SDWAN Cisco IOS XE TLS Syslog Configuration on syslog-ng Server

Introduction

This document describes a comprehensive guide to configuring a TLS Syslog server on SD-WAN Cisco IOS® XE devices.

Prerequisites

Before proceeding with the configuration of a TLS Syslog server on SD-WAN Cisco IOS XE devices, ensure that you meet the requirements:

Requirements

Cisco recommends that you have knowledge of these topics:

• SD-WAN Controllers - Ensure your network includes properly configured SD-WAN controllers.

• Cisco IOS XE SD-WAN Router - A compatible router running the Cisco IOS XE SD-WAN image.

• Syslog Server - An Ubuntu-based Syslog server, such as syslog-ng, in order to collect and manage log data.

Components Used

The information in this document is based on these software and hardware versions:

• vManage: Version 20.9.4

• Cisco IOS XE SD-WAN: Version 17.9.4

• Ubuntu: Version 22.04

• syslog-ng: Version 3.27

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.

Configuration

1. Installation of syslog-ng on Ubuntu Machine

In order to set up syslog-ng on your Ubuntu server, pursue these steps to ensure proper installation and configuration.

Step 1. Configure Network Settings

After installing Ubuntu Server, configure a static IP address and DNS server in order to ensure the machine can access the internet. This is crucial for downloading packages and updates.

Step 2. Install syslog-ng

Open a terminal on your Ubuntu machine and run:

sudo apt-get install syslog-ng
sudo apt-get install syslog-ng openssl

2. Install Root Certificate Authority on Syslog Server for Server Authentication

Create Directories and Generate Keys

cd /etc/syslog-ng
mkdir cert.d key.d ca.d
cd cert.d
openssl genrsa -out ca.key 2048
openssl req -new -x509 -key ca.key -out PROXY-SIGNING-CA.ca -days 730

# Copy key to the key.d folder
cp ca.key ../key.d

Calculate Fingerprint

Run the command and copy the output:

openssl x509 -in PROXY-SIGNING-CA.ca -fingerprint -noout | awk -F "=" '{print $2}' | sed 's/://g' | tee fingerprint.txt
# Example output: 54F371C8EE2BFB06E2C2D0944245C288FBB07163

3. Configure syslog-ng Server Configuration File

Edit the syslog-ng configuration file:

sudo nano /etc/syslog-ng/syslog-ng.conf

Add the configuration:

source s_src {
    network(
        ip(0.0.0.0) port(6514)
        transport("tls")
        tls(
            key-file("/etc/syslog-ng/key.d/ca.key")
            cert-file("/etc/syslog-ng/cert.d/PROXY-SIGNING-CA.ca")
            peer-verify(optional-untrusted)
        )
    );
};

destination remote {
    file("/var/log/syslog");
};

log { source(s_src); destination(remote); };

4. Install Root Certificate Authority on Cisco IOS XE SD-WAN Device for Server Authentication

Configure from CLI

1. Enter configuration mode:

config-t

2. Configure the trustpoint:

crypto pki trustpoint PROXY-SIGNING-CA
  enrollment url bootflash:
  revocation-check none
  rsakeypair PROXY-SIGNING-CA 2048
  subject-name cn=proxy-signing-cert
  fqdn none
  fingerprint 54F371C8EE2BFB06E2C2D0944245C288FBB07163 >> The fingerprint configured was obtained from the fingerprint.txt file above
commit

3. Copy the PROXY-SIGNING-CA.ca file from your syslog server to the router bootflash using the same name.

4. Authenticate the trustpoint:

crypto pki authenticate PROXY-SIGNING-CA

example:
Router#crypto pki authenticate PROXY-SIGNING-CA
Reading file from bootflash:PROXY-SIGNING-CA.ca
Certificate has the  attributes:
Fingerprint MD5: 7A97B30B 2AE458FF D9E7D91F 66488DCF
Fingerprint SHA1: 21E0F09B B67B2E9D 706DBE69 856E5AA3 D39A268A
Trustpoint Fingerprint: 21E0F09B B67B2E9D 706DBE69 856E5AA3 D39A268A
Certificate validated - fingerprints matched.
Trustpoint CA certificate accepted.

5. Enroll the trustpoint:

crypto pki enroll PROXY-SIGNING-CA

example:
vm32#crypto pki enroll PROXY-SIGNING-CA
Start certificate enrollment ..
The subject name in the certificate will include: cn=proxy-signing-cert
The fully-qualified domain name will not be included in the certificate
Certificate request sent to file system
The 'show crypto pki certificate verbose PROXY-SIGNING-CA' commandwill show the fingerprint.

6. Copy the PROXY-SIGNING-CA.req file from the router to the syslog server.

Sign the Certificate on the Syslog Server

openssl x509 -in PROXY-SIGNING-CA.req -req -CA PROXY-SIGNING-CA.ca -CAkey ca.key -out PROXY-SIGNING-CA.crt -CAcreateserial -extensions ca_extensions

7. Copy the generated file (PROXY-SIGNING-CA.crt) to the router bootflash. copy scp: bootflash:

8. Import the certificate:

crypto pki import PROXY-SIGNING-CA certificate
example:
Router# crypto pki import PROXY-SIGNING-CA certificate
% The fully-qualified domain name will not be included in the certificate
% Request to retrieve Certificate queued

Validate the Configuration

show crypto pki trustpoint PROXY-SIGNING-CA status

example:
Router#show crypto pki trustpoint PROXY-SIGNING-CA status
Trustpoint PROXY-SIGNING-CA:
Issuing CA certificate configured:
Subject Name:
o=Internet Widgits Pty Ltd,st=Some-State,c=AU
Fingerprint MD5: 7A97B30B 2AE458FF D9E7D91F 66488DCF
Fingerprint SHA1: 21E0F09B B67B2E9D 706DBE69 856E5AA3 D39A268A
Router General Purpose certificate configured:
Subject Name:
cn=proxy-signing-cert
Fingerprint MD5: 140A1EAB FE945D56 D1A53855 FF361F3F
Fingerprint SHA1: ECA67413 9C102869 69F582A4 73E2B98C 80EFD6D5
Last enrollment status: Granted
State:
Keys generated ............. Yes (General Purpose, non-exportable)
Issuing CA authenticated ....... Yes
Certificate request(s) ..... Yes

5. Configure TLS Syslog Server on Cisco IOS XE SD-WAN Router

Configure the syslog server using the commands:

logging trap syslog-format rfc5424
logging source-interface GigabitEthernet0/0/0
logging tls-profile tls-profile
logging host X.X.X.X transport tls profile tls-profile
tls-version TLSv1.2

6. Verifications

Check Logs on the Router

show logging

Showing last 10 lines
Log Buffer (512000 bytes):
Apr 9 05:59:48.025: %DMI-5-CONFIG_I: R0/0: dmiauthd: Configured from NETCONF/RESTCONF by admin, transaction-id 189410
Apr 9 05:59:48.709: %DMI-5-AUTH_PASSED: R0/0: dmiauthd: User 'vmanage-admin' authenticated successfully from 1.1.1.1:58393 for netconf over ssh. External groups:
Apr 9 05:59:50.015: %LINK-5-CHANGED: Interface GigabitEthernet0/0/1, changed state to administratively down
Apr 9 05:59:51.016: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/1, changed state to down
Apr 9 05:59:52.242: %SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100001 from console as admin on vty4294966494

Check Logs on the Syslog Server

tail -f /var/log/syslog

root@server1:/etc/syslog-ng# tail -f /var/log/syslog
Apr 9 15:51:14 10.66.91.94 188 <189>1 2024-04-09T05:51:51.037Z - - - - - BOM%DMI-5-AUTH_PASSED: R0/0: dmiauthd: User 'vmanage-admin' authenticated successfully from 1.1.1.1:38032 for netconf over ssh. External groups:
Apr 9 15:59:10 10.66.91.94 177 <189>1 2024-04-09T05:59:47.463Z - - - - - BOM%SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100001 from console as admin on vty4294966494
Apr 9 15:59:10 10.66.91.94 177 <189>1 2024-04-09T05:59:47.463Z - - - - - BOM%SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100001 from console as admin on vty4294966494
Apr 9 15:59:10 10.66.91.94 143 <189>1 2024-04-09T05:59:47.463Z - - - - - BOM%DMI-5-CONFIG_I: R0/0: dmiauthd: Configured from NETCONF/RESTCONF by admin, transaction-id 189410
Apr 9 15:59:11 10.66.91.94 188 <189>1 2024-04-09T05:59:48.711Z - - - - - BOM%DMI-5-AUTH_PASSED: R0/0: dmiauthd: User 'vmanage-admin' authenticated successfully from 1.1.1.1:58393 for netconf over ssh. External groups:
Apr 9 15:59:13 10.66.91.94 133 <189>1 2024-04-09T05:59:50.016Z - - - - - BOM%LINK-5-CHANGED: Interface GigabitEthernet0/0/1, changed state to administratively down
Apr 9 15:59:13 10.66.91.94 137 <189>1 2024-04-09T05:59:50.016Z - - - - - BOM%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/1, changed state to down
Apr 9 15:59:15 10.66.91.94 177 <189>1 2024-04-09T05:59:52.242Z - - - - - BOM%SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100001 from console as admin on vty4294966494
Apr 9 15:59:15 10.66.91.94 177 <189>1 2024-04-09T05:59:52.242Z - - - - - BOM%SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100001 from console as admin on vty4294966494
Apr 9 15:59:18 10.66.91.94 188 <189>1 2024-04-09T05:59:55.286Z - - - - - BOM%DMI-5-AUTH_PASSED: R0/0: dmiauthd: User 'vmanage-admin' authenticated successfully from 1.1.1.1:34575 for netconf over ssh. External groups:
Apr 9 15:59:21 10.66.91.94 113 <187>1 2024-04-09T05:59:58.882Z - - - - - BOM%LINK-3-UPDOWN: Interface GigabitEthernet0/0/1, changed state to up
Apr 9 15:59:21 10.66.91.94 135 <189>1 2024-04-09T05:59:59.882Z - - - - - BOM%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/1, changed state to up
Apr 9 15:59:28 10.66.91.94 177 <189>1 2024-04-09T06:00:05.536Z - - - - - BOM%SYS-5-CONFIG_P: Configured programmatically by process iosp_dmiauthd_conn_100001_vty_100001 from console as admin on vty4294966494
Apr 9 15:59:43 10.66.91.94 188 <189>1 2024-04-09T06:00:20.537Z - - - - - BOM%DMI-5-AUTH_PASSED: R0/0: dmiauthd: User 'vmanage-admin' authenticated successfully from 1.1.1.1:43530 for netconf over ssh. External groups:

Packet capture screenshot and you can see encrypted communications happening:

Trap logging: level informational, 6284 message lines logged
    Logging to 10.66.91.170  (tls port 6514, audit disabled,
          link up),
          131 message lines logged, 
          0 message lines rate-limited, 
          0 message lines dropped-by-MD, 
          xml disabled, sequence number disabled
          filtering disabled
          tls-profile: tls-proile
    Logging Source-Interface:       VRF Name:
    GigabitEthernet0/0/0            
TLS Profiles: 
    Profile Name: tls-proile
          Ciphersuites: Default
          Trustpoint: Default
          TLS version: TLSv1.2