Remove OpenSSL ENGINE code

[JosiahWI]

Commit a966bc4 (#11219) accidentally disabled OpenSSL ENGINE support entirely. Although it was unintentional, it seems clear no one is using that API by this point (no one has reported it was broken), and the API is gone in recent OpenSSL versions. This patch removes the dead logic.

[Copilot]

Pull request overview

This PR removes remaining OpenSSL ENGINE-specific code paths from ATS’s TLS utilities and build configuration, aligning with the stated goal of dropping a deprecated/removed OpenSSL API.

Changes:

• Removed ENGINE header usage and runtime ENGINE initialization in SSLPostConfigInitialize().
• Removed ENGINE-backed private key loading logic in SSLPrivateKeyHandler().
• Dropped CMake feature probes for ENGINE APIs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/iocore/net/SSLUtils.cc	Removes ENGINE-related initialization and private-key loading code in TLS setup/handling.
CMakeLists.txt	Removes OpenSSL ENGINE symbol checks from the build configuration.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (2)

src/iocore/net/SSLUtils.cc:775

• The log message still says "SSL engine configuration file", but this code path now just loads OpenSSL config modules via CONF_modules_load_file() (ENGINE support was removed). Keeping "engine" here is misleading for operators troubleshooting config load failures.

  if (SSLConfigParams::engine_conf_file) {
    OPENSSL_load_builtin_modules();
    if (CONF_modules_load_file(SSLConfigParams::engine_conf_file, nullptr, 0) <= 0) {
      char err_buf[256] = {0};
      ERR_error_string_n(ERR_get_error(), err_buf, sizeof(err_buf));
      Error("Could not load SSL engine configuration file %s: %s", SSLConfigParams::engine_conf_file, err_buf);
    }

src/iocore/net/SSLUtils.cc:856

• After removing ENGINE-based key loading, pkey is always default-initialized to null here, so if (pkey == nullptr) is now unconditional and adds an unnecessary indentation level. This is easier to read if the conditional wrapper is removed.

  // SSL_CTX_use_PrivateKey() takes its own reference on the key, so this
  // reference must be released on every exit.
  scoped_PKEY pkey;
  if (pkey == nullptr) {
    scoped_BIO bio(BIO_new_mem_buf(secret_data, secret_data_len));

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.