DPAPI Class

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The DPAPI class allows you to protect and unprotect data.

Syntax

DPAPI

Remarks

The class supports the classic Microsoft Windows Data Protection API (DPAPI) or CNG DPAPI implementation. The use of UseCNG determines which implementation is used.

The classic DPAPI functionality protects data on a single system. The CNG DPAPI is designed with modern use cases involved. In many cases, especially with cloud computing, protection and unprotection may be done on different systems. With this in mind the Microsoft CNG DPAPI allows encrypting to a set of principals that can be used to unprotect the data on other systems after authenticating.

Protecting Data

Protect protects the specified data.

The class supports protecting data using either the classic DPAPI or CNG DPAPI implementation. The use of UseCNG determines which implementation is used. The list of applicable properties differs depending on whether CNG DPAPI is being used.

When using classic DPAPI (UseCNG is False), the following optional properties are applicable:

• DataDescription
• Password
• PromptTitle
• PromptUser

When using CNG DPAPI (UseCNG is True), the following properties are applicable:

• ProtectionDescriptor (required)
• EscapeDescriptor
• UseStreamMode

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Code Example (Classic DPAPI - UseCNG is False)

//Protect Dpapi dpapi = new Dpapi(); dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Code Example (CNG DPAPI - UseCNG is True)

//Protect Dpapi dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.ProtectionDescriptor = "LOCAL=user"; dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Unprotecting Data

Unprotect unprotects the specified data.

The class supports unprotecting data using either the classic DPAPI or CNG DPAPI implementation. The use of UseCNG determines which implementation is used. The list of applicable properties differs depending on whether CNG DPAPI is being used.

When using classic DPAPI (UseCNG is False), the following optional properties are applicable:

• DataDescription (populated after completion)
• Password

When using CNG DPAPI (UseCNG is True), the following properties are applicable:

• ProtectionDescriptor (populated after completion)
• UseStreamMode

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Code Example (Classic DPAPI - UseCNG is False)

//Protect Dpapi dpapi = new Dpapi(); dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Code Example (CNG DPAPI - UseCNG is True)

//Protect Dpapi dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.ProtectionDescriptor = "LOCAL=user"; dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Property List

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

DataDescription Property (DPAPI Class)

The description of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetDataDescription();
int SetDataDescription(const char* lpszDataDescription);

Unicode (Windows)
LPWSTR GetDataDescription();
INT SetDataDescription(LPCWSTR lpszDataDescription);

char* ipworksencrypt_dpapi_getdatadescription(void* lpObj);
int ipworksencrypt_dpapi_setdatadescription(void* lpObj, const char* lpszDataDescription);

QString GetDataDescription();
int SetDataDescription(QString qsDataDescription);

Default Value

""

Remarks

This property specifies an optional description of the protected data.

This may be set before calling Protect. This property will be populated when calling Unprotect.

This setting is not applicable when UseCNG is set to True.

Data Type

String

InputFile Property (DPAPI Class)

The file to process.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetInputFile();
int SetInputFile(const char* lpszInputFile);

Unicode (Windows)
LPWSTR GetInputFile();
INT SetInputFile(LPCWSTR lpszInputFile);

char* ipworksencrypt_dpapi_getinputfile(void* lpObj);
int ipworksencrypt_dpapi_setinputfile(void* lpObj, const char* lpszInputFile);

QString GetInputFile();
int SetInputFile(QString qsInputFile);

Default Value

""

Remarks

This property specifies the file to be processed. Set this property to the full or relative path to the file which will be processed.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Data Type

String

InputMessage Property (DPAPI Class)

The message to process.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetInputMessage(char* &lpInputMessage, int &lenInputMessage);
int SetInputMessage(const char* lpInputMessage, int lenInputMessage);

Unicode (Windows)
INT GetInputMessage(LPSTR &lpInputMessage, INT &lenInputMessage);
INT SetInputMessage(LPCSTR lpInputMessage, INT lenInputMessage);

int ipworksencrypt_dpapi_getinputmessage(void* lpObj, char** lpInputMessage, int* lenInputMessage);
int ipworksencrypt_dpapi_setinputmessage(void* lpObj, const char* lpInputMessage, int lenInputMessage);

QByteArray GetInputMessage();
int SetInputMessage(QByteArray qbaInputMessage);

Default Value

""

Remarks

This property specifies the message to be processed.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Data Type

Binary String

OutputFile Property (DPAPI Class)

The output file when encrypting or decrypting.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetOutputFile();
int SetOutputFile(const char* lpszOutputFile);

Unicode (Windows)
LPWSTR GetOutputFile();
INT SetOutputFile(LPCWSTR lpszOutputFile);

char* ipworksencrypt_dpapi_getoutputfile(void* lpObj);
int ipworksencrypt_dpapi_setoutputfile(void* lpObj, const char* lpszOutputFile);

QString GetOutputFile();
int SetOutputFile(QString qsOutputFile);

Default Value

""

Remarks

This property specifies the file to which the output will be written when Encrypt or Decrypt is called. This may be set to an absolute or relative path.

This property is only applicable to Encrypt and Decrypt.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Data Type

String

OutputMessage Property (DPAPI Class)

The output message after processing.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetOutputMessage(char* &lpOutputMessage, int &lenOutputMessage);

Unicode (Windows)
INT GetOutputMessage(LPSTR &lpOutputMessage, INT &lenOutputMessage);

int ipworksencrypt_dpapi_getoutputmessage(void* lpObj, char** lpOutputMessage, int* lenOutputMessage);

QByteArray GetOutputMessage();

Default Value

""

Remarks

This property will be populated with the output from the operation if OutputFile is not set.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

This property is read-only and not available at design time.

Data Type

Binary String

Overwrite Property (DPAPI Class)

Indicates whether or not the class should overwrite files.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetOverwrite();
int SetOverwrite(int bOverwrite);

Unicode (Windows)
BOOL GetOverwrite();
INT SetOverwrite(BOOL bOverwrite);

int ipworksencrypt_dpapi_getoverwrite(void* lpObj);
int ipworksencrypt_dpapi_setoverwrite(void* lpObj, int bOverwrite);

bool GetOverwrite();
int SetOverwrite(bool bOverwrite);

Default Value

FALSE

Remarks

This property indicates whether or not the class will overwrite OutputFile. If Overwrite is False, an error will be thrown whenever OutputFile exists before an operation. The default value is False.

Data Type

Boolean

Password Property (DPAPI Class)

An optional password to further protect data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetPassword();
int SetPassword(const char* lpszPassword);

Unicode (Windows)
LPWSTR GetPassword();
INT SetPassword(LPCWSTR lpszPassword);

char* ipworksencrypt_dpapi_getpassword(void* lpObj);
int ipworksencrypt_dpapi_setpassword(void* lpObj, const char* lpszPassword);

QString GetPassword();
int SetPassword(QString qsPassword);

Default Value

""

Remarks

This property may be set to a password to protect the data further.

When protecting data without specifying a password any application running under the same user account can unprotect the data. By specifying a password another piece of information is required to unprotect the data.

This may be set before calling Protect. If a password was specified when protecting data it must be set before calling Unprotect.

This setting is not applicable when UseCNG is set to True.

Data Type

String

PromptTitle Property (DPAPI Class)

The title of the prompt window.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetPromptTitle();
int SetPromptTitle(const char* lpszPromptTitle);

Unicode (Windows)
LPWSTR GetPromptTitle();
INT SetPromptTitle(LPCWSTR lpszPromptTitle);

char* ipworksencrypt_dpapi_getprompttitle(void* lpObj);
int ipworksencrypt_dpapi_setprompttitle(void* lpObj, const char* lpszPromptTitle);

QString GetPromptTitle();
int SetPromptTitle(QString qsPromptTitle);

Default Value

""

Remarks

This property specifies the title of the prompt dialog if PromptUser is True. The default value is empty string.

This setting is not applicable when UseCNG is set to True.

Data Type

String

PromptUser Property (DPAPI Class)

Whether to display a prompt.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetPromptUser();
int SetPromptUser(int bPromptUser);

Unicode (Windows)
BOOL GetPromptUser();
INT SetPromptUser(BOOL bPromptUser);

int ipworksencrypt_dpapi_getpromptuser(void* lpObj);
int ipworksencrypt_dpapi_setpromptuser(void* lpObj, int bPromptUser);

bool GetPromptUser();
int SetPromptUser(bool bPromptUser);

Default Value

FALSE

Remarks

This property specifies whether a prompt is displayed when calling Protect. This dialog is created by the system and informs the user of the request action. The user may accept or cancel the request. If the user cancels the request the Protect method fails with an error.

When True the PromptTitle may be set to customize the window title.

This setting is not applicable when UseCNG is set to True. ;

Data Type

Boolean

ProtectionDescriptor Property (DPAPI Class)

The CNG protection descriptor.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetProtectionDescriptor();
int SetProtectionDescriptor(const char* lpszProtectionDescriptor);

Unicode (Windows)
LPWSTR GetProtectionDescriptor();
INT SetProtectionDescriptor(LPCWSTR lpszProtectionDescriptor);

char* ipworksencrypt_dpapi_getprotectiondescriptor(void* lpObj);
int ipworksencrypt_dpapi_setprotectiondescriptor(void* lpObj, const char* lpszProtectionDescriptor);

QString GetProtectionDescriptor();
int SetProtectionDescriptor(QString qsProtectionDescriptor);

Default Value

""

Remarks

This property specifies the protection descriptor rule string. The protection descriptor is used by the system to decide which entities can unprotect the data at a later time. This property must be specified before calling Protect. This property is populated after calling Unprotect.

Protection descriptors can be defined for the following types of authorization:

• A local user or machine
• An account or group in an Active Directory forest
• A set of web credentials
• A certificate in the user's certificate store

A local user or machine may be used for machines that are or are not on a domain. For instance:

• LOCAL=user
• LOCAL=machine

The use of SID and SDDL requires that the machine be part of a domain. For instance:

• SID=S-1-5-21-4392301 AND SID=S-1-5-21-3101812
• SDDL=O:S-1-5-5-0-290724G:SYD:(A;;CCDC;;;S-1-5-5-0-290724)(A;;DC;;;WD)

Certificates may also be used as a descriptor. To decrypt, the certificate with corresponding private key must be present in the user's certificate store. The public certificate can be specified as the SHA1 thumbprint (hash) of the certificate, or the base64 encoded certificate itself. For instance:

• CERTIFICATE=HashID:28ac375635b82ca3e20a1c9422145bc93965dae7
• CERTIFICATE=CertBlob:MIIC7TCCAdWgAw...pgpVgYpppr

The use of AND and OR operators are accepted in order to encrypt data for multiple parties or establish multiple conditions for decryption.

For more details about protection descriptors and accepted formats please refer to the Microsoft Documentation for Protection Descriptors

This setting is only applicable when UseCNG is set to True.

Data Type

String

UseCNG Property (DPAPI Class)

Whether to use CNG DPAPI.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetUseCNG();
int SetUseCNG(int bUseCNG);

Unicode (Windows)
BOOL GetUseCNG();
INT SetUseCNG(BOOL bUseCNG);

int ipworksencrypt_dpapi_getusecng(void* lpObj);
int ipworksencrypt_dpapi_setusecng(void* lpObj, int bUseCNG);

bool GetUseCNG();
int SetUseCNG(bool bUseCNG);

Default Value

FALSE

Remarks

The class supports protecting data using either the classic DPAPI or CNG DPAPI implementation. When set to True the CNG DPAPI implementation is sued. When set to False (default) the classic DPAPI implementation is used.

Data Type

Boolean

UseHex Property (DPAPI Class)

Whether input or output is hex encoded.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetUseHex();
int SetUseHex(int bUseHex);

Unicode (Windows)
BOOL GetUseHex();
INT SetUseHex(BOOL bUseHex);

int ipworksencrypt_dpapi_getusehex(void* lpObj);
int ipworksencrypt_dpapi_setusehex(void* lpObj, int bUseHex);

bool GetUseHex();
int SetUseHex(bool bUseHex);

Default Value

FALSE

Remarks

This property specifies whether the encrypted data is hex encoded.

If set to True, when Protect is called the class will perform the encryption as normal and then hex encode the output. OutputMessage or OutputFile will hold hex encoded data.

If set to True, when Unprotect is called the class will expect InputMessage or InputFile to hold hex encoded data. The class will then hex decode the data and perform decryption as normal.

Data Type

Boolean

Config Method (DPAPI Class)

Sets or retrieves a configuration setting.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* Config(const char* lpszConfigurationString);

Unicode (Windows)
LPWSTR Config(LPCWSTR lpszConfigurationString);

char* ipworksencrypt_dpapi_config(void* lpObj, const char* lpszConfigurationString);

QString Config(const QString& qsConfigurationString);

Remarks

Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Error Handling (C++)

This method returns a String value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

Protect Method (DPAPI Class)

Protects the data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Protect();

Unicode (Windows)
INT Protect();

int ipworksencrypt_dpapi_protect(void* lpObj);

int Protect();

Remarks

Protect protects the specified data.

The class supports protecting data using either the classic DPAPI or CNG DPAPI implementation. The use of UseCNG determines which implementation is used. The list of applicable properties differs depending on whether CNG DPAPI is being used.

When using classic DPAPI (UseCNG is False), the following optional properties are applicable:

• DataDescription
• Password
• PromptTitle
• PromptUser

When using CNG DPAPI (UseCNG is True), the following properties are applicable:

• ProtectionDescriptor (required)
• EscapeDescriptor
• UseStreamMode

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Code Example (Classic DPAPI - UseCNG is False)

//Protect Dpapi dpapi = new Dpapi(); dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Code Example (CNG DPAPI - UseCNG is True)

//Protect Dpapi dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.ProtectionDescriptor = "LOCAL=user"; dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Reset Method (DPAPI Class)

Resets the class.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Reset();

Unicode (Windows)
INT Reset();

int ipworksencrypt_dpapi_reset(void* lpObj);

int Reset();

Remarks

When called, the class will reset all of its properties to their default values.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

SetInputStream Method (DPAPI Class)

Sets the stream from which the class will read data to encrypt or decrypt.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int SetInputStream(IPWorksEncryptStream* sInputStream);

Unicode (Windows)
INT SetInputStream(IPWorksEncryptStream* sInputStream);

int ipworksencrypt_dpapi_setinputstream(void* lpObj, IPWorksEncryptStream* sInputStream);

int SetInputStream(IPWorksEncryptStream* sInputStream);

Remarks

This method sets the stream from which the class will read data to encrypt or decrypt.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

SetOutputStream Method (DPAPI Class)

Sets the stream to which the class will write encrypted or decrypted data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int SetOutputStream(IPWorksEncryptStream* sOutputStream);

Unicode (Windows)
INT SetOutputStream(IPWorksEncryptStream* sOutputStream);

int ipworksencrypt_dpapi_setoutputstream(void* lpObj, IPWorksEncryptStream* sOutputStream);

int SetOutputStream(IPWorksEncryptStream* sOutputStream);

Remarks

This method sets the stream to which the class will write encrypted or decrypted data.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Unprotect Method (DPAPI Class)

Unprotects the data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Unprotect();

Unicode (Windows)
INT Unprotect();

int ipworksencrypt_dpapi_unprotect(void* lpObj);

int Unprotect();

Remarks

Unprotect unprotects the specified data.

The class supports unprotecting data using either the classic DPAPI or CNG DPAPI implementation. The use of UseCNG determines which implementation is used. The list of applicable properties differs depending on whether CNG DPAPI is being used.

When using classic DPAPI (UseCNG is False), the following optional properties are applicable:

• DataDescription (populated after completion)
• Password

When using CNG DPAPI (UseCNG is True), the following properties are applicable:

• ProtectionDescriptor (populated after completion)
• UseStreamMode

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• SetInputStream
• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• SetOutputStream
• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

When using streams you may need to additionally set CloseInputStreamAfterProcessing or CloseOutputStreamAfterProcessing.

Code Example (Classic DPAPI - UseCNG is False)

//Protect Dpapi dpapi = new Dpapi(); dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Code Example (CNG DPAPI - UseCNG is True)

//Protect Dpapi dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.ProtectionDescriptor = "LOCAL=user"; dpapi.InputMessage = "test"; dpapi.Protect(); byte[] protectedData = dpapi.OutputMessageB; //Unprotect dpapi = new Dpapi(); dpapi.UseCNG = true; dpapi.InputMessageB = protectedData; dpapi.Unprotect(); Console.WriteLine(dpapi.OutputMessage); //outputs "test"

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Error Event (DPAPI Class)

Information about errors during data delivery.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireError(DPAPIErrorEventParams *e);

typedef struct {
  int ErrorCode;
  const char *Description;
  int reserved;
} DPAPIErrorEventParams;


Unicode (Windows)
virtual INT FireError(DPAPIErrorEventParams *e);

typedef struct {
  INT ErrorCode;
  LPCWSTR Description;
  INT reserved;
} DPAPIErrorEventParams;

#define EID_DPAPI_ERROR 1

virtual INT IPWORKSENCRYPT_CALL FireError(INT &iErrorCode, LPSTR &lpszDescription);

class DPAPIErrorEventParams {
public:
  int ErrorCode();

  const QString &Description();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void Error(DPAPIErrorEventParams *e);

// Or, subclass DPAPI and override this emitter function.
virtual int FireError(DPAPIErrorEventParams *e) {...}

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

ErrorCode contains an error code and Description contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Progress Event (DPAPI Class)

Fired as progress is made.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireProgress(DPAPIProgressEventParams *e);

typedef struct {
  int64 BytesProcessed;
  int PercentProcessed;
  int reserved;
} DPAPIProgressEventParams;


Unicode (Windows)
virtual INT FireProgress(DPAPIProgressEventParams *e);

typedef struct {
  LONG64 BytesProcessed;
  INT PercentProcessed;
  INT reserved;
} DPAPIProgressEventParams;

#define EID_DPAPI_PROGRESS 2

virtual INT IPWORKSENCRYPT_CALL FireProgress(LONG64 &lBytesProcessed, INT &iPercentProcessed);

class DPAPIProgressEventParams {
public:
  qint64 BytesProcessed();

  int PercentProcessed();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void Progress(DPAPIProgressEventParams *e);

// Or, subclass DPAPI and override this emitter function.
virtual int FireProgress(DPAPIProgressEventParams *e) {...}

Remarks

This event is fired automatically as data is processed by the class.

The PercentProcessed parameter indicates the current status of the operation.

The BytesProcessed parameter holds the total number of bytes processed so far.

IPWorksEncryptStream Type

Syntax

IPWorksEncryptStream (declared in ipworksencrypt.h)

Remarks

The DPAPI class includes one or more API members that take a stream object as a parameter. To use such API members, create a concrete class that implements the IPWorksEncryptStream interface and pass the DPAPI class an instance of that concrete class.

When implementing the IPWorksEncryptStream interface's properties and methods, they must behave as described below. If the concrete class's implementation does not behave as expected, undefined behavior may occur.

Properties
CanRead	Whether the stream supports reading. bool CanRead() { return true; }
CanSeek	Whether the stream supports seeking. bool CanSeek() { return true; }
CanWrite	Whether the stream supports writing. bool CanWrite() { return true; }
Length	Gets the length of the stream, in bytes. int64 GetLength() = 0;
Methods
Close	Closes the stream, releasing all resources currently allocated for it. void Close() {} This method is called automatically when an IPWorksEncryptStream object is deleted.
Flush	Forces all data held by the stream's buffers to be written out to storage. int Flush() { return 0; } Must return 0 if flushing is successful; or -1 if an error occurs or the stream is closed. If the stream does not support writing, this method must do nothing and return 0.
Read	Reads a sequence of bytes from the stream and advances the current position within the stream by the number of bytes read. int Read(void* buffer, int count) = 0; Buffer specifies the buffer to populate with data from the stream. Count specifies the number of bytes that should be read from the stream. Must return the total number of bytes read into Buffer; this may be less than Count if that many bytes are not currently available, or 0 if the end of the stream has been reached. Must return -1 if an error occurs, if reading is not supported, or if the stream is closed.
Seek	Sets the current position within the stream based on a particular point of origin. int64 Seek(int64 offset, int seekOrigin) = 0; Offset specifies the offset in the stream to seek to, relative to SeekOrigin. Valid values for SeekOrigin are: 0: Seek from beginning. 1: Seek from current position. 2: Seek from end. Must return the new position within the stream; or -1 if an error occurs, if seeking is not supported, or if the stream is closed (however, see note below). If -1 is returned, the current position within the stream must remain unchanged. Note: If the stream is not closed, it must always be possible to call this method with an Offset of 0 and a SeekOrigin of 1 to obtain the current position within the stream, even if seeking is not otherwise supported.
Write	Writes a sequence of bytes to the stream and advances the current position within the stream by the number of bytes written. int Write(const void* buffer, int count) = 0; Buffer specifies the buffer with data to write to the stream. Count specifies the number of bytes that should be written to the stream. Must return the total number of bytes written to the stream; this may be less than Count if that many bytes could not be written. Must return -1 if an error occurs, if writing is not supported, or if the stream is closed.

Config Settings (DPAPI Class)

Trappable Errors (DPAPI Class)

Error Handling (C++)

Call the GetLastErrorCode() method to obtain the last called method's result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. Known error codes are listed below. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

DPAPI Errors

	104   Cannot read or write file.
	109   Cannot protect data.
	110   Cannot unprotect data
	111   OutputFile already exists and Overwrite is False.
	304   Cannot write file.
	305   Cannot read file.
	306   Cannot create file.