ziutek / telnet

Package to handle a telnet connection

documentation

telnet's Issues

How to disable echo?

The code SetEcho(false) doesn't work in your code, but when I use telnet command in Linux shell, the echo mode is disabled.

Needs Tests

Conn.go should have a test_Conn.go file

SkipUntil leads to "index out of range" error in bufio

We sometimes use SkipUntil with a single string argument in our code, for example teln.SkipUntil("querymvisvc"), and this sometimes leads to the error stack below:

panic: runtime error: index out of range

goroutine 853 [running]:
bufio.(*Reader).ReadByte(0xc0024d57a0, 0x54f837, 0x0, 0x0)
	/usr/local/go/src/bufio/bufio.go:251 +0xcb
github.com/ziutek/telnet.(*Conn).tryReadByte(0xc00175ccc0, 0x560037, 0x0, 0x0)
	/go/pkg/mod/github.com/ziutek/[email protected]/conn.go:230 +0x33
github.com/ziutek/telnet.(*Conn).ReadByte(0xc00175ccc0, 0x37, 0x0, 0x0)
	/go/pkg/mod/github.com/ziutek/[email protected]/conn.go:261 +0x38
github.com/ziutek/telnet.(*Conn).readUntil(0xc00175ccc0, 0x5aec00, 0xc006c55130, 0x1, 0x1, 0xc002245538, 0x40bff8, 0x10, 0x570320, 0x1, ...)
	/go/pkg/mod/github.com/ziutek/[email protected]/conn.go:364 +0x12e
github.com/ziutek/telnet.(*Conn).SkipUntil(0xc00175ccc0, 0xc006c55130, 0x1, 0x1, 0x3, 0x3)
	/go/pkg/mod/github.com/ziutek/[email protected]/conn.go:405 +0x51
bitbucket.org/team/teamrepo/processor.queryDMC(0x5e2440, 0xc00175ccc0, 0xc003646223, 0x2, 0xc0002bf640, 0xe, 0xc0002bf638, 0x4, 0xc0002bf650, 0x6, ...)

How to send interrupt signal.

I want to send a interrupt signal to a running command.

found a whole new wolrd

telnet/examples/bat.org/main.go

Line 17 in c3b780d

t, err := telnet.Dial("tcp", "bat.org:23")

i was just reading the code , then 17hs past. :P

How to remove control characters on the output of telnet?

Hi, Ziutek. Maybe it's not proper to ask this question here, but it really confused me for several days.
I want to remove all control characters in the telnet output because there are too many special characters over there. For example, the telnet output is:

ae23        Enabled     Down    Disabled      Auto    Auto                                                    ^M^@^M
ae24        Enabled     Down    Disabled      Auto    Auto                                                    ^M^@^M
^[[J^M^@ --More-- (END) ^[[J^M^@ --More-- (END) ^[[J^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^H^[[J^[[J^[[J^M^@test.Int> exit

There are some extra characters including non-printable and printable like ^[, ^H, ^M, [J, --More-- (END) and so on. But this output is normal when printing on the screen:

ae23        Enabled     Down    Disabled      Auto    Auto
ae24        Enabled     Down    Disabled      Auto    Auto
test.Int> exit

All the control character are not shown. I know there is a way that uses col -b bash command to remove them. But it's not an effective way because telnet is an interactive way. Using os.exec to filter control characters for every command is not good.
So do you have any idea to remove all the control characters on the telnet output?

Two questions about telnet option

Hi, Dear Ziutek,

Sorry to bother you again. I have two questions about the telnet option recently. I used your library to telnet different switch and router. Some of them are OK, while some are not.

1. The "Password:" string didn't show
   After login into the switch using telnet, the Username: characters show normally. Some switches don't show the password: characters after typing the username. Actually, no response occurred whatever I type.
   In my experiments, some switches can display the password: character but some aren't. I can't find any help in the google results and (rfc854)[https://tools.ietf.org/html/rfc854]. Do you know it's telnet option problem or switch configuration problem?
   Supplement: the password: string can all be displayed normally when using (Linux telnet client)[https://linux.die.net/man/1/telnet].

2. "echo option" negotiate loop
   I didn't modify your code so that for every IAC WILL ECHO/255 251 1 reply IAC DO ECHO/255 253 2; for every IAC WON'T ECHO/255 252 1 reply IAC DON'T ECHO/255 254 1. This strategy should work OK according to the (rfc854)[https://tools.ietf.org/html/rfc854]. But some switches go into dead loop, here comes the print from debug:

received cmd: 251 1
received cmd: 251 1
received cmd: 251 1
received cmd: 251 3
received cmd: 253 24
received cmd: 253 31
received cmd: 252 1
received cmd: 251 1
received cmd: 254 24
received cmd: 254 31
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
received cmd: 251 1
received cmd: 252 1
.... // print omit: "255 251 1" and "255 252 1" display respectively

I don't know whether it's problem of switch telnet version. What I want is accept any echo configuration. Here comes the description of option response in rfc854:

If a party receives what appears to be a request to enter some mode it is already in, the request should not be acknowledged. This non-response is essential to prevent endless loops in the negotiation. It is required that a response be sent to requests for a change of mode -- even if the mode is not changed.

In my understanding, no response means enable. So I modify your code in func (c *Conn) cmd(cmd byte) that doesn't reply any do and don't when receive will and won't:

	switch o {
	case optEcho:
		// Accept any echo configuration.
		switch cmd {
		case cmdDo:
			if !c.cliEcho {
				c.cliEcho = true
				err = c.will(o)
			}
		case cmdDont:
			if c.cliEcho {
				c.cliEcho = false
				err = c.wont(o)
			}
		case cmdWill:
			// err = c.do(o) // erase
		case cmdWont:
			// err = c.dont(o) // erase
		}

It looks like the switch enable echo option which is what I want. Do you think it's a right way to erase these two line code to enable echo option?

centos telnet server send data mark(242)，function read get error

when i use ziutek/telnet connect a telnet server on centos 7。if server send data mark(242)，conn.read() get will unknown command error

Stuck on reading

When I tried to use this client to connect to some mud servers, I found that sometimes it doesn't print all the text. After some digging, I found that the program got stuck on conn.Read when it's fed with a big buffer.

After more digging, I found out that the c.r.Buffered() returns more than 0, so it get stuck at c.ReadByte() in the next iteration.
https://github.com/ziutek/telnet/blob/master/conn.go#L306

Also, I'm not sure if it's related, but usually it gets stuck in the middle on a line.

I'm not familiar with telnet or your client enough to solve this. Could you take a look?

Below is a snippet that can show the problem. You can run it multiple times to see how the problem is like.

func main() {
	conn, err := telnet.Dial("tcp", "bat.org:23")
	if err != nil {
		log.Fatal(err)
	}

	for {
		data := make([]byte, 512) // if I change the buffer size to 1, it doesn't hang
		n, err := conn.Read(data)
		if n > 0 {
			fmt.Print(string(data))
		}

		if err != nil {
			log.Fatal(err)
		}
	}
}

Missing license

I'd like to use this library, but without a license I cannot in good conscience include it in my code.

command data should be writeln to tcp Conn

Hi,
conn.go line 133
https://github.com/ziutek/telnet/blob/master/conn.go#L113

if _, err := c.Write(data); err != nil {

should be

if _, err := c.Conn.Write(data); err != nil {

fix is trivial, but if you want PR, i can send one this week.

Regards,
Jamil Djadala

Read until blank line

Hello,

I am using your library as part of connecting to systems to run a command, read the output, and then run another command. The system in question doesn't have a character as its prompt (e.g. no $ or >) and as such, I can't figure out what I should be passing to the ReadUntil() function. I was using a carriage return string "\r" but this isn't always effective as the output can be multiple lines.

Have you accounted for this use case?

Many thanks

EDIT: Perhaps there is some way to define a regex pattern that is matched?

Backspace not handled properly

Backspace echo's a ^H rather than performs a backspace....

i/o time out

Hello,
I am using the main.go example to connect to
telnet.reversebeacon.net:7000
and I receive a time out.

I can connect without any issues with other clients.
Any help?

Go version: 1.9.4
OS: Windows 7 Enterprise 64-bits.
No build errors.
Error recevied from the telnet server:
2018/02/12 18:30:33 Error: read tcp 192.168.1.5:54852->198.137.202.75:7000: i/o
timeout

Hope you can help me.
Thanks.

Cisco ASA 5505 connection issues

Hi, trying to connect to a Cisco ASA 5505, I found that the option subcommands SB and SE were not being catched, so I have added this codes cmdSB and cmdSE to line 111 of conn.go. That allowed me to connect and to send commands succesfully.

Regards,

Lucas

conn.Read Ctrl+c failed

unknown command: 242

Fortigate FortiOS connection issues

I am having some trouble with logging into Fortigate via telnet. Connecting and initial use works fine to Fortigate. This is a virtual instance on KVM (FortiGate-VM64-KVM). More specifically, Version: FortiGate-VM64-KVM v5.6.1,build1484,170727.

For reference: Example telnet connection (with regular telnet command):

Escape character is '^]'.

hostname login: admin
Password: **********
Welcome !

hostname #

when connecting with the telnet library, I can write "admin" and then read until "sword: "
Then writing the password "mypassword" followed by a newline, it echoes a "" for each letter.
Reading back, I get the "*********" however nothing more comes after that and the connection hangs.
It feels as if the password is not finished to enter and nothing more comes back after reading.
The password insertion is do is handled in the same way as the username insertion which works, so it is somewhat surprising.

Is it possible that the fortigate is using some option/setting that is not supported and is causing this behavior? Any ideas would be appreciated.

Thanks,
Gus