Windows 7 and Windows Server 2008 R2 djoin (Offline Domain Join) utility.

Posted by Matthieu Suiche on January 29, 2009 · 1 Comment 

Offline domain join is a new process that joins computers running Windows® 7 or Windows Server 2008 R2 to a domain in Active Directory Domain Services (AD DS)—without any network connectivity. This process includes a new command-line tool, Djoin.exe, which you can use to complete an offline domain join.

Run Djoin.exe to provision the computer account metadata. When you run the provisioning command, the computer account metadata is created in a .txt file that you specify as part of the command. After you run the provisioning command, you can either run Djoin.exe again to request the computer account metadata and insert it into the Windows directory of the destination computer.

Following section covers the content of these computer account metadata files.

Here is what we see when we open the output file into an hexadecimal editor.

We ignore two first bytes, and the following sequence of bytes is an unicode base64 encoded string.

Decoded base64 string is a DATA_BLOB encrypted by NetpEncodeProvisioningBlob / NetpDecodeProvisioningBlob private APIs from netjoin.dll which is new toWindows 7/Windows Server 2008 R2. Both functions calls NdrMesTypeDecode2 / NdrMesTypeEncode2 from RPCRT4.dll to perferm the encryption/decryption process.

This dll is pretty interesting because of NetpLogPrintHelper() calls, e.g. the following in NetpDumpBlobToLog() function:

  1. […]
  2. NetpLogPrintHelper("\tlpMachinePassword: %s\n", "omitted from log");
  3. […]

As you can see, sensitive information are removed from debug log (netsetup.log).

Decoded blob file contains a structure I called “PROVISION_DATA” which is composed of information about Domain Dns Policy, Domain Controller, miscelleneous information about the machine and so on.

  1. #define NETSETUP_PROVISION_DOWNLEVEL_PRIV_SUPPORT 0×1
  2. #define NETSETUP_PROVISION_REUSE_ACCOUNT 0×2
  3. #define NETSETUP_PROVISION_USE_DEFAULT_PASSWORD 0×4
  4. #define NETSETUP_PROVISION_SKIP_ACCOUNT_SEARCH 0×8
  5. #define NETSETUP_PROVISION_ONLINE_CALLER 0×40000000
  6. #define NETSETUP_PROVISION_CHECK_PWD_ONLY 0×80000000
  7.  
  8. typedef struct _DOMAIN_DNS_POLICY { // sizeof = 0×2C
  9.     TCHAR Name[4]; // 0×000
  10.     TCHAR DnsDomainName[4]; // 0×008
  11.     TCHAR DnsForestName[4]; // 0×010
  12.     GUID DomainGuid; // 0×018
  13.     PSID Sid; // 0×028
  14. } DOMAIN_DNS_POLICY, *PDOMAIN_DNS_POLICY;
  15.  
  16. typedef struct _DOMAIN_CONTROLLER { // size of = 0×30
  17.     PCHAR DomainControllerName; // 0×000
  18.     PCHAR DomainControllerAddress; // 0×004
  19.     ULONG DomainControllerAddressType; // 0×008
  20.     GUID DomainGuid; // 0×00C
  21.     PCHAR DomainName; // 0×01C
  22.     PCHAR DnsForestName; // 0×020
  23.     ULONG Flags; // 0×024
  24.     PCHAR DcSiteName; // 0×28
  25.     PCHAR ClientSiteName; // 0×2C
  26. } DOMAIN_CONTROLLER, *PDOMAIN_CONTROLLER;
  27.  
  28. typedef struct _DOMAIN_INFORMATION {
  29.     //
  30.     // Global Information
  31.     //
  32.     LPVOID lpDomainName; // 0×008
  33.     LPVOID lpMachineName; // 0×00C
  34.     LPVOID lpMachinePassword; // 0×010
  35.  
  36.     //
  37.     // Domain Policy
  38.     //
  39.     DOMAIN_DNS_POLICY DomainPolicy; // 0×014
  40.  
  41.     //
  42.     // Domain Controller
  43.     //
  44.     DOMAIN_CONTROLLER DomainController; // 0×048
  45.  
  46.     //
  47.     // Options – NETSETUP_PROVISION
  48.     //
  49.     ULONG Options; // 0×078
  50.  
  51. } DOMAIN_INFORMATION, *PDOMAIN_INFORMATION;
  52.  
  53. typedef struct _PROVISION_DATA {
  54.     //
  55.     // ODJ Blob
  56.     //
  57.     ULONG Version; // 0×000
  58.     ULONG Size; // 0×004
  59.  
  60.     PDOMAIN_INFORMATION DomainInformation;
  61.  
  62. } PROVISION_DATA, *PPROVISION_DATA;

I wrote a tool called “dinfo” for “Domain Information” to read these files, this tool works with user rights only under Windows 7 and Windows Server 2008 R2 because of dependency to netjoin.dll

Now it’s time to introduce dinfo.exe! Here is a screenshot of the tool in action.



PS1. Encoded data blob can also be retrived in the registry at the following magic key : “Software\Microsoft\Windows NT\CurrentVersion\UnattendSettings\Microsoft-Windows-UnattendedJoin\Identification”.

PS2. Thomas aime les nouilles.


Download dinfo version 1.0.20090128

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