Read Settings Hook

1#!/bin/bash
2# Example hook that reads plugin settings from .claude/my-plugin.local.md
3# Demonstrates the complete pattern for settings-driven hook behavior
4
5set -euo pipefail
6
7# Define settings file path
8SETTINGS_FILE=".claude/my-plugin.local.md"
9
10# Quick exit if settings file doesn't exist
11if [[ ! -f "$SETTINGS_FILE" ]]; then
12  # Plugin not configured - use defaults or skip
13  exit 0
14fi
15
16# Parse YAML frontmatter (everything between --- markers)
17FRONTMATTER=$(sed -n '/^---$/,/^---$/{ /^---$/d; p; }' "$SETTINGS_FILE")
18
19# Extract configuration fields
20ENABLED=$(echo "$FRONTMATTER" | grep '^enabled:' | sed 's/enabled: *//' | sed 's/^"\(.*\)"$/\1/')
21STRICT_MODE=$(echo "$FRONTMATTER" | grep '^strict_mode:' | sed 's/strict_mode: *//' | sed 's/^"\(.*\)"$/\1/')
22MAX_SIZE=$(echo "$FRONTMATTER" | grep '^max_file_size:' | sed 's/max_file_size: *//')
23
24# Quick exit if disabled
25if [[ "$ENABLED" != "true" ]]; then
26  exit 0
27fi
28
29# Read hook input
30input=$(cat)
31file_path=$(echo "$input" | jq -r '.tool_input.file_path // empty')
32
33# Apply configured validation
34if [[ "$STRICT_MODE" == "true" ]]; then
35  # Strict mode: apply all checks
36  if [[ "$file_path" == *".."* ]]; then
37    echo '{"hookSpecificOutput": {"permissionDecision": "deny"}, "systemMessage": "Path traversal blocked (strict mode)"}' >&2
38    exit 2
39  fi
40
41  if [[ "$file_path" == *".env"* ]] || [[ "$file_path" == *"secret"* ]]; then
42    echo '{"hookSpecificOutput": {"permissionDecision": "deny"}, "systemMessage": "Sensitive file blocked (strict mode)"}' >&2
43    exit 2
44  fi
45else
46  # Standard mode: basic checks only
47  if [[ "$file_path" == "/etc/"* ]] || [[ "$file_path" == "/sys/"* ]]; then
48    echo '{"hookSpecificOutput": {"permissionDecision": "deny"}, "systemMessage": "System path blocked"}' >&2
49    exit 2
50  fi
51fi
52
53# Check file size if configured
54if [[ -n "$MAX_SIZE" ]] && [[ "$MAX_SIZE" =~ ^[0-9]+$ ]]; then
55  content=$(echo "$input" | jq -r '.tool_input.content // empty')
56  content_size=${#content}
57
58  if [[ $content_size -gt $MAX_SIZE ]]; then
59    echo '{"hookSpecificOutput": {"permissionDecision": "deny"}, "systemMessage": "File exceeds configured max size: '"$MAX_SIZE"' bytes"}' >&2
60    exit 2
61  fi
62fi
63
64# All checks passed
65exit 0