NvtSession SOAP probe fails against cameras incompatible with TLS 1.3 or Expect:100-Continue

[kumaakh]

Summary

NvtSession.CreateSession(Uri[]) (multi-URI probe path) does not apply TLS 1.2 restriction or disable Expect: 100-Continue before probing candidate URIs. Cameras whose gSOAP stacks are incompatible with TLS 1.3 or that stall on Expect:100-Continue will always fail the probe — all candidate URIs are rejected and session creation fails.

Root cause

soapProbeWithTimeout sends a GetSystemDateAndTime SOAP request to each URI. For HTTPS probes, the default .NET TLS negotiation includes TLS 1.3, which certain embedded ONVIF cameras (e.g. Milesight) do not support. For HTTP probes, Expect: 100-Continue is enabled by default on .NET WebRequest, causing the camera to stall.

The single-URI CreateSession(deviceUri) overload sets ServicePointManager.FindServicePoint(deviceUri).Expect100Continue = false — but only for that one ServicePoint. The multi-URI probe path does not set the global ServicePointManager.Expect100Continue = false or SecurityProtocol = Tls12 before probing.

Reproduction

1. Create NvtSessionFactory targeting http://192.168.1.190/onvif/device_service (Milesight camera, port 80 open)
2. Call factory.CreateSession(uris) with the HTTP URI
3. Probe fails: camera stalls on Expect: 100-Continue
4. HTTPS fallback also fails: camera rejects TLS 1.3

Fix

Before the probe loop in CreateSession(Uri[]):

• Set ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
• Set ServicePointManager.Expect100Continue = false
• Set ServicePointManager.ServerCertificateValidationCallback to accept self-signed certs

Integration test evidence

Media2IntegrationTests — all 7 tests fail at CreateSession() with:

System.Exception: SOAP probe failed for all URIs (including HTTPS fallback)

Probe attempts: http://192.168.1.190/onvif/device_service, https://192.168.1.190/onvif/device_service, https://192.168.1.190:8443/onvif/device_service — all fail.