Wednesday, July 24, 2013

Developing microsoft LYNC client in c++

First for one of my visitors wish...I am going to start from step 13 .I will describe the previous step later.
Step 13 : gssapi-data generation .  It is the most crucial part of LYNC developement. It gives me lot of pain.
I will describe it easily...for some reason I cann't give you the code.

I will go to the process in straight forward way..

First take the challenge data that is gssapidata: from second 401 unauthorize response then decode it in Base64 .As you know there are three type in NTLM ....
They are  >>

Type1:This message contains the host name and the NT domain name of the client.
Type2: This message contains the server's NTLM challenge
Type3: This message contains the username, host name, NT domain name, and the two "responses".

You already understand what are the we need.This is Type2 from server as challenge and Type3 which you will send.For more detail about type see the link >>>ALL about NTLM TYPE

Please don't see their message format in stream of data.

The format of challenge data for type 2 is perfect as >>

For more easiness I will describe here because it pains me so much.

Type two message format is like>>>

    int 32bit    message_type;

    unsigned short    length |

    unsigned short    space  | -----------target name;

    unsigned int         offset |

    int 32bit    flags;
    unsigned char    challenge[8];
    guint8  zero1[8];

   unsigned short    length |

    unsigned short    space  | -----------target info;

    unsigned int         offset | 


    int 8bit  product_major_version |
    int 8bit  product_minor_version |
    int 16bit product_build                |--Version;  
    int 8bit  zero2[3]                          |
    int 8bit  ntlm_revision_current   |


Just broke the decrypted gssapi-data in that format thats all. 

Target name is just domain name take it as unicode .Now the target info it holds time info of server as milliseconds for synchronization or security as it is.AvPair

Allaways keep in mind that all the data store is in ARRAY[OFFSET]


unsigned char* target info;
target info = (unsigned char*)&(sDecoded64.c_str()[target_info.offset]);

You understand what i have indicated...... :)

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