Implementing Syslog Centralization With Rsyslog

Implementing Syslog Centralization with Rsyslog

When to Use

• When deploying or configuring implementing syslog centralization with rsyslog capabilities in your environment
• When establishing security controls aligned to compliance requirements
• When building or improving security architecture for this domain
• When conducting security assessments that require this implementation

Common Misconfigurations & Verification

• UDP (514) silently drops under load: @host (single @) sends UDP with no delivery guarantee; messages are lost on congestion with zero error. Use TCP/TLS (@@ / omfwd protocol="tcp") plus disk-assisted queues so spikes spool instead of vanishing.
• "TLS configured" but actually plaintext: imtcp/omfwd without StreamDriver="gtls" + StreamDriverMode="1" falls back to cleartext on 6514. Confirm with openssl s_client -connect server:6514 returning a cert, and tcpdump -A port 6514 showing ciphertext rather than readable log lines.
• Auth mode anon = any client accepted: StreamDriverAuthMode="anon" trusts any cert. Use x509/name with a permittedPeer list so only known clients forward; verify a client with the wrong CN is rejected.
• Queue not disk-assisted = restart loss: without queue.type="LinkedList" + queue.filename + queue.saveonshutdown="on", in-memory queues drop on rsyslog restart. Confirm a .qi/spool file exists under the queue path.
• Confirm delivery end to end: logger -n server -P 6514 -T "rsyslog-test" from a client, then verify the line lands in the per-host file (/var/log/remote/<host>/...). A reachable port is not the same as a stored log.

Prerequisites

• Familiarity with security operations concepts and tools
• Access to a test or lab environment for safe execution
• Python 3.8+ with required dependencies installed
• Appropriate authorization for any testing activities

Instructions

1. Install dependencies: pip install jinja2 paramiko
2. Generate TLS certificates for rsyslog server and clients using OpenSSL.
3. Run the agent to generate rsyslog server and client configurations:
   • Server: TLS listener on port 6514, per-host directory output, JSON-format templates
   • Client: TLS forwarding with disk-assisted queues for reliability
4. Deploy configurations to servers via SSH (paramiko).
5. Validate TLS connectivity and log delivery.

python scripts/agent.py --server-ip 10.0.0.1 --clients 10.0.0.10,10.0.0.11 --ca-cert ca.pem --output syslog_report.json

Examples

Server Configuration (TLS)

module(load="imtcp" StreamDriver.Name="gtls" StreamDriver.Mode="1"
       StreamDriver.Authmode="x509/name")
input(type="imtcp" port="6514")
template(name="PerHostLog" type="string" string="/var/log/remote/%HOSTNAME%/%PROGRAMNAME%.log")
*.* ?PerHostLog

Client Configuration (Reliable Forwarding)

action(type="omfwd" target="10.0.0.1" port="6514" protocol="tcp"
       StreamDriver="gtls" StreamDriverMode="1"
       StreamDriverAuthMode="x509/name"
       queue.type="LinkedList" queue.filename="fwdRule1"
       queue.maxdiskspace="1g" queue.saveonshutdown="on"
       action.resumeRetryCount="-1")