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c#.netssltrust

Could not establish trust relationship for SSL/TLS secure channel -- SOAP

I have a simple web service call, generated by a .NET (C#) 2.0 Windows app, via the web service proxy generated by Visual Studio, for a web service also written in C# (2.0). This has worked for several years, and continues to do so at the dozen or so places where it is running.

A new installation at a new site is running into a problem. When attempting to invoke the web service, it fails with the message saying:

Could not establish a trust relationship for the SSL/TLS secure channel

The URL of the web service uses SSL (https://) -- but this has been working for a long time (and continues to do so) from many other locations.

Where do I look? Could this be a security issue between Windows and .NET that is unique to this install? If so, where do I set up trust relationships? I'm lost!

Solution

  • Thoughts (based on pain in the past):

    • do you have DNS and line-of-sight to the server?
    • are you using the correct name from the certificate?
    • is the certificate still valid?
    • is a badly configured load balancer messing things up?
    • does the new server machine have the clock set correctly (i.e. so that the UTC time is correct [ignore local time, it is largely irrelevent]) - this certainly matters for WCF, so may impact regular SOAP?
    • is there a certificate trust chain issue? if you browse from the server to the soap service, can you get SSL?
    • related to the above - has the certificate been installed to the correct location? (you may need a copy in Trusted Root Certification Authorities)
    • is the server's machine-level proxy set correctly? (which different to the user's proxy); see proxycfg for XP / 2003 (not sure about Vista etc)