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Network Working Group M. Leech
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Request for Comments: 1929 Bell-Northern Research Ltd
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Category: Standards Track March 1996
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Username/Password Authentication for SOCKS V5
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This document specifies an Internet standards track protocol for the
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Internet community, and requests discussion and suggestions for
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improvements. Please refer to the current edition of the "Internet
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Official Protocol Standards" (STD 1) for the standardization state
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and status of this protocol. Distribution of this memo is unlimited.
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The protocol specification for SOCKS Version 5 specifies a
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generalized framework for the use of arbitrary authentication
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protocols in the initial socks connection setup. This document
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describes one of those protocols, as it fits into the SOCKS Version 5
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authentication "subnegotiation".
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Unless otherwise noted, the decimal numbers appearing in packet-
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format diagrams represent the length of the corresponding field, in
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octets. Where a given octet must take on a specific value, the
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syntax X'hh' is used to denote the value of the single octet in that
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field. When the word 'Variable' is used, it indicates that the
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corresponding field has a variable length defined either by an
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associated (one or two octet) length field, or by a data type field.
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2. Initial negotiation
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Once the SOCKS V5 server has started, and the client has selected the
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Username/Password Authentication protocol, the Username/Password
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subnegotiation begins. This begins with the client producing a
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Username/Password request:
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+----+------+----------+------+----------+
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|VER | ULEN | UNAME | PLEN | PASSWD |
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+----+------+----------+------+----------+
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| 1 | 1 | 1 to 255 | 1 | 1 to 255 |
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+----+------+----------+------+----------+
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Leech Standards Track [Page 1]
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RFC 1929 Username Authentication for SOCKS V5 March 1996
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The VER field contains the current version of the subnegotiation,
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which is X'01'. The ULEN field contains the length of the UNAME field
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that follows. The UNAME field contains the username as known to the
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source operating system. The PLEN field contains the length of the
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PASSWD field that follows. The PASSWD field contains the password
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association with the given UNAME.
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The server verifies the supplied UNAME and PASSWD, and sends the
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A STATUS field of X'00' indicates success. If the server returns a
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`failure' (STATUS value other than X'00') status, it MUST close the
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3. Security Considerations
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This document describes a subnegotiation that provides authentication
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services to the SOCKS protocol. Since the request carries the
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password in cleartext, this subnegotiation is not recommended for
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environments where "sniffing" is possible and practical.
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Bell-Northern Research Ltd
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P.O. Box 3511, Station C
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Phone: +1 613 763 9145
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Leech Standards Track [Page 2]
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