1// © 2016 and later: Unicode, Inc. and others.
2// License & terms of use: http://www.unicode.org/copyright.html
3/*
4********************************************************************************
5* Copyright (C) 2005-2015, International Business Machines
6* Corporation and others. All Rights Reserved.
7********************************************************************************
8*
9* File WINTZ.CPP
10*
11********************************************************************************
12*/
13
14#include "unicode/utypes.h"
15
16#if U_PLATFORM_USES_ONLY_WIN32_API
17
18#include "wintz.h"
19#include "charstr.h"
20#include "cmemory.h"
21#include "cstring.h"
22
23#include "unicode/ures.h"
24#include "unicode/unistr.h"
25#include "uresimp.h"
26
27#ifndef WIN32_LEAN_AND_MEAN
28# define WIN32_LEAN_AND_MEAN
29#endif
30# define VC_EXTRALEAN
31# define NOUSER
32# define NOSERVICE
33# define NOIME
34# define NOMCX
35#include <windows.h>
36
37U_NAMESPACE_BEGIN
38
39// Note these constants and the struct are only used when dealing with the fallback path for RDP sessions.
40
41// This is the location of the time zones in the registry on Vista+ systems.
42// See: https://docs.microsoft.com/windows/win32/api/timezoneapi/ns-timezoneapi-dynamic_time_zone_information
43#define WINDOWS_TIMEZONES_REG_KEY_PATH L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones"
44
45// Max length for a registry key is 255. +1 for null.
46// See: https://docs.microsoft.com/windows/win32/sysinfo/registry-element-size-limits
47#define WINDOWS_MAX_REG_KEY_LENGTH 256
48
49#if U_PLATFORM_HAS_WINUWP_API == 0
50
51// This is the layout of the TZI binary value in the registry.
52// See: https://docs.microsoft.com/windows/win32/api/timezoneapi/ns-timezoneapi-time_zone_information
53typedef struct _REG_TZI_FORMAT {
54 LONG Bias;
55 LONG StandardBias;
56 LONG DaylightBias;
57 SYSTEMTIME StandardDate;
58 SYSTEMTIME DaylightDate;
59} REG_TZI_FORMAT;
60
61#endif // U_PLATFORM_HAS_WINUWP_API
62
63/**
64* This is main Windows time zone detection function.
65*
66* It returns the Windows time zone converted to an ICU time zone as a heap-allocated buffer, or nullptr upon failure.
67*
68* We use the Win32 API GetDynamicTimeZoneInformation (which is available since Vista) to get the current time zone info,
69* as this API returns a non-localized time zone name which can be then mapped to an ICU time zone.
70*
71* However, in some RDP/terminal services situations, this struct isn't always fully complete, and the TimeZoneKeyName
72* field of the struct might be nullptr. This can happen with some 3rd party RDP clients, and also when using older versions
73* of the RDP protocol, which don't send the newer TimeZoneKeyNamei information and only send the StandardName and DaylightName.
74*
75* Since these 3rd party clients and older RDP clients only send the pre-Vista time zone information to the server, this means that we
76* need to fallback on using the pre-Vista methods to determine the time zone. This unfortunately requires examining the registry directly
77* in order to try and determine the current time zone.
78*
79* Note that this can however still fail in some cases though if the client and server are using different languages, as the StandardName
80* that is sent by client is localized in the client's language. However, we must compare this to the names that are on the server, which
81* are localized in registry using the server's language. Despite that, this is the best we can do.
82*
83* Note: This fallback method won't work for the UWP version though, as we can't use the registry APIs in UWP.
84*
85* Once we have the current Windows time zone, then we can then map it to an ICU time zone ID (~ Olsen ID).
86*/
87U_CAPI const char* U_EXPORT2
88uprv_detectWindowsTimeZone()
89{
90 // We first try to obtain the time zone directly by using the TimeZoneKeyName field of the DYNAMIC_TIME_ZONE_INFORMATION struct.
91 DYNAMIC_TIME_ZONE_INFORMATION dynamicTZI;
92 uprv_memset(&dynamicTZI, 0, sizeof(dynamicTZI));
93 SYSTEMTIME systemTimeAllZero;
94 uprv_memset(&systemTimeAllZero, 0, sizeof(systemTimeAllZero));
95
96 if (GetDynamicTimeZoneInformation(&dynamicTZI) == TIME_ZONE_ID_INVALID) {
97 return nullptr;
98 }
99
100 // If the DST setting has been turned off in the Control Panel, then return "Etc/GMT<offset>".
101 //
102 // Note: This logic is based on how the Control Panel itself determines if DST is 'off' on Windows.
103 // The code is somewhat convoluted; in a sort of pseudo-code it looks like this:
104 //
105 // IF (GetDynamicTimeZoneInformation != TIME_ZONE_ID_INVALID) && (DynamicDaylightTimeDisabled != 0) &&
106 // (StandardDate == DaylightDate) &&
107 // (
108 // (TimeZoneKeyName != Empty && StandardDate == 0) ||
109 // (TimeZoneKeyName == Empty && StandardDate != 0)
110 // )
111 // THEN
112 // DST setting is "Disabled".
113 //
114 if (dynamicTZI.DynamicDaylightTimeDisabled != 0 &&
115 uprv_memcmp(&dynamicTZI.StandardDate, &dynamicTZI.DaylightDate, sizeof(dynamicTZI.StandardDate)) == 0 &&
116 ((dynamicTZI.TimeZoneKeyName[0] != L'\0' && uprv_memcmp(&dynamicTZI.StandardDate, &systemTimeAllZero, sizeof(systemTimeAllZero)) == 0) ||
117 (dynamicTZI.TimeZoneKeyName[0] == L'\0' && uprv_memcmp(&dynamicTZI.StandardDate, &systemTimeAllZero, sizeof(systemTimeAllZero)) != 0)))
118 {
119 LONG utcOffsetMins = dynamicTZI.Bias;
120 if (utcOffsetMins == 0) {
121 return uprv_strdup("Etc/UTC");
122 }
123
124 // No way to support when DST is turned off and the offset in minutes is not a multiple of 60.
125 if (utcOffsetMins % 60 == 0) {
126 char gmtOffsetTz[11] = {}; // "Etc/GMT+dd" is 11-char long with a terminal null.
127 // Important note on the sign convention for zones:
128 //
129 // From https://en.wikipedia.org/wiki/Tz_database#Area
130 // "In order to conform with the POSIX style, those zone names beginning with "Etc/GMT" have their sign reversed
131 // from the standard ISO 8601 convention. In the "Etc" area, zones west of GMT have a positive sign and those
132 // east have a negative sign in their name (e.g "Etc/GMT-14" is 14 hours ahead of GMT)."
133 //
134 // Regarding the POSIX style, from https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
135 // "The offset specifies the time value you must add to the local time to get a Coordinated Universal Time value."
136 //
137 // However, the Bias value in DYNAMIC_TIME_ZONE_INFORMATION *already* follows the POSIX convention.
138 //
139 // From https://docs.microsoft.com/en-us/windows/win32/api/timezoneapi/ns-timezoneapi-dynamic_time_zone_information
140 // "The bias is the difference, in minutes, between Coordinated Universal Time (UTC) and
141 // local time. All translations between UTC and local time are based on the following formula:
142 // UTC = local time + bias"
143 //
144 // For example, a time zone that is 3 hours ahead of UTC (UTC+03:00) would have a Bias value of -180, and the
145 // corresponding time zone ID would be "Etc/GMT-3". (So there is no need to negate utcOffsetMins below.)
146 int ret = snprintf(gmtOffsetTz, sizeof(gmtOffsetTz), "Etc/GMT%+ld", utcOffsetMins / 60);
147 if (ret > 0 && ret < UPRV_LENGTHOF(gmtOffsetTz)) {
148 return uprv_strdup(gmtOffsetTz);
149 }
150 }
151 }
152
153 // If DST is NOT disabled, but the TimeZoneKeyName field of the struct is nullptr, then we may be dealing with a
154 // RDP/terminal services session where the 'Time Zone Redirection' feature is enabled. However, either the RDP
155 // client sent the server incomplete info (some 3rd party RDP clients only send the StandardName and DaylightName,
156 // but do not send the important TimeZoneKeyName), or if the RDP server has not appropriately populated the struct correctly.
157 //
158 // In this case we unfortunately have no choice but to fallback to using the pre-Vista method of determining the
159 // time zone, which requires examining the registry directly.
160 //
161 // Note that this can however still fail though if the client and server are using different languages, as the StandardName
162 // that is sent by client is *localized* in the client's language. However, we must compare this to the names that are
163 // on the server, which are *localized* in registry using the server's language.
164 //
165 // One other note is that this fallback method doesn't work for the UWP version, as we can't use the registry APIs.
166
167 // windowsTimeZoneName will point at timezoneSubKeyName if we had to fallback to using the registry, and we found a match.
168 WCHAR timezoneSubKeyName[WINDOWS_MAX_REG_KEY_LENGTH];
169 WCHAR *windowsTimeZoneName = dynamicTZI.TimeZoneKeyName;
170
171 if (dynamicTZI.TimeZoneKeyName[0] == 0) {
172
173// We can't use the registry APIs in the UWP version.
174#if U_PLATFORM_HAS_WINUWP_API == 1
175 (void)timezoneSubKeyName; // suppress unused variable warnings.
176 return nullptr;
177#else
178 // Open the path to the time zones in the Windows registry.
179 LONG ret;
180 HKEY hKeyAllTimeZones = nullptr;
181 ret = RegOpenKeyExW(HKEY_LOCAL_MACHINE, WINDOWS_TIMEZONES_REG_KEY_PATH, 0, KEY_READ,
182 reinterpret_cast<PHKEY>(&hKeyAllTimeZones));
183
184 if (ret != ERROR_SUCCESS) {
185 // If we can't open the key, then we can't do much, so fail.
186 return nullptr;
187 }
188
189 // Read the number of subkeys under the time zone registry path.
190 DWORD numTimeZoneSubKeys;
191 ret = RegQueryInfoKeyW(hKeyAllTimeZones, nullptr, nullptr, nullptr, &numTimeZoneSubKeys,
192 nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
193
194 if (ret != ERROR_SUCCESS) {
195 RegCloseKey(hKeyAllTimeZones);
196 return nullptr;
197 }
198
199 // Examine each of the subkeys to try and find a match for the localized standard name ("Std").
200 //
201 // Note: The name of the time zone subkey itself is not localized, but the "Std" name is localized. This means
202 // that we could fail to find a match if the RDP client and RDP server are using different languages, but unfortunately
203 // there isn't much we can do about it.
204 HKEY hKeyTimeZoneSubKey = nullptr;
205 ULONG registryValueType;
206 WCHAR registryStandardName[WINDOWS_MAX_REG_KEY_LENGTH];
207
208 for (DWORD i = 0; i < numTimeZoneSubKeys; i++) {
209 // Note: RegEnumKeyExW wants the size of the buffer in characters.
210 DWORD size = UPRV_LENGTHOF(timezoneSubKeyName);
211 ret = RegEnumKeyExW(hKeyAllTimeZones, i, timezoneSubKeyName, &size, nullptr, nullptr, nullptr, nullptr);
212
213 if (ret != ERROR_SUCCESS) {
214 RegCloseKey(hKeyAllTimeZones);
215 return nullptr;
216 }
217
218 ret = RegOpenKeyExW(hKeyAllTimeZones, timezoneSubKeyName, 0, KEY_READ,
219 reinterpret_cast<PHKEY>(&hKeyTimeZoneSubKey));
220
221 if (ret != ERROR_SUCCESS) {
222 RegCloseKey(hKeyAllTimeZones);
223 return nullptr;
224 }
225
226 // Note: RegQueryValueExW wants the size of the buffer in bytes.
227 size = sizeof(registryStandardName);
228 ret = RegQueryValueExW(hKeyTimeZoneSubKey, L"Std", nullptr, &registryValueType,
229 reinterpret_cast<LPBYTE>(registryStandardName), &size);
230
231 if (ret != ERROR_SUCCESS || registryValueType != REG_SZ) {
232 RegCloseKey(hKeyTimeZoneSubKey);
233 RegCloseKey(hKeyAllTimeZones);
234 return nullptr;
235 }
236
237 // Note: wcscmp does an ordinal (byte) comparison.
238 if (wcscmp(reinterpret_cast<WCHAR *>(registryStandardName), dynamicTZI.StandardName) == 0) {
239 // Since we are comparing the *localized* time zone name, it's possible that some languages might use
240 // the same string for more than one time zone. Thus we need to examine the TZI data in the registry to
241 // compare the GMT offset (the bias), and the DST transition dates, to ensure it's the same time zone
242 // as the currently reported one.
243 REG_TZI_FORMAT registryTziValue;
244 uprv_memset(&registryTziValue, 0, sizeof(registryTziValue));
245
246 // Note: RegQueryValueExW wants the size of the buffer in bytes.
247 DWORD timezoneTziValueSize = sizeof(registryTziValue);
248 ret = RegQueryValueExW(hKeyTimeZoneSubKey, L"TZI", nullptr, &registryValueType,
249 reinterpret_cast<LPBYTE>(&registryTziValue), &timezoneTziValueSize);
250
251 if (ret == ERROR_SUCCESS) {
252 if ((dynamicTZI.Bias == registryTziValue.Bias) &&
253 (memcmp((const void *)&dynamicTZI.StandardDate, (const void *)&registryTziValue.StandardDate, sizeof(SYSTEMTIME)) == 0) &&
254 (memcmp((const void *)&dynamicTZI.DaylightDate, (const void *)&registryTziValue.DaylightDate, sizeof(SYSTEMTIME)) == 0))
255 {
256 // We found a matching time zone.
257 windowsTimeZoneName = timezoneSubKeyName;
258 break;
259 }
260 }
261 }
262 RegCloseKey(hKeyTimeZoneSubKey);
263 hKeyTimeZoneSubKey = nullptr;
264 }
265
266 if (hKeyTimeZoneSubKey != nullptr) {
267 RegCloseKey(hKeyTimeZoneSubKey);
268 }
269 if (hKeyAllTimeZones != nullptr) {
270 RegCloseKey(hKeyAllTimeZones);
271 }
272#endif // U_PLATFORM_HAS_WINUWP_API
273 }
274
275 CharString winTZ;
276 UErrorCode status = U_ZERO_ERROR;
277 winTZ.appendInvariantChars(UnicodeString(true, windowsTimeZoneName, -1), status);
278
279 // Map Windows Timezone name (non-localized) to ICU timezone ID (~ Olson timezone id).
280 StackUResourceBundle winTZBundle;
281 ures_openDirectFillIn(winTZBundle.getAlias(), nullptr, "windowsZones", &status);
282 ures_getByKey(winTZBundle.getAlias(), "mapTimezones", winTZBundle.getAlias(), &status);
283 ures_getByKey(winTZBundle.getAlias(), winTZ.data(), winTZBundle.getAlias(), &status);
284
285 if (U_FAILURE(status)) {
286 return nullptr;
287 }
288
289 // Note: Since the ISO 3166 country/region codes are all invariant ASCII chars, we can
290 // directly downcast from wchar_t to do the conversion.
291 // We could call the A version of the GetGeoInfo API, but that would be slightly slower than calling the W API,
292 // as the A version of the API will end up calling MultiByteToWideChar anyways internally.
293 wchar_t regionCodeW[3] = {};
294 char regionCode[3] = {}; // 2 letter ISO 3166 country/region code made entirely of invariant chars.
295 int geoId = GetUserGeoID(GEOCLASS_NATION);
296 int regionCodeLen = GetGeoInfoW(geoId, GEO_ISO2, regionCodeW, UPRV_LENGTHOF(regionCodeW), 0);
297
298 const char16_t *icuTZ16 = nullptr;
299 int32_t tzListLen = 0;
300
301 if (regionCodeLen != 0) {
302 for (int i = 0; i < UPRV_LENGTHOF(regionCodeW); i++) {
303 regionCode[i] = static_cast<char>(regionCodeW[i]);
304 }
305 icuTZ16 = ures_getStringByKey(winTZBundle.getAlias(), regionCode, &tzListLen, &status);
306 }
307 if (regionCodeLen == 0 || U_FAILURE(status)) {
308 // fallback to default "001" (world)
309 status = U_ZERO_ERROR;
310 icuTZ16 = ures_getStringByKey(winTZBundle.getAlias(), "001", &tzListLen, &status);
311 }
312
313 // Note: We want the first entry in the string returned by ures_getStringByKey.
314 // However this string can be a space delimited list of timezones:
315 // Ex: "America/New_York America/Detroit America/Indiana/Petersburg ..."
316 // We need to stop at the first space, so we pass tzLen (instead of tzListLen) to appendInvariantChars below.
317 int32_t tzLen = 0;
318 if (tzListLen > 0) {
319 while (!(icuTZ16[tzLen] == u'\0' || icuTZ16[tzLen] == u' ')) {
320 tzLen++;
321 }
322 }
323
324 // Note: cloneData returns nullptr if the status is a failure, so this
325 // will return nullptr if the above look-up fails.
326 CharString icuTZStr;
327 return icuTZStr.appendInvariantChars(icuTZ16, tzLen, status).cloneData(status);
328}
329
330U_NAMESPACE_END
331#endif /* U_PLATFORM_USES_ONLY_WIN32_API */
332