Has Been Blocked By Cors Policy

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  1. From Origin Null Has Been Blocked By Cors Policy

Cross-origin resource sharing (CORS) is a mechanism that allows restricted resources on a web page to be requested from another domain outside the domain from which the first resource was served.[1] A web page may freely embed cross-origin images, stylesheets, scripts, iframes, and videos.[2] Certain 'cross-domain' requests, notably Ajax requests, are forbidden by default by the same-origin security policy.

CORS defines a way in which a browser and server can interact to determine whether or not it is safe to allow the cross-origin request.[3] It allows for more freedom and functionality than purely same-origin requests, but is more secure than simply allowing all cross-origin requests. The specification for CORS was originally published as a W3C Recommendation[4] but that document is obsolete.[5] The current actively-maintained specification that defines CORS is WHATWG's Fetch Living Standard.[6]

Nov 5, 2018 - Cross-Origin Resource Sharing (CORS) is a mechanism allowing (or. From origin 'has been blocked by CORS policy:. This redirection causes the AJAX request to become a CORS request since the destination domain changes and Azure AD by default does not allow cross origin request. Resolution The Application needs to check for the existence of the AppServiceAuthSession cookie or if the session is still authenticated before sending the AJAX request.

  • 4Headers

How CORS works[edit]

The CORS standard describes new HTTP headers which provide browsers a way to request remote URLs only when they have permission. Although some validation and authorization can be performed by the server, it is generally the browser's responsibility to support these headers and honor the restrictions they impose.

For Ajax and HTTP request methods that can modify data (usually HTTP methods other than GET, or for POST usage with certain MIME types), the specification mandates that browsers 'preflight' the request, soliciting supported methods from the server with an HTTP OPTIONS request method, and then, upon 'approval' from the server, sending the actual request with the actual HTTP request method. Servers can also notify clients whether 'credentials' (including Cookies and HTTP Authentication data) should be sent with requests.[7]

Simple example[edit]

Suppose a user visits http://www.example.com and the page attempts a cross-origin request to fetch the user's data from http://service.example.com. A CORS-compatible browser will attempt to make a cross-origin request to service.example.com as follows.

  1. The browser sends the OPTIONS request with an OriginHTTP header to service.example.com containing the domain that served the parent page:
  2. The server at service.example.com may respond with:
    • An Access-Control-Allow-Origin (ACAO) header in its response indicating which origin sites are allowed. For example: Since www.example.com matches the parent page, the browser then performs the cross-origin request.
    • An Access-Control-Allow-Origin (ACAO) header with a wildcard that allows all domains:
    • An error page if the server does not allow a cross-origin request

A wildcard same-origin policy is appropriate when a page or API response is considered completely public content and it is intended to be accessible to everyone, including any code on any site. For example, a freely-available web font on a public hosting service like Google Fonts.

A wildcard same-origin policy is also widely and appropriately used in the object-capability model, where pages have unguessable URLs and are meant to be accessible to anyone who knows the secret.

The value of '*' is special in that it does not allow requests to supply credentials, meaning it does not allow HTTP authentication, client-side SSL certificates, or cookies to be sent in the cross-domain request.[8]

Note that in the CORS architecture, the ACAO header is being set by the external web service (service.example.com), not the original web application server (www.example.com). Here, service.example.com uses CORS to permit the browser to authorize www.example.com to make requests to service.example.com.

Preflight example[edit]

When performing certain types of cross-domain Ajax requests, modern browsers that support CORS will insert an extra 'preflight' request to determine whether they have permission to perform the action.

If service.example.com is willing to accept the action, it may respond with the following headers:

From origin null has been blocked by cors policy

Headers[edit]

The HTTP headers that relate to CORS are

Request headers[edit]

  • Origin
  • Access-Control-Request-Method
  • Access-Control-Request-Headers

Response headers[edit]

  • Access-Control-Allow-Origin
  • Access-Control-Allow-Credentials
  • Access-Control-Expose-Headers
  • Access-Control-Max-Age
  • Access-Control-Allow-Methods
  • Access-Control-Allow-Headers

Browser support[edit]

CORS is supported by all browsers based on the following layout engines:

  • Blink- and Chromium-based browsers (Chrome 28+,[9][10]Opera 15+,[9]Amazon Silk, Android's 4.4+ WebView and Qt's WebEngine)
  • Gecko 1.9.1 (Firefox 3.5,[11] SeaMonkey 2.0[12]) and above.
  • MSHTML/Trident 6.0 (Internet Explorer 10) has native support.[13] MSHTML/Trident 4.0 & 5.0 (Internet Explorer 8 & 9) provide partial support via the XDomainRequest object.[1]
  • Presto-based browsers (Opera) implement CORS as of Opera 12.00[14] and Opera Mobile 12, but not Opera Mini.[15]
  • WebKit (Initial revision uncertain, Safari 4 and above,[1] Google Chrome 3 and above, possibly earlier).[16]
  • Microsoft Edge All versions. [17]

History[edit]

Cross-origin support was originally proposed by Matt Oshry, Brad Porter, and Michael Bodell of Tellme Networks in March 2004 for inclusion in VoiceXML 2.1[18] to allow safe cross-origin data requests by VoiceXML browsers. The mechanism was deemed general in nature and not specific to VoiceXML and was subsequently separated into an implementation NOTE.[19] The WebApps Working Group of the W3C with participation from the major browser vendors began to formalize the NOTE into a W3C Working Draft on track toward formal W3C Recommendation status.

In May 2006 the first W3C Working Draft was submitted.[20] In March 2009 the draft was renamed to 'Cross-Origin Resource Sharing'[21] and in January 2014 it was accepted as a W3C Recommendation.[22]

CORS vs JSONP[edit]

CORS can be used as a modern alternative to the JSONP pattern. While JSONP supports only the GET request method, CORS also supports other types of HTTP requests. Using CORS enables a web programmer to use regular XMLHttpRequest, which supports better error handling than JSONP. On the other hand, JSONP works on legacy browsers which predate CORS support. CORS is supported by most modern web browsers. Also, while JSONP can cause cross-site scripting (XSS) issues when the external site is compromised, CORS allows websites to manually parse responses to increase security.[3][23]

See also[edit]

References[edit]

  1. ^ abcon July 6, 2009 by Arun Ranganathan (2009-07-06). 'cross-site xmlhttprequest with CORS ✩ Mozilla Hacks – the Web developer blog'. Hacks.mozilla.org. Retrieved 2012-07-05.
  2. ^'Same-origin policy / Cross-origin network access'. MDN.
  3. ^ ab'Cross-domain Ajax with Cross-Origin Resource Sharing'. NCZOnline. Retrieved 2012-07-05.
  4. ^'Cross-Origin Resource Sharing'.
  5. ^'WebAppSec Working Group Minutes'.
  6. ^'Fetch Living Standard'.
  7. ^'cross-site xmlhttprequest with CORS'. MOZILLA. Retrieved 2012-09-05.
  8. ^Cross-Origin Resource Sharing. W3.org. Retrieved on 2014-04-12.
  9. ^ ab'Blink'. QuirksBlog. April 2013. Retrieved 4 April 2013.
  10. ^'Google going its own way, forking WebKit rendering engine'. Ars Technica. April 2013. Retrieved 4 April 2013.
  11. ^'HTTP access control (CORS) - MDN'. Developer.mozilla.org. Retrieved 2012-07-05.
  12. ^'Gecko - MDN'. Developer.mozilla.org. 2012-06-08. Retrieved 2012-07-05.
  13. ^Tony Ross; Program Manager; Internet Explorer (2012-02-09). 'CORS for XHR in IE10'. MSDN. Retrieved 2012-12-14.
  14. ^David Honneffer, Documentation Specialist (2012-06-14). '12.00 for UNIX Changelog'. Opera. Retrieved 2012-07-05.
  15. ^David Honneffer, Documentation Specialist (2012-04-23). 'Opera Software: Web specifications support in Opera Presto 2.10'. Opera.com. Retrieved 2012-07-05.
  16. ^'59940: Apple Safari WebKit Cross-Origin Resource Sharing Bypass'. Osvdb.org. Retrieved 2012-07-05.
  17. ^'Microsoft Edge deverloper's guide'.
  18. ^'Voice Extensible Markup Language (VoiceXML) 2.1'. W3.org. 2004-03-23. Retrieved 2012-07-05.
  19. ^'Authorizing Read Access to XML Content Using the <?access-control?> Processing Instruction 1.0'. W3.org. Retrieved 2012-07-05.
  20. ^'Authorizing Read Access to XML Content Using the <?access-control?> Processing Instruction 1.0 W3C - Working Draft 17 May 2006'. W3.org. Retrieved 17 August 2015.
  21. ^'Cross-Origin Resource Sharing - W3C Working Draft 17 March 2009'. W3.org. Retrieved 17 August 2015.
  22. ^'Cross-Origin Resource Sharing - W3C Recommendation 16 January 2014'. W3.org. Retrieved 17 August 2015.
  23. ^'When can I use... Cross Origin Resource Sharing'. caniuse.com. Retrieved 2012-07-12.

External links[edit]

  • Fetch Living Standard (the current specification for CORS)
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Cross-origin_resource_sharing&oldid=902210357'

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Comments

commented Oct 31, 2018

Hi,

I've an api in production using iris.

I've this configuration.

In front using chrome or firefox I get an error doing this :

The complete error :

Access to fetch at 'https://domain-name.com:8080/user/connect/' from origin 'http://10.18.206.202:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: Redirect is not allowed for a preflight request.

I allowed all origins in the cors configuration, tried using many IPs as sender (wifi IP, 127.0.0.1, localhost).
I also tried to add this in my initApp function :

What should I do to make it works?

commented Nov 1, 2018•
edited

Hello, you want help for a community-driven middleware from the iris-contrib/middleware repository, this is not the place for these things but the 1 line example tells you that you have to use the .AllowMethods('OPTIONS'), this is for the preflight request but I don't see that option at your code snippet, please try to add it and post here if that worked for you, thank you.

commented Nov 2, 2018•
edited

Hi,

Sorry for having posted that in the wrong place.

These are my routes

So even with this function it doesn't work.

Edit : I also use the last version of Iris.

commented Nov 2, 2018

Hi,

When you put .AllowMethods to a group of routes like this you will allow all these methods to passed for the routes that is part of that group, i.e userAPI.Post('connectcode', ...) will register for POST method but you are allowing it for GET, PUT, HEAD and DELETE (which I don't understand why). But anyway, again, the OPTIONS is missing from your code snippet.

Add .AllowMethods(iris.MethodOptions) to your userAPI.

From Origin Null Has Been Blocked By Cors Policy

commented Nov 3, 2018

Hi Kataras,

My bad, I misunderstood the function.

I add the .AllowMethods(iris.MethodOptions) and I get the same error.

here how it is now :
userAPI := api.App.Party('/user').AllowMethods(iris.MethodOptions)

Does it work for you ?

commented Nov 3, 2018•
edited

Hmmm yes it works here but it may be a js ajax request issue, but first please test that code snippet below, that worked for #847 (comment)

If that ^ does not work for you then it is a javascript fetch issue, if you read the mozzila's documentation at: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#Supplying_request_optionsyou will see that there is an option for cors, that is defaulted to 'same-origin' you have to change it to 'cors':

Thanks,
Gerasimos Maropoulos.

commented Nov 4, 2018•
edited

Hi Gerasimos,

Thank you for all your answers.
As you asked me I tried put the code you sent me in my user routes :

My Initialisation routes function looks like this :

I got the same error on the last version of chrome and firefox.
So I updated my fetch function to define the mode as cors.

Like this :

And still the same result, this error :

So I changed many parameters in the fetch function, trying also with axios, and still same error.

Actually the only way I found to received the request on the server was in setting the mode as no-cors.

In 2017 I used iris in back with reactjs in front, the same way I'm using it right now and it worked, I can't see what I changed.

I'll try tomorrow with a nodeJS server to check if it works.

Thank you,
Fantasim

commented Nov 4, 2018•
edited

Hi,

So as I said in the previous message, I tried with an express server with nodeJS and it works.
If you want to see my very basic express server :

I'm out of ideas to make it works with iris :/

commented Nov 6, 2018

Framework does not matter for headers and cors, just copy-paste carefully, without trailing spaces after commas and it will work, here you are:

commented Nov 6, 2018

Hi,

No It still doesn't work.
I even tried to start a new little iris project with a simple post request, that I installed on a distant server.

URL for the request : http://185.212.227.66:8082/v1/ if you want to try.

PS : Last year I used to use iris V6, so i tried to downgrade iris to use it with one of my old project.
So I used exactly the same fetch request (without the 'Access-Control-Allow-Origin', in header) and it works.

commented Nov 7, 2018

@Fantasim , do you want to join to our chat https://chat.iris-go.com and talk with me private (I need access to that url) to find out a solution? When we find a decent solution, and we will, we will push the solution down to the repository, sounds ok with you?

commented Nov 7, 2018

@kataras Send me a message when you are free, I'm on the chat with the same username than github.

commented Nov 8, 2018

I think you are calling wrong port.

commented Nov 22, 2018

@kataras has fixed the problem, it was a path problem :

If one day you meet the problem just use this option : here

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