expect always fails with "EXCESS TIME RECV_READY TIMEOUT, did you expect() before a send()" error

[nhtha]

Dear team, expect always fails with "EXCESS TIME RECV_READY TIMEOUT, did you expect() before a send()" error, including the demo. Please help me to fix it. I am using: Windows 11 Pro, Python 3.10 x64 to connect to Centos 7, 8, 9 machine. Best regards, Ha Nguyen

[fruch]

Hi @nhtha, that's too little information to help you

can you provide more details, on how you connect ? with user/password ? with ssh key ? which try of key ? can you provider a code snippet ? the sshd configuration you are using on the server end ?

[nhtha]

Hi Fruch, I'm using the demo itself with some slighly modifications on IP, user and password. Here is the code snippet: `from future import print_function import traceback

import paramiko from paramiko_expect import SSHClientInteraction

def main():

Set login credentials and the server prompt

HOSTNAME = '192.168.254.129'
USERNAME = 'nhtha'
PASSWORD = '123456'
# PROMPT = r'nhtha@centos8:~\$\s+'
PROMPT = r"\[.+@.+\]#|\[.+@.+\]\$"

# Use SSH client to login
try:
    # Create a new SSH client object
    client = paramiko.SSHClient()

    # Set SSH key parameters to auto accept unknown hosts
    client.load_system_host_keys()
    client.set_missing_host_key_policy(paramiko.AutoAddPolicy())

    # Connect to the host
    client.connect(hostname=HOSTNAME, username=USERNAME, password=PASSWORD)

    # Create a client interaction class which will interact with the host
    with SSHClientInteraction(client, timeout=10, display=False) as interact:
        interact.expect(PROMPT)

        # Run the first command and capture the cleaned output, if you want
        # the output without cleaning, simply grab current_output instead.
        interact.send('uname -a')
        interact.expect(PROMPT)
        cmd_output_uname = interact.current_output_clean

        # Now let's do the same for the ls command but also set a timeout for
        # this specific expect (overriding the default timeout)
        interact.send('ls -l /')
        interact.expect(PROMPT, timeout=5)
        cmd_output_ls = interact.current_output_clean

        # To expect multiple expressions, just use a list.  You can also
        # selectively take action based on what was matched.

        # Send the exit command and expect EOF (a closed session)
        interact.send('exit')
        interact.expect()

    # Print the output of each command
    print('-' * 79)
    print('Cleaned Command Output')
    print('-' * 79)
    print('uname -a output:')
    print(cmd_output_uname)
    print('ls -l / output:')
    print(cmd_output_ls)

except Exception:
    traceback.print_exc()
finally:
    try:
        client.close()
    except Exception:
        pass

if name == 'main': main() Here is the sshd configuration on the linux server end: # $OpenBSD: sshd_config,v 1.100 2016/08/15 12:32:04 naddy Exp $

This is the sshd server system-wide configuration file. See

sshd_config(5) for more information.

This sshd was compiled with PATH=/usr/local/bin:/usr/bin

The strategy used for options in the default sshd_config shipped with

OpenSSH is to specify options with their default value where

possible, but leave them commented. Uncommented options override the

default value.

If you want to change the port on a SELinux system, you have to tell

SELinux about this change.

semanage port -a -t ssh_port_t -p tcp #PORTNUMBER

#

Port 22

AddressFamily any

ListenAddress 0.0.0.0

ListenAddress ::

HostKey /etc/ssh/ssh_host_rsa_key

HostKey /etc/ssh/ssh_host_dsa_key

HostKey /etc/ssh/ssh_host_ecdsa_key HostKey /etc/ssh/ssh_host_ed25519_key

Ciphers and keying

RekeyLimit default none

Logging

SyslogFacility AUTH

SyslogFacility AUTHPRIV

LogLevel INFO

Authentication:

LoginGraceTime 2m

PermitRootLogin yes

StrictModes yes

MaxAuthTries 6

MaxSessions 10

PubkeyAuthentication yes

The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2

but this is overridden so installations will only check .ssh/authorized_keys

AuthorizedKeysFile .ssh/authorized_keys

AuthorizedPrincipalsFile none

AuthorizedKeysCommand none

AuthorizedKeysCommandUser nobody

For this to work you will also need host keys in /etc/ssh/ssh_known_hosts

HostbasedAuthentication no

Change to yes if you don't trust ~/.ssh/known_hosts for

HostbasedAuthentication

IgnoreUserKnownHosts no

Don't read the user's ~/.rhosts and ~/.shosts files

IgnoreRhosts yes

To disable tunneled clear text passwords, change to no here!

PasswordAuthentication yes

PermitEmptyPasswords no

PasswordAuthentication yes

Change to no to disable s/key passwords

ChallengeResponseAuthentication yes

ChallengeResponseAuthentication no

Kerberos options

KerberosAuthentication no

KerberosOrLocalPasswd yes

KerberosTicketCleanup yes

KerberosGetAFSToken no

KerberosUseKuserok yes

GSSAPI options

GSSAPIAuthentication yes

GSSAPIAuthentication no GSSAPICleanupCredentials no

GSSAPIStrictAcceptorCheck yes

GSSAPIKeyExchange no

GSSAPIEnablek5users no

Set this to 'yes' to enable PAM authentication, account processing,

and session processing. If this is enabled, PAM authentication will

be allowed through the ChallengeResponseAuthentication and

PasswordAuthentication. Depending on your PAM configuration,

PAM authentication via ChallengeResponseAuthentication may bypass

the setting of "PermitRootLogin without-password".

If you just want the PAM account and session checks to run without

PAM authentication, then enable this but set PasswordAuthentication

and ChallengeResponseAuthentication to 'no'.

WARNING: 'UsePAM no' is not supported in Red Hat Enterprise Linux and may cause several

problems.

UsePAM yes

AllowAgentForwarding yes

AllowTcpForwarding yes

GatewayPorts no X11Forwarding yes

X11DisplayOffset 10

X11UseLocalhost yes

PermitTTY yes

PrintMotd yes

PrintLastLog yes

TCPKeepAlive yes

UseLogin no

UsePrivilegeSeparation sandbox

PermitUserEnvironment no

Compression delayed

ClientAliveInterval 0

ClientAliveCountMax 3

ShowPatchLevel no

UseDNS yes

UseDNS no

PidFile /var/run/sshd.pid

MaxStartups 10:30:100

PermitTunnel no

ChrootDirectory none

VersionAddendum none

no default banner path

Banner none

Accept locale-related environment variables

AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE AcceptEnv XMODIFIERS

override default of no subsystems

Subsystem sftp /usr/libexec/openssh/sftp-server

Example of overriding settings on a per-user basis

Match User anoncvs

X11Forwarding no

AllowTcpForwarding no

PermitTTY no

ForceCommand cvs server`

Regards, Ha Nguyen

[fruch]

I would recommend enabling full log levels in the sshd side, to see what are the failures from its side.

Also I would note the version of open ssh being used on the server, and which paramiko version is used, I might be comptabiliy issues between them.

After that I would try a clean example of paramiko itself, and if that isn't working either, I would take the issue there.

[nhtha]

When enabling display, I can see that results of uname -a and ls -l command are printed out as below, looks like the send command work fine, but the expect command failed.

`Last login: Mon May 13 09:06:33 2024 from 192.168.254.1 [nhtha@centos7 ~]$ EXCESS TIME RECV_READY TIMEOUT, did you expect() before a send() uname -a Linux centos7 3.10.0-1160.114.2.el7.x86_64 #1 SMP Wed Mar 20 15:54:52 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux [nhtha@centos7 ~]$ EXCESS TIME RECV_READY TIMEOUT, did you expect() before a send() ls -l / total 24 lrwxrwxrwx. 1 root root 7 Jan 6 2020 bin -> usr/bin dr-xr-xr-x. 5 root root 4096 Apr 29 17:24 boot drwxr-xr-x. 21 root root 3440 May 12 19:55 dev drwxr-xr-x. 147 root root 8192 May 13 08:45 etc drwxr-xr-x. 3 root root 19 Jan 6 2020 home lrwxrwxrwx. 1 root root 7 Jan 6 2020 lib -> usr/lib lrwxrwxrwx. 1 root root 9 Jan 6 2020 lib64 -> usr/lib64 drwxr-xr-x. 2 root root 6 Apr 11 2018 media drwxr-xr-x. 3 root root 18 Apr 29 16:31 mnt drwxr-xr-x. 3 root root 16 Jan 6 2020 opt dr-xr-xr-x. 227 root root 0 May 12 19:55 proc dr-xr-x---. 9 root root 277 Apr 29 18:20 root drwxr-xr-x. 45 root root 1320 May 13 09:05 run drwxr-xr-x. 4 root sambashare 31 Apr 29 21:21 samba lrwxrwxrwx. 1 root root 8 Jan 6 2020 sbin -> usr/sbin drwxr-xr-x. 2 root root 6 Apr 11 2018 srv dr-xr-xr-x. 13 root root 0 May 12 19:55 sys drwxrwxrwt. 28 root root 4096 May 13 09:05 tmp drwxr-xr-x. 13 root root 155 Jan 6 2020 usr drwxr-xr-x. 22 root root 4096 Apr 29 21:40 var [nhtha@centos7 ~]$ EXCESS TIME RECV_READY TIMEOUT, did you expect() before a send() exit logout

Cleaned Command Output

uname -a output:

ls -l / output:`

I also enable the sshd debug log. Which log/file do I need to collect and send to this thread? Regards, Ha Nguyen

[nhtha]

I'm using: paramiko version 3.2.0, paramiko-expect version 0.3.5, OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017. Regards, Ha Nguyen

[nhtha]

A strange is : self.channel.recv_ready() is always False. Regards, Ha Nguyen

[nhtha]

I also tried with paramiko 3.4.0, the problem still happened in this version. Regards, Ha Nguyen

[nhtha]

The same error happened with Centos8 and Centos9 target host. Regards, Ha Nguyen

[nhtha]

I also tried with paramiko version 2.12.0, the result is the same. Regards, Ha Nguyen