Re: Possible addition to file API
On 8/21/10 3:39 PM, J David Eisenberg wrote: Is it possible to extend the spec to allow a script to read any file that can been loaded as part of the HTML page, such as animg/? That would be a security hole, sorry. I understand there are good security reasons for restricting file reads; you don't want someone else's web page to be able to go willy-nilly through your local hard disk and send all the information back to the Bad Guys. But this scenario is different; if you have loaded animg/, you must already have read permission for it No. The _user_ has read permissions for it. Your site may well not. I'm just asking to be able to access its bits. Right; that's what you can't have. Note that if you _are_ allowed to have the image bits, you can just use XMLHttpRequest to get them, right? Precedent: think oflink rel=stylesheet href=blah.css/; you have access to all the elements in that file via the DOM, and there's no security issue involved, even if it's a cross-domain href. All the browsers I know that implement the CSSOM block cross-domain CSSOM access. A few now go further and block certain cross-domain CSS loads period. That's because it is *not* an arbitrary file on the user's local file system; it's one that the author has explicitly specified and is allowed to read. You seem to be assuming that the author who put in the link is the same entity who put up the CSS file. This is precisely the assumption that fails in the cross-domain case. I think my suggestion here meets the same criteria. Am I missing something obvious on the security front? Yes. Reading information cross-domain without explicit opt-in by the domain being read from is a no-no, generally. -Boris
Re: Possible addition to file API
Take a look at this discussion of XHR.responseBlob: http://lists.w3.org/Archives/Public/public-webapps/2010JulSep/0536.html Eric On Sat, Aug 21, 2010 at 12:39 PM, J David Eisenberg jdavid.eisenb...@gmail.com wrote: At present, the only way a web page can read a file's binary data via the File API (http://dev.w3.org/2006/webapi/FileAPI) is if the person reading the page enters the file name in an input type=file/. The API applies to only local files, if I read it correctly. Is it possible to extend the spec to allow a script to read any file that can been loaded as part of the HTML page, such as an img/? This extension would let web pages read the EXIF data of an image that is part of an img element; a very useful capability for web apps. Similarly, you could access metadata from a file destined for an audio or video element. The spec seems to suggest that this is possible: http://dev.w3.org/2006/webapi/FileAPI/#url , but is it implemented in any browsers? I understand there are good security reasons for restricting file reads; you don't want someone else's web page to be able to go willy-nilly through your local hard disk and send all the information back to the Bad Guys. But this scenario is different; if you have loaded an img/, you must already have read permission for it, and its data is there in the browser. I'm just asking to be able to access its bits. Precedent: think of link rel=stylesheet href=blah.css/; you have access to all the elements in that file via the DOM, and there's no security issue involved, even if it's a cross-domain href. That's because it is *not* an arbitrary file on the user's local file system; it's one that the author has explicitly specified and is allowed to read. I think my suggestion here meets the same criteria. Am I missing something obvious on the security front? The back story for this idea (you may safely skip this portion if you are not interested): My brother and I have just spent the past few days looking over several large boxes of photos that my mom had stored away. Most of them had nothing written on the back, so we had no idea of where or when the pictures were taken, nor who the people in them were, nor what the picture meant to Mom. Obviously, metadata matters. This told me that I need to start using the comments feature in GIMP to add descriptions to my photos. A few days ago, some of our family got together and I told my cousin George that I'm going to start doing this. He said that was nice, but the only way to get the data out is to use a program similar to the one that you used when editing the image, and most people won't have that. So I thought, You know, it would be great if you could get access to an img/'s EXIF data from the browser.
Possible addition to file API
At present, the only way a web page can read a file's binary data via the File API (http://dev.w3.org/2006/webapi/FileAPI) is if the person reading the page enters the file name in an input type=file/. The API applies to only local files, if I read it correctly. Is it possible to extend the spec to allow a script to read any file that can been loaded as part of the HTML page, such as an img/? This extension would let web pages read the EXIF data of an image that is part of an img element; a very useful capability for web apps. Similarly, you could access metadata from a file destined for an audio or video element. The spec seems to suggest that this is possible: http://dev.w3.org/2006/webapi/FileAPI/#url , but is it implemented in any browsers? I understand there are good security reasons for restricting file reads; you don't want someone else's web page to be able to go willy-nilly through your local hard disk and send all the information back to the Bad Guys. But this scenario is different; if you have loaded an img/, you must already have read permission for it, and its data is there in the browser. I'm just asking to be able to access its bits. Precedent: think of link rel=stylesheet href=blah.css/; you have access to all the elements in that file via the DOM, and there's no security issue involved, even if it's a cross-domain href. That's because it is *not* an arbitrary file on the user's local file system; it's one that the author has explicitly specified and is allowed to read. I think my suggestion here meets the same criteria. Am I missing something obvious on the security front? The back story for this idea (you may safely skip this portion if you are not interested): My brother and I have just spent the past few days looking over several large boxes of photos that my mom had stored away. Most of them had nothing written on the back, so we had no idea of where or when the pictures were taken, nor who the people in them were, nor what the picture meant to Mom. Obviously, metadata matters. This told me that I need to start using the comments feature in GIMP to add descriptions to my photos. A few days ago, some of our family got together and I told my cousin George that I'm going to start doing this. He said that was nice, but the only way to get the data out is to use a program similar to the one that you used when editing the image, and most people won't have that. So I thought, You know, it would be great if you could get access to an img/'s EXIF data from the browser.
