228 lines
9.8 KiB
Plaintext
228 lines
9.8 KiB
Plaintext
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CAT Working Group Mike Swift
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draft-trostle-win2k-cat-kerberos-set-passwd-00.txt Microsoft
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February 2000 Jonathan Trostle
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Category: Informational Cisco Systems
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John Brezak
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Microsoft
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Extending Change Password for Setting Kerberos Passwords
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0. Status Of This Memo
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This document is an Internet-Draft and is in full conformance with
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all provisions of Section 10 of RFC2026.
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Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF), its areas, and its working groups. Note that
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other groups may also distribute working documents as
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Internet-Drafts.
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Internet-Drafts are draft documents valid for a maximum of six
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months and may be updated, replaced, or obsoleted by other
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documents at any time. It is inappropriate to use Internet-
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Drafts as reference material or to cite them other than as
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"work in progress."
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The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/ietf/1id-abstracts.txt
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The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html.
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Comments and suggestions on this document are encouraged. Comments
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on this document should be sent to the CAT working group discussion
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list:
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ietf-cat-wg@stanford.edu
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1. Abstract
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The Kerberos [1] change password protocol [2], does not allow for
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an administrator to set a password for a new user. This functionality
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is useful in some environments, and this proposal extends [2] to
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allow password setting. The changes are: adding new fields to the
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request message to indicate the principal which is having its
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password set, not requiring the initial flag in the service ticket,
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using a new protocol version number, and adding three new result
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codes.
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2. The Protocol
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The service must accept requests on UDP port 464 and TCP port 464 as
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well. The protocol consists of a single request message followed by
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a single reply message. For UDP transport, each message must be fully
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contained in a single UDP packet.
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For TCP transport, there is a 4 octet header in network byte order
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precedes the message and specifies the length of the message. This
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requirement is consistent with the TCP transport header in 1510bis.
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Request Message
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| message length | protocol version number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| AP_REQ length | AP_REQ data /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/ KRB-PRIV message /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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All 16 bit fields are in big-endian order.
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message length field: contains the number of bytes in the message
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including this field.
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protocol version number: contains the hex constant 0xff80 (big-endian
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integer).
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AP-REQ length: length of AP-REQ data, in bytes. If the length is zero,
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then the last field contains a KRB-ERROR message instead of a KRB-PRIV
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message.
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AP-REQ data: (see [1]) The AP-REQ message must be for the service
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principal kadmin/changepw@REALM, where REALM is the REALM of the user
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who wishes to change/set his password. The ticket in the AP-REQ must
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must include a subkey in the Authenticator. To enable setting of
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passwords, it is not required that the initial flag be set in the
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Kerberos service ticket.
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KRB-PRIV message (see [1]) This KRB-PRIV message must be generated
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using the subkey from the authenticator in the AP-REQ data.
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The user-data component of the message consists of the following ASN.1
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structure encoded as an OCTET STRING:
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ChangePasswdData ::= SEQUENCE {
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newpasswd[0] OCTET STRING,
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targname[2] PrincipalName OPTIONAL,
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targrealm[3] Realm OPTIONAL
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}
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The server must verify the AP-REQ message, check whether the client
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principal in the ticket is authorized to set/change the password
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(either for that principal, or for the principal in the targname
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field if present), and decrypt the new password. The server also
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checks whether the initial flag is required for this request,
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replying with status 0x0007 if it is not set and should be. An
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authorization failure is cause to respond with status 0x0005. For
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forward compatibility, the server should be prepared to ignore fields
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after targrealm in the structure that it does not understand.
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The newpasswd field contains the cleartext password, and the server
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should apply any local policy checks including password policy checks.
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The server then generates the appropriate keytypes from the password
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and stores them in the KDC database. If all goes well, status 0x0000
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is returned to the client in the reply message (see below).
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Reply Message
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| message length | protocol version number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| AP_REP length | AP-REP data /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/ KRB-PRIV message /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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All 16 bit fields are in big-endian order.
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message length field: contains the number of bytes in the message
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including this field.
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protocol version number: contains the hex constant 0x0001 (big-endian
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integer). (The reply message has the same format as in [2]).
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AP-REP length: length of AP-REP data, in bytes. If the length is zero,
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then the last field contains a KRB-ERROR message instead of a KRB-PRIV
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message.
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AP-REP data: the AP-REP is the response to the AP-REQ in the request
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packet.
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KRB-PRIV from [2]: This KRB-PRIV message must be generated using the
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subkey in the authenticator in the AP-REQ data.
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The server will respond with a KRB-PRIV message unless it cannot
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decode the client AP-REQ or KRB-PRIV message, in which case it will
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respond with a KRB-ERROR message. NOTE: Unlike change password version
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1, the KRB-ERROR message will be sent back without any encapsulation.
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The user-data component of the KRB-PRIV message, or e-data component
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of the KRB-ERROR message, must consist of the following data.
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| result code | result string /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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result code (16 bits) (result codes 0-4 are from [2]):
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The result code must have one of the following values (big-
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endian integer):
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KRB5_KPASSWD_SUCCESS 0 request succeeds (This value is not
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allowed in a KRB-ERROR message)
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KRB5_KPASSWD_MALFORMED 1 request fails due to being malformed
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KRB5_KPASSWD_HARDERROR 2 request fails due to "hard" error in
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processing the request (for example,
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there is a resource or other problem
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causing the request to fail)
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KRB5_KPASSWD_AUTHERROR 3 request fails due to an error in
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authentication processing
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KRB5_KPASSWD_SOFTERROR 4 request fails due to a "soft" error
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in processing the request
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KRB5_KPASSWD_ACCESSDENIED 5 requestor not authorized
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KRB5_KPASSWD_BAD_VERSION 6 protocol version unsupported
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KRB5_KPASSWD_INITIAL_FLAG_NEEDED 7 initial flag required
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0xFFFF if the request fails for some other reason.
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Although only a few non-zero result codes are specified here,
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the client should accept any non-zero result code as indicating
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failure.
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result string - from [2]:
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This field should contain information which the server thinks
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might be useful to the user, such as feedback about policy
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failures. The string must be encoded in UTF-8. It may be
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omitted if the server does not wish to include it. If it is
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present, the client should display the string to the user.
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This field is analogous to the string which follows the numeric
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code in SMTP, FTP, and similar protocols.
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3. References
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[1] J. Kohl, C. Neuman. The Kerberos Network Authentication
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Service (V5). Request for Comments 1510.
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[2] M. Horowitz. Kerberos Change Password Protocol.
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ftp://ds.internic.net/internet-drafts/
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draft-ietf-cat-kerb-chg-password-02.txt
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4. Expiration Date
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This draft expires in August 2000.
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5. Authors' Addresses
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Jonathan Trostle
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Cisco Systems
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170 W. Tasman Dr.
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San Jose, CA 95134
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Email: jtrostle@cisco.com
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Mike Swift
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1 Microsoft Way
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Redmond, WA 98052
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mikesw@microsoft.com
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John Brezak
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1 Microsoft Way
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Redmond, WA 98052
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jbrezak@microsoft.com
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