Justin is correct. They may have been trying to avoid the client POST to the token endpoint with the code.
That is a separate issue from the question of using a fragment encoded GET 302 or a JS POST redirect to return from the authorization endpoint. The response via the browser is smaller and faster if you are using code. The direct call via the back channel from the client to the server should not be a big deal in reality. If they are larger than Google and have a real performance issue we can talk. In the mean time for server based clients the recommendation is to use a confidential client with code. John B. > On Jul 1, 2016, at 5:01 PM, Oleg Gryb <oleg_g...@yahoo.com> wrote: > > AFAIR, they were talking about cost of this additional POST on the server > side, which was not good for high volume traffic (millions requests per day). > I'll try to dig it out to find more details. > > > From: Liyu Yi <liy...@gmail.com> > To: John Bradley <ve7...@ve7jtb.com> > Cc: Oleg Gryb <o...@gryb.info>; Jim Manico <j...@manicode.com>; > "oauth@ietf.org" <oauth@ietf.org> > Sent: Friday, July 1, 2016 1:42 PM > Subject: Re: [OAUTH-WG] Security concern for URI fragment as Implicit grant > > BTW, I do not see any significant performance concerns for post. Parsing and > executing the Javascript logic for post operation will be on the client side, > no extra server load is introduced. > > Plus post will remove the size restriction of the URL length. > > -- Liyu > > On Fri, Jul 1, 2016 at 1:35 PM, Liyu Yi <liy...@gmail.com > <mailto:liy...@gmail.com>> wrote: > Thanks for the great comments and advices. > > I think it is a good idea for the working group to revise the fragment part > in the spec, since there might be public available tools already implemented > this approach and people can end up with a solution with serious security > loopholes. > > The re-append issue can be mitigate by a logic on Resource Server which > carefully re-writes/removes the fragment in any redirect, if the the redirect > can not be avoided. > > -- Liyu > > > On Fri, Jul 1, 2016 at 11:33 AM, John Bradley <ve7...@ve7jtb.com > <mailto:ve7...@ve7jtb.com>> wrote: > This behaviour started changing around 2011 > > From HTTP/1.1 > See https://tools.ietf.org/html/rfc7231#section-7.1.2 > <https://tools.ietf.org/html/rfc7231#section-7.1.2>I > f the Location value provided in a 3xx (Redirection) response does > not have a fragment component, a user agent MUST process the > redirection as if the value inherits the fragment component of the > URI reference used to generate the request target (i.e., the > redirection inherits the original reference's fragment, if any). > > For example, a GET request generated for the URI reference > "http://www.example.org/~tim <http://www.example.org/~tim>" might result > in a 303 (See Other) > response containing the header field: > > Location: /People.html#tim > > which suggests that the user agent redirect to > "http://www.example.org/People.html#tim > <http://www.example.org/People.html#tim>” > > Likewise, a GET request generated for the URI reference > "http://www.example.org/index.html#larry > <http://www.example.org/index.html#larry>" might result in a 301 > (Moved Permanently) response containing the header field: > > Location: http://www.example.net/index.html > <http://www.example.net/index.html> > > which suggests that the user agent redirect to > "http://www.example.net/index.html#larry > <http://www.example.net/index.html#larry>", preserving the original > fragment identifier. > > > This blog also explores the change. > https://blogs.msdn.microsoft.com/ieinternals/2011/05/16/url-fragments-and-redirects/ > > <https://blogs.msdn.microsoft.com/ieinternals/2011/05/16/url-fragments-and-redirects/> > > >> On Jul 1, 2016, at 1:05 PM, Oleg Gryb <oleg_g...@yahoo.com >> <mailto:oleg_g...@yahoo.com>> wrote: >> >> "Browsers now re-append fragments across 302 redirects unless they are >> explicitly cleared this makes fragment encoding less safe than it was when >> originally specified" - thanks Jim. Looks like a good reason for vetting >> this flow out. >> >> John, >> Please provide more details/links about re-appending fragments. >> >> Thanks, >> Oleg. >> >> >> From: Jim Manico <j...@manicode.com <mailto:j...@manicode.com>> >> To: Oleg Gryb <o...@gryb.info <mailto:o...@gryb.info>> >> Cc: "oauth@ietf.org <mailto:oauth@ietf.org>" <oauth@ietf.org >> <mailto:oauth@ietf.org>>; Liyu Yi <liy...@gmail.com >> <mailto:liy...@gmail.com>> >> Sent: Thursday, June 30, 2016 10:25 PM >> Subject: Re: [OAUTH-WG] Security concern for URI fragment as Implicit grant >> >> Oleg! Hello! Great to see you pop up here with a similar concern. >> >> John Bradley just answered this thread with the details I was looking for >> (thanks John, hat tip your way). >> >> He also mentioned details about fragment leakage: >> >> "Browsers now re-append fragments across 302 redirects unless they are >> explicitly cleared this makes fragment encoding less safe than it was when >> originally specified" >> >> Again, I'm new here but I'm grateful for this conversation. >> >> Aloha, >> -- >> Jim Manico >> @Manicode >> >> On Jul 1, 2016, at 1:24 AM, Oleg Gryb <oleg_g...@yahoo.com >> <mailto:oleg_g...@yahoo.com>> wrote: >> >>> We've discussed access tokens in URI back in 2010 >>> (https://www.ietf.org/mail-archive/web/oauth/current/msg04043.html >>> <https://www.ietf.org/mail-archive/web/oauth/current/msg04043.html>). There >>> were two major objectives when I was saying that it's not secure: >>> >>> 1. Fragment is not sent to a server by a browser. When I've asked if this >>> is true for every browser in the world, nobody was able to answer. >>> 2. Replacing with POST would mean a significant performance impact in some >>> high volume implementations (I think it was Goole folks who were saying >>> this, but I don't remember now). >>> >>> AFAIR, nobody was arguing about browsing history, so it's valid. >>> >>> So, 6 years later we're at square one with this and I hope that this time >>> the community will be more successful with getting rid of secrets in URL. >>> >>> BTW, Jim, if you can come up with other scenarios when fragments can leak, >>> please share. It'll probably help the community with solving this problem >>> faster than in 6 years. >>> >>> Thanks, >>> Oleg. >>> >>> >>> From: Jim Manico <j...@manicode.com <mailto:j...@manicode.com>> >>> To: Liyu Yi <liy...@gmail.com <mailto:liy...@gmail.com>>; oauth@ietf.org >>> <mailto:oauth@ietf.org> >>> Sent: Wednesday, June 29, 2016 7:30 AM >>> Subject: Re: [OAUTH-WG] Security concern for URI fragment as Implicit grant >>> >>> > Shouldn’t it be more secure if we change to use a post method for access >>> > token, similar to the SAML does? >>> I say yes. But please note I'm very new at this and someone with more >>> experience will have more to say or correct my comments. >>> Here are a few more details to consider. >>> 1) OAuth is a framework and not a standard, per se. Different authorization >>> servers will have different implementations that are not necessarily >>> compatible with other service providers. So there is no standard to break, >>> per se. >>> 2) Sensitive data in a URI is a bad idea. They leak all over the place even >>> over HTTPS. Even in fragments. >>> 3) Break the "rules" and find a way to submit sensitive data like access >>> tokens, session information or any other (even short term) sensitive data >>> in a secure fashion. This includes POST, JSON data payloads over PUT/PATCH >>> and other verbs - all over well configured HTTPS. >>> 4) If you really must submit sensitive data over GET , consider JWT/JWS/JWE >>> (with limited scopes/lifetimes) to provide message level confidentiality >>> and integrity. >>> Aloha, >>> Jim Manico >>> Manicode Security >>> https://www.manicode.com <https://www.manicode.com/> >>> On 6/27/16 9:30 PM, Liyu Yi wrote: >>>> While we are working on a project with OAuth2 implementation, one question >>>> arises from our engineers. >>>> We noticed at >>>> <https://tools.ietf.org/html/draft-ietf-oauth-v2-31#page-30>https://tools.ietf.org/html/draft-ietf-oauth-v2-31#page-30 >>>> <https://tools.ietf.org/html/draft-ietf-oauth-v2-31#page-30>, it is >>>> specified that >>>> >>>> (C) Assuming the resource owner grants access, the authorization >>>> server redirects the user-agent back to the client using the >>>> redirection URI provided earlier. The redirection URI includes >>>> the access token in the URI fragment. >>>> >>>> For my understanding, the browser keeps the URI fragment in the history, >>>> and this introduces unexpected exposure of the access token. A user >>>> without authorization for the resource can get the access token as long as >>>> he has the access to the browser. This can happen in a shared computer in >>>> library, or for an IT staff who works on other employee’s computer. >>>> >>>> Shouldn’t it be more secure if we change to use a post method for access >>>> token, similar to the SAML does? >>>> I feel there might be something I missed here. Any advices will be >>>> appreciated. >>>> >>>> >>>> _______________________________________________ >>>> OAuth mailing list >>>> OAuth@ietf.org <mailto:OAuth@ietf.org> >>>> https://www.ietf.org/mailman/listinfo/oauth >>>> <https://www.ietf.org/mailman/listinfo/oauth> >>> >>> -- >>> >>> _______________________________________________ >>> OAuth mailing list >>> OAuth@ietf.org <mailto:OAuth@ietf.org> >>> https://www.ietf.org/mailman/listinfo/oauth >>> <https://www.ietf.org/mailman/listinfo/oauth> >>> >>> >> >> _______________________________________________ >> OAuth mailing list >> OAuth@ietf.org <mailto:OAuth@ietf.org> >> https://www.ietf.org/mailman/listinfo/oauth >> <https://www.ietf.org/mailman/listinfo/oauth> >> >> > > > > >
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