strongSwan -- Double-free when destroying certain cloned identities that can lead to remote code execution

R. Elliott Childre reports:

The clone() method of the identification_t class doesn't correctly handle identities that have an empty but non-NULL encoding. Both objects will point to the same location, resulting in a double-free once the second object is destroyed. This can lead to a crash and could potentially be exploitable for remote code execution. Affected are all strongSwan versions since 4.3.3.

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