ms-chap.txt

pptp第二层隧道模块

            OUT 16-octet              PasswordHash )
        {
            Use the MD4 algorithm [4] to irreversibly hash Password
            into PasswordHash.  Only the password is hashed without
            including any terminating 0.
        }

    The "use Windows NT compatible challenge response" flag, if 1,
    indicates that the Windows NT response is provided and should be
    used in preference to the LAN Manager response.  The LAN Manager
    response will still be used if the account does not have a Windows
    NT password hash, e.g. if the password has not been changed since
    the account was uploaded from a LAN Manager 2.x account database.
    The LAN Manager response need not be provided (set to 0's) if the
    implementation expects all user accounts to be stored only in
    fresh Windows NT account databases or ones where all uploaded
    passwords have been changed.  However, doing so may sacrifice
    downward compatibility with non-Windows-NT servers.

    If the flag is 0, the Windows NT response is ignored and the LAN
    Manager response is used.  If the password is LAN Manager
    compatible, interoperability may be achieved without providing the
    Windows NT challenge response (set to 0's), and providing only the
    LAN Manager response.  This is what Microsoft Windows95 does,
    though this may change in the future.  Doing so may sacrifice
    interoperability with OEM-specific versions of Windows NT designed
    for maximum security in Windows-NT-only networks.

    Implementors seeking the broadest possible interoperability are
    advised to supply both responses when the password is LAN Manager
    compatible.  This is what Microsoft Windows NT does.







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    The Name field identifies the authenticatee's user account name.
    The Windows NT domain name may prefix the user's account name in
    the typical Windows NT format, e.g. "redmond\stevec" where
    "redmond" is a Windows NT domain containing the user account
    "stevec".  If a domain is not provided, the backslash should also
    be omitted, e.g. "stevec".


5. Success Packet

    The Success packet is identical in format to the standard CHAP
    Success packet.


6. Failure Packet

    The Failure packet is identical in format to the standard CHAP
    Failure packet.  There is, however, formatted text stored in the
    Message field which, contrary to the standard CHAP rules, does
    affect the protocol.  The Message field format is:

        "E=eeeeeeeeee R=r C=cccccccccccccccc V=vvvvvvvvvv"

    where

        The "eeeeeeeeee" is the decimal error code (need not be 10
        digits) corresponding to one of those listed below, though
        implementations should deal with codes not on this list
        gracefully.

            646 ERROR_RESTRICTED_LOGON_HOURS
            647 ERROR_ACCT_DISABLED
            648 ERROR_PASSWD_EXPIRED
            649 ERROR_NO_DIALIN_PERMISSION
            691 ERROR_AUTHENTICATION_FAILURE
            709 ERROR_CHANGING_PASSWORD

        The "r" is a flag set to "1" if a retry is allowed, and "0" if
        not.  When authenticator sets this flag to "1" it disables
        short timeouts, expecting the authenticatee to prompt the user
        for new credentials and resubmit the response.

        The "cccccccccccccccc" is 16 hex digits representing an ASCII
        representation of a new challenge value.  This field is
        optional.  If it is not sent, authenticator expects the
        resubmitted response to be calculated based on the previous
        challenge value plus decimal 23 in the first octet, i.e. the
        one immediately following the Value Size field.  Windows95
        authenticators may send this field.  Windows NT authenticators
        do not, but may in the future.  Both systems implement
        authenticatee support of this field.




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        The "vvvvvvvvvv" is the decimal version code (need not be 10
        digits) indicating the MS-CHAP protocol version supported on
        the server.  Currently, this is interesting only in selecting
        a Change Password packet type.  If the field is not present
        the version should be assumed 1.

    Implementations should accept but ignore additional text they do
    not recognize.


7. Change Password Packet (version 1)

    The version 1 Change Password packet does not appear in standard
    CHAP.  It allows the authenticatee to change the password on the
    account specified in the previous Response packet.  The version 1
    Change Password packet should be sent only if the authenticator
    reports ERROR_PASSWD_EXPIRED (E=648) in the Message field of the
    Failure packet.

    This packet type is supported by Windows NT 3.5 and 3.51.  It is
    not supported by Windows95, though this may change in the future.
    See also Change Password Packet (version 2).

    The format of this packet is as follows:

       1 octet : Code (=5)
       1 octet : Identifier
       2 octets: Length (=72)
      16 octets: Encrypted LAN Manager Old password Hash
      16 octets: Encrypted LAN Manager New Password Hash
      16 octets: Encrypted Windows NT Old Password Hash
      16 octets: Encrypted Windows NT New Password Hash
       2 octets: Password Length
       2 octets: Flags


    Code

        5


    Identifier

        The Identifier field is one octet and aids in matching
        requests and replies.  The value is the Identifier of the
        received Failure packet to which this packet responds plus 1.


    Length

        72




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    Encrypted LAN Manager New Password Hash
    Encrypted LAN Manager Old Password Hash

        These fields contain the LAN Manager password hash of the new
        and old passwords encrypted with an 8-octet key value [6], as
        output by the pseudo-code routine LmEncryptedPasswordHash
        below.

        LmEncryptedPasswordHash(
            IN  0-to-14-oem-char Password,
            IN  8-octet          KeyValue,
            OUT 16-octet         Cypher )
        {
            LmPasswordHash(
                Password,
                giving PasswordHash )

            PasswordHashEncryptedWithBlock(
                PasswordHash,
                KeyValue,
                giving Cypher )
        }

        PasswordHashEncryptedWithBlock(
            IN  16-octet PasswordHash,
            IN  7-octet  Block,
            OUT 16-octet Cypher )
        {
            DesEncrypt(
                1st 8-octets PasswordHash,
                1st 7-octets Block,
                giving 1st 8-octets Cypher )

            DesEncrypt(
                2nd 8-octets PasswordHash,
                1st 7-octets Block,
                giving 2nd 8-octets Cypher )
        }


    Encrypted Windows NT New Password Hash
    Encrypted Windows NT Old Password Hash

        These fields contain the Windows NT password hash of the new
        and old passwords encrypted with an 8-octet key value [6], as
        output by the pseudo-code routine NtEncryptedPasswordHash
        below.








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        NtEncryptedPasswordHash(
            IN  0-to-14-oem-char Password
            IN  8-octet          Challenge
            OUT 16-octet         Cypher )
        {
            NtPasswordHash(
                Password,
                giving PasswordHash )

            PasswordHashEncryptedWithBlock(
                PasswordHash,
                Challenge,
                giving Cypher )
        }


    Password Length

        The length in octets of the LAN Manager compatible form of the
        new password.  If this value is less than or equal to 14 it is
        assumed that the encrypted LAN Manager password hash fields
        are valid.  Otherwise, it is assumed these fields are not
        valid, in which case the Windows NT compatible passwords must
        be provided.


    Flags

        Bit field of option flags where 0 is the least significant bit
        of the 16-bit quantity:

            0    : Set 1 indicates that the encrypted Windows NT
                   hashed passwords are valid and should be used.  If
                   0, the Windows NT fields are not used and the LAN
                   Manager fields must be provided.

                   For the broadest possible interoperability,
                   implementations are encouraged to provide both the
                   Windows NT and LAN Manager fields when the password
                   is LAN Manager compatible.  This is what Windows NT
                   does.

            1-15 : Reserved, always set 0.












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8. Change Password Packet (version 2)

    The version 2 Change Password packet does not appear in standard
    CHAP.  It allows the authenticatee to change the password on the
    account specified in the previous Response packet.  The version 2
    Change Password packet should be sent only if the authenticator
    reports ERROR_PASSWD_EXPIRED (E=648) and a version of 2 or more in
    the Message field of the Failure packet.

    This packet type is supported by Windows NT 3.51.  It is not
    supported by Windows NT 3.5 or Windows95, though the latter may
    change in the future.  The version 2 change password packet type
    is preferable to the version 1 type and should be offered and
    accepted where possible.

    The format of this packet is as follows:

         1 octet  : Code (=6)
         1 octet  : Identifier
         2 octet  : Length (=1070)
       516 octets : Password Encrypted with Old NT Hash
        16 octets : Old NT Hash Encrypted with New NT Hash
       516 octets : Password Encrypted with Old LM Hash
        16 octets : Old LM Hash Encrypted With New NT Hash
        24 octets : LAN Manager compatible challenge response
        24 octets : Windows NT compatible challenge response
         2-octet  : Flags


    Code

        6


    Identifier

        The Identifier field is one octet and aids in matching
        requests and replies.  The value is the Identifier of the
        received Failure packet to which this packet responds plus 1.


    Length

        1118


    Password Encrypted with Old NT Hash

        This field contains the PWBLOCK form of the new Windows NT
        password encrypted with the old Windows NT password hash, as
        output by the NewPasswordEncryptedWithOldNtPasswordHash
        routine below:



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        datatype-PWBLOCK
        {
            256-unicode-char Password
            4-octets         PasswordLength
        }

        NewPasswordEncryptedWithOldNtPasswordHash(
            IN  0-to-256-unicode-char NewPassword,
            IN  0-to-256-unicode-char OldPassword,
            OUT datatype-PWBLOCK      EncryptedPwBlock )
        {
            NtPasswordHash(
                OldPassword,
                giving PasswordHash )

            EncryptPwBlockWithPasswordHash(
                NewPassword,
                PasswordHash,
                giving EncryptedPwBlock )
        }

        EncryptPwBlockWithPasswordHash(
            IN  0-to-256-unicode-char Password,
            IN  16-octet              PasswordHash,
            OUT datatype-PWBLOCK      PwBlock )
        {
            Fill ClearPwBlock with random octet values
            lstrcpyW( to ClearPwBlock.Password, from Password )
            ClearPwBlock.PasswordLength = lstrlenW( Password )

            Rc4Encrypt(
                ClearPwBlock,
                sizeof( ClearPwBlock ),
                PasswordHash,
                sizeof( PasswordHash ),
                giving PwBlock )
        }