On Apr 20, 2010, at 12:45 PM, Jeremy Orlow wrote:
Agreed. Can you give us a pointer to the email thread this decision
was made on?
Discussion was on the IETF hybi list (which is trying to standardize
the WebSocket protocol). I encourage anyone in the WebKit community
who is interested in WebSocket to join the hybi list: https://www.ietf.org/mailman/listinfo/hybi
On Tue, Apr 20, 2010 at 12:12 PM, Alex Russell
<slightly...@google.com> wrote:
Hate to ask a dumb question, but why MD5? Isn't it on its last legs as
a secure hash? New protocols should be avoiding it.
In the case of WebSocket protocol, the hash doesn't need to be
cryptographically secure. Forging the hash is not a consideration. To
give a rough outline, the hash is used like this:
1) The browser sends a few pieces of information to the server
(including the Origin, a string specifically identifying the WebSocket
protocol, etc).
2) The server combines some of this info and computes a hash.
3) The hash is returned to the client, which verifies it.
Steps 2 and 3 are the ones that use MD5. The reason for this handshake
is to defend against cross-protocol attacks. The server responds with
information based on unique parts of the request, to avoid the
likelihood that a response from a non-WebSocket server won't
accidentally look like a valid handshake. A hash is used to reduce the
risk that a server that just echoes back pieces of the response may
look like a valid handshake respnse.
I don't believe a cryptographically secure hash is needed here, it
could have been something as simple as CRC-32, for example. I think
the reason to pick MD5 was that it's well known and widely available
as a library for many popular programming languages.
Regards,
Maciej
On Tue, Apr 20, 2010 at 11:48 AM, Michael Nordman
<micha...@google.com> wrote:
> In webcore, should we use the same impl on all platforms rather
than use
> cryptdll on windows and md5.cc elsewhere?
> For chrome, I don't think we can have a dependency between
> WebKit/WebKit/chromium and /src/base/, and 'base' depending on
'webkit' also
> doesn't work. How can we avoid replicating the code? I guess having
> webcore's MD5 be platform specific could help us along those lines?
>
> On Tue, Apr 20, 2010 at 4:12 AM, Maciej Stachowiak <m...@apple.com>
wrote:
>>
>> On Apr 20, 2010, at 3:32 AM, Fumitoshi Ukai (鵜飼文敏) wrote:
>>
>> I'm implementing new protocol of WebSocket
>> ( http://www.whatwg.org/specs/web-socket-protocol/ ).
>> Since it now requires MD5 in handshake, I wonder how I could add
MD5 in
>> WebCore. For now, there is no MD5 in WebCore. It is in
>> WebKitTools/DumpRenderTree to get message digest of image file.
>> I'm thinking to add new header file as WebCore/platform/MD5.h,
which
>> provides the following functions.
>> struct MD5_CTX;
>> void MD5_Init(MD5_CTX*);
>> void MD5_Update(MD5_CTX*, unsigned char* input, unsigned length);
>> void MD5_Final(unsigned char hash[16], MD5_CTX*);
>> In Windows platform, it is implemented using "Cryptdll.dll". Is
it ok to
>> copy WebKitTools/DumpRenderTree/win/MD5.cpp to WebCore/platform/
win/MD5.cpp,
>> or move?
>> In Mac platform, it is provided by <CommonCrypto/CommonDigest.h>
with
>> #define COMMON_DIGEST_FOR_OPENSSL ?
>> In Chromium, there is chrome/src/base/md5.{h,cc}. Should I copy
this in
>> WebCore/platform/chromium, or add dependency to base from WebCore?
>> How about other ports? is it ok to link openssl or some other
library?
>> (or use implementation used in chromium?)
>> I'm also wonder I need to put these functions in namespace WebCore.
>>
>> If you put this code in WebCore, it should go in the WebCore
namespace. I
>> think it would also be a good idea to turn the API into something
more
>> WebCore-ish, something like:
>> namespace WebCore {
>> class MD5 {
>> MD5(); // what was MD5_Init
>> addBytes(uint8_t* input, size_t length); // what was
MD5_Update ;
>> or maybe this should take a Vector<uint8_t>?
>> Vector<uint8_t, 16> checksum(); // what was MD5_Final
>> };
>> }
>> (The key point being to match the coding style guidelines for
names, but
>> it also seems better to use a class here instead of a struct and
functions
>> that take a pointer to it.)
>> Regards,
>> Maciej
>>
>> _______________________________________________
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>> webkit-dev@lists.webkit.org
>> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
>>
>
>
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