libprov - a small library of helpers for OpenSSL 3 providers

Currently available routines:

• ERR helpers

  OpenSSL's ERR functions do not lend themselves very well to provider's own error tables, because they can't pass the provider's handle to the error record building routines. This is due to certain limitations with the base C standard requirements for OpenSSL itself (C90).

  These helpers are replacements of OpenSSL's ERR_raise() and ERR_raise_data() that take better advantage of more modern C standards. C99 required.

  See the comments in include/prov/err.h for more information.

• NUM helper

  Converting OSSL_PARAM numbers to native numbers present a bit of a challenge, as they are variable length, and may need some adaption to fit into native numbers.

  provnum_get() and provnum_set() claim to be universally applicable functions for converting an OSSL_PARAM number to a native integer or bignum implementations.

• OSSL_PARAM parsing helper

  Parsing OSSL_PARAM keys can be done in many ways, with various performance problems. A simple (even naïve) way was to loop over the params and strcasecmp() them with known names. Depending on the strcasecmp() implementation, that can be rather slow.

  perl/gen_param_LL.pl takes a specification in form of a perl ARRAY, which contains a C function name (for example, "parse_params") as first item, followed by a series of tuples of this form:

  NAME => "key"

  Each such NAME becomes a couple of C macros:

  • S_NAME, with the "key" string as its value.
  • V_NAME, with a unique generated integer as its value.

  The function name that's given at the start of the function becomes a C function that is called with a single argument, the key to parse. As a test, the following should always be true:

  parse_params(S_NAME) == V_NAME

  When looking through an OSSL_PARAM array, the easy way is to do something like this:

  const OSSL_PARAM *p;
  
  for (p = params; p->key != NULL; p++) {
      switch (parse_params(p->key)) {
      case V_NAME:
          /* Do whatever's needed */
          break;
      ...
      }
  }