1NaCl(1)                     General Commands Manual                    NaCl(1)
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NAME

6       CurveCP — Message-handling programs
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SYNOPSIS

9       curvecpclient  [-q  (optional)]   [-Q (optional)]  [-v (optional)]  [-c
10       keydir(optional)]  [sname]  [pk]  [ip]  [port]  [ext]  [prog]
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DESCRIPTION

13       This manual page documents briefly the CurveCP commands.
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15       A traditional UNIX-style server such as ftpd handles just  one  network
16       connection,  reading  input  from stdin and writing output to stdout. A
17       "superserver" such as inetd or tcpserver listens  for  network  connec‐
18       tions and starts a separate server process for each connection.
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20       The  CurveCP  command-line tools have an extra level of modularity. The
21       curvecpserver  superserver listens for network  connections.  For  each
22       connection,  curvecpserver  starts  the curvecpmessage message handler;
23       curvecpmessage then starts a server such as ftpd.  Then  ftpd  sends  a
24       stream  of  data  to  curvecpmessage,  which  in turn sends messages to
25       curvecpserver, which encrypts and authenticates the messages and  sends
26       them  inside  network  packets. At the same time curvecpclient receives
27       network packets, verifies and decrypts messages inside the packets, and
28       passes the messages to curvecpmessage; curvecpmessage sends a stream of
29       data to ftpd.  The same curvecpmessage tool is also  used  by  curvecp‐
30       client.
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32       curvecpserver and curvecpclient can use programs other than curvecpmes‐
33       sage. Those programs can directly generate messages in the CurveCP mes‐
34       sage format without talking to separate tools such as ftpd; or they can
35       support a completely different protocol that reuses  CurveCP's  crypto‐
36       graphic layer but transmits different kinds of messages.
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38       This  page explains what programmers have to do to write curvecpmessage
39       replacements that talk to curvecpserver and curvecpclient.
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Incoming messagess

42       File descriptor 8 is a pipe. Read from  this  pipe  a  length  byte  n,
43       between  1 and 68, and a 16*n-byte message. Repeat.  The pipe is set to
44       non-blocking mode; be prepared for EAGAIN and EWOULDBLOCK, even in  the
45       middle of a message.
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47       This  pipe  reading  must  always  be  active.  The  curvecpclient  and
48       curvecpserver programs assume that every message is  read  immediately.
49       If  you  can't  handle a message immediately, read it and put it onto a
50       queue. If you don't have queue space,  throw  the  message  away;  this
51       shouldn't  cause  trouble,  since you have to be able to handle missing
52       messages in any case.
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Outgoing messagess

55       File descriptor 9 is a pipe. Write  to  this  pipe  a  length  byte  n,
56       between  1 and 68, and a 16*n-byte message. Repeat.  The pipe is set to
57       non-blocking mode; be prepared for EAGAIN and EWOULDBLOCK, even in  the
58       middle of a message.
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60       As  a  client,  do  not  use  length bytes above 40 until a message has
61       arrived from the server. (The messages inside CurveCP Initiate  packets
62       are limited to 640 bytes.)
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64       The  CurveCP server does not start until it has received a message from
65       the client. Furthermore, the CurveCP server must receive  this  message
66       within  60  seconds  of  the  client starting up. (The CurveCP Initiate
67       packet is valid for only 60 seconds  after  the  corresponding  CurveCP
68       Cookie  packet.)  This does not mean that the client must start sending
69       messages immediately, but it does mean that waiting  for  more  than  a
70       second to send a message is a bad idea.
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OPTIONS

73       How to use curvecpclient:
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75       -q           optional
76                 no error messages
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78       -Q           optional
79                 print error messages (default)
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81       -v           optional
82                 print extra information
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84       -c keydir           optional
85                 use this public-key directory
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87       sname     server's name
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89       pk        server's public key
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91       ip        server's IP address
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93       port      server's UDP port
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95       ext       server's extension
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97       prog      run this client
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SEE ALSO

100       curvecpserver (1), curvecpmessage (1), inetd (8), tcpserver (1).
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AUTHOR

103       This  manual  page  was  written  by  Sergiusz Pawlowicz debian@pawlow‐
104       icz.name for the Debian system (and may be used by others). The  source
105       of this page is a webpage http://curvecp.org/messageapi.html .  Permis‐
106       sion is granted to copy, distribute and/or modify this  document  under
107       public domain.
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110       This  manual page was rewritten for the Debian distribution because the
111       original program does not have a manual page.
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