SSH Secure-RPC Weak Encrypted Authentication Vulnerability

SSH is a package designed to encrypt traffic between two end points using the IETF specified SSH protocol. The SSH1 package is distributed and maintained by SSH Communications Security.

A problem exists which could allow the discovery of the secret key used to encrypt traffic on the local host. When using SUN-DES-1 to share keys with other hosts on the network to facilitate secure communication via protocols such as NFS and NIS+, the keys are shared between hosts using the private key of the user and a cryptographic algorithm to secure the contents of the key, which is stored on the NIS+ primary. The problem occurs when the key is encrypted with the SUN-DES-1 magic phrase prior to having done a keylogin (the keyserv does not have the users DH private key). A design flaw in the software that shares the key with the NIS+ master will inconsistently return the correct value for an attempted keyshare that has failed. A step in the private key encryption process is skipped, and the users private key is then encrypted only with the public key of the target server and the SUN-DES-1 magic phrase, a phrase that is guessable due to the way it is generated. A user from the same host can then execute a function that returns another users magic phrase, and use this to decrypt the private key of the victim. This makes it possible for a user with malicious intent to gain knowledge of a users secret key, and decrypt sensitive traffic between two hosts, with the possibility of gaining access and elevated privileges on the hosts and/or NIS+ domain. This reportedly affects the SSH2 series of the software package.


 

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