Obtaining Alternate Digest Credentials

To obtain credentials other than those associated with the current logon session, populate a SEC_WINNT_AUTH_IDENTITY structure with information for the alternate security principal. Pass the structure to the AcquireCredentialsHandle function using the pAuthData parameter.

The following table describes the members of the SEC_WINNT_AUTH_IDENTITY structure.

Member	Description
User	Null-terminated string containing the name of the security principal whose credentials will be used to establish a security context.
UserLength	The length of the User member, in characters. Omit the terminating null.
Domain	Null-terminated string that identifies the domain containing the account of the security principal.
DomainLength	The length of the Domain member, in characters. Omit the terminating null.
Password	Null-terminated string containing the password of the security principal.
PasswordLength	The length of the Password member, in characters. Omit the terminating null.
Flags	Indicates whether the string members are in ANSI or Unicode format.

 

The following table lists the valid values for the Flags member of the structure.

Constant	Description
SEC_WINNT_AUTH_IDENTITY_ANSI	Strings in this structure are in ANSI format.
SEC_WINNT_AUTH_IDENTITY_UNICODE	Strings in this structure are in Unicode format.

 

The structure and constants are declared in the Rpcdce.h header file distributed with the Platform Software Development Kit (SDK).

The following example demonstrates a client-side call to obtain Digest credentials for a specific user account.

#include <windows.h>

#ifdef UNICODE
  ClientAuthID.Flags = SEC_WINNT_AUTH_IDENTITY_UNICODE;
#else
  ClientAuthID.Flags = SEC_WINNT_AUTH_IDENTITY_ANSI;
#endif

void main()
{
    SECURITY_STATUS SecStatus; 
    TimeStamp tsLifetime; 
    CredHandle hCred;
    SEC_WINNT_AUTH_IDENTITY ClientAuthID;
    LPTSTR UserName = TEXT("ASecurityPrinciple");
    LPTSTR DomainName = TEXT("AnAuthenticatingDomain");

    // Initialize the memory.
    ZeroMemory( &ClientAuthID, sizeof(ClientAuthID) );

    // Specify string format for the ClientAuthID structure.


    // Specify an alternate user, domain and password.
      ClientAuthID.User = (unsigned char *) UserName;
      ClientAuthID.UserLength = _tcslen(UserName);

      ClientAuthID.Domain = (unsigned char *) DomainName;
      ClientAuthID.DomainLength = _tcslen(DomainName);

    // Password is an application-defined LPTSTR variable
    // containing the user password.
      ClientAuthID.Password = Password;
      ClientAuthID.PasswordLength = _tcslen(Password);

    // Get the client side credential handle.
    SecStatus = AcquireCredentialsHandle (
      NULL,                  // Default principal.
      WDIGEST_SP_NAME,       // The Digest SSP. 
      SECPKG_CRED_OUTBOUND,  // Client will use the credentials.
      NULL,                  // Do not specify LOGON id.
      &ClientAuthID,         // User information.
      NULL,                  // Not used with Digest SSP.
      NULL,                  // Not used with Digest SSP.
      &hCred,                // Receives the credential handle.
      &tsLifetime            // Receives the credential time limit.
    );
}

The _tcslen function returns the string length in characters, not including the terminating null character.

If your application can use the credentials established at logon, see Obtaining Default Digest Credentials.