daniel.haxx.se

As the primary curl author, I’m finding the comments here interesting. That blog entry “Teaching wget About Root Certificates” is about how you can get cacerts for wget by downloading them from curl’s web site, and people quickly point out how getting cacerts from an untrusted third party place of course is an ideal situation for an MITM “attack”.

Of course you can’t trust any files off a HTTP site or a HTTPS site without a “trusted” certificate, but thinking that the curl project would run one of those just to let random people load PEM files from our site seems a bit weird. Thus, we also provide the scripts we do all this with so that you can run them yourself with whatever input data you need, preferably something you trust. The more paranoid you are, the harder that gets of course.

On Fedora, curl does come with ca certs (at least I’m told recent Fedoras do) and even if it doesn’t, you can actually point curl to use whatever cacert you like and since most default installs of curl uses OpenSSL like wget does, you could tell curl to use the same cacert your wget install uses.

This last thing gets a little more complicated when one of the two gets compiled with a SSL library that doesn’t easily support PEM (read: NSS), but in the case of curl in recent Fedora they build it with NSS but with an additional patch that allows it to still be able to read PEM files.

yassl is a (in comparison) small SSL/TLS library that libcurl can be built to use instead of using one of the other SSL/TLS libraries libcurl supports (OpenSSL, GnuTLS, NSS and QSSL). However, yassl differs somewhat from the others in the way that it provides an OpenSSL-emulating API layer so that in libcurl we pretty much use exactly the same code for OpenSSL as we do for yassl.

yassl claimed this libcurl support for several years ago and indeed libcurl builds fine with it and you can even do some basic SSL operations with it, but the emulation is just not good enough to let the curl test suite go through so lots of stuff breaks when libcurl is built with yassl.

I did this same test 15 months ago and it had roughly the same problems then.

As far as I know, the other three main libraries are much more stable (the QSSL/QsoSSL library is only available on the AS/400 platform and thus I don’t personally know much about how it performs) and thus they remain the libraries I recommend users to select from if they want something that’s proven working.

Since the dawn of time (at least it feels that long) we’ve included a copy of a ca cert bundle in the curl releases. That ca cert bundle originates from Netscape 4.72 and no cert has been added to it since the year 2000(!)

Instead, we’ve offered things like an easy downloadable version from our web site, and documented that this is what you often need to do.

Anyway, we were recently triggered by a bug report and are discussing updating the bundle in the curl tarballs – we’ll just need to sort out the license situation first but we’re slowly progressing there and I think we’re pretty fine with things as they are right now.

However, the question is perhaps better put the other way: why should we bother to include a ca cert bundle in the first place? Most users will already have one in their system (since basically all SSL-based applications want one) and those that don’t can very easily get an updated one using our online server or a recent perl script added to the curl source tree.

I hope I don’t have to tell you that I value all input I can get on this issue!

Dave Jones blogged about his recent problems with curl on Fedora 8. It seems to be a problem somewhere in or related to the NSS library, that Fedora links curl to for SSL/TLS these days.

What I find a bit annoying with this situation, is that I’m using Debian unstable and I’m dist-upgrading fairly frequently to be able to run on the bleeding edge and yet I don’t have the equivalent NSS version Fedora has and what’s perhaps worse is: I don’t even know how to get it and build my own local version! Is Fedora using their own patched version of this (rhetorical question as I’m quite sure they are)? Is it possible to get that version or patch so that I can build it and test on my non- Fedora development machine(s) ?

So, even though it really isn’t my problem or my issue to deal with, I couldn’t even try out his problem on my own!