Authentication

Required request headers

Every request (except /v1/health) must carry these four headers. If any is missing or invalid, the server rejects with HTTP 401.

Header	Format	Description
KH-Key	kh_live_[A-Z0-9]{32}	Public key identifier. Not a secret, may appear in logs.
KH-Timestamp	Unix seconds (10 digits)	Current timestamp. Tolerance window +-300s.
KH-Nonce	22-44 base64url chars	Single-use value per request. Cached for 600s, then reusable.
KH-Signature	64 hex	HMAC-SHA256(secret, signing_string), hex-encoded.

Building the signing string

The string to sign is composed of five components joined by newline (\n).

signing_string = METHOD + "\n"
               + PATH    + "\n"
               + TIMESTAMP + "\n"
               + NONCE   + "\n"
               + SHA256_HEX(BODY)

signature = HEX( HMAC_SHA256(secret, signing_string) )

PATH includes the full request path including query string, but no host or fragment. BODY is the raw body bytes; for GET/DELETE without a body, BODY is the empty string whose SHA256 is the well-known constant e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.

Reference implementations

PHP:

$method = 'POST';
$path   = '/v1/orders';
$body   = json_encode(['product_id' => 42, 'billing_cycle' => 'monthly']);
$ts     = (string) time();
$nonce  = bin2hex(random_bytes(16));

$signing = "{$method}\n{$path}\n{$ts}\n{$nonce}\n" . hash('sha256', $body);
$sig = hash_hmac('sha256', $signing, $KH_SECRET);

$ch = curl_init('https://www.kernelhost.com/cp/kh_reseller_api/v1/orders');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_CUSTOMREQUEST  => 'POST',
    CURLOPT_POSTFIELDS     => $body,
    CURLOPT_HTTPHEADER     => [
        'Content-Type: application/json',
        "KH-Key: {$KH_KEY}",
        "KH-Timestamp: {$ts}",
        "KH-Nonce: {$nonce}",
        "KH-Signature: {$sig}",
        'Idempotency-Key: ' . bin2hex(random_bytes(16)),
    ],
]);
$res = curl_exec($ch);

Node.js:

import crypto from 'crypto';

const method = 'POST';
const path   = '/v1/orders';
const body   = JSON.stringify({ product_id: 42, billing_cycle: 'monthly' });
const ts     = Math.floor(Date.now() / 1000).toString();
const nonce  = crypto.randomBytes(16).toString('hex');

const bodyHash = crypto.createHash('sha256').update(body).digest('hex');
const signing  = `${method}\n${path}\n${ts}\n${nonce}\n${bodyHash}`;
const sig      = crypto.createHmac('sha256', KH_SECRET).update(signing).digest('hex');

const res = await fetch('https://www.kernelhost.com/cp/kh_reseller_api/v1/orders', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json',
        'KH-Key': KH_KEY,
        'KH-Timestamp': ts,
        'KH-Nonce': nonce,
        'KH-Signature': sig,
        'Idempotency-Key': crypto.randomBytes(16).toString('hex'),
    },
    body,
});

Replay protection

A successfully signed request CANNOT be replayed. The server stores every nonce for 600s in the database; a second request with the same nonce is rejected with replay_detected. Likewise a request whose timestamp deviates more than 300s from server time is rejected.

Scope model

Each key has an explicit scope list. Routes check the required scope; if missing, HTTP 403 forbidden_scope. Writing and sensitive scopes must be explicitly enabled at key creation.

• read:products, read:orders, read:services, read:billing, read:webhooks
• read:credentials (Reading service credentials (root passwords, FTP, VNC). Produces an extra audit entry credentials.read per call.)
• write:orders (Place and pay orders.)
• write:services (Run service actions (start/stop/reboot/reinstall/terminate).)
• write:webhooks (Set webhook URL.)