[http] CORS Access-Control-Allow-Headers wildcard being ignored?

I am having trouble getting a cross domain CORS request to work correctly using Chrome.

Request Headers:

Accept:*/*
Accept-Charset:ISO-8859-1,utf-8;q=0.7,*;q=0.3
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-US,en;q=0.8
Access-Control-Request-Headers:origin, content-type
Access-Control-Request-Method:POST
Connection:keep-alive
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4

Response headers:

Access-Control-Allow-Headers:*
Access-Control-Allow-Origin:*
Allow:GET, POST, OPTIONS
Content-Length:0
Date:Tue, 30 Oct 2012 20:04:28 GMT
Server:BaseHTTP/0.3 Python/2.7.3

Error:

XMLHttpRequest cannot load domain. Request header field Content-Type is not allowed by Access-Control-Allow-Headers.

And the python code serving the options request is:

self.send_response(200)
self.send_header('Allow', 'GET, POST, OPTIONS')
self.send_header('Access-Control-Allow-Origin', '*')
self.send_header('Access-Control-Allow-Headers', '*')
self.send_header('Content-Length', '0')
self.end_headers()

It seems the Access-Control-Allow-Origin wildcard is being ignored?

I found that Access-Control-Allow-Headers: * should be set ONLY for OPTIONS request. If you return it for POST request then browser cancel the request (at least for chrome)

The following PHP code works for me

// Allow CORS
if (isset($_SERVER['HTTP_ORIGIN'])) {
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
    header('Access-Control-Allow-Credentials: true');    
    header("Access-Control-Allow-Methods: GET, POST, OPTIONS"); 
}   
// Access-Control headers are received during OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
    header("Access-Control-Allow-Headers: *");
}

I found similar questions with some misleading response:

• Server thread says that this is 2 years bug of chrome: Access-Control-Allow-Headers does not match with localhost. It's wrong: I can use CORS to my local server with Post normally
• Access-Control-Allow-Headers does accept wildcards. It's also wrong, wildcard works for me (I tested only with Chrome)

This take me half day to figure out the issue.

Happy coding

here's the incantation for nginx, inside a

location / {
    # Simple requests
    if ($request_method ~* "(GET|POST)") {
      add_header "Access-Control-Allow-Origin"  *;
    }

    # Preflighted requests
    if ($request_method = OPTIONS ) {
      add_header "Access-Control-Allow-Origin"  *;
      add_header "Access-Control-Allow-Methods" "GET, POST, OPTIONS, HEAD";
      add_header "Access-Control-Allow-Headers" "Authorization, Origin, X-Requested-With, Content-Type, Accept";
    }

}

Quoted from monsur,

The Access-Control-Allow-Headers header does not allow wildcards. It must be an exact match: http://www.w3.org/TR/cors/#access-control-allow-headers-response-header.

So here is my php solution.

if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
  $headers=getallheaders();
  @$ACRH=$headers["Access-Control-Request-Headers"];
  header("Access-Control-Allow-Headers: $ACRH");
}

Those CORS headers do not support * as value, the only way is to replace * with this:

Accept, Accept-CH, Accept-Charset, Accept-Datetime, Accept-Encoding, Accept-Ext, Accept-Features, Accept-Language, Accept-Params, Accept-Ranges, Access-Control-Allow-Credentials, Access-Control-Allow-Headers, Access-Control-Allow-Methods, Access-Control-Allow-Origin, Access-Control-Expose-Headers, Access-Control-Max-Age, Access-Control-Request-Headers, Access-Control-Request-Method, Age, Allow, Alternates, Authentication-Info, Authorization, C-Ext, C-Man, C-Opt, C-PEP, C-PEP-Info, CONNECT, Cache-Control, Compliance, Connection, Content-Base, Content-Disposition, Content-Encoding, Content-ID, Content-Language, Content-Length, Content-Location, Content-MD5, Content-Range, Content-Script-Type, Content-Security-Policy, Content-Style-Type, Content-Transfer-Encoding, Content-Type, Content-Version, Cookie, Cost, DAV, DELETE, DNT, DPR, Date, Default-Style, Delta-Base, Depth, Derived-From, Destination, Differential-ID, Digest, ETag, Expect, Expires, Ext, From, GET, GetProfile, HEAD, HTTP-date, Host, IM, If, If-Match, If-Modified-Since, If-None-Match, If-Range, If-Unmodified-Since, Keep-Alive, Label, Last-Event-ID, Last-Modified, Link, Location, Lock-Token, MIME-Version, Man, Max-Forwards, Media-Range, Message-ID, Meter, Negotiate, Non-Compliance, OPTION, OPTIONS, OWS, Opt, Optional, Ordering-Type, Origin, Overwrite, P3P, PEP, PICS-Label, POST, PUT, Pep-Info, Permanent, Position, Pragma, ProfileObject, Protocol, Protocol-Query, Protocol-Request, Proxy-Authenticate, Proxy-Authentication-Info, Proxy-Authorization, Proxy-Features, Proxy-Instruction, Public, RWS, Range, Referer, Refresh, Resolution-Hint, Resolver-Location, Retry-After, Safe, Sec-Websocket-Extensions, Sec-Websocket-Key, Sec-Websocket-Origin, Sec-Websocket-Protocol, Sec-Websocket-Version, Security-Scheme, Server, Set-Cookie, Set-Cookie2, SetProfile, SoapAction, Status, Status-URI, Strict-Transport-Security, SubOK, Subst, Surrogate-Capability, Surrogate-Control, TCN, TE, TRACE, Timeout, Title, Trailer, Transfer-Encoding, UA-Color, UA-Media, UA-Pixels, UA-Resolution, UA-Windowpixels, URI, Upgrade, User-Agent, Variant-Vary, Vary, Version, Via, Viewport-Width, WWW-Authenticate, Want-Digest, Warning, Width, X-Content-Duration, X-Content-Security-Policy, X-Content-Type-Options, X-CustomHeader, X-DNSPrefetch-Control, X-Forwarded-For, X-Forwarded-Port, X-Forwarded-Proto, X-Frame-Options, X-Modified, X-OTHER, X-PING, X-PINGOTHER, X-Powered-By, X-Requested-With

.htaccess Example (CORS Included):

<IfModule mod_headers.c>
  Header unset Connection
  Header unset Time-Zone
  Header unset Keep-Alive
  Header unset Access-Control-Allow-Origin
  Header unset Access-Control-Allow-Headers
  Header unset Access-Control-Expose-Headers
  Header unset Access-Control-Allow-Methods
  Header unset Access-Control-Allow-Credentials

  Header set   Connection                         keep-alive
  Header set   Time-Zone                          "Asia/Jerusalem"
  Header set   Keep-Alive                         timeout=100,max=500
  Header set   Access-Control-Allow-Origin        "*"
  Header set   Access-Control-Allow-Headers       "Accept, Accept-CH, Accept-Charset, Accept-Datetime, Accept-Encoding, Accept-Ext, Accept-Features, Accept-Language, Accept-Params, Accept-Ranges, Access-Control-Allow-Credentials, Access-Control-Allow-Headers, Access-Control-Allow-Methods, Access-Control-Allow-Origin, Access-Control-Expose-Headers, Access-Control-Max-Age, Access-Control-Request-Headers, Access-Control-Request-Method, Age, Allow, Alternates, Authentication-Info, Authorization, C-Ext, C-Man, C-Opt, C-PEP, C-PEP-Info, CONNECT, Cache-Control, Compliance, Connection, Content-Base, Content-Disposition, Content-Encoding, Content-ID, Content-Language, Content-Length, Content-Location, Content-MD5, Content-Range, Content-Script-Type, Content-Security-Policy, Content-Style-Type, Content-Transfer-Encoding, Content-Type, Content-Version, Cookie, Cost, DAV, DELETE, DNT, DPR, Date, Default-Style, Delta-Base, Depth, Derived-From, Destination, Differential-ID, Digest, ETag, Expect, Expires, Ext, From, GET, GetProfile, HEAD, HTTP-date, Host, IM, If, If-Match, If-Modified-Since, If-None-Match, If-Range, If-Unmodified-Since, Keep-Alive, Label, Last-Event-ID, Last-Modified, Link, Location, Lock-Token, MIME-Version, Man, Max-Forwards, Media-Range, Message-ID, Meter, Negotiate, Non-Compliance, OPTION, OPTIONS, OWS, Opt, Optional, Ordering-Type, Origin, Overwrite, P3P, PEP, PICS-Label, POST, PUT, Pep-Info, Permanent, Position, Pragma, ProfileObject, Protocol, Protocol-Query, Protocol-Request, Proxy-Authenticate, Proxy-Authentication-Info, Proxy-Authorization, Proxy-Features, Proxy-Instruction, Public, RWS, Range, Referer, Refresh, Resolution-Hint, Resolver-Location, Retry-After, Safe, Sec-Websocket-Extensions, Sec-Websocket-Key, Sec-Websocket-Origin, Sec-Websocket-Protocol, Sec-Websocket-Version, Security-Scheme, Server, Set-Cookie, Set-Cookie2, SetProfile, SoapAction, Status, Status-URI, Strict-Transport-Security, SubOK, Subst, Surrogate-Capability, Surrogate-Control, TCN, TE, TRACE, Timeout, Title, Trailer, Transfer-Encoding, UA-Color, UA-Media, UA-Pixels, UA-Resolution, UA-Windowpixels, URI, Upgrade, User-Agent, Variant-Vary, Vary, Version, Via, Viewport-Width, WWW-Authenticate, Want-Digest, Warning, Width, X-Content-Duration, X-Content-Security-Policy, X-Content-Type-Options, X-CustomHeader, X-DNSPrefetch-Control, X-Forwarded-For, X-Forwarded-Port, X-Forwarded-Proto, X-Frame-Options, X-Modified, X-OTHER, X-PING, X-PINGOTHER, X-Powered-By, X-Requested-With"
  Header set   Access-Control-Expose-Headers      "Accept, Accept-CH, Accept-Charset, Accept-Datetime, Accept-Encoding, Accept-Ext, Accept-Features, Accept-Language, Accept-Params, Accept-Ranges, Access-Control-Allow-Credentials, Access-Control-Allow-Headers, Access-Control-Allow-Methods, Access-Control-Allow-Origin, Access-Control-Expose-Headers, Access-Control-Max-Age, Access-Control-Request-Headers, Access-Control-Request-Method, Age, Allow, Alternates, Authentication-Info, Authorization, C-Ext, C-Man, C-Opt, C-PEP, C-PEP-Info, CONNECT, Cache-Control, Compliance, Connection, Content-Base, Content-Disposition, Content-Encoding, Content-ID, Content-Language, Content-Length, Content-Location, Content-MD5, Content-Range, Content-Script-Type, Content-Security-Policy, Content-Style-Type, Content-Transfer-Encoding, Content-Type, Content-Version, Cookie, Cost, DAV, DELETE, DNT, DPR, Date, Default-Style, Delta-Base, Depth, Derived-From, Destination, Differential-ID, Digest, ETag, Expect, Expires, Ext, From, GET, GetProfile, HEAD, HTTP-date, Host, IM, If, If-Match, If-Modified-Since, If-None-Match, If-Range, If-Unmodified-Since, Keep-Alive, Label, Last-Event-ID, Last-Modified, Link, Location, Lock-Token, MIME-Version, Man, Max-Forwards, Media-Range, Message-ID, Meter, Negotiate, Non-Compliance, OPTION, OPTIONS, OWS, Opt, Optional, Ordering-Type, Origin, Overwrite, P3P, PEP, PICS-Label, POST, PUT, Pep-Info, Permanent, Position, Pragma, ProfileObject, Protocol, Protocol-Query, Protocol-Request, Proxy-Authenticate, Proxy-Authentication-Info, Proxy-Authorization, Proxy-Features, Proxy-Instruction, Public, RWS, Range, Referer, Refresh, Resolution-Hint, Resolver-Location, Retry-After, Safe, Sec-Websocket-Extensions, Sec-Websocket-Key, Sec-Websocket-Origin, Sec-Websocket-Protocol, Sec-Websocket-Version, Security-Scheme, Server, Set-Cookie, Set-Cookie2, SetProfile, SoapAction, Status, Status-URI, Strict-Transport-Security, SubOK, Subst, Surrogate-Capability, Surrogate-Control, TCN, TE, TRACE, Timeout, Title, Trailer, Transfer-Encoding, UA-Color, UA-Media, UA-Pixels, UA-Resolution, UA-Windowpixels, URI, Upgrade, User-Agent, Variant-Vary, Vary, Version, Via, Viewport-Width, WWW-Authenticate, Want-Digest, Warning, Width, X-Content-Duration, X-Content-Security-Policy, X-Content-Type-Options, X-CustomHeader, X-DNSPrefetch-Control, X-Forwarded-For, X-Forwarded-Port, X-Forwarded-Proto, X-Frame-Options, X-Modified, X-OTHER, X-PING, X-PINGOTHER, X-Powered-By, X-Requested-With"
  Header set   Access-Control-Allow-Methods       "CONNECT, DEBUG, DELETE, DONE, GET, HEAD, HTTP, HTTP/0.9, HTTP/1.0, HTTP/1.1, HTTP/2, OPTIONS, ORIGIN, ORIGINS, PATCH, POST, PUT, QUIC, REST, SESSION, SHOULD, SPDY, TRACE, TRACK"
  Header set   Access-Control-Allow-Credentials   "true"

  Header set DNT "0"
  Header set Accept-Ranges "bytes"
  Header set Vary "Accept-Encoding"
  Header set X-UA-Compatible "IE=edge,chrome=1"
  Header set X-Frame-Options "SAMEORIGIN"
  Header set X-Content-Type-Options "nosniff"
  Header set X-Xss-Protection "1; mode=block"
</IfModule>

F.A.Q:

• Why Access-Control-Allow-Headers, Access-Control-Expose-Headers, Access-Control-Allow-Methods values are super long?

  Those do not support the * syntax, so I've collected the most common (and exotic) headers from around the web, in various formats #1 #2 #3 _{(and I will update the list from time to time)}

• Why do you use Header unset ______ syntax?

  GoDaddy servers (which my website is hosted on..) have a weird bug where if the headers are already set, the previous value will join the existing one.. (instead of replacing it) this way I "pre-clean" existing values _{(really just a a quick && dirty solution)}

• Is it safe for me to use 'as-is'?

  Well.. mostly the answer would be YES since the .htaccess is limiting the headers to the scripts (PHP, HTML, ...) and resources (.JPG, .JS, .CSS) served from the following "folder"-location. You optionally might want to remove the Access-Control-Allow-Methods lines. _{Also Connection, Time-Zone, Keep-Alive and DNT, Accept-Ranges, Vary, X-UA-Compatible, X-Frame-Options, X-Content-Type-Options and X-Xss-Protection are just a suggestion I'm using for my online-service.. feel free to remove those too...}

_{taken from my comment above}