Backporting and git-buildpackage

For working with Debian packages, one method of maintaining them is to put them in git and use git-buildpackage to build them right out of the git repository.  There are a few pitfalls with it, notably around if you forget to import the upstream you get this strange treeish related error which still throws me at first when I see it.

Part of maintaining packages is to be able to fix security bugs in older versions of them that are found in stable and even sometimes old stable (jessie and wheezy respectively at the time of writing).  At first I used to do this outside git because to me there wasn’t a clear way of doing it within it.  This is not too satisfactory because it means you lose the benefits of using git in the first place, and for distributions you are more likely to need collaboration with, such as working with the security team or help with backporting.

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WordPress 4.0.1 fixes for Debian stable

Previously I posted a short article about the WordPress package for Debian and how that SID was getting the updated WordPress 4.0.1 which had some security fixes.

The question a lot of people were asking was: What about stable (or Wheezy).  After way too much time due to other pressing issues, I have just uploaded the patched WordPress debian package for stable.  The fixed version has the catchy number of 3.6.1~deb7u5.  This package has all of the relevant patches that went in from WordPress 3.7.4 to 3.7.5 and there are even CVE IDs for this package (and 4.0.1 which all this stems from).

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Linux Capabilities

I was recently updating some code that uses fping. Initially it used exec() that was redirected to a temporary file but I changed it to use popen.  While it had been a while since I’ve done this sort of thing, I do recall there was an issue with running popen on setuid binary.  A later found it is mainly around setuid scripts which are very problematic and there are good reasons why you don’t do this.

Anyhow, the program worked fine which surprised me. Was fping setuid root to get the raw socket?

$ ls -l /usr/bin/fping
-rwxr-xr-x 1 root root 31464 May  6 21:42 /usr/bin/fping

It wasn’t which at first all I thought “ok, so that’s why popen is happy”. The way that fping and other programs work is they bind to a raw socket. This socket sits below the normal type sockets such as the ones used for TCP and UDP and normal users cannot use them by default. So how did fping work it’s magic and get access to this socket? It used Capabilities.

 

Previously getting privileged features had a big problem; it was an all or nothing thing. You want access to a raw socket? Sure, be setuid but that means you also could, for example, read any file on the system or set passwords. Capabilites provide a way of giving programs some better level of access, but not a blank cheque.

The tool getcap is the way of determining what capabilities are found on a file. These capabilities are attributes on the file which, when the file is run, turn into capabilities or extra permissions. fping has the capability cap_net_raw+ep applied to it. This gives access to the RAW and PACKET sockets which is what fping needs. The +ep after the capability name means it is an Effective and Permitted capability, which describes what happens with child processes and dropping privileges.

I hadn’t seen these Capabilities before. They are a nice way to give your programs the access they need, but limiting the risk of something going wrong and having a rouge program running as root.

No more dspam, now what?

I was surprised at first to see that a long-standing bug in dspam had been fixed. Until that is, I realised it was from the Debian ftp masters and the reason the bug was closing was that dspam was being removed from the Debian archive.

 

Damn!

 

So, now what? What is a good replacement for dspam that is actually maintained? I don’t need anti-virus because mutt just ignores those sorts of things and besides youbankdetails.zip.exe doesn’t run too well on Debian. dspam basically used tokens to find common patterns of spam and ham, with you bouncing misses so it learnt from its mistakes. Already got postgrey running for greylisting so its really something that does the bayesan filtering.

 

Some intial comments:

  • bogfilter looks interesting and seems the closest thing so far
  • cluebringer aka policyd seems like a policy and bld type of spam filter, not bayesan
  • I’ve heard crm114 is good but hard to use
  • spamassasin – I used to use this, not sure why I stopped

There really is only me on the mailserver with a pretty light load so no need to worry about efficiencies.  Not sure if it matters but my MTA is postfix and I already use procmail for delivery.

 

 

WordPress 3.8 for Debian

Well if you can read this then you know it’s working.  After way too many weeks, Debian will have WordPress version 3.8.  Thanks to Raphaël for his kind assistance and answering my questions about how it was built.  The upload is still gurgling along and will make it there in its own time. He said Handing over packages is hard, I’d agree but say taking over them is too.

So, what does WordPress 3.8 look like?  From the “frontend” I didn’t really notice much.  The big changes, at least cosmetically, seem to be for the admin backend.  It just look slicker and cleaner.

Hopefully Debian users find the update useful and I’ve not broken anything.  There’s always the BTS if there is.  I’ve deliberately tried to minimise the changes for this version to limit the breakage.

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