openssl: add a simple smoke test for the legacy provider

This change adds a simple smoke test for the legacy provider to ensure
that the provider doesn't break in the future when performing updates.

This is not a functional or system test; the OpenSSL test suite does a
much better job at doing this than we can.

MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D53045

secure/lib/libcrypto/Makefile

@@ -682,6 +682,9 @@ buildasm cleanasm:
 	    ${.TARGET:S/build/all/:S/asm$//}
 .endfor
 
+HAS_TESTS=	yes
+SUBDIR.${MK_TESTS}=	tests
+
 .include <bsd.lib.mk>
 
 .if ${MACHINE} == "powerpc"

secure/lib/libcrypto/tests/Makefile

@@ -0,0 +1,5 @@
+PACKAGE=		tests
+
+ATF_TESTS_SH+=		libcrypto_test
+
+.include <bsd.test.mk>

secure/lib/libcrypto/tests/libcrypto_test.sh

@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2025 Enji Cooper
+
+atf_test_case legacy_provider
+legacy_provider_head() {
+	atf_set "descr" "daemon should drop privileges"
+}
+legacy_provider_body() {
+	local passphrase="test"
+	local plaintext="test"
+
+	export OPENSSL_CONF="$PWD/openssl.conf"
+	cat > "$OPENSSL_CONF" <<EOF
+HOME = .
+
+openssl_conf = openssl_init
+
+[openssl_init]
+providers = provider_sect
+
+# List of providers to load
+[provider_sect]
+default = default_sect
+legacy = legacy_sect
+
+[default_sect]
+activate = 1
+
+[legacy_sect]
+activate = 1
+EOF
+
+	echo "$plaintext" | atf_check -s exit:0 -e empty -o not-empty \
+	    openssl rc4 -e -k "$passphrase" -a -pbkdf2
+}
+
+atf_init_test_cases() {
+	atf_add_test_case legacy_provider
+}