#!/usr/bin/env python3
"""
Enkrypt AI Guardrails - UserPromptSubmit Hook for Claude Code
This hook runs when the user submits a prompt, before Claude processes it.
It can:
- Add context to the conversation (stdout with exit code 0)
- Block prompts (exit code 2 or JSON with decision: "block")
- Validate prompt content
Hook Input (via stdin):
{
"session_id": "abc123",
"transcript_path": "/path/to/transcript.jsonl",
"cwd": "/current/directory",
"permission_mode": "default",
"hook_event_name": "UserPromptSubmit",
"prompt": "The user's prompt text"
}
Hook Output:
- Exit code 0: Success, stdout added as context
- Exit code 2: Block prompt, stderr shown to user
- JSON output with decision control for advanced use
"""
import sys
import json
from enkrypt_guardrails import (
read_hook_input,
check_with_enkrypt_api,
is_hook_enabled,
format_blocking_error,
create_json_output,
output_json,
output_error,
log_event,
log_security_alert,
)
def main():
"""Main entry point for UserPromptSubmit hook."""
# Read input from stdin
input_data = read_hook_input()
if not input_data:
# No input, allow through
sys.exit(0)
hook_name = "UserPromptSubmit"
prompt = input_data.get("prompt", "")
session_id = input_data.get("session_id", "")
cwd = input_data.get("cwd", "")
# Log the hook invocation
log_event("hook_invoked", {
"hook": hook_name,
"session_id": session_id,
"prompt_length": len(prompt),
"cwd": cwd,
})
# Check if guardrails are enabled
if not is_hook_enabled(hook_name):
sys.exit(0)
# Skip empty prompts
if not prompt or not prompt.strip():
sys.exit(0)
# Check with Enkrypt API
should_block, violations, raw_result = check_with_enkrypt_api(prompt, hook_name)
if should_block:
# Log security alert
log_security_alert(
"prompt_blocked",
{
"violations": violations,
"prompt_preview": prompt[:200] if len(prompt) > 200 else prompt,
},
{"session_id": session_id, "cwd": cwd}
)
# Option 1: Use exit code 2 with stderr (simpler)
# error_message = format_blocking_error(violations, hook_name)
# output_error(error_message)
# sys.exit(2)
# Option 2: Use JSON output with decision control (more flexible)
detector_names = [v["detector"] for v in violations]
output = create_json_output(
hook_event_name=hook_name,
decision="block",
reason=f"Prompt blocked by Enkrypt Guardrails: {', '.join(detector_names)}. Please rephrase your request.",
)
output_json(output)
sys.exit(0)
# Log successful check
log_event("hook_completed", {
"hook": hook_name,
"session_id": session_id,
"blocked": False,
})
# Success - allow the prompt
# Optionally add context (printed to stdout will be added to conversation)
# print("Additional context: Current time is ...")
sys.exit(0)
if __name__ == "__main__":
main()
