Network

Pointless respecifying FTP URI

There’s this person wiIETFthin IETF who seems to possess endless energy and a never-ending wish to clean up tiny details within the IETF processes. He continuously digs up specifications that need to be registered or submitted again somewhere due to some process. Often under loud protests from fellow IETFers since it steals time and energy from people on the lists for discussions and reviews – only to satisfy some administrative detail. Time and energy perhaps better spent on things like new protocols and interesting new technologies.

This time, he has deemed that the FTP a FILE URI specs need to be registered properly, and alas he has submitted his first suggested update of the FTP URI.

From my work with curl I have of course figured out a few problems with RFC1738 that I don’t think we should just repeat in a new version of the spec. It turns out I’m not alone in thinking this work isn’t really good like this, and I posted a second mail to clarify my points.

We’re not working on fixing the problems with FTP URIs that are present in RFC1738 so just rephrasing those into a new spec is a bad idea.

We could possibly start the work on fixing the problems, but so far I’ve seen no such will or efforts and I don’t plan on pushing for that myself either.

Please tell me or the ftpext2 group where I or the others are wrong or right or whatever!

Blogging

11 years of me

On May 11th 2000 I posted by first blog entry that is still available online on advogato.org. No surprise but it was curl-related.

The full post was:

I was made aware of the fact that curl is not really dealing well with the directory part of an ftp URL.

I was gonna quote the appropriate text piece from RFC1738 (yes, it is obsoleted by RFC2396 although 1738 has more detailed info about particular protocols like ftp) to someone when I noticed that I had interpreted it wrong when I read it before.

The difference between getting a file relative the login directory or with absolute path. It turns out you have to get a path like ftp.site.com/%2etmp/ if you want have the absolute path “/tmp”. Oh well, I have it support my old way as well even if that isn’t following the RFC just to allow people using that way to be able to use the new one unmodifed…

… which I guess proves that even though lots of time has passed, I still occupy myself with the same kind of hobbies and side- projects…

cURL and libcurl, Technology

US patent 6,098,180

5 Comments

(I am not a lawyer, this is not legal advice and these are not legal analyses, just my personal observations and ramblings. Please correct me where I’m wrong or add info if you have any!)

At 3:45 pm on March 18th 2011, the company Content Delivery Solutions LLC filed a complaint in a court in Texas, USA. The defendants are several bigwigs and the list includes several big and known names of the Internet:

  • Akamai
  • AOL
  • AT&T
  • CD Networks
  • Globalscape
  • Google
  • Limelight Networks
  • Peer 1 Network
  • Research In Motion
  • Savvis
  • Verizon
  • Yahoo!

The complaint was later amended with an additional patent (filed on April 18th), making it list three patents that these companies are claimed to violate (I can’t find the amended version online though). Two of the patents ( 6,393,471 and 6,058,418) are for marketing data and how to use client info to present ads basically. The third is about file transfer resumes.

I was contacted by a person involved in the case at one of the defendants’. This unspecified company makes one or more products that use “curl“. I don’t actually know if they use the command line tool or the library – but I figure that’s not too important here. curl gets all its superpowers from libcurl anyway.

This Patent Troll thus basically claims that curl violates a patent on resumed file transfers!

The patent in question that would be one that curl would violate is the US patent 6,098,180 which basically claims to protect this idea:

A system is provided for the safe transfer of large data files over an unreliable network link in which the connection can be interrupted for a long period of time.

The patent describes several ways in how it may detect how it should continue the transfer from such a break. As curl only does transfer resumes based on file name and an offset, as told by the user/application, that could be the only method that they can say curl would violate of their patent.

The patent goes into detail in how a client first sends a “signature” and after an interruption when the file transfer is about to continue, the client would ask the server about details of what to send in the continuation. With a very vivid imagination, that could possibly equal the response to a FTP SIZE command or the Content-Length: response in a HTTP GET or HEAD request.

A more normal reader would rather say that no modern file transfer protocol works as described in that patent and we should go with “defendant is not infringing, move on nothing to see here”.

But for the sake of the argument, let’s pretend that the patent actually describes a method of file transfer resuming that curl uses.

The ‘180 (it is referred to with that name within the court documents) patent was filed at February 18th 1997 (and issued on August 1, 2000). Apparently we need to find prior art that was around no later than February 17th 1996, that is to say one year before the filing of the stupid thing. (This I’ve been told, I had no idea it could work like this and it seems shockingly weird to me.)

What existing tools and protocols did resumed transfers in February 1996 based on a file name and a file offset?

Lots!

Thank you all friends for the pointers and references you’ve brought to me.

  • The FTP spec RFC 959 was published in October 1985. FTP has a REST command that tells at what offset to “restart” the transfer at. This was being used by FTP clients long before 1996, and an example is the known Kermit FTP client that did offset-based file resumed transfer in 1995.
  • The HTTP header Range: introduces this kind of offset-based resumed transfer, although with a slightly fancier twist. The Range: header was discussed before the magic date, as also can be seen on the internet already in this old mailing list post from December 1995.
  • One of the protocols from the old days that those of us who used modems and BBSes in the old days remember is zmodem. Zmodem was developed in 1986 and there’s this zmodem spec from 1988 describing how to do file transfer resumes.
  • A slightly more modern protocol that I’ve unfortunately found no history for before our cut-off date is rsync, as I could only find the release mail for rsync 1.0 from June 1996. Still long before the patent was filed obviously, and also clearly showing that the one year margin is silly as for all we know they could’ve come up with the patent idea after reading the rsync releases notes and still rsync can’t be counted as prior art.
  • Someone suggested GetRight as a client doing this, but GetRight wasn’t released in 1.0 until Febrary 1997 so unfortunately that didn’t help our case even if it seems to have done it at the time.
  • curl itself does not pre-date the patent filing. curl was first released in March 1998, and the predecessor was started around summer-time 1997. I don’t have any remaining proofs of that, and it still wasn’t before “the date” so I don’t think it matters much now.

At the time of this writing I don’t know where this will end up or what’s going to happen. Time will tell.

This Software patent obviously is a concern mostly to US-based companies and those selling products in the US. I am neither a US citizen nor do I have or run any companies based in the US. However, since curl and libcurl are widely used products that are being used by several hundred companies already, I want to help bring out as much light as possible onto this problem.

The patent itself is of course utterly stupid and silly and it should never have been accepted as it describes trivially thought out ideas and concepts that have been thought of and implemented already decades before this patent was filed or granted although I claim that the exact way explained in the patent is not frequently used. Possibly the protocol using a method that is closed to the description of the patent is zmodem.

I guess I don’t have to mention what I think about software patents.

I’m convinced that most or all download tools and browsers these days know how to resume a previously interrupted transfer this way. Why wouldn’t these guys also approach one of the big guys (with thick wallets) who also use this procedure? Surely we can think of a few additional major players with file tools that can resume file transfers and who weren’t targeted in this suit!

I don’t know why. Clearly they’ve not backed down from attacking some of the biggest tech and software companies.

patent drawing

(Illustration from the ‘180 patent.)

Electronics, Network, Web

The cookie RFC 6265

4 Comments

http://www.rfc-editor.org/rfc/rfc6265.txt is out!

Back when I was a HTTP rookie in the late 90s, I once expected that there was this fine RFC document somewhere describing how to do HTTP cookies. I was wrong. A lot of others have missed that document too, both before and after my initial search.

I was wrong in the sense that sure there were RFCs for cookies. There were even two of them (RFC2109 and RFC2965)! The only sad thing was however that both of them were totally pointless as in effect nobody (servers nor clients) implemented cookies like that so they documented idealistic protocols that didn’t exist in the real world. This sad state has made people fall into cookie problems all the way into modern days when they’ve implemented services according to those RFCs and then blame their browser for failing.

cookie

It turned out that the only document that existed that were being used, was the original Netscape cookie document. It can’t even be called a specification because it is so short and is so lacking in details that it leaves large holes open and forces implementers to guess about the missing pieces. A sweet irony in itself is the fact that even Netscape removed the document from their site so the only place to find this document is at archive.org or copies like the one I link to above at the curl.haxx.se site. (For some further and more detailed reading about the history of cookies and a bunch of the flaws in the protocol/design, I recommend Michal Zalewski’s excellent blog post HTTP cookies, or how not to design protocols.)

While HTTP was increasing in popularity as a protocol during the 00s and still is, and more and more stuff get done in browsers and everything and everyone are using cookies, the protocol was still not documented anywhere as it was actually used.

Somewhat modeled after the httpbis working group (which is working on updating and bugfixing the HTTP 1.1 spec), IETF setup a mailing list named httpstate in the early 2009 to start discussing what problems there are with cookies and all related matters. After lively discussions throughout the year, the working group with the same name as the mailinglist was founded at December 11th 2009.

One of the initial sparks to get the httpstate group going came from Bill Corry who said this about the start:

In late 2008, Jim Manico and I connected to create a specification for
HTTPOnly — we saw the security issues arising from how the browser vendors
were implementing HTTPOnly in varying ways[1] due to a lack of a specification
and formed an ad-hoc working group to tackle the issue[2].
When I approached the IETF about forming a charter for an official working
group, I was told that I was <quote> “wasting my time” because cookies itself
did not have a proper specification, so it didn’t make sense to work on a spec
for HTTPOnly.  Soon after, we pursued reopening the IETF httpstate Working
Group to tackle the entire cookie spec, not just HTTPOnly.  Eventually Adam
Barth would become editor and Jeff Hodges our chair.

In late 2008, Jim Manico and I connected to create a specification for HTTPOnly — we saw the security issues arising from how the browser vendors were implementing HTTPOnly in varying ways[1] due to a lack of a specification and formed an ad-hoc working group to tackle the issue[2].

When I approached the IETF about forming a charter for an official working group, I was told that I was <quote> “wasting my time” because cookies itself did not have a proper specification, so it didn’t make sense to work on a spec for HTTPOnly.  Soon after, we pursued reopening the IETF httpstate Working Group to tackle the entire cookie spec, not just HTTPOnly. Eventually Adam Barth would become editor and Jeff Hodges our chair.

Since then Adam Barth has worked fiercely as author of the specification and lots of people have joined in and contributed their views, comments and experiences, and we have over time really nailed down how cookies work in the wild today. The current spec now actually describes how to send and receive cookies, the way it is done by existing browsers and clients. Of course, parts of this new spec say things I don’t think it should, like how it deals with the order of cookies in headers, but as everything in life we needed to compromise and I seemed to be rather lonely on my side of that “fence”.
I must stress that the work has only involved to document how things work today and not to invent or create anything new. We don’t fix any of the many known problems with cookies, but we describe how you write your protocol implementation if you want to interact fine with existing infrastructure.

The new spec explicitly obsoletes the older RFC2965, but doesn’t obsolete RFC2109. That was done already by RFC2965. (I updated this paragraph after my initial post.)

Oh, and yours truly is mentioned in the ending “acknowledgements” section. It’s actually the second RFC I get to be mentioned in, the first being RFC5854.

Future

I am convinced that I will get reason to get back to the cookie topic soon and describe what is being worked on for the future. Once the existing cookies have been documented, there’s a desire among people to design something that overcomes the problems with the existing protocol. Adam’s CAKE proposal being one of the attempts and ideas in the pipe.

Another parallel IETF effort is the http-auth mailing list in which lots of discussions around HTTP authentication is being held, and as they often today involve cookies there’s a lot of talk about them there as well. See for example Timothy D. Morgan’s document Weaning the Web off of Session Cookies.

I’ll certainly track the development. And possibly even participate in shaping how this will go. We’ll see.

(cookie image source)

c-ares, cURL and libcurl

libcurl’s name resolving

Recently we’ve put in some efforts into remodeling libcurl’s code that handles name resolves, and then in particular the two asynchronous name resolver backends that we support: c-ares and threaded.

Name resolving in general in libcurl

libcurl can be built to do name resolves using different means. The primary difference between them is that they are either synchronous or asynchronous. The synchronous way makes the operation block during name resolves and there’s no “decent” way to abort the resolves if they take longer time than the program wants to allow it (other than using signals and that’s not what we consider a decent way).

Asynch resolving in libcurl

This is done using one of two ways: by building libcurl with c-ares support or by building libcurl and tell it to use threads to solve the problem. libcurl can be built using either mechanism on just about all platforms, but on Windows the build defaults to using the threaded resolver.

The c-ares solution

c-ares’ primary benefit is that it is an asynchronous name resolver library so it can do name resolves without blocking without requiring a new thread. It makes it use less resources and remain a perfect choice even if you’d scale up your application up to and beyond an insane number of simultaneous connections. Its primary drawback is that since it isn’t based on the system default name resolver functions, they don’t work exactly like the system name resolver functions and that causes trouble at times.

The threaded solution

By making sure the system functions are still used, this makes name resolving work exactly as with the synchronous solution, but thanks to the threading it doesn’t block. The downside here is of course that it uses a new thread for every name resolve, which in some cases can become quite a large number and of course creating and killing threads at a high rate is much more costly than sticking with the single thread.

Pluggable

Now we’ve made sure that we have an internal API that both our asynchronous name resolvers implement, and all code internally use this API. It makes the code a lot cleaner than the previous #ifdef maze for the different approaches, and it has the side-effect that it should allow much easier pluggable backends in case someone would like to make libcurl support another asynchronous name resolver or system.

This is all brand new in the master branch so please try it out and help us polish the initial quirks that may still exist in the code.

There is no current plan to allow this plugging to happen run-time or using any kind of external plugins. I don’t see any particular benefit for us to do that, but it would give us a lot more work and responsibilities.

cURL

cURL and libcurl, Network, Web

HTTP transfer compression

HTTP is a protocol that looks simple in its simplest form and its readability can easily fool you into believing an implementation is straight forward and quickly done.

That’s not the reality though. HTTP is a very big protocol with lots of corners and twisting mazes that one can get lost in. Even after having been the primary author of curl for 13+ years, there are still lots of HTTP things I don’t master.

To name an example of an area with little known quirks, there’s a funny situation when it comes to how HTTP supports and doesn’t support compression of data and compression of data in transfer.

No header compression

A little flaw in HTTP in regards to compression is that there’s no way to compress headers, in either direction. No matter what we do, we must send the text as-is and both requests and responses are sometimes very big these days. Especially taken into account how cookies are always inserted in requests if they match. Anyway, this flaw is nothing we can do anything about in HTTP 1.1 so we need to live with it.

On the other side, compression of the response body is supported.

Compressing data

Compression of data can be done in two ways: either the actual transfer is compressed or the body data is compressed. The difference is subtle, but when the body data is compressed there’s really nothing that mandates that the client has to uncompress it for the end user, and if the transfer is compressed the receiver must uncompress it in order to deal with the transfer properly.

For reasons that are unknown to me, HTTP clients and servers started out supporting compression only using the Content-Encoding style. It means that the client tells the server what kind of content encodings it supports (using Accept-Encoding:) and the server then sends the response data using one of the supported encodings. The client then decides on its own that if it gets the content in one of the compressed formats that it said it can handle, it will automatically uncompress that on arrival.

The HTTP protocol designers however intended this kind of automatic compression and subsequent uncompress to be done using Transfer-Encoding, as the end result is the completely transparent and the uncompress action is implied and intended by the protocol design. This is done by the client telling the server what transfer encodings it supports with the TE: header and the server adds a Transfer-Encoding: header in the response telling how the transfer is encoded.

HTTP 1.1 introduced a mandatory encoding that all servers can use whenever they feel like it: chunked encoding, so all HTTP 1.1 clients already have to deal with Transfer-Encoding to some degree.

Surely curl is better than all those other guys, right?

Not really. Not yet anyway.

curl has a long history of copying its behavior from what the browsers do, in order to allow users to basically script anything imaginable that is HTTP-like with curl. In this vein, we implemented compression support the same way as all the browsers did it: the content encoding style. (I have reason to believe that at least Opera actually supports or used to support compressed Transfer-Encoding.)

Starting now (code pushed to git repo just after the 7.21.5 release), we’ve taken steps to improve things. We’re changing gears and we’re introducing support for asking for and using compressed Transfer-Encoding. This will start out as an optional feature/flag (–tr-encoding / CURLOPT_TRANSFER_ENCODING) so that we can start out and see how servers in the wild behave and that we can deal with them properly. Then possibly we can switch the default in the future to always ask for compressed transfers. At least for the command line tool.

We know from the little tests we are aware of, that there are at least one known little problem or shall we call it a little detail to keep on eye at, with introducing compressed Transfer-Encoding. As has been so fine reported several years ago in the opera blog Browser sniffing gone wrong (again): Cars.com, there are cases where this may cause the server to send data that gets compressed twice (using both Content and Transfer Encoding) and that needs to be taken care of properly by the client.

At the time of this writing, I’ve not yet taken care of the double-compress case in the code, but I intend to get on to it within shortly.

I’m otherwise very interested in hearing what kind of experience people will have from this. What servers and sites will support this as documented and intended?

cURL and libcurl

Shipping curl 7.21.5

I don’t usually post anything here when we do curl releases, pretty much because we do them bimonthly on a fairly steady schedule so there should be little surprise to anyone interested by the time they get public.

But hey, this is hard work and just to remind you all what’s going on I thought I’d throw in a mention of what we’ve spent the last two months doing. curl and libcurl 7.21.5 is released today.

The five notable changes introduced this time include:

The CURLOPT_SOCKOPTFUNCTION callback can now return information back to libcurl that the socket libcurl operates on is already connected. This is useful for applications that do a lot of fiddling on their own and possibly provide its own socket to start with using the CURLOPT_OPENSOCKETFUNCTION.

curl the tool got support for the –netrc-file option, that allows a user to point out a specific .netrc file instead of always forcing the user to use the fixed $HOME/.netrc one.

Brand new support for building libcurl with the cyassl library for SSL/TLS support. Previously curl only had support for the older OpenSSL emulation API that cyassl used to provide, but starting now we’re using cyassl directly and it is now a proper SSL citizen among the seven SSL libraries curl supports.

Since the previous release when we shipped the first support for TLS-SRP that required GnuTLS, the OpenSSL project accepted patches that introduced TLS-SRP into their official version as well and accordingly we have received patches that now allow users to use TLS-SRP with libcurl built against (a new enough) OpenSSL as well.

We have started to re-use two error codes a bit differently within libcurl, so that it now can return: CURLE_NOT_BUILT_IN (4) when an application tries to use a feature that was missing or was explicitly disabled at build-time and CURLE_UNKNOWN_OPTION (48) when the application has passed in an option that isn’t known or recognized.

And we’re counting more than 40 bugfixes worth mentioning. The most important ones are possibly:

If using the multi interface doing RTSP, libcurl could crash when trying to re-use a previous connection.

POP3 didn’t do TLS properly, it issued the wrong command to start TLS and it didn’t send the password correctly once it did switch to TLS!

When using the multi interface, there could be times when the timeout didn’t trigger so it wouldn’t close lingering connections even when asked to do so.

SFTP and SFP with the multi_socket interface were not working correctly and would very easily end up with stalled transfers due to the application being told to wait for the wrong action (or none at all).

If told to use the CCC command (which is used with FTP-SSL when the client asks the server to switch off from an SSL connection back to plain TCP again), curl would disable SSL on the connection but then use the wrong socket reader function and crash.

… but of course, if you’ve suffered from a particular bug in a previous release I’m sure you’ll consider the exact bug fix that corrects your problem to be the most important one!

Not to forget, the great people apart from yours truly that have contributed with code and insights since the previous release. Without them, the above list of changes and bugfixes just wouldn’t exist. The friends we have to thank are (in no particular order):

Mike Crowe, Kamil Dudka, Julien Chaffraix, Hoi-Ho Chan, Ben Noordhuis, Dan Fandrich, Henry Ludemann, Karl M, Manuel Massing, Marcus Sundberg, Stefan Krause, Todd A Ouska, Saqib Ali, Andre Guibert de Bruet, Tor Arntsen, Vincent Torri, Dave Reisner, Chris Smowton, Tinus van den Berg, Hongli Lai, Gisle Vanem, Andrei Benea, Mehmet Bozkurt

… and now back to working towards the next release. To be expected in roughly two months. Repeat.

Network

Future transports, the video

The talk I did at FSCONS 2010 titled “Future Transports” has now been made available online and you can see the whole thing. It is split up in three separate video snippets. Click on the picture below to get started:

fscons2010-futuretransports

I originally put the videos embedded here on my blog, but it turned out to be a really certain way to kill Firefox so it turned out to be annoying. Now you’ll instead get handed over to the video on vimeo’s site.

Network

IRC use is declining

I discovered IRC around 1993.

Back then, before EFnet split in two, the IRC channel I frequented was #amiga and we were a small bunch of people from all over the globe who got to know each other pretty good. In the 90s I participated in one of my first open source projects and we created the IRC bot we named Dancer. Dancer was a really talented “defence bot” back in the days of the “wild west” of IRC when channel take overs, flood attacks and nick collisions were widespread and frequently occurring. Dancer helped us keep things calm. Later on, I was part of the team that created and setup the new IRC network called amiganet.

I’ve been using IRC on and off since those days in the early 1990s and still today I hang out on 5-6 channels on freenode every day.

IRC was launched to the world already 1988, almost 23 years ago. I’ve been trying to document the basic history of IRC and when I updated that page the other day with some usage numbers for freenode, I decided to have a look around the net to see if there are any general numbers for IRC usage at large, and I found out that usage is decreasing all over and has been doing so for years. Without research, I figure IRC users are either old farts like myself or at least very tech oriented and geeky. Younger, newer and less techy people use other means of communication.

IRC never “took off” among the general public. In general, I find that general people prefer various IM systems (something that I’ve never understood or adopted myself) and most “ordinary”humans I know don’t even know what IRC is. Possibly, the fact that the IRC protocol never got very good (there’s only that original spec from ’93), that there’s a million completely separated IRC networks with no cross-network messages or that all IRC networks still today suffer from netsplits and other artifacts due deficiencies in how the IRC servers are talking to each other.

5-6 years ago the four most popular networks were all over 100,000 users regularly. Quakenet were well over 200,000. Last year, only Quakenet reached over 100,000. It seems basically all of  them have roughly half the numbers they had 2004.

Graphs from irc.netsplit.de:

2004

IRC usage 2004

2010

IRC usage 2010

Mail

Email asking for my products

In my mini-series of strange mails I receive, here’s another one:

Subject: Product Request

Hello,
I am interested in purchasing some of your products, I will like to know
if youcan ship directly to SPAIN , I also want you to know my mode of
payment for this order is via Credit Card. Get back to me if you can ship
to that destination and also if you accept the payment type I indicated.
Kindly return this email with your price list of your products..

I assume I’ll never figure out what products he speaks of, or how on earth he ended up sending me this… I’ll admit I was tempted to make up some “interesting” products to offer.

Update: I was informed that this is probably “just” another online fraud attempt. How boring.

curl, open source and networking