1 """Telnet functions and constants for the mudpy engine."""
3 # Copyright (c) 2004-2018 Jeremy Stanley <fungi@yuggoth.org>. Permission
4 # to use, copy, modify, and distribute this software is granted under
5 # terms provided in the LICENSE file distributed with this software.
9 # telnet options (from bsd's arpa/telnet.h since telnetlib's are ambiguous)
10 TELOPT_BINARY = 0 # transmit 8-bit data by the receiver (rfc 856)
11 TELOPT_ECHO = 1 # echo received data back to the sender (rfc 857)
12 TELOPT_SGA = 3 # suppress transmission of the go ahead character (rfc 858)
13 # TELOPT_TTYPE = 24 # exchange terminal type information (rfc 1091)
14 TELOPT_EOR = 25 # transmit end-of-record after transmitting data (rfc 885)
15 TELOPT_NAWS = 31 # negotiate about window size (rfc 1073)
16 TELOPT_LINEMODE = 34 # cooked line-by-line input mode (rfc 1184)
28 EOR = 239 # end-of-record signal (rfc 885)
29 SE = 240 # end of subnegotiation parameters (rfc 854)
30 GA = 249 # go ahead signal (rfc 854)
31 SB = 250 # what follows is subnegotiation of the indicated option (rfc 854)
32 WILL = 251 # desire or confirmation of performing an option (rfc 854)
33 WONT = 252 # refusal or confirmation of performing an option (rfc 854)
34 DO = 253 # request or confirm performing an option (rfc 854)
35 DONT = 254 # demand or confirm no longer performing an option (rfc 854)
36 IAC = 255 # interpret as command escape character (rfc 854)
38 # RFC 1143 option negotiation states
39 NO = 0 # option is disabled
40 YES = 1 # option is enabled
41 WANTNO = 2 # demanded disabling option
42 WANTYES = 3 # requested enabling option
43 WANTNO_OPPOSITE = 4 # demanded disabling option but queued an enable after it
44 WANTYES_OPPOSITE = 5 # requested enabling option but queued a disable after it
46 # RFC 1143 option negotiation parties
51 def telnet_proto(*arguments):
52 """Return a concatenated series of Telnet protocol commands."""
53 return bytes((arguments))
56 def send_command(user, *command):
57 """Sends a Telnet command string to the specified user's socket."""
58 user.send(telnet_proto(IAC, *command), raw=True)
61 def is_enabled(user, telopt, party, state=YES):
62 """Indicates whether a specified Telnet option is enabled."""
63 if (telopt, party) in user.telopts and user.telopts[
71 def enable(user, telopt, party):
72 """Negotiates enabling a Telnet option for the indicated user's socket."""
77 if not (telopt, party) in user.telopts or user.telopts[
80 user.telopts[(telopt, party)] = WANTYES
81 send_command(user, txpos, telopt)
82 elif user.telopts[(telopt, party)] is WANTNO:
83 user.telopts[(telopt, party)] = WANTNO_OPPOSITE
84 elif user.telopts[(telopt, party)] is WANTYES_OPPOSITE:
85 user.telopts[(telopt, party)] = WANTYES
88 def disable(user, telopt, party):
89 """Negotiates disabling a Telnet option for the user's socket."""
94 if not (telopt, party) in user.telopts:
95 user.telopts[(telopt, party)] = NO
96 elif user.telopts[(telopt, party)] is YES:
97 user.telopts[(telopt, party)] = WANTNO
98 send_command(user, txneg, telopt)
99 elif user.telopts[(telopt, party)] is WANTYES:
100 user.telopts[(telopt, party)] = WANTYES_OPPOSITE
101 elif user.telopts[(telopt, party)] is WANTNO_OPPOSITE:
102 user.telopts[(telopt, party)] = WANTNO
105 def negotiate_telnet_options(user):
106 """Reply to and remove telnet negotiation options from partial_input."""
108 # make a local copy to play with
109 text = user.partial_input
111 # start at the begining of the input
114 # as long as we haven't checked it all
116 while position < len_text:
118 # jump to the first IAC you find
119 position = text.find(telnet_proto(IAC), position)
121 # if there wasn't an IAC in the input or it's at the end, we're done
122 if position < 0 or position >= len_text - 1:
125 # the byte following the IAC is our command
126 command = text[position+1]
128 # replace a double (literal) IAC if there's a CR+NUL or CR+LF later
131 text.find(b"\r\0", position) > 0 or
132 text.find(b"\r\n", position) > 0):
134 text = text[:position] + text[position + 1:]
138 # implement an RFC 1143 option negotiation queue here
139 elif len_text > position + 2 and WILL <= command <= DONT:
140 telopt = text[position+2]
141 if telopt in supported:
152 if (telopt, party) not in user.telopts:
153 user.telopts[(telopt, party)] = NO
155 if user.telopts[(telopt, party)] is NO:
156 user.telopts[(telopt, party)] = YES
157 send_command(user, txpos, telopt)
158 elif user.telopts[(telopt, party)] is WANTNO:
159 user.telopts[(telopt, party)] = NO
160 elif user.telopts[(telopt, party)] is WANTNO_OPPOSITE:
161 user.telopts[(telopt, party)] = YES
162 elif user.telopts[(telopt, party)] is WANTYES_OPPOSITE:
163 user.telopts[(telopt, party)] = WANTNO
164 send_command(user, txneg, telopt)
166 user.telopts[(telopt, party)] = YES
168 if user.telopts[(telopt, party)] is YES:
169 user.telopts[(telopt, party)] = NO
170 send_command(user, txneg, telopt)
171 elif user.telopts[(telopt, party)] is WANTNO_OPPOSITE:
172 user.telopts[(telopt, party)] = WANTYES
173 send_command(user, txpos, telopt)
175 user.telopts[(telopt, party)] = NO
176 elif command is WILL:
177 send_command(user, DONT, telopt)
179 send_command(user, WONT, telopt)
180 text = text[:position] + text[position + 3:]
182 # subnegotiation options
183 elif len_text > position + 4 and command is SB:
184 telopt = text[position + 2]
185 if telopt is TELOPT_NAWS:
187 text[position + 3] * 256 + text[position + 4])
188 end_subnegotiation = text.find(telnet_proto(IAC, SE), position)
189 if end_subnegotiation > 0:
190 text = text[:position] + text[end_subnegotiation + 2:]
194 # otherwise, strip out a two-byte IAC command
195 elif len_text > position + 2:
196 mudpy.misc.log("Unknown Telnet IAC command %s ignored." % command)
197 text = text[:position] + text[position + 2:]
199 # and this means we got the begining of an IAC
203 # replace the input with our cleaned-up text
204 user.partial_input = text