Learning has never been so easy!
This guide will walk you through the basics of hardening SSH access to your Cisco ASA firewall using ASDM. If you're like me, you'd rather have a GUI than spending the day Googling CLI commands.
Asa Enable Asdm
Oct 15, 2014 The ASA will retain all keys over a reboot as long as a 'write mem' is done after the keys are created. This applies to the 'Key' that is created by 'crypto key generate rsa' and the 'Key.server' key that is created upon the first ssh connection to the ASA. Cisco ASA Allow SSH – Via ASDM (version shown 6.4(7)) 1. Connect via ASDM Navigate to Configuration Device Management Management Access ASDM/HTTPS/Telnet/SSH Add Select SSH Supply the IP and subnet OK. (Note you can set both the timeout, and the SSH versions you will accept, on this page also).
Sshexchangeidentification: Connection closed by remote host Fail to establish SSH session because RSA host key retrieval failed. Source: Link Now you need to configure the authentication piece of remote access for the connection. On the left side select Users/AAA- AAA Access. Under the Authentication Tab, Check SSH and select Server Group: LOCAL. This will allow you authenticate with a local user. Jul 19, 2017 Today we are heading forward in our journey where we will configure our Cisco ASA to get accessed from the firewall admin's local system via ASDM & SSH. Configuring ASDM & SSH on Cisco ASA. Under 'Specify the addresses of all hosts/networks which are allowed to access the ASA using ASDM/HTTPS/Telnet/SSH', you should add the static IPs of the devices or servers you wish to access the firewall from. Click Add on the right. Select the radio button next to SSH. Select 'Inside' as the interface.
4 Steps total
Step 1: Login to ASDM
Step 2: Change the default allow SSH version from 1 to 2
Go to Configuration > Device Management > Management Access > ASDM/HTTPS/Telnet/SSH
Under SSH Settings, change the value of 'Allowed SSH Version(s)' from 1 to 2.
Step 3: Change the default Diffie-Hellman group from 1 to 14
Remain in Configuration > Device Management > Management Access > ASDM/HTTPS/Telnet/SSH
Under SSH Settings, change the radio toggle of 'DH Key Exchange' from Group 1 to Group 14.
Step 4: Lock down SSH access to the firewall
Remain in Configuration > Device Management > Management Access > ASDM/HTTPS/Telnet/SSH
Under 'Specify the addresses of all hosts/networks which are allowed to access the ASA using ASDM/HTTPS/Telnet/SSH', you should add the static IPs of the devices or servers you wish to access the firewall from.
Click Add on the right.
Select the radio button next to SSH.
Generate Ssh Key Windows
Select 'Inside' as the interface.
Enter the static IP of the device/server.
Enter 255.255.255.255 as the subnet mask.
Click OK.
Repeat for all remaining devices/servers or specify any outside IPs which are static that require remote access.
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WARNING: If your firewall has 0.0.0.0 'any' enabled by default, make sure you save your changes by adding your static IP first before deleting the 'any' entry. Otherwise, your session will disconnect.
You may repeat the last step for hardening access to ASDM as well.
3 Comments
- Sonoraalexthompson4 Oct 16, 2018 at 06:51pmThank you for the guide! For accessing the ASA through SSH, what devices would you recommend connecting from (a server, etc) from a security standpoint?
- Ghost Chilistarg33ker Oct 16, 2018 at 06:56pmI only connect to the ASA from our Hyper-V host.
- Sonoraalexthompson4 Oct 16, 2018 at 07:02pmThat's a good idea! I shall have to work on implementing it at my workplace.