md5_ctx_t
#define PROV_MD5_CTX(ctx) ((md5_ctx_t *)(ctx)->cc_provider_private)
ctx_len = sizeof (md5_ctx_t);
ctx->cc_provider_private = kmem_alloc(sizeof (md5_ctx_t),
kmem_free(ctx->cc_provider_private, sizeof (md5_ctx_t));
kmem_free(ctx->cc_provider_private, sizeof (md5_ctx_t));
kmem_free(ctx->cc_provider_private, sizeof (md5_ctx_t));