[Bug 1891021] [NEW] Specifying a port in telnetrc is not working

[Dongho Chang]

Public bug reported:


1) Ubuntu release
 Description:	Ubuntu 18.04.3 LTS
 Release:	18.04
2) Package version
 telnet:
  Installed: 0.17-41
  Candidate: 0.17-41
  Version table:
 *** 0.17-41 500
        500 http://kr.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status

3) What expected to happen

 - 1. Specify a port in telnetrc ( $HOME/.telnetrc) as follows
     *  DEFAUT:8023 mode character
 - 2. telnet a host with specific port
     * telnet 192.168.1.1 8023
 - The expected is that "mode character" command is executed as soon as server is connected, according to "man telnet"

4) What happened instead
  - The command in telnetrc specifying a port is not executed
  - But If not specifying a port, the command is executed as expected

5) Cause of Bug
  - telnetrc parsing routine ( readrc() function in telnet/command.cc ) has a flaw in comparing the port number of command-line with that of telnetrc
  - To proceed command processing, the result of string compare MUST not negated
  - The patch is as follows
--- a/telnet/commands.cc
+++ b/telnet/commands.cc
@@ -2135,7 +2135,7 @@ static void readrc(const char *m1, const char *m2, const char *port,
                continue;
     while (fgets(line, sizeof(line), rcfile)) {
        ...
        if (gotmachine == 0) {
            ...
 
            if (line[0] == ':') {
-               if (!strncasecmp(&line[1], port, lport))
+               if (strncasecmp(&line[1], port, lport))
                    continue;
                strncpy(line, &line[lport + 1], sizeof(line) - lport - 1);
            }
           ...
        }
        ...
        process_command(&cmdtab, margc, margv);

** Affects: netkit-telnet (Ubuntu)
     Importance: Undecided
         Status: New

** Patch added: "Bug in comparing port strings in readrc() is fixed"
   https://bugs.launchpad.net/bugs/1891021/+attachment/5400372/+files/patch-port_in_telnetrc.txt

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https://bugs.launchpad.net/bugs/1891021

Title:
  Specifying  a port in telnetrc is not working

Status in netkit-telnet package in Ubuntu:
  New

Bug description:
  
  1) Ubuntu release
   Description:	Ubuntu 18.04.3 LTS
   Release:	18.04
  2) Package version
   telnet:
    Installed: 0.17-41
    Candidate: 0.17-41
    Version table:
   *** 0.17-41 500
          500 http://kr.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
          100 /var/lib/dpkg/status

  3) What expected to happen

   - 1. Specify a port in telnetrc ( $HOME/.telnetrc) as follows
       *  DEFAUT:8023 mode character
   - 2. telnet a host with specific port
       * telnet 192.168.1.1 8023
   - The expected is that "mode character" command is executed as soon as server is connected, according to "man telnet"

  4) What happened instead
    - The command in telnetrc specifying a port is not executed
    - But If not specifying a port, the command is executed as expected

  5) Cause of Bug
    - telnetrc parsing routine ( readrc() function in telnet/command.cc ) has a flaw in comparing the port number of command-line with that of telnetrc
    - To proceed command processing, the result of string compare MUST not negated
    - The patch is as follows
  --- a/telnet/commands.cc
  +++ b/telnet/commands.cc
  @@ -2135,7 +2135,7 @@ static void readrc(const char *m1, const char *m2, const char *port,
                  continue;
       while (fgets(line, sizeof(line), rcfile)) {
          ...
          if (gotmachine == 0) {
              ...
   
              if (line[0] == ':') {
  -               if (!strncasecmp(&line[1], port, lport))
  +               if (strncasecmp(&line[1], port, lport))
                      continue;
                  strncpy(line, &line[lport + 1], sizeof(line) - lport - 1);
              }
             ...
          }
          ...
          process_command(&cmdtab, margc, margv);

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