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make MAC check robust against unpadded vs padded base64 differences #1378

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merged 1 commit into from
May 20, 2020
Merged

make MAC check robust against unpadded vs padded base64 differences #1378

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2 changes: 1 addition & 1 deletion src/crypto/SecretStorage.js
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Original file line number Diff line number Diff line change
Expand Up @@ -167,7 +167,7 @@ export class SecretStorage extends EventEmitter {
if (info.algorithm === SECRET_STORAGE_ALGORITHM_V1_AES) {
if (info.mac) {
const {mac} = await SecretStorage._calculateKeyCheck(key, info.iv);
return info.mac === mac;
return info.mac.replace(/=+$/g, '') === mac.replace(/=+$/g, '');
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is info mac one mac or multiple, one per line? just wondering about the point of the g modifier

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Just one. The g probably isn't needed (but shouldn't be harmful either). It was just copied from encodeUnpaddedBase64 in src/crypto/olmlib.js

} else {
// if we have no information, we have to assume the key is right
return true;
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4 changes: 2 additions & 2 deletions src/crypto/aes.js
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Expand Up @@ -84,9 +84,9 @@ async function decryptNode(data, key, name) {
const [aesKey, hmacKey] = deriveKeysNode(key, name);

const hmac = crypto.createHmac("sha256", hmacKey)
.update(data.ciphertext, "base64").digest("base64");
.update(data.ciphertext, "base64").digest("base64").replace(/=+$/g, '');

if (hmac !== data.mac) {
if (hmac !== data.mac.replace(/=+$/g, '')) {
throw new Error(`Error decrypting secret ${name}: bad MAC`);
}

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