tzcode: Add test case for setugid programs

Fixes:		a6b19979bf ("tzcode: Fix TZ for non-setugid programs")
Differential Revision:	https://reviews.freebsd.org/D52124

lib/libc/tests/stdtime/Makefile

@@ -1,8 +1,10 @@
 .include <src.opts.mk>
 
 ATF_TESTS_C+=		strptime_test
-.if ${MK_DETECT_TZ_CHANGES} != "no"
 ATF_TESTS_C+=		detect_tz_changes_test
+
+.if ${MK_DETECT_TZ_CHANGES} != "no"
+CFLAGS.detect_tz_changes_test+= -DDETECT_TZ_CHANGES
 .endif
 
 TESTSDIR:=	${TESTSBASE}/${RELDIR:C/libc\/tests/libc/}

lib/libc/tests/stdtime/detect_tz_changes_test.c

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <sys/param.h>
+#include <sys/conf.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
 
@@ -41,6 +43,8 @@ static const struct tzcase {
 };
 
 static const time_t then = 1751328000; /* 2025-07-01 00:00:00 UTC */
+
+#ifdef DETECT_TZ_CHANGES
 static const char *tz_change_interval_sym = "__tz_change_interval";
 static int *tz_change_interval_p;
 static const int tz_change_interval = 3;
@@ -272,6 +276,21 @@ ATF_TC_BODY(detect_tz_changes, tc)
 	ATF_REQUIRE(WIFEXITED(status));
 	ATF_REQUIRE_EQ(0, WEXITSTATUS(status));
 }
+#endif /* DETECT_TZ_CHANGES */
+
+static void
+test_tz_env(const char *tzval, const char *expect)
+{
+	char buf[128];
+	struct tm *tm;
+	size_t len;
+
+	setenv("TZ", tzval, 1);
+	ATF_REQUIRE((tm = localtime(&then)) != NULL);
+	len = strftime(buf, sizeof(buf), "%z (%Z)", tm);
+	ATF_REQUIRE(len > 0);
+	ATF_CHECK_STREQ(expect, buf);
+}
 
 ATF_TC(tz_env);
 ATF_TC_HEAD(tz_env, tc)
@@ -280,25 +299,37 @@ ATF_TC_HEAD(tz_env, tc)
 }
 ATF_TC_BODY(tz_env, tc)
 {
-	char buf[128];
-	const struct tzcase *tzcase = NULL;
-	struct tm *tm;
-	size_t len;
+	const struct tzcase *tzcase;
 
-	for (tzcase = tzcases; tzcase->tzfn != NULL; tzcase++) {
-		setenv("TZ", tzcase->tzfn, 1);
-		ATF_REQUIRE((tm = localtime(&then)) != NULL);
-		len = strftime(buf, sizeof(buf), "%z (%Z)", tm);
-		ATF_REQUIRE(len > 0);
-		ATF_REQUIRE_STREQ(tzcase->expect, buf);
-	}
+	for (tzcase = tzcases; tzcase->tzfn != NULL; tzcase++)
+		test_tz_env(tzcase->tzfn, tzcase->expect);
+}
+
+ATF_TC(tz_env_setugid);
+ATF_TC_HEAD(tz_env_setugid, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Test TZ environment variable "
+		"in setugid process");
+	atf_tc_set_md_var(tc, "require.user", "root");
+}
+ATF_TC_BODY(tz_env_setugid, tc)
+{
+	const struct tzcase *tzcase;
+
+	ATF_REQUIRE_EQ(0, seteuid(UID_NOBODY));
+	ATF_REQUIRE(issetugid());
+	for (tzcase = tzcases; tzcase->tzfn != NULL; tzcase++)
+		test_tz_env(tzcase->tzfn, tzcase->expect);
 }
 
 ATF_TP_ADD_TCS(tp)
 {
+#ifdef DETECT_TZ_CHANGES
 	debugging = !getenv("__RUNNING_INSIDE_ATF_RUN") &&
 	    isatty(STDERR_FILENO);
 	ATF_TP_ADD_TC(tp, detect_tz_changes);
+#endif /* DETECT_TZ_CHANGES */
 	ATF_TP_ADD_TC(tp, tz_env);
+	ATF_TP_ADD_TC(tp, tz_env_setugid);
 	return (atf_no_error());
 }