Configure your mobile app or IoT device

const defaultData = { temperatures: [] }

const getCache = key => TEMPERATURES.get(key)
const setCache = (key, data) => TEMPERATURES.put(key, data)

async function addTemperature(request) {

    // Pull previously recorded temperatures for this client.
    const ip = request.headers.get('CF-Connecting-IP')
    const cacheKey = `data-${ip}`
    let data
    const cache = await getCache(cacheKey)
    if (!cache) {
        await setCache(cacheKey, JSON.stringify(defaultData))
        data = defaultData
    } else {
        data = JSON.parse(cache)
    }

    // Append the recorded temperatures with the submitted reading (assuming it has both temperature and a timestamp).
    try {
        const body = await request.text()
        const val = JSON.parse(body)

        if (val.temperature && val.time) {
            data.temperatures.push(val)
            await setCache(cacheKey, JSON.stringify(data))
            return new Response("", { status: 201 })
        } else {
            return new Response("Unable to parse temperature and/or timestamp from JSON POST body", { status: 400 })
        }
    } catch (err) {
        return new Response(err, { status: 500 })
    }
}

function compareTimestamps(a,b) {
    return -1 * (Date.parse(a.time) - Date.parse(b.time))
}

// Return the 5 most recent temperature measurements.
async function getTemperatures(request) {
    const ip = request.headers.get('CF-Connecting-IP')
    const cacheKey = `data-${ip}`

    const cache = await getCache(cacheKey)
    if (!cache) {
        return new Response(JSON.stringify(defaultData), { status: 200, headers: { 'content-type': 'application/json' } })
    } else {
        data = JSON.parse(cache)
        const retval = JSON.stringify(data.temperatures.sort(compareTimestamps).splice(0,5))
        return new Response(retval, { status: 200, headers: { 'content-type': 'application/json' } })
    }
}

async function handleRequest(request) {

    if (request.method === 'POST') {
        return addTemperature(request)
    } else {
        return getTemperatures(request)
    }

}

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

$ TEMPERATURE=$(echo $((361 + RANDOM %11)) | awk '{printf("%.2f",$1/10.0)}')
$ TIMESTAMP=$(date -u +"%Y-%m-%dT%H:%M:%SZ")

$ echo -e "$TEMPERATURE\n$TIMESTAMP"
36.70
2020-09-28T02:54:56Z

$ curl -v -H "Content-Type: application/json" -d '{"temperature":'''$TEMPERATURE''', "time": "'''$TIMESTAMP'''"}' https://shield.upinatoms.com/temps 2>&1 | grep "< HTTP/2"
< HTTP/2 201

$ curl -s https://shield.upinatoms.com/temps | jq .
[
  {
    "temperature": 36.3,
    "time": "2020-09-28T02:57:49Z"
  },
  {
    "temperature": 36.7,
    "time": "2020-09-28T02:54:56Z"
  },
  {
    "temperature": 36.2,
    "time": "2020-09-28T02:33:08Z"
  }
]

# Generate a private key and CSR for the iOS device.

$ cat <<'EOF' | tee -a csr.json
{
    "hosts": [
        "ios-bootstrap.devices.upinatoms.com"
    ],
    "CN": "ios-bootstrap.devices.upinatoms.com",
    "key": {
        "algo": "rsa",
        "size": 2048
    },
    "names": [{
        "C": "US",
        "L": "Austin",
        "O": "Temperature Testers, Inc.",
        "OU": "Tech Operations",
        "ST": "Texas"
    }]
}
EOF

$ cfssl genkey csr.json | cfssljson -bare certificate
2020/09/27 21:28:46 [INFO] generate received request
2020/09/27 21:28:46 [INFO] received CSR
2020/09/27 21:28:46 [INFO] generating key: rsa-2048
2020/09/27 21:28:47 [INFO] encoded CSR

$ mv certificate-key.pem ios-key.pem
$ mv certificate.csr ios.csr

# Do the same for the IoT sensor.

$ sed -i.bak 's/ios-bootstrap/sensor-001/g' csr.json
$ cfssl genkey csr.json | cfssljson -bare certificate
...
$ mv certificate-key.pem sensor-key.pem
$ mv certificate.csr sensor.csr

// now ask that these CSRs be signed by the private CA issued for your zone
// we need to replace actual newlines in the CSR with ‘\n’ before POST’ing
$ CSR=$(cat ios.csr | perl -pe 's/\n/\\n/g')
$ request_body=$(< <(cat <<EOF
{
  "validity_days": 3650,
  "csr":"$CSR"
}
EOF
))

// save the response so we can view it and then extra the certificate
$ curl -H 'X-Auth-Email: YOUR_EMAIL' -H 'X-Auth-Key: YOUR_API_KEY' -H 'Content-Type: application/json' -d "$request_body" https://api.cloudflare.com/client/v4/zones/YOUR_ZONE_ID/client_certificates > response.json

$ cat response.json | jq .
{
  "success": true,
  "errors": [],
  "messages": [],
  "result": {
    "id": "7bf7f70c-7600-42e1-81c4-e4c0da9aa515",
    "certificate_authority": {
      "id": "8f5606d9-5133-4e53-b062-a2e5da51be5e",
      "name": "Cloudflare Managed CA for account 11cbe197c050c9e422aaa103cfe30ed8"
    },
    "certificate": "-----BEGIN CERTIFICATE-----\nMIIEkzCCA...\n-----END CERTIFICATE-----\n",
    "csr": "-----BEGIN CERTIFICATE REQUEST-----\nMIIDITCCA...\n-----END CERTIFICATE REQUEST-----\n",
    "ski": "eb2a48a19802a705c0e8a39489a71bd586638fdf",
    "serial_number": "133270673305904147240315902291726509220894288063",
    "signature": "SHA256WithRSA",
    "common_name": "ios-bootstrap.devices.upinatoms.com",
    "organization": "Temperature Testers, Inc.",
    "organizational_unit": "Tech Operations",
    "country": "US",
    "state": "Texas",
    "location": "Austin",
    "expires_on": "2030-09-26T02:41:00Z",
    "issued_on": "2020-09-28T02:41:00Z",
    "fingerprint_sha256": "84b045d498f53a59bef53358441a3957de81261211fc9b6d46b0bf5880bdaf25",
    "validity_days": 3650
  }
}

$ cat response.json | jq .result.certificate | perl -npe 's/\\n/\n/g; s/"//g' > ios.pem

# Now ask that the second client certificate signing request be signed.

$ CSR=$(cat sensor.csr | perl -pe 's/\n/\\n/g')
$ request_body=$(< <(cat <<EOF
{
  "validity_days": 3650,
  "csr":"$CSR"
}
EOF
))

$ curl -H 'X-Auth-Email: YOUR_EMAIL' -H 'X-Auth-Key: YOUR_API_KEY' -H 'Content-Type: application/json' -d "$request_body" https://api.cloudflare.com/client/v4/zones/YOUR_ZONE_ID/client_certificates | perl -npe 's/\\n/\n/g; s/"//g' > sensor.pem

$ openssl pkcs12 -export -out bootstrap-cert.pfx -inkey ios-key.pem -in ios.pem
Enter Export Password:
Verifying - Enter Export Password:

<uses-permission android:name="android.permission.INTERNET" />

private OkHttpClient setUpClient() {
    try {
        final String SECRET = "secret"; // You may also store this String somewhere more secure.
        CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");

        // Get private key
        InputStream privateKeyInputStream = getResources().openRawResource(R.raw.key);
        byte[] privateKeyByteArray = new byte[privateKeyInputStream.available()];
        privateKeyInputStream.read(privateKeyByteArray);

        String privateKeyContent = new String(privateKeyByteArray, Charset.defaultCharset())
                .replace("-----BEGIN PRIVATE KEY-----", "")
                .replaceAll(System.lineSeparator(), "")
                .replace("-----END PRIVATE KEY-----", "");

        byte[] rawPrivateKeyByteArray = Base64.getDecoder().decode(privateKeyContent);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(rawPrivateKeyByteArray);

        // Get certificate
        InputStream certificateInputStream = getResources().openRawResource(R.raw.cert);
        Certificate certificate = certificateFactory.generateCertificate(certificateInputStream);

        // Set up KeyStore
        KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
        keyStore.load(null, SECRET.toCharArray());
        keyStore.setKeyEntry("client", keyFactory.generatePrivate(keySpec), SECRET.toCharArray(), new Certificate[]{certificate});
        certificateInputStream.close();

        // Set up Trust Managers
        TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
        trustManagerFactory.init((KeyStore) null);
        TrustManager[] trustManagers = trustManagerFactory.getTrustManagers();

        // Set up Key Managers
        KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
        keyManagerFactory.init(keyStore, SECRET.toCharArray());
        KeyManager[] keyManagers = keyManagerFactory.getKeyManagers();

        // Obtain SSL Socket Factory
        SSLContext sslContext = SSLContext.getInstance("TLS");
        sslContext.init(keyManagers, trustManagers, new SecureRandom());
        SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();

        // Finally, return the client, which will then be used to make HTTP calls.
        OkHttpClient client = new OkHttpClient.Builder()
                .sslSocketFactory(sslSocketFactory, (X509TrustManager) trustManagers[0])
                .build();

        return client;

    } catch (CertificateException | IOException | NoSuchAlgorithmException | KeyStoreException | UnrecoverableKeyException | KeyManagementException | InvalidKeySpecException e) {
        e.printStackTrace();
        return null;
    }
}

import requests
import json
from datetime import datetime

def readSensor():

    # Takes a reading from a temperature sensor and store it to temp_measurement

    dateTimeObj = datetime.now()
    timestampStr = dateTimeObj.strftime('%Y-%m-%dT%H:%M:%SZ')

    measurement = {'temperature':str(temp_measurement),'time':timestampStr}
    return measurement

def main():

    print("Cloudflare API Shield [IoT device demonstration]")

    temperature = readSensor()
    payload = json.dumps(temperature)

    url = 'https://shield.upinatoms.com/temps'
    json_headers = {'Content-Type': 'application/json'}
    cert_file = ('/etc/ssl/certs/sensor.pem', '/etc/ssl/private/sensor-key.pem')

    r = requests.post(url, headers = json_headers, data = payload, cert = cert_file)

    print("Request body: ", r.request.body)
    print("Response status code: %d" % r.status_code)

Cloudflare API Shield [IoT device demonstration]
Request body:  {"temperature": "36.5", "time": "2020-09-28T15:52:19Z"}
Response status code: 403

Cloudflare API Shield [IoT device demonstration]
Request body:  {"temperature": "36.5", "time": "2020-09-28T15:56:45Z"}
Response status code: 201