Support clients using CR+NUL to signal EOL

IETF RFC 854 requires that a Telnet server accept CR+NUL
interchangeably with CR+LF to indicate end of an input line from any
NVT (client). CR+NUL also happens to be the default behavior of
popular Telnet clients specifically when communicating on TCP port
23 (as opposed to non-default ports where more liberal protocol
fallbacks get employed). Previously these clients would need to `set
crlf` in their .telnetrc or at a telnet> command prompt as a
workaround.

Alter the selftest framework to send \r\0 from the NVT as an EOL to
make sure this does not regress, and add a test to explicitly end a
command with a \r\n just to make sure we can continue to support
CR+LF from clients.

diff --git a/mudpy/misc.py b/mudpy/misc.py
index bae94b6..4e43353 100644 (file)
--- a/mudpy/misc.py
+++ b/mudpy/misc.py
@@ -843,11 +843,15 @@ class User:
             mudpy.telnet.negotiate_telnet_options(self)
 
             # separate multiple input lines
-            new_input_lines = self.partial_input.split(b"\n")
+            new_input_lines = self.partial_input.split(b"\r\0")
+            if len(new_input_lines) == 1:
+                new_input_lines = new_input_lines[0].split(b"\r\n")
 
             # if input doesn't end in a newline, replace the
             # held partial input with the last line of it
-            if not self.partial_input.endswith(b"\n"):
+            if not (
+                    self.partial_input.endswith(b"\r\0") or
+                    self.partial_input.endswith(b"\r\n")):
                 self.partial_input = new_input_lines.pop()
 
             # otherwise, chop off the extra null input and reset

diff --git a/mudpy/telnet.py b/mudpy/telnet.py
index 245f44a..ed99faf 100644 (file)
--- a/mudpy/telnet.py
+++ b/mudpy/telnet.py
@@ -125,9 +125,11 @@ def negotiate_telnet_options(user):
         # the byte following the IAC is our command
         command = text[position+1]
 
-        # replace a double (literal) IAC if there's an LF later
+        # replace a double (literal) IAC if there's a CR+NUL or CR+LF later
         if command is IAC:
-            if text.find(b"\n", position) > 0:
+            if (
+                    text.find(b"\r\0", position) > 0 or
+                    text.find(b"\r\n", position) > 0):
                 position += 1
                 text = text[:position] + text[position + 1:]
             else:

diff --git a/mudpy/tests/selftest.py b/mudpy/tests/selftest.py
index 799ac50..179871e 100644 (file)
--- a/mudpy/tests/selftest.py
+++ b/mudpy/tests/selftest.py
@@ -158,18 +158,25 @@ test_admin_setup = (
     (2, "Whom would you like to awaken?", ""),
 )
 
+test_crlf_eol = (
+    # Send a CR+LF at the end of the line instead of the default CR+NUL,
+    # to make sure they're treated the same
+    (2, "> ", b"say I use CR+LF as my EOL, not CR+NUL.\r\n"),
+    (2, r'You say, "I use CR\+LF as my EOL, not CR\+NUL\.".*> ', ""),
+)
+
 test_telnet_iac = (
     # Send a double (escaped) IAC byte within other text, which should get
     # unescaped and deduplicated to a single \xff in the buffer and then
     # the line of input discarded as a non-ASCII sequence
-    (2, "> ", b"say argle\xff\xffbargle\r\n"),
+    (2, "> ", b"say argle\xff\xffbargle\r\0"),
     (2, r"Non-ASCII characters from admin: b'say argle\\xffbargle'.*> ", ""),
 )
 
 test_telnet_unknown = (
     # Send an unsupported negotiation command #127 which should get filtered
     # from the line of input
-    (2, "> ", b"say glop\xff\x7fglyf\r\n"),
+    (2, "> ", b"say glop\xff\x7fglyf\r\0"),
     (2, r'Unknown Telnet IAC command 127 ignored\..*"Glopglyf\.".*> ', ""),
 )
 
@@ -296,6 +303,7 @@ dialogue = (
     (test_actor_disappears, "actor spontaneous disappearance"),
     (test_account1_teardown, "second account teardown"),
     (test_admin_setup, "admin account setup"),
+    (test_crlf_eol, "send crlf from the client as eol"),
     (test_telnet_iac, "escape stray telnet iac bytes"),
     (test_telnet_unknown, "strip unknown telnet command"),
     (test_admin_restriction, "restricted admin commands"),
@@ -446,7 +454,7 @@ def main():
                 break
             if type(answer) is str:
                 tlog("luser%s sending: %s" % (conversant, answer), quiet=True)
-                lusers[conversant].write(("%s\r\n" % answer).encode("utf-8"))
+                lusers[conversant].write(("%s\r\0" % answer).encode("utf-8"))
                 captures[conversant] += "%s\r\n" % answer
             elif type(answer) is bytes:
                 tlog("luser%s sending raw bytes: %s" % (conversant, answer),