SysteMajik Consulting

  • Adding SHA-2 to tinyca

    Google has announced a sunset for SHA-1 certificate signatures in Chrome. SHA-2 (aka SHA-256, SHA-384, and SHA-512) is the remaining option for certificate signatures. I decided to upgrade my certificates to SHA-2 (256 bits). However, when I tried to use tinyca2 to generate a SHA-2 certificate, I found it was not supported.

    As tinyca2 is a Perl package, I looked at the code to see how difficult it would be to update. The code is easy to read and well modularized. Adding the SHA-2 involves changes to the GUI, REQ, CERT, and OpenSSL components. I updated six files, although support can be added with fewer changes.

    Patches are attached at the end of this post. An additional patch to apply the selected digest when creating sub-CAs (thanks to Cédric Dufour) has been included.

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  • Disabling SSLv3 to block Poodle

    The new Poodle vulnerability lead me to disable SSLv3 on my Ubuntu server. I have TLS/SSL enabled on three services: apache2, exim4, and dovecot2. Each service required a different method to disable SSLv3. While SSLv3 is mostly history, the techniques I used can be applied to other TLS versions.

    Ubuntu uses configuration files split into small pieces. The method should apply to other distributions, although the configuration files may be arranged differently.

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  • Disable TraceClassUnloading in Java 6

    I recently discovered logs filling up with log messages for classes being unloaded during garbage collection. After a little research, I found that the TraceClassUnloading switch gets turned on by the Xloggc switch. After a little testing, I found that this can be resolved by adding the argument -XX:-TraceClassUnloading after the -Xloggc argument.

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  • Hostnames for eximstats Rejections

    I use eximstats to report my daily email traffic. I have a fairly high rate of rejections and wanted hostnames listed in the rejection reports. To resolve this I developed a patch to capture the hostname related to the IP address, and add this data to the rejection reports.

    The enhanced list saves me the effort of looking up IP addresses that were repeatedly addressed. Occasionally, these are from legitimate servers that have been misconfigured. DNS problems are often the cause.

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  • Faking IMAP for Exchange Email

    For years I have had problems getting IMAP access to exchange servers. Many organizations don’t enable IMAP on their Exchange servers, and others don’t do it right. I recently came across a solution that works with the Microsoft WebMail interface to provide an IMAP and/or POP3 access to the mail servers. This allows the use of IMAP mail clients like Thunderbird or Microsoft Live Mail.

    This article describes the solution as I have implemented it. It uses the open-source DavMail Gateway written in Java. It accesses a WebMail server and provides access via standard protocols like IMAP, SMTP, and CalDav. This program can be configured for personal use on a desktop, or group use on a server. When configuring a server, it is recommended that you provide SSL keys so that secure protocols can be used.

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  • Providing IPv6 DNS resolver data with radvd

    One nagging issue I had with IPv6 was how to distribute DNS server addresses and search lists to my clients. It took a little research to find the solution. On IPv4 I had been using DHCP to do this, but DHCP didn’t seem to be the right approach for IPv6. radvd can be used to distribute both types of data. This article covers setup on Ubuntu and OpenWRT. The Ubuntu (Debian) examples below should work with any distribution using/etc/radvd.conf to configure radvd.

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  • Detecting Email Server Forgery

    Most of the spam I received has been sent by servers forging or otherwise obscuring their server identity. RFC2505 states that the server identity and sender address are easily forged. Of these, it is easiest to identify server forgery. Very little, if any, of the personal email has a forged server identity. Unfortunately, legitimate bulk and automated email often show signs of server identity. If you deliver either of these types of emails, this article will provide information on fixing the situation.

    The rules here apply to emails originating from the Internet only. Mail User Agents submitting email are expected to violate these rules. MUAs should use an authenticated encrypted connection to the Submission port (576). Relay servers should not apply these rules to connections originating from the local network.

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  • Securing your Email Reputation with SPF

    SPF (Server Policy Framework) is a simple means to limit the ability of others to forge your identity in email. I first implemented it after a forged identity under my domain was used to send Spam. Once SPF was configured,  the bounce messages quickly dropped off.

    Although not as frequently implemented as sender address checks, SPF can be used to prevent forgery of the HELO identity. My mail server uses SPF to check the Identity of the server. This is easier to configure and more reliable than checking the domain in the Mail from address. Even though I treat Neutral and Softfail policies as a Fail policy, I have not detected any false negatives. I verify both the address returned by the PTR record for the host and the address in the HELO command. This is primarily because the PTR record is more likely to have a valid domain.

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  • Setting Up BackupPC on Windows

    My original intent in setting up BackupPC was to be able to backup my laptops. They mainly run Windows and have a lot of shared files. Therefore I wanted a backup solution that handled de-duplication. BackupPC was just what I needed. I have already posted an article about Setting Up BackupPC on Ubuntu that includes setting up a server.

    This article covers setting up BackupPC on Windows using rsyncd as the protocol. (I tried using Samba, but didn’t like the results with Windows Home editions.) This is done with an extremely minimal cygwin install available from the BackupPC site on SourceForge. The backups described here are not designed for bare metal recovery. They should include all the user’s files and some of the configuration data for installed applications.

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  • Setting Up BackupPC on Ubuntu

    I recently started to do regular backups of all my systems using BackupPC. It uses the rsync protocol to limit the amount of data transferred during backups. Once the initial backup is done, future backups only need to copy incremental changes. This requires far fewer resources than other software I have used

    This article covers setting up the server on Ubuntu and configuring backups for Ubuntu and OpenWRT. A future article will cover backing up Windows systems using an rsyncd daemon process.

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