Endless Loop During Command Search

[machste]

Hi all,

I found the following issue with the libcli. Entering a mode and issuing the same command by mistake, causes the main loop to hang forever. This can be simply reproduced with the test program, as shown below:

$ telnet 127.0.0.1 8000
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
libcli test environment

Username: fred
Password:  

router> enable
Password: 
router# configure terminal 

router(config)# interface test0/0

router(config-test)# interface

At this point, the CLI hangs and won't return a prompt.

I did some research by myself and think there's something wrong here:

libcli/libcli.c

Line 2913 in b6ff35c

if (again_config) {

As a workaround, I removed this check and it works for me so far.

Best regards,
Stefan Mächler

[RobSanders]

Stefan, Thank you - will investigate.

…

-Rob Robert Sanders Senior Secure Systems Engineer – G2CI, North America Forcepoint O: +1.703-896-4762 www.forcepoint.com<http://www.forcepoint.com> From: Stefan Mächler <notifications@github.com> Reply-To: dparrish/libcli <reply@reply.github.com> Date: Monday, February 22, 2021 at 10:11 AM To: dparrish/libcli <libcli@noreply.github.com> Cc: Subscribed <subscribed@noreply.github.com> Subject: EXTERNAL: [dparrish/libcli] Endless Loop During Command Search (#69) Hi all, I found the following issue with the libcli. Entering a mode and issuing the same command by mistake, causes the main loop to hang forever. This can be simply reproduced with the test program, as shown below: $ telnet 127.0.0.1 8000 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. libcli test environment Username: fred Password: router> enable Password: router# configure terminal router(config)# interface test0/0 router(config-test)# interface At this point, the CLI hang and won't return a prompt. Best regards, Stefan Mächler — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#69>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AHHFTFZQDOEVDIL7BA6VLO3TAJX2DANCNFSM4YAWBWLQ>.

[RobSanders]

Stefan, Found it, problem has been around since V1.10.0. When the internal routine ‘cli_find_command()’ was refactored into ‘cli_int_locate_command()’ one line was missed. We haven’t seen it in our internal application because our ‘command modes’ are not purely hierarchical, but instead totally distinct. By this I mean a command must be located w/in the current command mode, or be marked as MODE_ANY, in order to be selectable. To do this we use negative command modes. Anyway, the missing line would have forced the command mode to be the mode of the ‘matching’ command from a different mode. Without this change the code looped forever trying to find a matching command. Will queue up a patch and submit shortly...

…

-Rob Robert Sanders Senior Secure Systems Engineer – G2CI, North America Forcepoint O: +1.703-896-4762 www.forcepoint.com<http://www.forcepoint.com> From: "Sanders, Robert" <rsanders@forcepointgov.com> Date: Monday, February 22, 2021 at 10:29 AM To: dparrish/libcli <reply@reply.github.com>, dparrish/libcli <libcli@noreply.github.com> Cc: Subscribed <subscribed@noreply.github.com> Subject: Re: EXTERNAL: [dparrish/libcli] Endless Loop During Command Search (#69) Stefan, Thank you - will investigate.

-Rob Robert Sanders Senior Secure Systems Engineer – G2CI, North America Forcepoint O: +1.703-896-4762 www.forcepoint.com<http://www.forcepoint.com> From: Stefan Mächler <notifications@github.com> Reply-To: dparrish/libcli <reply@reply.github.com> Date: Monday, February 22, 2021 at 10:11 AM To: dparrish/libcli <libcli@noreply.github.com> Cc: Subscribed <subscribed@noreply.github.com> Subject: EXTERNAL: [dparrish/libcli] Endless Loop During Command Search (#69) Hi all, I found the following issue with the libcli. Entering a mode and issuing the same command by mistake, causes the main loop to hang forever. This can be simply reproduced with the test program, as shown below: $ telnet 127.0.0.1 8000 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. libcli test environment Username: fred Password: router> enable Password: router# configure terminal router(config)# interface test0/0 router(config-test)# interface At this point, the CLI hang and won't return a prompt. Best regards, Stefan Mächler — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#69>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AHHFTFZQDOEVDIL7BA6VLO3TAJX2DANCNFSM4YAWBWLQ>.

[RobSanders]

Stefan, have an pull request pending with the bug fix for your issue if you want to test. This will also bump the version to V1.10.6

[machste]

Hi Rob,
thank you for reacting so fast. :-)
Stefan

[RobSanders]

No worries - advance notice that 1.10.7 is forthcoming - someone on my team just found an issue with the change I did in 1.10.5 for formatting the help message for a command with a long name (greater than 20 odd characters) - affects the help display for showing possible completions of options/arguments....Not a fatal bug, but produces an extra linefeed on each line..... Hope to have that fixed today or tomorrow - Robert Sanders Senior Secure Systems Engineer – G2CI, North America Forcepoint O: +1.703-896-4762 www.forcepoint.com<http://www.forcepoint.com> From: Stefan Mächler <notifications@github.com> Reply-To: dparrish/libcli <reply@reply.github.com> Date: Wednesday, February 24, 2021 at 8:10 AM To: dparrish/libcli <libcli@noreply.github.com> Cc: Rob Sanders <rsanders@forcepoint.com>, Comment <comment@noreply.github.com> Subject: EXTERNAL: Re: [dparrish/libcli] Endless Loop During Command Search (#69) Hi Rob, thank you for reacting so fast. :-) Stefan — You are receiving this because you commented. Reply to this email directly, view it on GitHub<#69 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AHHFTFYJ37HQOMRB7I7CFW3TAT3ENANCNFSM4YAWBWLQ>.

[RobSanders]

Fixed in V1.10.6