matrix-android-sdk2 vulnerable to impersonation via forwarded Megolm sessions

matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the key forwarding strategy implemented in the matrix-android-sdk2 that is too permissive. Starting with version 1.5.1, the default policy for accepting key forwards has been made more strict in the matrix-android-sdk2. The matrix-android-sdk2 will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately (for example, by showing a warning for such messages). As a workaroubnd, current users of the SDK can disable key forwarding in their forks using `CryptoService#enableKeyGossiping(enable: Boolean)`.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

未进行实体认证的密钥交换

Matrix 安全漏洞

Matrix是一个雄心勃勃的新生态系统，用于开放联合即时消息和 VoIP。 Matrix matrix-android-sdk2 1.5.1之前的版本存在安全漏洞，该漏洞源于其矩阵-android-sdk2在接收端实现了过于宽松的密钥转发策略导致与恶意主服务器合作的攻击者可以构建看似来自其他人的消息。

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