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Campaign for a new HTTP Error code: 451 - Blocked for legal reasons (451unavailable.org)
362 points by JayEnn on Aug 15, 2013 | hide | past | web | favorite | 88 comments

Seems like a good idea, but the wrong way to achieve it. The right way, as I understand it, would be to write it up as an RFC and submit it to the IETF; and to contribute code for it to some of the popular web servers (apache, nginx, etc). The site doesn't make any mention of either of those things.

Edit: oops, I was wrong. There is an RFC and it's linked from http://www.451unavailable.org/what-is-error-451/

Since the sites blocked on ISP level code contribution to apache/nginx or other web servers is irrelevant.

Disclaimer: I work for an ISP and every ISP in Russia is legally required to do the censorship (and mirror all traffic to FSB black boxes, but that's another story). I'm not partucilarly happy with the situation, but can't do anything about that.

Nginx is totally relevant as many ISPs including our use GNU/Linux boxes running Nginx as a highly performant transparent proxy (there are TPROXY patches for Nginx) to dive into HTTP traffic and do URL filtering (obviously, after initial crude IP-based filtering). Costs less than those fancy Cisco solutions, and it's not like we're willing to spend additional money on something that downgrades the service.

Also, there are cases where actual sites are legally forced to remove resources. Well, not really forced, but it's just a sort request too many sites can't really decline. You either comply and remove a single page (blocking for Russian visitors only seems sufficient), or get blocked on ISP level and since many ISPs (including several giant ones) just blacklist a whole IP address, that means your site becomes completely unavailable.

> I work for an ISP and every ISP in Russia is legally required to do the censorship (and mirror all traffic to FSB black boxes, but that's another story).

I hate the censorship but I like the fact you're not gagged and can talk about the fact traffic is being mirrored.

OR, he's not allowed to, and he's doing it anyway.

Nope, it's codified in the law, in a legalese, but right in the open.

The sad thing is, practically nobody cared about that, for years. The dissatisfaction became visible only when government granted themselves an ability not only sniff on others communications (which is obviously invisible to end user) but also actively censor them.

Given that Russia appears to be engaged in even broader surveillance and monitoring than the U.S., I find it odd that Snowden would be granted temporary asylum there for speaking out about a similar program in the U.S. It makes the whole situation look more like a political game.

If a russian speaking about Russia surveilance asked for asylum in the US, do you expect the US to deny or grant it?

He shouldn't be required to fight that battle as well; he's done more than we could possibly ask of somebody already. Russia is providing him with a certain degree of safety, he shouldn't be obligated to reject that.

could you post some authoritative proof/references for the black boxes?

Authorative: http://minsvyaz.ru/common/upload/prikaz_16-01-2008_N6.pdf (sorry, the document's in Russian and I can't find any translation, nor skilled enough to do that myself) - I'm not a lawyer, but in my understanding (as I was explained) this decree contains requirements to networks that ISPs must conform to (otherwise they can't get the license and provide services), and it states (in thick legalese) that all subscriber-generated traffic must be mirrored to operational search activities control ("пункт управления ОРМ"), which is usually (but maybe not universally) a black box sitting in a rack.

Non-authorative reference: http://en.wikipedia.org/wiki/SORM#SORM-2

From what I've heard, SORM-2 hardware is a secured 1U *nix-based server (peer was not sure whenever it was BSD or GNU/Linux variant), running some kind of sniffer (probably pcap-based) software with some FSB's in-house tools. They are supposed to be dormant for the most of time, but nobody except FSB knows what they're actually doing (and they don't have to report when they're doing a lawful intercetion).

You can think of this as a blueprint for snoopworthy governments around the world including all US or Russian allies.

Think about that! (and submit a patch to support 451 in your favourite web server / framework).

thank you very much!

Requirement to install them is called SORM-2:



DMCA requests could be served as 451 as well, it's not just ISP-based blocking.

Then to make things easier, some people need an http verb called patch_legal, to take down pages for dmca and other legal reasons.

I once worked somewhere where some resources could not be displayed to all clients. We chose to (ab)use HTTP 409 Conflict.

> 10.4.10 409 Conflict

> The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough

> information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.

> Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might use the 409 response to indicate that it can't complete the request. In this case, the response entity would likely contain a list of the differences between the two versions in a format defined by the response Content-Type.

Discussion on HN from when the IETF Draft was created https://news.ycombinator.com/item?id=4099751

My blog post which helped inspire it http://shkspr.mobi/blog/2012/06/there-is-no-http-code-for-ce...

Simultaneously glad and disgusted that there is a campaign around this.

Is this saying:

"As a web user I want our ISPs/governments to give us a nice error page so we understand what is going on when they DNS block or seize websites"

Or is it saying:

"As a web-master, when have to take down content due to legal proceedings I want a nice HTTP code to return"

They give example of the first (Virgin Media), but that takes down an entire domain, so it's kind of irrelevant if the correct HTTP code is returned, it's not like that is going to be resolved quickly. 503 would be the correct code here.

The second might be useful to spiders (who might want to back-off spidering so often for a while), but then wouldn't you just want to show your users a 404 with a nice reason why the content has gone.

I understood it as the latter. Something that a webmaster can display to show a DMCA or geographical legal issue.

It's good for both cases, isn't it? It's usefull for informing your users what is happenning.

> but then wouldn't you just want to show your users a 404 with a nice reason why the content has gone.

A 451 with a nice reason why the content was gone is better.

I don't get it? There are already drafts for it, which were created close in time to when Bradbury died.


A draft is not an implementation. And an implementation in browsers is not an implementation in providers or webservers.

This is a very good way to make people aware of legal blocking, and to make sure that it is adopted.

Surprised no one has made any reference to Farenheit 451.

Allow me to be the first.

Thankfully websites are not flammable.

The error code for censorship is the reference. I guess not everyone would recognize that, but I immediately noticed.

I'm also surprised (this Error Code was first mentioned, as far as I know, when Ray Bradbury died)… but I like the subtle Element of not Mentioning it.

For some reason, this article is blocked from my work due to proxy avoidance.

Somehow seems fitting.

Surely this should be within the 5xx range of status codes? I get there's a reference to be had using 451 but this is more of a server error than client.

No, I'd say it's a 4xx error. Have a look at https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

Usually, 5xx means that the client could retry the request at a later time, and have it succeed. 4xx means the client should expect the request to fail forever unless something is changed.

Some HTTP clients (not browsers, but other things) take advantage of this by showing the user an error dialog on a 4xx error, but just retry at a later time on a 5xx error.

Is the 451 a reference to something?

Yes, Fahrenheit 451 by Ray Bradbury.

A dystopian novel about a world where all books are banned and fire squads roam around to burn them.

Going by something someone has put on wikipedia "A reference to the 1953 dystopian novel Fahrenheit 451, where books are outlawed".

On that note it looks like Microsoft have already dibs'd 451 for an Exchange ActiveSync redirect anyway.

Almost certainly Ray Bradbury's book Fahrenheit 451

I was about to write a +1, but then I realised:

- 4xx isn't appropriate as it's not a client error. - 5xx isn't appropriate because it's not a server error either.

"The 4xx class of status code is intended for cases in which the client seems to have erred"


"Response status codes beginning with the digit '5' indicate cases in which the server is aware that it has encountered an error or is otherwise incapable of performing the request."

There's always that quote people chuck around a lot about censorship being an error so the internet routes around it. By that definition the server knows it has errored so it should be a 5xx response.

[Nerdit: Fixed the quote marks]

I'd consider it as much of an error as a 404 in this context.

1) Link works: 200

2) Take down notice arrives


3) Link not found: 404


3) Link not available: 451

I'd argue it's a client error. Whoever's hosting the info is happy to host it, while the client needs to go vote out the politician that censored it.

What if the client is not from a nation that is causing the server to refuse to serve the content? It's very much a server error.

I think it is a 4xx client error, and not necessarily one that needs a new status code. It seems to me that it is a fairly simple case of 403 Forbidden:

  The server understood the request, but is refusing to 
  fulfill it. Authorization will not help and the request 
  SHOULD NOT be repeated. If the request method was not HEAD 
  and the server wishes to make public why the request has 
  not been fulfilled, it SHOULD describe the reason for the 
  refusal in the entity. If the server does not wish to make 
  this information available to the client, the status code 
  404 (Not Found) can be used instead.

From http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

"10.4 Client Error 4xx

The 4xx class of status code is intended for cases in which the client seems to have erred. "

The client has not erred by requested a document that exists and which the server can technically provide (separately, the server has not erred by refusing to provide a document to the client which the exists and which access control would allow the client to have, because a government is threatening the server operator in some manner).

> The client has not erred by requested a document that exists and which the server can technically provide

The client has erred in requesting a document which the server is legally forbidden to provide to that client. As specified for 403, the server understands the request and refuses to fulfill it.

Admittedly, a hypothetical 6xx Third-Party Interference series of error codes might be useful for these kind of cases (and some instances currently handled by 503.)

>> The client has erred

> The client has not erred... the server understands the request and refuses to fulfill it.

As I see it, the server is not refusing anything. +1 6xx Third-Party Interference.

Let's just agree to disagree.

Well, the cool thing about HTTP error codes is that you don't need a campaign or get permission from the W3C, you can just start using them if you want.

Yes, but that's true of other standards. Eg, I can start putting <haiku> tags in my HTML if I want.

The issue is whether anyone else will expect this tag or code and do anything meaningful with it.

I get what you mean but I don't think this is the same thing. HTML has a DTD, something that people conform to when writing, so your <haiku> tag would not follow that guideline, whereas companies like Twitter can implement their own error codes as they see fit. See error code 420, Enhance Your Calm.[0]

[0]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

Well, sure, just like I can create my invented domain name like hacker.news and use my own IP addresse without being allocated them. The Internet interoperates by everyone agreeing to follow the same agreed conventions, but there is no rule that says you have to. The registry for HTTP status codes has no 420 code and could be assigned for a different purpose in the future: http://www.iana.org/assignments/http-status-codes

Yes, they can respond with 420. However, my browser does not have a predetermined response for that. Whereas if they respond with 200 or 302 or 404, all browsers know what to do; that's what it means to be a "standard".

> HTML has a DTD

Tangentially to your point, that's only true of the 4.x and earlier versions of HTML which are SGML applications, WHATWG HTML / W3C HTML5 is not SGML-based and does not have a DTD.

Eg, I can start putting <haiku> tags in my HTML if I want. The issue is whether anyone else will expect this tag or code and do anything meaningful with it.

You mean like this? https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custo...

Honestly, people who believe in this strongly enough should just start using them and provide themselves as examples of good use cases. That doesn't mean it shouldn't be campaigned for to get more people to use it.

There is a lot of discussion below on whether 451 is the right error code and how to implement it properly, but I'm missing one thing - what's the benefit of doing it as a status code at all?

If you're going to say that it raises censorship awareness - Internet protocols are intended as useful technical standards for programs to communicate, not vehicles for political goals.

What is the technical benefit of failing with a different error code? Is there need for client software to react differently to a 451 and a 403? The status code is not intended for the human user. If we want to raise awareness, than we already have means to do that - a 403 with a descriptive page citing the reasons. Many websites already do that when complying to DMCA takedowns.

Some sites in Russia actually return 451:

curl -I http://lurkmore.to/Конопля

I have no idea what this is or what 451 means in this context, but I'm upvoting this as a legitimate technical reason not to use 451.

Technically speaking 403 can be returned if it's blocked for legal reasons, but obviously it would be nice to know why it is forbidden.

There is some reasoning about this on: http://www.451unavailable.org/why-do-we-need-error-451

Still, imho, 4XX could be a response for a given URL, but when "a website is blocked" (from the text of the previous URL), we should go to 5XX, as in 503 - service unavailable.

5xx does not really make sense for a single page removed due to DMCA.

Yes, I don't know if two codes (one for URL and one for the entire site) could make sense in this case.

does it really matter if it's 5xx or 4xx?

Yes. 400 responses are because of client error. 500 responses are for server error.

Legal restrictions on content are almost always issues on the client side, otherwise they should not be made available at all.

Consider for example the blocking of sites in the UK, or the blocking of the PirateBay website in the Netherlands. Those are all very limited audiences where the location of the client is causing a legal reason why the content can not be displayed.

541, then?

I bet you they are really happy you submitted this smack in the middle of the holiday of their main employee/volunteer :-).

Messages to their volunteer address get a vacation message that they're away until September 1st.

We should absolutely not be standardizing censorship.

In this form I totally agree. Reason being that by haveing a block at the web server level in essence places the blocking to be done by the hosting site and blocking based upon location and content. This places the onus of censorship upon the host, which they can already code for if they want.

Not sure placeing the onus of censorship into the hands of the host and not the goverment with there IP/DNS blocks or however they impose such blocks (China has a nice firewall for outside China sites and I dare to think of how they block a website inside China though can bet it is just as effective).

That all said the posiblility to volantarly do the blocking in a way that the powers that be will accept and with that allow there country's owners to see parts of yoru site that are legal and not the illegal parts for them. Well that would possibily have uses and opens your site up still instead of a blanket ban.

  Piratebay has legal torrents, yet they are blocked as some form of descrimnation blanket ban.  So it does have it's possibilities, albiet a dangerous path that should not be tread lightly.

I got Access Denied at work...

Is this really necessary? How about 456 - unavailable because someone spilled coffee on our backend server? Or 467 - unavailable because garden gnomes invaded our offices?

I can see some reasoning behind this, but the reasoning is that the emphasis of the problem is "people are angry at the site because something is blocked so let's show an error code reflecting the real reason." Using 451 would take the emphasis away from the site and onto the legal oppressor.

On the other hand, why not inverse all inaccessible content to legal oppressors? Change the default meaning of 403 for example to "Access denied for permissive or legal reasons".

Change the default meaning of 403? I don't think that's a good idea. When a user needs to be logged in to do something and they aren't, you show them 403. When access is restricted to people outside a network, they see 403. It'll be hard to force a new behaviour onto the existing web, easier to add a new HTTP code.

My understanding is that the server should respond with 401 Unauthorized when someone is attempting to access a resource that requires authentication. What is the case for using 403 instead?

OK, 401 makes more sense in that context. But another 403 case would be "the authorized user lacks permission to open resource."

When they have authenticated (logged on), but they still do not have access to that particular resource (but may have access to others).

The whole point of this is wrong... The internet is free, content shouldn't be blocked for legal reasons

The internet is _not_ free, obviously, because content has been blocked for legal reasons in certain regions of the world.

I agree with your sentiment though - the internet _should_ be free.

The whole point of this is right, its highlighting the government breaking the Internet.

Content shouldn't be blocked, the Internet should be free and open. However without letting people know what's happening they will not complain.

Of course what the browser should display is:

451: The Right Honourable Claire Perry MP has deemed that you shouldn't be able to look at this site.

I have no clue about US politics but this sounds cool!

In case you didn't know, MP Clair Perry is a British Member of Parliament, sadly. She is one of those people who know better, than us "plebs".

IMHO, she is ignorant(1) and irrational(1), and there for scared witless of the internet, so she seeks to control it. I don't think she knows how wrong she is, there for I don't see her as evil, as such. However, it does seem our vote whore of a Prime Minister listens to her every word, hence the attempts to block porn and make people opt in to avoid the blocks, since her position ties in to an awful lot of right wing voters, who are equally, if not more, ignorant and irrational. They are the kind of people who genuinely believed Rock and Roll was the work of the devil, and that black people are a different species.

(1)I use these words for their real meaning and not the insult, judgement, or political value. I honestly think many people literally do not understand the technical issues, and act illogically as a result. I believe this is a lot to do with the traditional media, who politicians rely on, issuing scare stories about the internet because their business were and still are threatened by it. My "evil" in this is those who spread the lies, ie, the media. I hate to admit this, but in many ways I see the likes of Clair Perry as well intentioned victims and mules of the media.

Yet it is, because the courts have a different opinion on this, and they decide what happens. So it's better to make it clear to the end user when it happens, so at least they are not kept in the dark, or are basically lied to, about the reason why they cannot see the document.

should != is

And the distance between them is measured as response code 451

452 Blocked for reasons which may or may not be legal but I probably shouldn't say either way

How does this interact with the effort to encourage the use of HTTPS everywhere?

If the 451 code is returned by the web server because the site got a DMCA request, then HTTPS doesn't matter because the destination web server already decrypted the session to find the request that you're making before returning the code.

Unfortunately, that page return 200 OK. Why does not it return 451 status code?

That would be great when you have to block access to OFAC listed countries

Tried to open this link at work. Blocked for legal reasons :)

That is a dumb error code.

404 already exists.

404 is for "not found". 451 would be for "found, but we can't show it to you".

> 451 would be for "found, but we can't show it to you".

"The server understood the request, but is refusing to fulfill it" is already 403.

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