The SSH (“Secure Shell”) protocol is a method for secure remote login from one system to another. Sysadmins and users use a secure channel over an unsecured network in a client-server architecture format for connecting an SSH client with an SSH server. Security ssh server is an important task. There is a tool called ssh_scan from Mozilla which act as a prototype SSH configuration and policy scanner for your SSHD.
Benefits of ssh_scan
From the project home page:
- Minimal Dependancies – Uses native Ruby and BinData to do its work, no heavy dependancies.
- Not Just a Script – Implementation is portable for use in another project or for automation of tasks.
- Simple – Just point ssh_scan at an SSH service and get a JSON report of what it supports and its policy status.
- Configurable – Make your own custom policies that fit your unique policy requirements.
Install dependancies
Type the following apt-get command/apt command to install ruby and gem on Debian/Ubuntu Linux:
$ sudo apt-get install ruby gem
Sample outputs:
Install ssh_scan
Type the following command to install ssh_scan as a gem:
$ sudo gem install ssh_scan
Sample outputs:
How do I use ssh_scan?
The syntax is:
$ ssh_scan -t ip
$ ssh_scan -t server
$ ssh_scan -t server1.cyberciti.biz
For example scan a ssh server installed at 192.168.2.15, enter:
$ ssh_scan -t 192.168.2.15
Sample outputs:
I, [2017-04-25T16:12:11.019160 #32317] INFO -- : You're using the latest version of ssh_scan 0.0.19
[
{
"ssh_scan_version": "0.0.19",
"ip": "192.168.2.15",
"port": 22,
"server_banner": "SSH-2.0-OpenSSH_7.4p1 Ubuntu-10",
"ssh_version": 2.0,
"os": "ubuntu",
"os_cpe": "o:canonical:ubuntu",
"ssh_lib": "openssh",
"ssh_lib_cpe": "a:openssh:openssh:7.4p1",
"cookie": "82d7cc908765f03154b10d5cdf14195a",
"key_algorithms": [
"curve25519-sha256",
"[email protected]",
"ecdh-sha2-nistp256",
"ecdh-sha2-nistp384",
"ecdh-sha2-nistp521",
"diffie-hellman-group-exchange-sha256",
"diffie-hellman-group16-sha512",
"diffie-hellman-group18-sha512",
"diffie-hellman-group14-sha256",
"diffie-hellman-group14-sha1"
],
"server_host_key_algorithms": [
"ssh-rsa",
"rsa-sha2-512",
"rsa-sha2-256",
"ecdsa-sha2-nistp256",
"ssh-ed25519"
],
"encryption_algorithms_client_to_server": [
"[email protected]",
"aes128-ctr",
"aes192-ctr",
"aes256-ctr",
"[email protected]",
"[email protected]"
],
"encryption_algorithms_server_to_client": [
"[email protected]",
"aes128-ctr",
"aes192-ctr",
"aes256-ctr",
"[email protected]",
"[email protected]"
],
"mac_algorithms_client_to_server": [
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"hmac-sha2-256",
"hmac-sha2-512",
"hmac-sha1"
],
"mac_algorithms_server_to_client": [
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"[email protected]",
"hmac-sha2-256",
"hmac-sha2-512",
"hmac-sha1"
],
"compression_algorithms_client_to_server": [
"none",
"[email protected]"
],
"compression_algorithms_server_to_client": [
"none",
"[email protected]"
],
"languages_client_to_server": [
],
"languages_server_to_client": [
],
"hostname": "m6700",
"auth_methods": [
"publickey",
"password"
],
"fingerprints": {
"rsa": {
"known_bad": "false",
"md5": "1d:14:84:f0:c7:21:10:0e:30:d9:f9:59:6b:c3:95:97",
"sha1": "70:ac:7c:2c:94:54:aa:09:f2:58:f3:48:f0:9e:f2:a0:a2:37:f1:0a",
"sha256": "6d:d8:20:c6:8e:e7:db:0d:94:9d:34:66:ba:b7:9c:68:8a:ea:79:19:a6:0d:76:cc:ec:fe:82:21:68:a5:64:74"
}
},
"start_time": "2017-04-25 16:12:11 +0000",
"end_time": "2017-04-25 16:12:11 +0000",
"scan_duration_seconds": 0.118730486,
"duplicate_host_key_ips": [
],
"compliance": {
"policy": "Mozilla Modern",
"compliant": false,
"recommendations": [
"Remove these Key Exchange Algos: curve25519-sha256, diffie-hellman-group16-sha512, diffie-hellman-group18-sha512, diffie-hellman-group14-sha256, diffie-hellman-group14-sha1",
"Remove these MAC Algos: [email protected], [email protected], [email protected], hmac-sha1",
"Remove these Authentication Methods: password"
],
"references": [
"https://wiki.mozilla.org/Security/Guidelines/OpenSSH"
]
}
}
]
To see all other options, enter:
$ ssh_scan -h
Sample outputs:
ssh_scan v0.0.19 (https://github.com/mozilla/ssh_scan)
Usage: ssh_scan [options]
-t, --target [IP/Range/Hostname] IP/Ranges/Hostname to scan
-f, --file [FilePath] File Path of the file containing IP/Range/Hostnames to scan
-T, --timeout [seconds] Timeout per connect after which ssh_scan gives up on the host
-L, --logger [Log File Path] Enable logger
-O, --from_json [FilePath] File to read JSON output from
-o, --output [FilePath] File to write JSON output to
-p, --port [PORT] Port (Default: 22)
-P, --policy [FILE] Custom policy file (Default: Mozilla Modern)
--threads [NUMBER] Number of worker threads (Default: 5)
--fingerprint-db [FILE] File location of fingerprint database (Default: ./fingerprints.db)
--suppress-update-status Do not check for updates
-u, --unit-test [FILE] Throw appropriate exit codes based on compliance status
-V [STD_LOGGING_LEVEL],
--verbosity
-v, --version Display just version info
-h, --help Show this message
Examples:
ssh_scan -t 192.168.1.1
ssh_scan -t server.example.com
ssh_scan -t ::1
ssh_scan -t ::1 -T 5
ssh_scan -f hosts.txt
ssh_scan -o output.json
ssh_scan -O output.json -o rescan_output.json
ssh_scan -t 192.168.1.1 -p 22222
ssh_scan -t 192.168.1.1 -p 22222 -L output.log -V INFO
ssh_scan -t 192.168.1.1 -P custom_policy.yml
ssh_scan -t 192.168.1.1 --unit-test -P custom_policy.yml