mediar-ai/packages/skills/skills/whatsapp-web-decrypt

WhatsApp Web Message Decryption & Analysis

Decrypt and read WhatsApp Web messages via live browser interception using Playwright. Intercepts crypto.subtle.decrypt to capture plaintext message content, encryption keys, and sender metadata. Also analyzes WhatsApp IndexedDB metadata for contacts, groups, social graph, and communication patterns.

Part 1: Live Message Decryption (Playwright)

How It Works

WhatsApp Web encrypts messages in IndexedDB (msgRowOpaqueData) using AES-CBC-128 with keys derived via HKDF-SHA256. The crypto happens on the main thread (not Web Workers). By intercepting crypto.subtle before page JS loads, we capture plaintext output and extractable keys.

Prerequisites

• Playwright MCP browser (or any Playwright-based browser automation)
• WhatsApp Web logged in (or QR code scan needed)

Step 1: Navigate to WhatsApp Web

Use browser_navigate to go to https://web.whatsapp.com
Wait for the page to load. If QR code appears, user must scan it.
Use browser_snapshot to verify the chat list is visible.

Step 2: Install the crypto interceptor

Use browser_run_code with this exact code to install the interceptor via addInitScript (runs before any page JS on reload):

async (page) => {
    await page.addInitScript(() => {
        const scope = (typeof globalThis !== 'undefined') ? globalThis : self;
        scope.__waCaptured = { decrypt: [], deriveKey: [], importKey: [] };

        // Force all imported/generated keys to be extractable
        const origImportKey = crypto.subtle.importKey.bind(crypto.subtle);
        crypto.subtle.importKey = function(format, keyData, algorithm, extractable, keyUsages) {
            return origImportKey(format, keyData, algorithm, true, keyUsages);
        };

        const origGenerateKey = crypto.subtle.generateKey.bind(crypto.subtle);
        crypto.subtle.generateKey = function(algorithm, extractable, keyUsages) {
            return origGenerateKey(algorithm, true, keyUsages);
        };

        // Capture HKDF key derivations with extractable output
        const origDeriveKey = crypto.subtle.deriveKey.bind(crypto.subtle);
        crypto.subtle.deriveKey = async function(algorithm, baseKey, derivedKeyType, extractable, keyUsages) {
            const result = await origDeriveKey(algorithm, baseKey, derivedKeyType, true, keyUsages);
            try {
                const raw = await crypto.subtle.exportKey('raw', result);
                const b64 = btoa(String.fromCharCode(...new Uint8Array(raw)));
                scope.__waCaptured.deriveKey.push({
                    ts: Date.now(),
                    alg: algorithm.name,
                    saltLen: algorithm.salt ? algorithm.salt.byteLength : 0,
                    derivedAlg: derivedKeyType.name,
                    derivedLen: derivedKeyType.length,
                    keyB64: b64,
                    usages: keyUsages
                });
            } catch(e) {}
            return result;
        };

        // Capture all decrypt operations with plaintext output
        const origDecrypt = crypto.subtle.decrypt.bind(crypto.subtle);
        crypto.subtle.decrypt = async function(algorithm, key, data) {
            const result = await origDecrypt(algorithm, key, data);
            let keyB64 = null;
            try {
                const raw = await crypto.subtle.exportKey('raw', key);
                keyB64 = btoa(String.fromCharCode(...new Uint8Array(raw)));
            } catch(e) { keyB64 = 'export-failed'; }

            const entry = {
                ts: Date.now(),
                alg: algorithm.name,
                key: keyB64,
                inSize: data.byteLength,
                outSize: result.byteLength
            };

            // Capture decrypted output (up to 1500 bytes) for text extraction
            if (result.byteLength > 0 && result.byteLength < 500000) {
                const slice = new Uint8Array(result.slice(0, Math.min(1500, result.byteLength)));
                entry.outB64 = btoa(String.fromCharCode(...slice));
            }
            scope.__waCaptured.decrypt.push(entry);
            return result;
        };
    });

    // Reload to trigger fresh decryption of all cached messages
    await page.reload({ waitUntil: 'networkidle' });
    // Wait for WhatsApp to load and decrypt messages
    await new Promise(r => setTimeout(r, 8000));
    return 'Interceptor installed and page reloaded. Decryptions are being captured.';
}

Step 3: Collect captured decryptions

Wait 10-15 seconds after reload, then extract with browser_run_code:

async (page) => {
    const data = await page.evaluate(() => {
        const c = (globalThis || self).__waCaptured;
        if (!c) return JSON.stringify({error: 'no captures'});
        return JSON.stringify({
            decryptCount: c.decrypt.length,
            deriveKeyCount: c.deriveKey.length,
            derivedKeys: c.deriveKey,
            sample: c.decrypt.slice(0, 5)
        });
    });
    return data;
}

Step 4: Extract and parse message text

Decrypted output is protobuf. Extract text with browser_run_code:

async (page) => {
    const result = await page.evaluate(() => {
        const c = (globalThis || self).__waCaptured;
        if (!c) return JSON.stringify({error: 'no captures'});

        function readVarint(bytes, pos) {
            let result = 0, shift = 0;
            while (pos < bytes.length) {
                const byte = bytes[pos];
                result |= (byte & 0x7f) << shift;
                shift += 7; pos++;
                if (!(byte & 0x80)) return [result, pos];
            }
            return [null, pos];
        }

        function parseProtobufText(bytes) {
            if (!bytes || bytes[0] !== 0x0a) return null;
            let pos = 1;
            let [outerLen, p1] = readVarint(bytes, pos);
            if (outerLen === null || p1 >= bytes.length) return null;
            pos = p1;
            if (bytes[pos] !== 0x0a) return null;
            pos++;
            let [textLen, p2] = readVarint(bytes, pos);
            if (textLen === null || textLen <= 0 || p2 + textLen > bytes.length) return null;
            pos = p2;
            try {
                return new TextDecoder('utf-8').decode(bytes.slice(pos, pos + textLen));
            } catch(e) { return null; }
        }

        function extractSender(bytes) {
            try {
                const str = Array.from(bytes).map(b => String.fromCharCode(b)).join('');
                const match = str.match(/(\d+@(?:s\.whatsapp\.net|lid|g\.us))/);
                return match ? match[1] : null;
            } catch(e) { return null; }
        }

        const messages = [];
        for (const d of c.decrypt) {
            if (!d.outB64 || d.alg !== 'AES-CBC') continue;
            try {
                const bytes = Uint8Array.from(atob(d.outB64), c => c.charCodeAt(0));
                const text = parseProtobufText(bytes);
                if (text && text.length > 0) {
                    messages.push({
                        text: text,
                        sender: extractSender(bytes),
                        ts: d.ts
                    });
                }
            } catch(e) {}
        }

        return JSON.stringify({
            totalDecrypts: c.decrypt.length,
            textMessages: messages.length,
            messages: messages
        });
    });
    return result;
}

Step 5: Navigate to more chats for additional messages

WhatsApp only decrypts messages for loaded chats. To capture more:

• Use browser_snapshot to see the chat list
• Click on different chats using browser_click with the ref for each chat
• Wait 3-5 seconds between clicks for decryption to complete
• Re-run Step 4 to collect newly decrypted messages

After the initial page reload (Step 2), WhatsApp decrypts all cached/visible messages (~700-1000+). Clicking individual chats adds more but the bulk comes from the reload.

Key Technical Details

• Crypto happens on the main thread, not Web Workers (3 workers exist but don't do message crypto)
• page.addInitScript() is critical -- must run BEFORE page JS to force extractable: true on all key imports
• Decrypted output is protobuf: field 1 (wire type 2) -> field 1 (wire type 2) = message text
• Sender JID appears as string like [email protected] or 123456@lid
• AES-GCM operations are noise protocol frames (not message content)
• Keys are session-specific (HKDF-SHA256 with 128-byte salt) -- captured keys only work for the session they were captured in

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Part 2: Metadata Analysis (Offline from IndexedDB)

WhatsApp Web stores 51 IndexedDB object stores. Message bodies are encrypted but all metadata is plaintext.

Available Stores

| Store | What's in it | |-------|-------------| | contact | Phone numbers, names, isAddressBook, isBusiness | | chat | Chat IDs, last message timestamps, unread counts, mute/archive state | | group-metadata | Group subjects, creation dates, owner phone number | | participant | Group member phone lists | | message | Message type, from/to/author, timestamps, media metadata (NOT body text) | | reactions | Emoji reactions with sender, timestamp | | profile-pic-thumb | Profile picture CDN URLs | | verified-business-name | Business names linked to phone numbers | | blocklist | Blocked phone numbers | | device-list | Linked devices per user |

Contact Name Lookup

WhatsApp uses two ID formats. Build a unified phone-to-name map:

contacts = {}  # phone -> name
lid_to_phone = {}  # lid -> phone
for record in rows:
    val = json.loads(record[0])
    cid = val.get('id', '')
    name = val.get('name', '')
    pnum = cid.split('@')[0]
    phone_field = val.get('phoneNumber', '')
    if phone_field:
        phone = phone_field.split('@')[0]
        lid_to_phone[pnum] = phone
        if name:
            contacts[phone] = name
    if name and '@c.us' in cid:
        contacts[pnum] = name

Inner Circle Detection

Count how many groups each person shares with the account owner:

your_groups = set()
person_groups = {}
for record in participants:
    gid = record['groupId']
    for p in record['participants']:
        phone = p.split('@')[0]
        resolved = lid_to_phone.get(phone, phone)
        if resolved == YOUR_NUMBER:
            your_groups.add(gid)
        person_groups.setdefault(resolved, set()).add(gid)
shared = {p: len(gs & your_groups) for p, gs in person_groups.items() if p != YOUR_NUMBER}
top_connections = sorted(shared.items(), key=lambda x: -x[1])

Message Metadata Fields

• type: chat, image, video, ptt (voice), document, sticker, location, vcard, revoked
• t: unix timestamp
• from: sender ([email protected] or [email protected])
• author: in group messages, the actual sender
• ack: delivery status (0=sent, 1=delivered, 2=read)
• isForwarded, forwardingScore: forwarding chain info

Known Limitations

• Session-specific keys: HKDF-derived keys change per browser session (128-byte salt)
• Offline decryption: Does not work across sessions -- keys from one session can't decrypt another session's data
• Record cap: IndexedDB stores may cap at ~1000 records
• Contact names: Only available for address book contacts
• lid-to-phone mapping: Incomplete for some contacts