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I was a consultant on the IBM AS/400 for nearly 20 years. In the past I have used TN5250 to connect to the 400. Lately I've been getting a lot of emails with possible remote consulting gigs. I tried to configure the program and see the following error messages:

checking for OpenSSL headers... -I/usr/include
checking for CRYPTO_num_locks in -lcrypto... no
configure: error: ** Unable to find OpenSSL libraries!

I'm using Ubuntu 23.10. How can I get these libraries installed in case I need the program?

terdon
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vdubeau
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1 Answers1

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Based on the error messages you reported, it looks like you already have the needed libraries - in particular, libcrypto (which is provided by the libssl3 package, with development headers and library links provided by libssl-dev). However your version of libcrypto apparently does not contain the CRYPTO_num_locks symbol.

In general, these kind of API incompatibilities indicate that the libraries are either too old or too new for the software you are trying to build. In this case, the most recent source I could locate for TN5250 is this sourceforge project, in which the majority of the files appear to date from 2008. Meanwhile, the OpenSSL CHANGES.md file describes CRYPTO_num_locks as a "new function" in the description of Changes between 0.9.3a and 0.9.4 [09 Aug 1999]. I can't find any mention of when it was removed - I suspect it was as part of the migration to platform-specific "native" thread implementations (Windows threads / pthreads)1.

Interestingly, while the configure script checks for CRYPTO_num_locks, I can't find anywhere that it is actually used in the source code. However it certainly uses SSLv2_client_method, which was removed in OpenSSL 1.1.02.

If you don't require SSL support, then it looks like you can straightforwardly configure and build TN5250 without it3:

./configure --with-ssl=no
make

If you do find yourself needing an SSL-enabled telnet client in 2024, then you should probably be using SSH instead - if you are required to use the TN5250 client, you could consider tunnelling a telnet over SSH.

  1. see Changes between 1.0.2h and 1.1.0 [25 Aug 2016]

  2. see SSLv23_client_method - HISTORY

  3. at least, that works on my Ubuntu 22.04 VM.

steeldriver
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