivileged:-"1"}          # Use existing or default
  
  # Priority 2: Load app defaults (may override above)
  if [ -f "$(get_app_defaults_path)" ]; then
    load_vars_file "$(get_app_defaults_path)"
  fi
  
  # Priority 3: Load user defaults
  if [ -f "/usr/local/community-scripts/default.vars" ]; then
    load_vars_file "/usr/local/community-scripts/default.vars"
  fi
  
  # Priority 4: Apply built-in defaults (lowest)
  CORE_COUNT=${var_cpu:-"${APP_CPU_DEFAULT:-2}"}
  RAM_SIZE=${var_ram:-"${APP_RAM_DEFAULT:-1024}"}
  
  # Result: var_cpu has been set through precedence chain
}

---

Data Flow Diagrams

Installation Flow: Advanced Settings

┌──────────────┐
│  Start Script│
└──────┬───────┘
       │
       v
┌──────────────────────────────┐
│ Display Installation Mode    │
│ Menu (5 options)             │
└──────┬───────────────────────┘
       │ User selects "Advanced Settings"
       v
┌──────────────────────────────────┐
│ Call: base_settings()            │
│ (Apply built-in defaults)        │
└──────┬───────────────────────────┘
       │
       v
┌──────────────────────────────────┐
│ Call: advanced_settings()        │
│ (Show 19-step wizard)            │
│ - Ask CPU, RAM, Disk, Network... │
└──────┬───────────────────────────┘
       │
       v
┌──────────────────────────────────┐
│ Show Summary                     │
│ Review all chosen values         │
└──────┬───────────────────────────┘
       │ User confirms
       v
┌──────────────────────────────────┐
│ Create Container                 │
│ Using current variable values    │
└──────┬───────────────────────────┘
       │
       v
┌──────────────────────────────────┐
│ Installation Complete            │
└──────┬───────────────────────────┘
       │
       v
┌──────────────────────────────────────┐
│ Offer: Save as App Defaults?         │
│ (Save current settings)              │
└──────┬───────────────────────────────┘
       │
       ├─ YES → Save to defaults/<app>.vars
       │
       └─ NO  → Exit

Variable Resolution Flow

CONTAINER CREATION STARTED
         │
         v
   ┌─────────────────────┐
   │ Check ENVIRONMENT   │
   │ for var_cpu, var_..│
   └──────┬──────────────┘
          │ Found? Use them (Priority 1)
          │ Not found? Continue...
          v
   ┌──────────────────────────┐
   │ Load App Defaults        │
   │ /defaults/<app>.vars     │
   └──────┬───────────────────┘
          │ File exists? Parse & load (Priority 2)
          │ Not found? Continue...
          v
   ┌──────────────────────────┐
   │ Load User Defaults       │
   │ /default.vars            │
   └──────┬───────────────────┘
          │ File exists? Parse & load (Priority 3)
          │ Not found? Continue...
          v
   ┌──────────────────────────┐
   │ Use Built-in Defaults    │
   │ (Hardcoded values)       │
   └──────┬───────────────────┘
          │
          v
   ┌──────────────────────────┐
   │ All Variables Resolved   │
   │ Ready for container      │
   │ creation                 │
   └──────────────────────────┘

---

Security Model

Threat Model

Threat	Mitigation
Arbitrary Code Execution	No source or eval; manual parsing only
Variable Injection	Whitelist of allowed variable names
Command Substitution	_sanitize_value() blocks $(), backticks, etc.
Path Traversal	Files locked to /usr/local/community-scripts/
Permission Escalation	Files created with restricted permissions
Information Disclosure	Sensitive variables not logged

Security Controls

1. Input Validation

# Only specific variables allowed
if ! _is_whitelisted_key "$key"; then
  skip_this_variable
fi

# Values sanitized
if ! val="$(_sanitize_value "$value")"; then
  reject_entire_line
fi

2. Safe File Parsing

# ❌ DANGEROUS (OLD)
source /path/to/config.conf
# Could execute: rm -rf / or any code

# ✅ SAFE (NEW)
load_vars_file "/path/to/config.conf"
# Only reads var_name=value pairs, no execution

3. Whitelisting

# Only these variables can be configured
var_cpu, var_ram, var_disk, var_brg, ...
var_hostname, var_pw, var_ssh, ...

# NOT allowed:
var_malicious, var_hack, custom_var, ...

4. Value Constraints

# No command injection patterns
if [[ "$value" =~ ($|`|;|&|<\() ]]; then
  reject_value
fi

---

Implementation Details

Module: build.func

Load Order (in actual scripts):

1. #!/usr/bin/env bash - Shebang
2. source /dev/stdin <<<$(curl ... api.func) - API functions
3. source /dev/stdin <<<$(curl ... build.func) - Build functions
4. variables() - Initialize variables
5. check_root() - Security check
6. install_script() - Main flow

Key Sections:

# Section 1: Initialization & Variables
- variables()
- NSAPP, var_install, INTEGER pattern, etc.

# Section 2: Storage Management
- storage_selector()
- ensure_storage_selection_for_vars_file()

# Section 3: Base Settings
- base_settings()          # Apply defaults to all var_*
- echo_default()           # Display current settings

# Section 4: Variable Loading
- load_vars_file()         # Safe parsing
- _is_whitelisted_key()    # Validation
- _sanitize_value()        # Threat mitigation

# Section 5: Defaults Management
- default_var_settings()   # Load user defaults
- get_app_defaults_path()  # Get app defaults path
- maybe_offer_save_app_defaults()  # Save option

# Section 6: Installation Flow
- install_script()         # Main entry point
- advanced_settings()      # 19-step wizard

Regex Patterns Used

Pattern	Purpose	Example Match
^[0-9]+([.][0-9]+)?$	Integer validation	4, 192.168
^var_[a-z_]+$	Variable name	var_cpu, var_ssh
*'$('*	Command substitution	$(whoami)
*\*`	Backtick substitution	`cat /etc/passwd`

---

Appendix: Migration Reference

Old Pattern (Deprecated)

# ❌ OLD: config-file.func
source config-file.conf          # Executes arbitrary code
if [ "$USE_DEFAULTS" = "yes" ]; then
  apply_settings_directly
fi

New Pattern (Current)

# ✅ NEW: load_vars_file()
if load_vars_file "$(get_app_defaults_path)"; then
  echo "Settings loaded securely"
fi

Function Mapping

Old	New	Location
read_config()	load_vars_file()	build.func
write_config()	_build_current_app_vars_tmp()	build.func
None	maybe_offer_save_app_defaults()	build.func
None	get_app_defaults_path()	build.func

---

End of Technical Reference