[NPM:GHSA-R48R-J8FX-MQ2C] matrix-js-sdk subject to user spoofing via Olm/Megolm protocol confusion
Impact
An attacker cooperating with a malicious homeserver can construct messages that legitimately appear to have come from another person, without any indication such as a grey shield.
Additionally, a sophisticated attacker cooperating with a malicious homeserver could employ this vulnerability to perform a targeted attack in order to send fake to-device messages appearing to originate from another user. This can allow, for example, to inject the key backup secret during a self-verification, to make a targeted device start using a malicious key backup spoofed by the homeserver.
These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm.
Patches
matrix-js-sdk has been modified to only accept Olm-encrypted to-device messages.
Out of caution, several other checks have been audited or added:
- Cleartext m.room_key
, m.forwarded_room_key
and m.secret.send
to_device messages are discarded.
- Secrets received from untrusted devices are discarded.
- Key backups are only usable if they have a valid signature from a trusted device (no more local trust, or trust-on-decrypt).
- The origin of a to-device message should only be determined by observing the Olm session which managed to decrypt the message, and not by using claimed sender_key, user_id, or any other fields controllable by the homeserver.
Workarounds
As this attack requires coordination between a malicious home server and an attacker, if you trust your home server no particular workaround is needed. Notice that the backup spoofing attack is a particularly sophisticated targeted attack.
We are not aware of this attack being used in the wild, though specifying a false positive-free way of noticing malicious key backups key is challenging.
As an abundance of caution, to avoid malicious backup attacks, you should not verify your new logins using emoji/QR verifications methods until patched. Prefer verifying with your security passphrase instead.
References
For more information
If you have any questions or comments about this advisory, e-mail us at security@matrix.org.
Package | Affected Version |
---|---|
pkg:npm/matrix-js-sdk | < 19.7.0 |
Package | Fixed Version |
---|---|
pkg:npm/matrix-js-sdk | = 19.7.0 |
- ID
- NPM:GHSA-R48R-J8FX-MQ2C
- Severity
- high
- URL
- https://github.com/advisories/GHSA-r48r-j8fx-mq2c
- Published
-
2022-09-30T00:41:24
(2 years ago) - Modified
-
2023-01-30T05:02:55
(19 months ago) - Rights
- NPM Security Team
- Other Advisories
Type | Package URL | Namespace | Name / Product | Version | Distribution / Platform | Arch | Patch / Fix |
---|---|---|---|---|---|---|---|
Affected | pkg:npm/matrix-js-sdk | matrix-js-sdk | < 19.7.0 | ||||
Fixed | pkg:npm/matrix-js-sdk | matrix-js-sdk | = 19.7.0 |
# CVE | Description | CVSS | EPSS | EPSS Trend (30 days) | Affected Products | Weaknesses | Security Advisories | Exploits | PoC | Pubblication Date | Modification Date |
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# CVE | Description | CVSS | EPSS | EPSS Trend (30 days) | Affected Products | Weaknesses | Security Advisories | PoC | Pubblication Date | Modification Date |