Category: System Administration

Apache HTTPD Log File Analysis — Hits by IP Address

When we are decommissioning a website (or web server), I always watch the log files to ensure there aren’t a lot of people still accessing it. Sometimes there are and it’s worth tracking them down individually to clue them into the site’s eminent demise. Usually there aren’t, and it’s just a confirmation that our decommissioning efforts won’t be impactful.

This python script looks for IP addresses in the log files and outputs each IP & it’s access count per log file. Not great if you’ll see a bunch of IP addresses in the recorded URI string, but it’s good enough for 99% of our log data.

import os
import re
from collections import Counter

def parseApacheHTTPDLog(strLogFile):
    regexIPAddress = r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}'

    with open(strLogFile) as f:
        objLog = f.read()
        listIPAddresses = re.findall(regexIPAddress,objLog)
        counterAccessByIP = Counter(listIPAddresses)
        for strIP, iAccessCount in counterAccessByIP.items():
            print(f"{strLogFile}\t{str(strIP)}\t{str(iAccessCount)}")

if __name__ == '__main__':
    strLogDirectory = '/var/log/httpd/'
    for strFileName in os.listdir(strLogDirectory):
        if strFileName.__contains__("access_log"):
        #if strFileName.__contains__("hostname.example.com") and strFileName.__contains__("access_log"):
            parseApacheHTTPDLog(f"{strLogDirectory}{strFileName}")

Reverse Proxying WebSockets through mod_proxy — HTTP Failback

I’ve been successfully reverse proxying MQTT over WebSockets via Apache HTTPD for quite some time now. The last few weeks, my phone isn’t able to connect. There’s no good rational presented (and manually clicking the “send data” button on my client successfully connects). It was time to upgrade the server anyway. Once I got the latest Linux distro on the server, I couldn’t connect at all to my MQTT server. The error log showed AH00898: Error reading from remote server returned by /mqtt

Evidently, httpd 2.4.47 added functionality to upgrade and tunnel in accordance with RFC 7230. And that doesn’t work at all in my scenario. Haven’t dug in to the why of it yet, but adding ProxyWebsocketFallbackToProxyHttp Off to the reverse proxy config allowed me to successfully communicate with the MQTT server through the reverse proxy.

(Not) Finding the Rygel Log File

We’ve spent a lot of time trying to get a log file from the rygel server … setting the log level in the config file didn’t seem to do anything useful. And I cannot even find a log file. The only output we’re able to find is formed by running the binary from the command line. Where is that log file?!? Hey — there isn’t one. All of this log level setting has to do with what’s written to STDOUT and STDERR. You can either modify the unit file to tee the output off to a file or run it from the command line

To get debugging output, use

G_MESSAGES_DEBUG=all rygel -g 5

To tee the output off to a file,
rygel -g *:5 2>&1 | tee -a /path/to/rygel.log

 

Brinqa Remediation – mDNS

Some systems were found to be responding to mDNS requests (5353/udp). Linux hosts were running the avahi-daemon which provides this service. As the auto-discovery service is not used for service identification, the avahi-daemon was disabled.

Confirm response is seen on 5353/udp prior to change:

nmap -P0 -p 5353 -sU hostname.example.net

SSH to host identified as responding to mDNS requests. Disable the avahi-daemon then stop the avahi-daemon:

systemctl disable avahi-daemon
systemctl stop avahi-daemon

 

Verify that 5353/udp is no longer open by repeating the nmap command.

Fin.

Useful Bash Commands

Viewing Log Files

Tailing the File

When the same file name is used when logs are rotated (i.e. app.log is renamed to app.yyyymmdd.log and a new app.log is created), use the -F flag to follow the name instead of the file descriptor

tail -F /var/log/app.log

Tailing with Filtering

When you are looking for something specific in the log file, it often helps to run the log output through grep. This example watches a sendmail log for communication with the host 10.5.5.5

tail -F /var/log/maillog | grep "10.5.5.5"

Handling Log Files with Date Specific Naming

I alias out commands for viewing commonly read log files. This is easy enough when the current log file is always /var/log/application/content.log, but some active log files have date components in the file name. As an example, our Postgresql servers have the short day-of-week string in the log. Use command substitution to get the date-specific elements from the date executable. Here, I tail a file named postgresql-Tue.log on Tuesday. Since logs rotate to a new name, tail -F doesn’t really do anything. You’ll still need to ctrl-c the tail and restart it for the next day.

tail -f /pgdata/log/postgresql-$(date +%a).log

Apache HTTPD and DER Encoded Certificate

We are in the process of updating one of the web servers at work to a newer OS – along with a newer Apache HTTPD and PHP iteration. Ran into a snag just setting up the SSL web site – we couldn’t get HTTPD started with our Venafi certificate.

[Fri Jan 28 14:35:05.092086 2022] [ssl:emerg] [pid 57739:tid 139948816931136] AH02561: Failed to configure certificate hostname.example.com:443:0, check /path/to/certs/production/server.crt

[Fri Jan 28 14:35:05.092103 2022] [ssl:emerg] [pid 57739:tid 139948816931136] SSL Library Error: error:0909006C:PEM routines:get_name:no start line (Expecting: CERTIFICATE) — Bad file contents or format – or even just a forgotten SSLCertificateKeyFile?

[Fri Jan 28 14:35:05.092115 2022] [ssl:emerg] [pid 57739:tid 139948816931136] SSL Library Error: error:140AD009:SSL routines:SSL_CTX_use_certificate_file:PEM lib

The certificate was DER encoded – that’s not what I use, but it was working on the old server.

I think there might be something between httpd-2.4.6-97 and httpd-2.4.37-43 that stopped DER encoded certificates from working. Rather than figure out some way to coerce HTTPD to use this DER file that I don’t really care if I’ve got … I just used a quick command to export the B64 version of the certificate, copied the header/footer/stuff in between, and made a base-64 encoded certificate file.

openssl x509 -inform DER -in server.crt | openssl x509 -text

And, voila, we’ve got a web server.

 

Squid Custom Error

We’ve been having a challenge with Anya getting her school work completed. Part of the problem is the school’s own fault — they provide a site where kids are encouraged to read, but don’t provide any way to ensure this reading is done after classwork has been completed. But, even if that site didn’t exist … the Internet has all sorts of fun ways you can find to waste some time.

So her computer now routes through my proxy server. I’d set up a squid server so *I* could use the Internet unfettered whilst VPN’d in to work. It’s really annoying to get told you’re a naughty hacker every time you want to see some code example on StackOverflow!

While I didn’t really care about the default messages for my use (nor did I actually block anything for it to matter), I want Anya to be able to differentiate between “technical problem” the site didn’t load and “you are not allowed to be using this site now” the site didn’t load. So I customized the Squid error message for access denied. This can quickly be done by editing /usr/share/squid/errors/en-us/ERR_ACCESS_DENIED (you’ll need to make a backup of your version & may need to replace the file when upgrading squid in the future).

 

Bash – Spaces, Quotes, and String Replacement

Had to figure out how to do string replacement (Scott wanted to convert WMA files to similarly named MP3 files) and pass a single parameter that has spaces into a shell script.

${original_string/thing_to_find/thing_to_replace_there} does string replacement. And $@ is the unexpanded parameter set. So this wouldn’t work if we were trying to pass in more than one parameter (well, it *would* … I’d just have to custom-handle parameter expansion in the script)