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Add attachment digests

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// FREEBIE
This commit is contained in:
lilia 2017-03-07 16:54:15 -08:00
parent f1a1a819ba
commit 43de0cc2ec
5 changed files with 65 additions and 10 deletions
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27
libtextsecure/crypto.js
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@ -10,6 +10,23 @@
var calculateMAC = libsignal.crypto.calculateMAC;
var verifyMAC = libsignal.crypto.verifyMAC;
function verifyDigest(data, theirDigest) {
return crypto.subtle.digest({name: 'SHA-256'}, data).then(function(ourDigest) {
var a = new Uint8Array(ourDigest);
var b = new Uint8Array(theirDigest);
var result = 0;
for (var i=0; i < theirDigest.byteLength; ++i) {
result = result | (a[i] ^ b[i]);
}
if (result !== 0) {
throw new Error('Bad digest');
}
});
}
function calculateDigest(data) {
return crypto.subtle.digest({name: 'SHA-256'}, data);
}
window.textsecure = window.textsecure || {};
window.textsecure.crypto = {
// Decrypts message into a raw string
@ -39,7 +56,7 @@
});
},
decryptAttachment: function(encryptedBin, keys) {
decryptAttachment: function(encryptedBin, keys, theirDigest) {
if (keys.byteLength != 64) {
throw new Error("Got invalid length attachment keys");
}
@ -56,6 +73,10 @@
var mac = encryptedBin.slice(encryptedBin.byteLength - 32, encryptedBin.byteLength);
return verifyMAC(ivAndCiphertext, mac_key, mac, 32).then(function() {
if (theirDigest !== undefined) {
return verifyDigest(encryptedBin, theirDigest);
}
}).then(function() {
return decrypt(aes_key, ciphertext, iv);
});
},
@ -79,7 +100,9 @@
var encryptedBin = new Uint8Array(16 + ciphertext.byteLength + 32);
encryptedBin.set(ivAndCiphertext);
encryptedBin.set(new Uint8Array(mac), 16 + ciphertext.byteLength);
return encryptedBin.buffer;
return calculateDigest(encryptedBin.buffer).then(function(digest) {
return { ciphertext: encryptedBin.buffer, digest: digest };
});
});
});
},