include timegm fallback

.gitignore

@@ -129,6 +129,7 @@ include/openssl/*.h
 !/crypto/compat/posix_win.c
 !/crypto/compat/bsd_asprintf.c
 !/crypto/compat/inet_pton.c
+!/crypto/compat/timegm.c
 !/crypto/compat/ui_openssl_win.c
 !/crypto/CMakeLists.txt
 /crypto

crypto/Makefile.am

@@ -73,6 +73,12 @@ if !HAVE_INET_PTON
 libcompat_la_SOURCES += compat/inet_pton.c
 endif
 
+if !HAVE_TIMEGM
+if !HAVE__MKGMTIME
+libcompat_la_SOURCES += compat/timegm.c
+endif
+endif
+
 if !HAVE_REALLOCARRAY
 libcompat_la_SOURCES += compat/reallocarray.c
 endif

crypto/compat/timegm.c

@@ -0,0 +1,71 @@
+/*
+ * timegm shims based on example code from in the glibc timegm manpage.
+ *
+ * These should be replaced with lockless versions that do not require
+ * modifying global state.
+ */
+
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _WIN32
+#include <windows.h>
+time_t
+timegm(struct tm *tm)
+{
+	time_t ret;
+	char *tz, *buf;
+	static volatile HANDLE mtx = NULL;
+
+	if (!mtx) {
+		HANDLE p = CreateMutex(NULL, FALSE, NULL);
+		if (InterlockedCompareExchangePointer(
+		    (void **)&mtx, (void *)p, NULL))
+			CloseHandle(p);
+	}
+	WaitForSingleObject(mtx, INFINITE);
+	tz = getenv("TZ");
+	if (tz) {
+		if (asprintf(&buf, "TZ=%s", tz) == -1)
+			buf = NULL;
+	}
+	putenv("TZ=UTC");
+	tzset();
+	ret = mktime(tm);
+	if (buf) {
+		putenv(buf);
+		free(buf);
+	} else
+		putenv("TZ=");
+	tzset();
+	ReleaseMutex(mtx);
+	return ret;
+}
+#else
+#include <pthread.h>
+time_t
+timegm(struct tm *tm)
+{
+	time_t ret;
+	char *tz;
+	static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
+
+	pthread_mutex_lock(&mtx);
+	tz = getenv("TZ");
+	if (tz)
+		tz = strdup(tz);
+	setenv("TZ", "", 1);
+	tzset();
+	ret = mktime(tm);
+	if (tz) {
+		setenv("TZ", tz, 1);
+		free(tz);
+	} else
+		unsetenv("TZ");
+	tzset();
+	pthread_mutex_unlock(&mtx);
+	return ret;
+}
+#endif

include/compat/limits.h

@@ -3,9 +3,6 @@
  * limits.h compatibility shim
  */
 
-#ifndef LIBCRYPTOCOMPAT_LIMITS_H
-#define LIBCRYPTOCOMPAT_LIMITS_H
-
 #ifdef _MSC_VER
 #if _MSC_VER >= 1900
 #include <../ucrt/limits.h>
@@ -22,5 +19,3 @@
 #define PATH_MAX MAXPATHLEN
 #endif
 #endif
-
-#endif

include/compat/time.h

@@ -14,6 +14,10 @@
 #include_next <time.h>
 #endif
 
-#ifdef _WIN32
+#ifndef HAVE_TIMEGM
+#ifdef  HAVE__MKGMTIME
 #define timegm(tm) _mkgmtime(tm)
+#else
+time_t timegm(struct tm *tm);
+#endif
 #endif

m4/check-libc.m4

@@ -4,6 +4,7 @@ AC_CHECK_HEADERS([err.h readpassphrase.h])
 # Check for general libc functions
 AC_CHECK_FUNCS([asprintf inet_pton memmem readpassphrase reallocarray])
 AC_CHECK_FUNCS([strlcat strlcpy strndup strnlen strsep strtonum])
+AC_CHECK_FUNCS([timegm _mkgmtime])
 AM_CONDITIONAL([HAVE_ASPRINTF], [test "x$ac_cv_func_asprintf" = xyes])
 AM_CONDITIONAL([HAVE_INET_PTON], [test "x$ac_cv_func_inet_pton" = xyes])
 AM_CONDITIONAL([HAVE_MEMMEM], [test "x$ac_cv_func_memmem" = xyes])
@@ -15,6 +16,8 @@ AM_CONDITIONAL([HAVE_STRNDUP], [test "x$ac_cv_func_strndup" = xyes])
 AM_CONDITIONAL([HAVE_STRNLEN], [test "x$ac_cv_func_strnlen" = xyes])
 AM_CONDITIONAL([HAVE_STRSEP], [test "x$ac_cv_func_strsep" = xyes])
 AM_CONDITIONAL([HAVE_STRTONUM], [test "x$ac_cv_func_strtonum" = xyes])
+AM_CONDITIONAL([HAVE_TIMEGM], [test "x$ac_cv_func_timegm" = xyes])
+AM_CONDITIONAL([HAVE__MKGMTIME], [test "x$ac_cv_func__mkgmtime" = xyes])
 ])
 
 AC_DEFUN([CHECK_SYSCALL_COMPAT], [