I know that HTTP is hyper text transfer protocol, and I know that's how (along with HTTPS) one accesses a website. However, what does just a // do? For instance, to access Google's copy of jQuery, one would use the url //ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js, as opposed to http://....
What exactly is the difference? What does just // indicate?
Thanks.
By saying on // it means use whatever protocol (IE: http vs https) your user is currently hittin for that resource.
So you don't have to worry about dealing with http: vs https: management yourself.
Avoiding potential browser security warnings. It would be good practice to stick with this approach.
For example: If your user is accessing http://yourdomain/ that script file would automatically be treated as http://ajax.googleapis.com/...
if your current request is http
//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js
will be treated as
http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js
if your current request is https
//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js
will be treated as
https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js
Related
I have an app that requires users to enter database passwords. These passwords will not be saved on the server, and the server does not need to remember anything about the database after the request. If it's my understanding, most web servers will log get requests, and the browser can as well (does it do this even for fetch() requests?). I do not want to put databases at risk, but I also understand that you should not use a body in GET requests.
I am also not creating resources, so from what I also understand, I should not be using a POST request. Is there a safe way to send a get request with the password (over https) that makes sure it is not logged on the server? This would be an app that anyone could start - so I have no idea what their server configuration could be so I couldn't specifically disable it on one server to ignore it.
so from what I also understand, I should not be using a POST request.
Your understanding is incorrect. POST is the appropriate verb when none of the other verbs make sense. From the spec:
The POST method requests that the target resource process the representation enclosed in the request according to the resource's own specific semantics.
Put simply, that means POST does whatever the service says it does. It isn't safe, idempotent, or cacheable so there are disadvantages to just using it for everything, but the intent is for it to be the catch-all verb.
You should not use GET because, as you mentioned, you should not include a body and URLs often get logged, which would expose your credentials.
If the client for your app is going to be a browser you can just use https only cookies to handle the authentication flow. In case if you want it to extend or use it in any other type of client, you can use the Authorization HTTP header.
I am creating a REST API in Go, and I want to build URLs to other resources in my replies.
Based on the http.Response I can get the Host and URL.
However, how would I go about getting the transport scheme used by the server? http or https?
I attemped to check if server.TLSConfig is nil and then assuming it is using http since it says this in the documentation for http.Server:
TLSConfig *tls.Config // optional TLS config, used by ListenAndServeTLS
But it turns out this exists even when I do not run the server with ListenAndServeTLS.
Or is this way of building my URLs the wrong way of doing things? Is there some other normal way of doing this?
My preferred solution when running http and https is just to run a simple listener on :80 that redirects all traffic to https. Then any real traffic can be assumed to be https.
Alternately I believe you can access a request's URL at req.URL.Scheme to see the protocol.
Or do you mean for the entire application? If you accept configuration to switch between http and https, then can't you look at that and see which they chose? I guess I'm missing some context maybe.
It is also common practice for apps to take a baseURL via flag or config to generate external urls with.
I need to send different resources (specially images) for same urls depending on a complex logic based on different factors (cookie, IP, time, random). I want to take advantage of CDNs (cache, availability, proximity). So, I want this CDN to make a call to my server in order to decide which resource serve to any request. It is very important to not use redirects, so the user will never see a 30X status code.
For clarification:
User makes a request to http://resources.mydomain.com/img/a.jpg, which domain is under CDN
CDN makes a call to my server, sending url requested, cookies and user IP
My server returns the name of the real resource to serve (http://hidden.mydomain.com/img/a-version3.jpg)
CDN requests that image if not in cache
CDN responds to user request sending a-version3.jpg data, but without any redirect
Is it possible using any current commercial solution?
Yes, I think it is already supported by CDNetworks long time ago.
It is called "Origin Logic Control" now. You can check the description from http://www.cdnetworks.com/wp-content/uploads/2013/08/CDNetworks-ContentAccel-DS-EN2.pdf:
Allows a customer’s domain to require checking with the origin on every request.
You can return a special HTTP header (or special HTTP body, I am not sure now) to tell CDNetworks to return resources directly (and using cached version if available), not 30x status code.
You can enable Redirect Chasing to get what you are looking for. Alternatively, look at the Akamai blog post on Edge Redirect for a faster option.
My question might sound stupid, but I just wanted to be sure:
Is it possible to send an HTTP response before having the request for that resource?
Say for example you have an HTML page index.html that only shows a picture called img.jpg.
Now, if your server knows that a visitor will request the HTML file and then the jpg image every time:
Would it be possible for the server to send the image just after the HTML file to save time?
I know that HTTP is a synchronous protocol, so in theory it should not work, but I just wanted someone to confirm it (or not).
A recent post by Jacques Mattheij, referencing your very question, claims that although HTTP was designed as a synchronous protocol, the implementation was not. In practise the browser (he doesn't specify which exactly) accepts answers to requests have not been sent yet.
On the other hand, if you are looking to something less hacky, you could have a look at :
push techniques that allows the server to send content to the browser. The modern implementation that replace long-polling/Comet "hacks" are the websockets. You may want to have a look at socket.io also.
Alternatively you may want to have a look at client-side routing. Some implementations combine this with caching techniques (like in derby.js I believe).
If someone requests /index.html and you send two responses (one for /index.html and the other for /img.jpg), how do you know the recipient will get the two responses and know what to do with them before the second request goes in?
The problem is not really with the sending. The problem is with the receiver possibly getting unexpected data.
One other issue is that you're denying the client the ability to use HTTP caching tools like If-Modified-Since and If-None-Match (i.e. the client might not want /img.jpg to be sent because it already has a cached copy).
That said, you can approximate the server-push benefits by using Comet techniques. But that is much more involved than simply anticipating incoming HTTP requests.
You'll get a better result by caching resources effectively, i.e. setting proper cache headers and configuring your web server for caching. You can also inline images using base 64 encoding, if that's a specific concern.
You can also look at long polling javascript solutions.
You're looking for server push: it isn't available in HTTP. Protocols like SPDY have it, but you're out of luck if you're restricted to HTTP.
I don't think it is possible to mix .html and image in the same HTTP response. As for sending image data 'immediately', right after the first request - there is a concept of 'static resources' which could be of help (but it will require client to create a new reqest for a specific resource).
There are couple of interesting things mentioned in the the article.
No it is not possible.
The first line of the request holds the resource being requested so you wouldn't know what to respond with unless you examined the bytes (at least one line's worth) of the request first.
No. HTTP is defined as a request/response protocol. One request: one response. Anything else is not HTTP, it is something else, and you would have to specify it properly and implement it completely at both ends.
I have a stylesheet that loads images from an external domain and I need it to load from https:// from secure order pages and http:// from other pages, based on the current URL. I found that starting the URL with a double slash inherits the current protocol. Do all browsers support this technique?
HTML ex:
<img src="//cdn.domain.example/logo.png" />
CSS ex:
.class { background: url(//cdn.domain.example/logo.png); }
If the browser supports RFC 1808 Section 4, RFC 2396 Section 5.2, or RFC 3986 Section 5.2, then it will indeed use the page URL's scheme for references that begin with "//".
When used on a link or #import, IE7/IE8 will download the file twice per http://paulirish.com/2010/the-protocol-relative-url/
Update from 2014:
Now that SSL is encouraged for everyone and doesn’t have performance concerns, this technique is now an anti-pattern. If the asset you need is available on SSL, then always use the https:// asset.
One downside occurs if your URLs are viewed outside the context of a web page. For example, an email message sitting in an email client (say, Outlook) effectively has no URL, and when you're viewing a message containing a protocol-relative URL, there is no obvious protocol context at all (the message itself is independent of the protocol used to fetch it, whether it's POP3, IMAP, Exchange, uucp or whatever) so the URL has no protocol to be relative to. I've not investigated compatibility with email clients to see what they do when presented with a missing protocol handler - I'm guessing that most will take a guess at http. Apple Mail refuses to let you enter a URL without a protocol. It's analogous to the way that relative URLs do not work in email because of a similarly missing context.
Similar problems could occur in other non-HTTP contexts such as in tweets, SMS messages, Word documents etc.
The more general explanation is that anonymous protocol URLs cannot work in isolation; there must be a relevant context. In a typical web page it's thus fine to pull in a script library that way, but any external links should always specify a protocol. I did try one simple test: //stackoverflow.com maps to file:///stackoverflow.com in all browsers I tried it in, so they really don't work by themselves.
The reason could be to provide portable web pages. If the outer page is not transported encrypted (http), why should the linked scripts be encrypted? This seems to be an unnecessary performance loss. In case, the outer page is securely transported encrypted (https), then the linked content should be encrypted, too. If the page is encrypted, the linked content not, IE seems to issue a Mixed Content warning. The reason is that an attacker can manipulate the scripts on the way. See http://ie.microsoft.com/testdrive/Browser/MixedContent/Default.html?o=1 for a longer discussion.
The HTTPS Everywhere campaign from the EFF suggests to use https whenever possible. We have the server capacity these days to serve web pages always encrypted.
Just for completeness. This was mentioned in another thread:
The "two forward slashes" are a common shorthand for "whatever protocol is being used right now"
if (plain http environment) {
use 'http://example.com/my-resource.js'
} else {
use 'https://example.com/my-resource.js'
}
Please check the full thread.
It seems to be a pretty common technique now. There is no downside, it only helps to unify the protocol for all assets on the page so should be used wherever possible.