‘ENGINE_free’ is deprecated: Since OpenSSL 3.0 at tlsio_openssl.c

[matsujirushi]

Hi,
When I compiled iothub_ll_telemetry_sample on Ubuntu 22.04, I got a compilation error at the OpenSSL call part.

Error message:

/home/azureuser/azure-iot-sdk-c/c-utility/adapters/tlsio_openssl.c: In function ‘engine_destroy’:
/home/azureuser/azure-iot-sdk-c/c-utility/adapters/tlsio_openssl.c:762:9: error: ‘ENGINE_free’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
  762 |         ENGINE_free(tls->engine); // Release structural reference.
      |         ^~~~~~~~~~~
In file included from /home/azureuser/azure-iot-sdk-c/c-utility/adapters/tlsio_openssl.c:9:
/usr/include/openssl/engine.h:493:27: note: declared here
  493 | OSSL_DEPRECATEDIN_3_0 int ENGINE_free(ENGINE *e);
      |                           ^~~~~~~~~~~
/home/azureuser/azure-iot-sdk-c/c-utility/adapters/tlsio_openssl.c: In function ‘engine_load’:
/home/azureuser/azure-iot-sdk-c/c-utility/adapters/tlsio_openssl.c:772:5: error: ‘ENGINE_by_id’ is deprecated: Since OpenSSL 3.0 [-Werror=deprecated-declarations]
  772 |     tls->engine = ENGINE_by_id(tls->engine_id);
      |     ^~~
In file included from /home/azureuser/azure-iot-sdk-c/c-utility/adapters/tlsio_openssl.c:9:
/usr/include/openssl/engine.h:336:31: note: declared here
  336 | OSSL_DEPRECATEDIN_3_0 ENGINE *ENGINE_by_id(const char *id);
      |                               ^~~~~~~~~~~~
...

Is there any way to avoid the error?

Azure IoT C SDK:

git clone -b LTS_07_2022_Ref01 https://github.com/Azure/azure-iot-sdk-c.git
cd azure-iot-sdk-c
git submodule update --init

cmake:

$ cmake -DCMAKE_BUILD_TYPE=Debug -Dbuild_service_client=OFF -Dbuild_provisioning_service_client=OFF -Duse_amqp=OFF -Duse_http=OFF ..
...
-- IoT Client SDK Version = 1.9.0
...
-- Found OpenSSL: /usr/lib/x86_64-linux-gnu/libcrypto.so (found version "3.0.2")  
...

[danewalton]

Hi @matsujirushi
This is currently a work in progress here: #2346

You may try the branch yourself. Right now we are looking to fix our E2E tests and once that works, it should be merged.

[matsujirushi]

Hi @danewalton ,
Thanks for information.
That branch is compiled and working.
Thank you very much!

git checkout origin/dane/openssl3
git submodule update --init