rexecd.tproj/rexecd.8

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  32 .\"     @(#)rexecd.8    8.3 (Berkeley) 6/1/94
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  34 .Dd June 1, 1994
  35 .Dt REXECD 8
  36 .Os BSD 4.2
  37 .Sh NAME
  38 .Nm rexecd
  39 .Nd remote execution server
  40 .Sh SYNOPSIS
  41 .Nm rexecd
  42 .Sh DESCRIPTION
  43 .Nm Rexecd
  44 is the server for the
  45 .Xr rexec 3
  46 routine.  The server provides remote execution facilities
  47 with authentication based on user names and
  48 passwords.
  49 .Pp
  50 .Nm Rexecd
  51 listens for service requests at the port indicated in
  52 the ``exec'' service specification; see
  53 .Xr services 5 .
  54 When a service request is received the following protocol
  55 is initiated:
  56 .Bl -enum
  57 .It
  58 The server reads characters from the socket up
  59 to a NUL
  60 .Pq Ql \e0
  61 byte.  The resultant string is
  62 interpreted as an
  63 .Tn ASCII
  64 number, base 10.
  65 .It
  66 If the number received in step 1 is non-zero,
  67 it is interpreted as the port number of a secondary
  68 stream to be used for the
  69 .Em stderr .
  70 A second connection is then created to the specified
  71 port on the client's machine.
  72 .It
  73 A NUL terminated user name of at most 16 characters
  74 is retrieved on the initial socket.
  75 .It
  76 A NUL terminated, unencrypted password of at most
  77 16 characters is retrieved on the initial socket.
  78 .It
  79 A NUL terminated command to be passed to a
  80 shell is retrieved on the initial socket.  The length of
  81 the command is limited by the upper bound on the size of
  82 the system's argument list.
  83 .It
  84 .Nm Rexecd
  85 then validates the user as is done at login time
  86 and, if the authentication was successful, changes
  87 to the user's home directory, and establishes the user
  88 and group protections of the user.
  89 If any of these steps fail the connection is
  90 aborted with a diagnostic message returned.
  91 .It
  92 A NUL byte is returned on the initial socket
  93 and the command line is passed to the normal login
  94 shell of the user.  The
  95 shell inherits the network connections established
  96 by
  97 .Nm rexecd .
  98 .El
  99 .Sh DIAGNOSTICS
 100 Except for the last one listed below,
 101 all diagnostic messages are returned on the initial socket,
 102 after which any network connections are closed.
 103 An error is indicated by a leading byte with a value of
 104 1 (0 is returned in step 7 above upon successful completion
 105 of all the steps prior to the command execution).
 106 .Pp
 107 .Bl -tag -width Ds
 108 .It Sy username too long
 109 The name is
 110 longer than 16 characters.
 111 .It Sy password too long
 112 The password is longer than 16 characters.
 113 .It Sy command too long
 114 The command line passed exceeds the size of the argument
 115 list (as configured into the system).
 116 .It Sy Login incorrect.
 117 No password file entry for the user name existed.
 118 .It Sy Password incorrect.
 119 The wrong password was supplied.
 120 .ne 1i
 121 .It Sy \&No remote directory.
 122 The
 123 .Xr chdir
 124 command to the home directory failed.
 125 .It Sy Try again.
 126 A
 127 .Xr fork
 128 by the server failed.
 129 .It Sy <shellname>: ...
 130 The user's login shell could not be started.
 131 This message is returned
 132 on the connection associated with the
 133 .Em stderr ,
 134 and is not preceded by a flag byte.
 135 .El
 136 .Sh SEE ALSO
 137 .Xr rexec 3
 138 .Sh BUGS
 139 Indicating ``Login incorrect'' as opposed to ``Password incorrect''
 140 is a security breach which allows people to probe a system for users
 141 with null passwords.
 142 .Pp
 143 A facility to allow all data and password exchanges to be encrypted should be
 144 present.
 145 .Sh HISTORY
 146 The
 147 .Nm
 148 command appeared in
 149 .Bx 4.2 .