Monday, January 15, 2018

RDBMS -- diagnosing & solving "ORA-28750: unknown error" in UTL_HTTP - TLS communication

As you may remember, I wrote a blog post about this ORA-28750 before.. (in 2015).

In that blog post, I was addressing this issue with the SHA2 certification lack, and as for the solution , I recommended upgrading the database for the fix .. (this was tested and worked)
I also recommended using a GeoTrustSSLCA-G3 type server side certificate for the workaround. (this was tested and worked)

Later on, last week ; we encountered this error in a database and the server side certificate was GeoTrustSSLCA-G3 certificate.. The code was doing "UTL_HTTP.begin_request" and failing with ORA-28750.
So, the fix and the workaround that I documented earlier, were not applicable in this case.. (DB was up-to-date and the certificate was already GeoTrust..G3)..

As you may guess, this time, there was a more detailed diagnostic needed.

So we followed the note:

"How To Investigate And Troubleshoot SSL/TLS Issues on the DB Client SQLNet Layer (Doc ID 2238096.1)"

We took a tcpdump..  (with the related IP addresses to have a consolidated tcp output..)

Example: tcpdump -i em1 dst -s0 -w /tmp/erman_tcpdump.log

In order to see the character strings properly, we opened the tcpdump's output using Wireshark. *

When we opened the output with Wireshark; we concantrated on the TLS V1.2 protocol type communication and we saw an ALERT just after the first HELLO message;

The problem was obvious.. TLS V1.2 communication was throwing Unsupported Exception error.

This error redirected us to the Document named:  UTL_HTTP : ORA-28750: unknown error | unsupported extension (Doc ID 2174046.1)

This document was basically saying "apply patch 23115139", however; this patch was not written for Oracle Database running on Linux X86-64.. In addition to that, our PSU Version was and the patch was not for it.  

So we needed find another patch which includes the same fix and it was required to be appropriate for our DB & PSU Version..

Now look what we found :) ;

Patch 27194186: MERGE REQUEST ON TOP OF DATABASE PSU FOR BUGS 23115139 26963526

Well.. We applied patch 27194186 and our problem solved.

Now, by the help of this issue and its resolution; I can give 2 important messages; 

1) Use wireshark or a similar tool to analyze the tcpdump outputs.  (analyze the dumps by concantrating on TLS protocol messages)

2) Dont surrender even when the patch that is recommended by Oracle Documents, isn't compatible with your RDBMS and PSU versions.. 
Most of the time, you can find another patch (maybe merged), which is compatible with your RDBMS & PSU versions and that patch may include the same fix + more :)

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