OpenSSL engine removal and fsverity-utils compilation issue

[Disha Goel <disgoel@linux.ibm.com>]

Hi,

Some distributions have started removing OpenSSL engine support, replacing
engine.h with an empty dummy header file. As a result, fsverity-utils fails
to compile with the following error.

Is there any plan to address this issue and support these distributions?

Please seehttps://fedoraproject.org/wiki/Changes/OpensslDeprecateEngine for more details.

# make
   CC       lib/compute_digest.o
   CC       lib/enable.o
   CC       lib/hash_algs.o
   CC       lib/sign_digest.o
lib/sign_digest.c: In function ‘load_pkcs11_private_key’:
lib/sign_digest.c:350:9: error: implicit declaration of function ‘ENGINE_load_dynamic’ [-Wimplicit-function-declaration]
   350 |         ENGINE_load_dynamic();
       |         ^~~~~~~~~~~~~~~~~~~
lib/sign_digest.c:351:18: error: implicit declaration of function ‘ENGINE_by_id’ [-Wimplicit-function-declaration]
   351 |         engine = ENGINE_by_id("dynamic");
       |                  ^~~~~~~~~~~~
lib/sign_digest.c:351:16: error: assignment to ‘ENGINE *’ {aka ‘struct engine_st *’} from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   351 |         engine = ENGINE_by_id("dynamic");
       |                ^
lib/sign_digest.c:356:14: error: implicit declaration of function ‘ENGINE_ctrl_cmd_string’ [-Wimplicit-function-declaration]
   356 |         if (!ENGINE_ctrl_cmd_string(engine, "SO_PATH",
       |              ^~~~~~~~~~~~~~~~~~~~~~
lib/sign_digest.c:363:14: error: implicit declaration of function ‘ENGINE_init’ [-Wimplicit-function-declaration]
   363 |             !ENGINE_init(engine)) {
       |              ^~~~~~~~~~~
lib/sign_digest.c:365:17: error: implicit declaration of function ‘ENGINE_free’ [-Wimplicit-function-declaration]
   365 |                 ENGINE_free(engine);
       |                 ^~~~~~~~~~~
lib/sign_digest.c:368:21: error: implicit declaration of function ‘ENGINE_load_private_key’ [-Wimplicit-function-declaration]
   368 |         *pkey_ret = ENGINE_load_private_key(engine, sig_params->pkcs11_keyid,
       |                     ^~~~~~~~~~~~~~~~~~~~~~~
lib/sign_digest.c:368:19: error: assignment to ‘EVP_PKEY *’ {aka ‘struct evp_pkey_st *’} from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   368 |         *pkey_ret = ENGINE_load_private_key(engine, sig_params->pkcs11_keyid,
       |                   ^
lib/sign_digest.c:370:9: error: implicit declaration of function ‘ENGINE_finish’ [-Wimplicit-function-declaration]
   370 |         ENGINE_finish(engine);
       |         ^~~~~~~~~~~~~
make: *** [Makefile:134: lib/sign_digest.o] Error 1

------
Thanks
Disha