Matrix JavaScript SDK vulnerable to key/device identifier confusion in SAS verification

Matrix JavaScript SDK is the Matrix Client-Server software development kit (SDK) for JavaScript. Prior to version 19.7.0, an attacker cooperating with a malicious homeserver could interfere with the verification flow between two users, injecting its own cross-signing user identity in place of one of the users’ identities. This would lead to the other device trusting/verifying the user identity under the control of the homeserver instead of the intended one. The vulnerability is a bug in the matrix-js-sdk, caused by checking and signing user identities and devices in two separate steps, and inadequately fixing the keys to be signed between those steps. Even though the attack is partly made possible due to the design decision of treating cross-signing user identities as Matrix devices on the server side (with their device ID set to the public part of the user identity key), no other examined implementations were vulnerable. Starting with version 19.7.0, the matrix-js-sdk has been modified to double check that the key signed is the one that was verified instead of just referencing the key by ID. An additional check has been made to report an error when one of the device ID matches a cross-signing key. As this attack requires coordination between a malicious homeserver and an attacker, those who trust their homeservers do not need a particular workaround.

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

未进行实体认证的密钥交换

Matrix 授权问题漏洞

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 JavaScript SDK 19.7.0之前版本存在安全漏洞，该漏洞源于在两个单独的步骤中检查和签署用户身份和设备，并且未充分修复这些步骤之间要签署的密钥而引起的。

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