- TCP fingerprint
- JA4 fingepriint
- TLS SHA1 certificate (if present), or JA3S fingerprint (is SHA1 is missing)
By default the fingerprint uses the client and server fingerprints (format 0)
and combines them. However you can chnge it format (eg. use only the client info,
format 1) with
--cfg NULL,metadata.ndpi_fingerprint_format,X
where X is the fingerprint format.
By default nDPI fingerprint is enabled but you can enable/disble it as follows
--cfg NULL,metadata.ndpi_fingerprint,0
The idea is to remove the limitation of only two protocols ("master" and
"app") in the flow classifcation.
This is quite handy expecially for STUN flows and, in general, for any
flows where there is some kind of transitionf from a cleartext protocol
to TLS: HTTP_PROXY -> TLS/Youtube; SMTP -> SMTPS (via STARTTLS msg).
In the vast majority of the cases, the protocol stack is simply
Master/Application.
Examples of real stacks (from the unit tests) different from the standard
"master/app":
* "STUN.WhatsAppCall.SRTP": a WA call
* "STUN.DTLS.GoogleCall": a Meet call
* "Telegram.STUN.DTLS.TelegramVoip": a Telegram call
* "SMTP.SMTPS.Google": a SMTP connection to Google server started in
cleartext and updated to TLS
* "HTTP.Google.ntop": a HTTP connection to a Google domain (match via
"Host" header) and to a ntop server (match via "Server" header)
The logic to create the stack is still a bit coarse: we have a decade of
code try to push everything in only ywo protocols... Therefore, the
content of the stack is still **highly experimental** and might change
in the next future; do you have any suggestions?
It is quite likely that the legacy fields "master_protocol" and
"app_protocol" will be there for a long time.
Add some helper to use the stack:
```
ndpi_stack_get_upper_proto();
ndpi_stack_get_lower_proto();
bool ndpi_stack_contains(struct ndpi_proto_stack *s, u_int16_t proto_id);
bool ndpi_stack_is_tls_like(struct ndpi_proto_stack *s);
bool ndpi_stack_is_http_like(struct ndpi_proto_stack *s);
```
Be sure new stack logic is compatible with legacy code:
```
assert(ndpi_stack_get_upper_proto(&flow->detected_protocol.protocol_stack) ==
ndpi_get_upper_proto(flow->detected_protocol));
assert(ndpi_stack_get_lower_proto(&flow->detected_protocol.protocol_stack) ==
ndpi_get_lower_proto(flow->detected_protocol));
```
