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89 lines
2.9 KiB
TypeScript
89 lines
2.9 KiB
TypeScript
const { encrypt, decrypt, calculateMAC, verifyMAC } = window.libsignal.crypto;
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// tslint:disable: binary-expression-operand-order
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// tslint:disable: restrict-plus-operands
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async function verifyDigest(data: ArrayBuffer, theirDigest: ArrayBuffer) {
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return crypto.subtle.digest({ name: 'SHA-256' }, data).then(ourDigest => {
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const a = new Uint8Array(ourDigest);
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const b = new Uint8Array(theirDigest);
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let result = 0;
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for (let i = 0; i < theirDigest.byteLength; i += 1) {
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// tslint:disable-next-line: no-bitwise
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result |= a[i] ^ b[i];
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}
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if (result !== 0) {
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throw new Error('Bad digest');
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}
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});
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}
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async function calculateDigest(data: ArrayBuffer) {
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return crypto.subtle.digest({ name: 'SHA-256' }, data);
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}
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export async function decryptAttachment(
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encryptedBin: ArrayBuffer,
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keys: ArrayBuffer,
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theirDigest: ArrayBuffer
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) {
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if (keys.byteLength !== 64) {
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throw new Error('Got invalid length attachment keys');
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}
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if (encryptedBin.byteLength < 16 + 32) {
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throw new Error('Got invalid length attachment');
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}
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const aesKey = keys.slice(0, 32);
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const macKey = keys.slice(32, 64);
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const iv = encryptedBin.slice(0, 16);
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const ciphertext = encryptedBin.slice(16, encryptedBin.byteLength - 32);
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const ivAndCiphertext = encryptedBin.slice(0, encryptedBin.byteLength - 32);
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const mac = encryptedBin.slice(encryptedBin.byteLength - 32, encryptedBin.byteLength);
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return verifyMAC(ivAndCiphertext, macKey, mac, 32)
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.then(async () => {
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if (!theirDigest) {
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throw new Error('Failure: Ask sender to update Signal and resend.');
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}
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return verifyDigest(encryptedBin, theirDigest);
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})
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.then(() => decrypt(aesKey, ciphertext, iv));
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}
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export async function encryptAttachment(
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plaintext: ArrayBuffer,
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keys: ArrayBuffer,
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iv: ArrayBuffer
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) {
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if (!(plaintext instanceof ArrayBuffer) && !ArrayBuffer.isView(plaintext)) {
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throw new TypeError(
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`\`plaintext\` must be an \`ArrayBuffer\` or \`ArrayBufferView\`; got: ${typeof plaintext}`
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);
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}
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if (keys.byteLength !== 64) {
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throw new Error('Got invalid length attachment keys');
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}
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if (iv.byteLength !== 16) {
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throw new Error('Got invalid length attachment iv');
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}
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const aesKey = keys.slice(0, 32);
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const macKey = keys.slice(32, 64);
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return encrypt(aesKey, plaintext, iv).then((ciphertext: any) => {
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const ivAndCiphertext = new Uint8Array(16 + ciphertext.byteLength);
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ivAndCiphertext.set(new Uint8Array(iv));
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ivAndCiphertext.set(new Uint8Array(ciphertext), 16);
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return calculateMAC(macKey, ivAndCiphertext.buffer).then(async (mac: any) => {
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const encryptedBin = new Uint8Array(16 + ciphertext.byteLength + 32);
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encryptedBin.set(ivAndCiphertext);
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encryptedBin.set(new Uint8Array(mac), 16 + ciphertext.byteLength);
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return calculateDigest(encryptedBin.buffer).then(digest => ({
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ciphertext: encryptedBin.buffer,
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digest,
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}));
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});
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});
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}
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