RUSTSEC-2025-0004

In `openssl` versions before `0.10.70`, `ssl::select_next_proto` can return a slice pointing into the `server` argument's buffer but with a lifetime bound to the `client` argument. In situations where the `server` buffer's lifetime is shorter than the `client` buffer's, this can cause a use after free. This could cause the server to crash or to return arbitrary memory contents to the client.

`openssl` 0.10.70 fixes the signature of `ssl::select_next_proto` to properly constrain the output buffer's lifetime to that of both input buffers.

In standard usage of `ssl::select_next_proto` in the callback passed to `SslContextBuilder::set_alpn_select_callback`, code is only affected if the `server` buffer is constructed *within* the callback. For example:

Not vulnerable - the server buffer has a `'static` lifetime: ```rust builder.set_alpn_select_callback(|_, client_protos| { ssl::select_next_proto(b"\x02h2", client_protos).ok_or_else(AlpnError::NOACK) }); ```

Not vulnerable - the server buffer outlives the handshake: ```rust let server_protos = b"\x02h2".to_vec(); builder.set_alpn_select_callback(|_, client_protos| { ssl::select_next_proto(&server_protos, client_protos).ok_or_else(AlpnError::NOACK) }); ```

Vulnerable - the server buffer is freed when the callback returns: ```rust builder.set_alpn_select_callback(|_, client_protos| { let server_protos = b"\x02h2".to_vec(); ssl::select_next_proto(&server_protos, client_protos).ok_or_else(AlpnError::NOACK) }); ```