# Authentication Guide

CRM property endpoints support two authentication methods:

- API key authentication with HMAC request signing.
- OAuth bearer tokens issued by Quardlyn's CRM authorization platform.

API key/HMAC authentication remains supported for backward compatibility.

## Required Headers

```text
X-CRM-Key: crm_key_...
X-CRM-Timestamp: 1782820800
X-CRM-Nonce: unique-nonce-123
X-CRM-Signature: hex-encoded-hmac
Content-Type: application/json
Idempotency-Key: optional-but-recommended
```

## OAuth Bearer Tokens

Providers using the OAuth-style authorization platform can call the same CRM API v1 endpoints with:

```text
Authorization: Bearer qat_...
Content-Type: application/json
Idempotency-Key: optional-but-recommended
```

Bearer tokens are short-lived and scoped. The existing signed header flow is still valid and unchanged.

## Signature String

Build the canonical string exactly as:

```text
METHOD
PATH
UNIX_TIMESTAMP
NONCE
SHA256_HEX(REQUEST_BODY)
```

Example:

```text
POST
/api/v1/crm/properties
1782820800
nonce-123
4b4f0e...
```

Then sign it:

```text
HMAC_SHA256_HEX(canonical_string, signing_secret)
```

## Timestamp

Use Unix time in seconds. Requests outside the allowed clock-skew window are rejected as `unauthorized`.

## Nonce

Use a unique nonce per request. Recommended length is 16 to 64 characters.

## Body Hash

Hash the exact request body bytes sent over the wire. For empty lifecycle bodies, hash the empty string.

## Idempotency

Send one of:

- `Idempotency-Key`
- `X-Idempotency-Key`
- `X-Request-Id`
- `X-Provider-Request-Id`
- `X-Event-Id`

The same completed request returns the previous successful response. A duplicate request still processing returns `already_processing`.

## PHP Signature Example

```php
$body = json_encode($payload);
$bodyHash = hash('sha256', $body);
$canonical = implode("\n", [$method, $path, $timestamp, $nonce, $bodyHash]);
$signature = hash_hmac('sha256', $canonical, $signingSecret);
```

## Node.js Signature Example

```js
const bodyHash = crypto.createHash('sha256').update(body).digest('hex');
const canonical = [method, path, timestamp, nonce, bodyHash].join('\n');
const signature = crypto.createHmac('sha256', signingSecret).update(canonical).digest('hex');
```

## Python Signature Example

```python
body_hash = hashlib.sha256(body.encode("utf-8")).hexdigest()
canonical = "\n".join([method, path, timestamp, nonce, body_hash])
signature = hmac.new(secret.encode("utf-8"), canonical.encode("utf-8"), hashlib.sha256).hexdigest()
```