DownlevelVerifyScripts function

Article
11/06/2023

Compares two enumerated lists of scripts.

Note

This function is used only by applications that run on pre-Windows Vista operating systems. Its use requires the download package. Applications that only run on Windows Vista and later should call VerifyScripts.

Syntax

BOOL DownlevelVerifyScripts(
  _In_ DWORD   dwFlags,
  _In_ LPCWSTR lpLocaleScripts,
  _In_ int     cchLocaleScripts,
  _In_ LPCWSTR lpTestScripts,
  _In_ int     cchTestScripts
);

Parameters

dwFlags [in]

Flags specifying script verification options.

Value	Meaning
VS_ALLOW_LATIN	Allow "Latn" (Latin script) in the test list, even if it is not in the locale list.

lpLocaleScripts [in]

Pointer to the locale list, the enumerated list of scripts for a given locale. This list is typically populated by calling DownlevelGetLocaleScripts.

cchLocaleScripts [in]

Size, in characters, of the string indicated by lpLocaleScripts. The application sets this parameter to -1 if the string is null-terminated. If this parameter is set to 0, the function fails.

lpTestScripts [in]

Pointer to the test list, a second enumerated list of scripts. This list is typically populated by calling DownlevelGetStringScripts.

cchTestScripts [in]

Size, in characters, of the string indicated by lpTestScripts. The application sets this parameter to -1 if the string is null-terminated. If this parameter is set to 0, the function fails.

Return value

Returns TRUE if the test list is non-empty and all items in the list are also included in the locale list. Otherwise, the function returns FALSE.

A return value of FALSE can indicate that the test list contains an item that is not in the locale list, or it can indicate an error. To distinguish between these two cases, the application can call GetLastError. If DownlevelVerifyScripts has successfully determined that there is an item in the test list that is not in the locale list, GetLastError returns ERROR_SUCCESS. Otherwise, GetLastError can return one of the following error codes:

ERROR_INVALID_FLAGS. The values supplied for flags were not valid.
ERROR_INVALID_PARAMETER. Any of the parameter values was invalid.

Remarks

This function compares strings, such as "Latn;Cyrl;", that consist of a series of 4-character script names, with each script name followed by a semicolon. It also has a special case to account for the fact that the Latin script is often used in languages and locales for which it is not native.

This function is useful as part of a strategy to mitigate security issues related to internationalized domain names (IDNs).

The following are examples of the return of this function and a subsequent call to GetLastError in various scenarios. The last two examples illustrate, respectively, a case in which the test list lacks a terminating semicolon (malformed string) and a case in which the test list is empty.

"Locale" string	"Test" string	dwFlags	Return value	GetLastError return
Hani;Hira;Kana;	Hani;	N/A	TRUE	N/A
Hani;Hira;Kana;	Hani;Latn;	0	FALSE	ERROR_SUCCESS
Hani;Hira;Kana;	Hani;Latn;	VS_ALLOW_LATIN	TRUE	N/A
Hani;Hira;Kana;	Cyrl;	N/A	FALSE	ERROR_SUCCESS
Hani;Hira;Kana;	Cyrl;	N/A	FALSE	ERROR_INVALID_PARAMETER
Hani;Hira;Kana;		N/A	FALSE	ERROR_SUCCESS

The required header file and DLL are part of the "Microsoft Internationalized Domain Name (IDN) Mitigation APIs" download available from archive.org.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Redistributable	Microsoft Internationalized Domain Name (IDN) Mitigation APIs onWindows XP with SP2,Windows Server 2003 with SP1, orWindows Vista
Header	Idndl.h
DLL	Idndl.dll