feat(code): add secret detection hook (#67)

This change introduces a new hook that runs before a file is written or edited. The hook executes a script that scans the file content for patterns that match common secret formats, such as API keys, AWS keys, and private keys.

If a potential secret is found, the script exits with a non-zero status code, which blocks the file operation and prevents the secret from being committed. The script also provides a user-friendly error message with the filename, line number, and a suggestion to use environment variables.

This helps to prevent accidental commits of sensitive credentials to the repository.

claude/code/hooks.json

@@ -21,6 +21,16 @@
           }
         ],
         "description": "Block random .md file creation"
+      },
+      {
+        "matcher": "tool == \"Write\" || tool == \"Edit\"",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "echo \"${tool_input.content}\" | ${CLAUDE_PLUGIN_ROOT}/scripts/detect-secrets.sh ${tool_input.filepath}"
+          }
+        ],
+        "description": "Detect secrets in code before writing or editing files."
       }
     ],
     "PostToolUse": [

claude/code/scripts/detect-secrets.sh

@@ -0,0 +1,73 @@
+#!/bin/bash
+
+# Patterns for detecting secrets
+PATTERNS=(
+  # API keys (e.g., sk_live_..., ghp_..., etc.)
+  "[a-zA-Z0-9]{32,}"
+  # AWS keys
+  "AKIA[0-9A-Z]{16}"
+  # Private keys
+  "-----BEGIN (RSA|DSA|EC|OPENSSH) PRIVATE KEY-----"
+  # Passwords in config
+  "(password|passwd|pwd)\s*[=:]\s*['\"][^'\"]+['\"]"
+  # Tokens
+  "(token|secret|key)\s*[=:]\s*['\"][^'\"]+['\"]"
+)
+
+# Exceptions for fake secrets
+EXCEPTIONS=(
+  "password123"
+  "your-api-key-here"
+  "xxx"
+  "test"
+  "example"
+)
+
+# File to check is passed as the first argument
+FILE_PATH=$1
+
+# Function to check for secrets
+check_secrets() {
+  local input_source="$1"
+  local file_path="$2"
+  local line_num=0
+  while IFS= read -r line; do
+    line_num=$((line_num + 1))
+    for pattern in "${PATTERNS[@]}"; do
+      if echo "$line" | grep -qE "$pattern"; then
+        # Check for exceptions
+        is_exception=false
+        for exception in "${EXCEPTIONS[@]}"; do
+          if echo "$line" | grep -qF "$exception"; then
+            is_exception=true
+            break
+          fi
+        done
+
+        if [ "$is_exception" = false ]; then
+          echo "⚠️ Potential secret detected!"
+          echo "File: $file_path"
+          echo "Line: $line_num"
+          echo ""
+          echo "Found: $line"
+          echo ""
+          echo "This looks like a production secret."
+          echo "Use environment variables instead."
+          echo ""
+
+          # Propose a fix (example for a PHP config file)
+          if [[ "$file_path" == *.php ]]; then
+            echo "'stripe' => ["
+            echo "    'secret' => env('STRIPE_SECRET'),  // ✓"
+            echo "]"
+          fi
+          exit 1
+        fi
+      fi
+    done
+  done < "$input_source"
+}
+
+check_secrets "/dev/stdin" "$FILE_PATH"
+
+exit 0