I'm having trouble generating an email notice when someone is trying to do an ssh bruteforce attack on my server with Bro (v2.4.1). I have a Bro script like this which redefines the max login attemps to 5 per 24 hours:
#load protocols/ssh/detect-bruteforcing
redef SSH::password_guesses_limit=5;
redef SSH::guessing_timeout=1440 mins;
hook Notice::policy(n: Notice::Info)
{
if ( n$note == SSH::Password_Guessing && /192\.168\.178\.16/ in n$sub )
add n$actions[Notice::ACTION_EMAIL];
}
where 192.168.178.16 is the local ip of my server and I've made sure the script gets loaded by including it in $PREFIX/site/local.bro. The output of broctl scripts shows that the script is loaded just fine on startup. However, I never receive any email notice of ssh bruteforcing attacks.
Connection summaries, dropped packets and invalid ssl certificate notices are emailed just fine, so it's not an email configuration issue. When I check the ssh log output like so:
sudo cat /opt/bro/logs/current/ssh.log | bro-cut -d ts uid id.orig_h id.orig_p id.resp_h id.resp_p version auth_success direction client server cipher_alg
The 6 failed login attemps (that I generated for testing this) are logged just fine in /opt/bro/logs/current/ssh.log:
2016-11-11T14:45:08+0100 CRoENl2L4n5RIkMd0l 84.241.*.* 43415 192.168.178.16 22 2 - INBOUND SSH-2.0-JuiceSSH SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3 aes128-ctr
2016-11-11T14:45:13+0100 CMflWI2ESA7KVZ3Cmk 84.241.*.* 43416 192.168.178.16 22 2 - INBOUND SSH-2.0-JuiceSSH SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3 aes128-ctr
2016-11-11T14:45:17+0100 CZuyQO2NxvmpsmsWwg 84.241.*.* 43417 192.168.178.16 22 2 - INBOUND SSH-2.0-JuiceSSH SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3 aes128-ctr
2016-11-11T14:45:20+0100 CC86Fi3IGZIFCoot2l 84.241.*.* 43418 192.168.178.16 22 2 - INBOUND SSH-2.0-JuiceSSH SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3 aes128-ctr
2016-11-11T14:45:25+0100 CHqcJ93qRhONQC1bm4 84.241.*.* 43419 192.168.178.16 22 2 - INBOUND SSH-2.0-JuiceSSH SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3 aes128-ctr
2016-11-11T14:45:28+0100 CdV0xh1rI4heYaFDH2 84.241.*.* 43420 192.168.178.16 22 2 - INBOUND SSH-2.0-JuiceSSH SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3 aes128-ctr
However I never get any email notice of this happening. The only reason I can think of is I have password login over ssh disabled, so maybe the login attemps without a private key are not firing the ssh_failed_login events in Bro? The auth_success column in above table shows a "-" for the failed login attemps whereas a succesfull login shows a "T", so maybe that should be a "F" in order for the event to fire?
Any help or suggestions is greatly appreciated!
Due to SSH being encrypted, we've had to resort to heuristics for detection of successful and unsuccessful authentications. Those heuristics have improved through time but are still far from perfect. If the "auth_success" column is unset like it is in the examples you provided it means that Bro was unable to make the guess if the login was successful or not.
The reason that the bruteforce detection script isn't working is because it's never detecting an unsuccessful login. Your suspicion at the end of your question is correct.
Related
using centos7 and denyhosts 2.9 i noticed some strange behavior.
My config is set to:
DENY_THRESHOLD_INVALID = 3
DENY_THRESHOLD_VALID = 10
Which, in my understanding is like: after 3 failed login attempts of NON-EXISTING users from hosts X, deny that host.
After 10 failed logins attempts from EXISTING users from hosts X, deny that host.
While the latter works just fine, the DENY_THRESHOLD_INVALID = 3 setting does not work.
What i noticed is that the /var/log/secure, that danyhosts parses, does handly logns from non-existing accounts and logins from account that exist but are using the wrong pasword, are handled differently.
Aug 10 12:32:42 ftp sshd[27176]: Invalid user adminx from xxx.128.30.135 port 42800
Aug 10 12:32:42 ftp sshd[27176]: input_userauth_request: invalid user adminx [preauth]
Aug 10 12:32:42 ftp sshd[27176]: Connection closed by xxx.128.30.135 port 42800 [preauth]
vs.
Aug 10 12:33:46 ftp sshd[27238]: Failed password for exchange from xxx.128.30.135 port 42802 ssh2
Does anyone know of denyhosts has problems parsing the /var/log/secure file on centos with non-existing accounts vs. existing accounts that use wrong passwords?
Denyhosts debug log also does not say anything. It seems to ignore the login attempt from non-existend users.
any help would be appreciated. Thanks.
I'm learning the basics on paramiko and for that purpose I setup a basic lab where I connect an Ubuntu VM to a router emulated in EVE-ng.
The first step was to generate a key pair in the client via ssh-Keygen
Next I loaded the public key to the remote server (the Cisco router) using the following command:
ip ssh pubkey-chain
username administrator
key-hash ssh-rsa 97D0E9B5630D05D78EA9531053124BFF
Right after that I was able to login to the Cisco router from the Ubuntu VM:
$ ssh administrator#192.168.1.1
7206_1.rt#
Then, from the same client I started a Python shell session and tried to establish an SSH session using Paramiko:
import paramiko
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('192.168.1.1', username='administrator', password='password', key_filename= '/home/administrator/.ssh/id_rsa.pub')
But this time I got the following exception:
Exception: Illegal info request from server
Traceback (most recent call last):
File "/usr/local/lib/python3.8/dist-packages/paramiko/transport.py", line 2109, in run
handler(self.auth_handler, m)
File "/usr/local/lib/python3.8/dist-packages/paramiko/auth_handler.py", line 661, in _parse_userauth_info_request
raise SSHException("Illegal info request from server")
paramiko.ssh_exception.SSHException: Illegal info request from server
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.8/dist-packages/paramiko/client.py", line 435, in connect
self._auth(
File "/usr/local/lib/python3.8/dist-packages/paramiko/client.py", line 764, in _auth
raise saved_exception
File "/usr/local/lib/python3.8/dist-packages/paramiko/client.py", line 751, in _auth
self._transport.auth_password(username, password)
File "/usr/local/lib/python3.8/dist-packages/paramiko/transport.py", line 1498, in auth_password
raise SSHException("No existing session")
paramiko.ssh_exception.SSHException: No existing session
The remote router SSH debug shows that authentication failed:
*Aug 16 01:18:07.295: SSH2 0: MAC compared for #5 :ok
*Aug 16 01:18:07.299: SSH2 0: input: padlength 16 bytes
*Aug 16 01:18:07.299: SSH2 0: Using method = publickey
*Aug 16 01:18:07.307: SSH2 0: send:packet of length 432 (length also includes padlen of 4)
*Aug 16 01:18:07.307: SSH2 0: computed MAC for sequence no.#5 type 60
*Aug 16 01:18:07.311: SSH2 0: Authenticating 'administrator' with method: publickey
*Aug 16 01:18:07.327: SSH2 0: SSH ERROR closing the connection
*Aug 16 01:18:07.331: SSH2 0: send:packet of length 80 (length also includes padlen of 15)
*Aug 16 01:18:07.331: SSH2 0: computed MAC for sequence no.#6 type 1
*Aug 16 01:18:07.335: SSH2 0: Pubkey Authentication failed for user administrator
*Aug 16 01:18:07.335: SSH0: password authentication failed for administrator
At this point I can't tell whether the issue is in the server or in the router as all works fine when connecting directly from server to router without Paramiko.
Thanks.
Ok, looks like by default, Paramiko searches for discoverable private key files in ~/.ssh/ that's fine if trying to connect to another server, but since it's trying to reach a router, this feature needs to be disabled by setting look_for_keys to False. That fixed the issue (as long as this is not a production environment) which is my case.
In case it helps anyone else, I was receiving this same "Illegal info request from server" error because the password being used had a flag on it that it needed to be updated. I only saw this when logging in manually via WinSCP.
Authentication is done via public key at /home/administrator/.ssh/id_rsa.pub
Not quite: it is done using the private key of the local user you are using when typing:
ssh administrator#192.168.1.1
'administrator' is the name of the remote account used to open a session on the remote server 192.168.1.1
The authentication, on the remote side, will be done using ~administrator/.ssh/authorized_keys (again, on the remote machine), to check if the local ~/.ssh/id_rsa.pub public key was properly registered in the remote ~administrator/.ssh/authorized_keys.
Your local account might be also 'administrator', but that same local account might not be the same when executing the Python shell.
When you see
Authenticating 'administrator' with method: publickey
SSH is talking of the remote 'administrator' account on the remote server, irrespective of the local user account you are in.
For some reason I can't log in to the server with SSH. I wrote to the server administrator and he told me that connection is blocked by sshguard. In addition, he sent me a list of my login attempts ( sudo grep publickey\ for\ <myusername> /var/log/auth command output). It looked like this:
.
.
.
May 12 21:38:16 boss sshd[3003]: Failed publickey for <myusername> from
<myip> port 24057 ssh2: RSA
SHA256:hqddgd...VHhFM
May 12 21:38:16 boss sshd[3003]: Failed publickey for <myusername> from
<myip> port 24057 ssh2: RSA
SHA256:1NwYXJ66...+U5MqJ0
May 12 21:38:21 boss sshd[3003]: Accepted publickey for <myusername> from
<myip> port 24057 ssh2: RSA
SHA256:A6uQ/jb...I9UjXzc
May 12 21:39:29 boss sshd[3151]: Failed publickey for <myusername> from
<myip> port 23837 ssh2: RSA
SHA256:hqddgd...VHhFM
May 12 21:39:30 boss sshd[3151]: Failed publickey for <myusername> from
<myip> port 23837 ssh2: RSA
SHA256:1NwYXJ66...+U5MqJ0
.
.
.
Whenever I tried to log in I sent keys that had checksums in order: hqddgd...VHhFM, 1NwYXJ66...+U5MqJ0, A6uQ/jb...I9UjXzc. The third time my connection was always accepted. I don't know if this is a coincidence, but I have exactly three keys in the ~/.ssh/ directory. In addition, the ~/.ssh/config file looks like this:
Host <server to which I want to log in>
HostName <nice domain>
User <myusername>
IdentityFile ~/.ssh/<myusername>
Host <another server>
HostName <nice domain>
User <another username>
IdentityFile ~/.ssh/<another username>
Why is this happening? Why SSH sends different keys with this same configuration?
You must add this line to your configuration file:
IdentitiesOnly=yes
I am unable to access Linux EC2 instance through SSH or browser-based SSH.
Instance id: i-01a3cdf3b36ff6d4f
Inbound rules:
HTTP TCP 80 0.0.0.0/0
SSH TCP 22 0.0.0.0/0
Outbound rules:
All traffic All All 0.0.0.0/0
Pls check below logs after running command from windows :
ssh -vvv -i "keypair.ppk" ec2-user#ec2-<IP>.ap-south-1.compute.amazonaws.com
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\PuTTY (64-bit)>ssh -vvv -i "aws-lfd.pem" ec2-user#ec2-13-234-238-12.ap-south-1.compute.amazonaws.com
OpenSSH_for_Windows_7.6p1, LibreSSL 2.6.4
debug3: Failed to open file:C:\\Users\\b.tembhurne/.ssh/config error:2
debug3: Failed to open file:C:\\ProgramData\\ssh/ssh_config error:2
debug2: resolving "ec2-13-234-238-12.ap-south-1.compute.amazonaws.com" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to ec2-13-234-238-12.ap-south-1.compute.amazonaws.com [13.234.238.12] port 22.
I checked for config file it does not exist in above location. Do I need to create one manually? If so, What should it look like?
Pls help to resolve this issue.
A Connection timed out indicates that no response was received, which is typically caused by an incorrect network configuration (eg Security Group).
I would recommend that you start by launching a new Amazon EC2 instance in the same subnet, then check whether you can connect. This way, you'll know whether it is a network setting or a problem with the instance.
If that doesn't work, things to check are:
Instance is running Linux (so it can receive SSH requests)
Security Group is permitting inbound access on port 22 (SSH) from your IP address or 0.0.0.0/0
Instance is in a public subnet, which is defined as having a Route Table that points to an Internet Gateway
Your network needs to permit an outbound SSH connection (so try another network, such as home vs work, or tethered via your phone)
Slackware OS, trying to setup fetchmail
I have coded this .fetchmailrc file:
set daemon 600 //fetches mail every hour or 60 minutes.
set logfile /root/fetchmail.log
poll 10.200.***.** protocol POP3
user "bob" password "bob" is "bob" here preconnect "date>>/root/fetchmail.log"
ssl
no rewrite
keep
It worked before but now it is failing to retrieve mail, i checked the fetchmail.log file and i get this error:
Thu Nov 5 10:15:32 GMT 2015
fetchmail: connection errors for this poll:
name 0: connection to 10.200.***.**:pop3s [10.200.***.**/995] failed: Connection refused.
fetchmail: POP3 connection to 10.200.***.** failed: Connection refused
fetchmail: Query status=2 (SOCKET)
I've reset the daemons, ended the process and no progress.
I had exactly the same problem on a Mageia 5 Linux. Apparently, I
solved it by redoing network configuration, which the Mageia can do
with a single click on the relevant Configure button in the Network
Center window.
I did not touch my .fetchmailrc file.