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ICU-21352 ICU4C: Windows time zone detection can fail in RDP sessions with some 3rd party software and older RDP clients

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Jeff Genovy 2020-10-23 13:23:03 -07:00 • committed by Yoshito Umaoka
parent c7024d5faa
commit df72f8cbaf
1 changed files with 165 additions and 8 deletions
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173
icu4c/source/common/wintz.cpp
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@ -36,17 +36,58 @@
U_NAMESPACE_BEGIN
// Note these constants and the struct are only used when dealing with the fallback path for RDP sesssions.
// This is the location of the time zones in the registry on Vista+ systems.
// See: https://docs.microsoft.com/windows/win32/api/timezoneapi/ns-timezoneapi-dynamic_time_zone_information
#define WINDOWS_TIMEZONES_REG_KEY_PATH L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones"
// Max length for a registry key is 255. +1 for null.
// See: https://docs.microsoft.com/windows/win32/sysinfo/registry-element-size-limits
#define WINDOWS_MAX_REG_KEY_LENGTH 256
#if U_PLATFORM_HAS_WINUWP_API == 0
// This is the layout of the TZI binary value in the registry.
// See: https://docs.microsoft.com/windows/win32/api/timezoneapi/ns-timezoneapi-time_zone_information
typedef struct _REG_TZI_FORMAT {
LONG Bias;
LONG StandardBias;
LONG DaylightBias;
SYSTEMTIME StandardDate;
SYSTEMTIME DaylightDate;
} REG_TZI_FORMAT;
#endif // U_PLATFORM_HAS_WINUWP_API
/**
* Main Windows time zone detection function.
* Returns the Windows time zone converted to an ICU time zone as a heap-allocated buffer, or nullptr upon failure.
* This is main Windows time zone detection function.
*
* It returns the Windows time zone converted to an ICU time zone as a heap-allocated buffer, or nullptr upon failure.
*
* Note: We use the Win32 API GetDynamicTimeZoneInformation (available since Vista+) to get the current time zone info.
* This API returns a non-localized time zone name, which is mapped to an ICU time zone ID (~ Olsen ID).
* We use the Win32 API GetDynamicTimeZoneInformation (which is available since Vista) to get the current time zone info,
* as this API returns a non-localized time zone name which can be then mapped to an ICU time zone.
*
* However, in some RDP/terminal services situations, this struct isn't always fully complete, and the TimeZoneKeyName
* field of the struct might be NULL. This can happen with some 3rd party RDP clients, and also when using older versions
* of the RDP protocol, which don't send the newer TimeZoneKeyNamei information and only send the StandardName and DaylightName.
*
* Since these 3rd party clients and older RDP clients only send the pre-Vista time zone information to the server, this means that we
* need to fallback on using the pre-Vista methods to determine the time zone. This unfortunately requires examining the registry directly
* in order to try and determine the current time zone.
*
* Note that this can however still fail in some cases though if the client and server are using different languages, as the StandardName
* 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
* are localized in registry using the server's language. Despite that, this is the best we can do.
*
* Note: This fallback method won't work for the UWP version though, as we can't use the registry APIs in UWP.
*
* Once we have the current Windows time zone, then we can then map it to an ICU time zone ID (~ Olsen ID).
*/
U_CAPI const char* U_EXPORT2
uprv_detectWindowsTimeZone()
{
// Obtain the DYNAMIC_TIME_ZONE_INFORMATION info to get the non-localized time zone name.
// We first try to obtain the time zone directly by using the TimeZoneKeyName field of the DYNAMIC_TIME_ZONE_INFORMATION struct.
DYNAMIC_TIME_ZONE_INFORMATION dynamicTZI;
uprv_memset(&dynamicTZI, 0, sizeof(dynamicTZI));
SYSTEMTIME systemTimeAllZero;
@ -93,15 +134,131 @@ uprv_detectWindowsTimeZone()
}
}
// If DST is NOT disabled, but we have an empty TimeZoneKeyName, then it is unclear
// what we should do as this should not happen.
// If DST is NOT disabled, but the TimeZoneKeyName field of the struct is NULL, then we may be dealing with a
// RDP/terminal services session where the 'Time Zone Redirection' feature is enabled. However, either the RDP
// client sent the server incomplete info (some 3rd party RDP clients only send the StandardName and DaylightName,
// but do not send the important TimeZoneKeyName), or if the RDP server has not appropriately populated the struct correctly.
//
// In this case we unfortunately have no choice but to fallback to using the pre-Vista method of determining the
// time zone, which requires examining the registry directly.
//
// Note that this can however still fail though if the client and server are using different languages, as the StandardName
// 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 are *localized* in registry using the server's language.
//
// One other note is that this fallback method doesn't work for the UWP version, as we can't use the registry APIs.
// windowsTimeZoneName will point at timezoneSubKeyName if we had to fallback to using the registry, and we found a match.
WCHAR timezoneSubKeyName[WINDOWS_MAX_REG_KEY_LENGTH];
WCHAR *windowsTimeZoneName = dynamicTZI.TimeZoneKeyName;
if (dynamicTZI.TimeZoneKeyName[0] == 0) {
// We can't use the registry APIs in the UWP version.
#if U_PLATFORM_HAS_WINUWP_API == 1
(void)timezoneSubKeyName; // suppress unused variable warnings.
return nullptr;
#else
// Open the path to the time zones in the Windows registry.
LONG ret;
HKEY hKeyAllTimeZones = nullptr;
ret = RegOpenKeyExW(HKEY_LOCAL_MACHINE, WINDOWS_TIMEZONES_REG_KEY_PATH, 0, KEY_READ,
reinterpret_cast<PHKEY>(&hKeyAllTimeZones));
if (ret != ERROR_SUCCESS) {
// If we can't open the key, then we can't do much, so fail.
return nullptr;
}
// Read the number of subkeys under the time zone registry path.
DWORD numTimeZoneSubKeys;
ret = RegQueryInfoKeyW(hKeyAllTimeZones, nullptr, nullptr, nullptr, &numTimeZoneSubKeys,
nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr);
if (ret != ERROR_SUCCESS) {
RegCloseKey(hKeyAllTimeZones);
return nullptr;
}
// Examine each of the subkeys to try and find a match for the localized standard name ("Std").
//
// Note: The name of the time zone subkey itself is not localized, but the "Std" name is localized. This means
// that we could fail to find a match if the RDP client and RDP server are using different languages, but unfortunately
// there isn't much we can do about it.
HKEY hKeyTimeZoneSubKey = nullptr;
ULONG registryValueType;
WCHAR registryStandardName[WINDOWS_MAX_REG_KEY_LENGTH];
for (DWORD i = 0; i < numTimeZoneSubKeys; i++) {
// Note: RegEnumKeyExW wants the size of the buffer in characters.
DWORD size = UPRV_LENGTHOF(timezoneSubKeyName);
ret = RegEnumKeyExW(hKeyAllTimeZones, i, timezoneSubKeyName, &size, nullptr, nullptr, nullptr, nullptr);
if (ret != ERROR_SUCCESS) {
RegCloseKey(hKeyAllTimeZones);
return nullptr;
}
ret = RegOpenKeyExW(hKeyAllTimeZones, timezoneSubKeyName, 0, KEY_READ,
reinterpret_cast<PHKEY>(&hKeyTimeZoneSubKey));
if (ret != ERROR_SUCCESS) {
RegCloseKey(hKeyAllTimeZones);
return nullptr;
}
// Note: RegQueryValueExW wants the size of the buffer in bytes.
size = sizeof(registryStandardName);
ret = RegQueryValueExW(hKeyTimeZoneSubKey, L"Std", nullptr, &registryValueType,
reinterpret_cast<LPBYTE>(registryStandardName), &size);
if (ret != ERROR_SUCCESS || registryValueType != REG_SZ) {
RegCloseKey(hKeyTimeZoneSubKey);
RegCloseKey(hKeyAllTimeZones);
return nullptr;
}
// Note: wcscmp does an ordinal (byte) comparison.
if (wcscmp(reinterpret_cast<WCHAR *>(registryStandardName), dynamicTZI.StandardName) == 0) {
// Since we are comparing the *localized* time zone name, it's possible that some languages might use
// the same string for more than one time zone. Thus we need to examine the TZI data in the registry to
// compare the GMT offset (the bias), and the DST transition dates, to ensure it's the same time zone
// as the currently reported one.
REG_TZI_FORMAT registryTziValue;
uprv_memset(&registryTziValue, 0, sizeof(registryTziValue));
// Note: RegQueryValueExW wants the size of the buffer in bytes.
DWORD timezoneTziValueSize = sizeof(registryTziValue);
ret = RegQueryValueExW(hKeyTimeZoneSubKey, L"TZI", nullptr, &registryValueType,
reinterpret_cast<LPBYTE>(&registryTziValue), &timezoneTziValueSize);
if (ret == ERROR_SUCCESS) {
if ((dynamicTZI.Bias == registryTziValue.Bias) &&
(memcmp((const void *)&dynamicTZI.StandardDate, (const void *)&registryTziValue.StandardDate, sizeof(SYSTEMTIME)) == 0) &&
(memcmp((const void *)&dynamicTZI.DaylightDate, (const void *)&registryTziValue.DaylightDate, sizeof(SYSTEMTIME)) == 0))
{
// We found a matching time zone.
windowsTimeZoneName = timezoneSubKeyName;
break;
}
}
}
RegCloseKey(hKeyTimeZoneSubKey);
hKeyTimeZoneSubKey = nullptr;
}
if (hKeyTimeZoneSubKey != nullptr) {
RegCloseKey(hKeyTimeZoneSubKey);
}
if (hKeyAllTimeZones != nullptr) {
RegCloseKey(hKeyAllTimeZones);
}
#endif // U_PLATFORM_HAS_WINUWP_API
}
CharString winTZ;
UErrorCode status = U_ZERO_ERROR;
winTZ.appendInvariantChars(UnicodeString(TRUE, dynamicTZI.TimeZoneKeyName, -1), status);
winTZ.appendInvariantChars(UnicodeString(TRUE, windowsTimeZoneName, -1), status);
// Map Windows Timezone name (non-localized) to ICU timezone ID (~ Olson timezone id).
StackUResourceBundle winTZBundle;