<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div><br></div><div><br></div><div><span id="zwchr" data-marker="__DIVIDER__">----- On Mar 9, 2017, at 10:00 PM, Ingela Andin <ingela@andin.se> wrote:<br></span></div><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" data-mce-style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><div dir="ltr">Hi Andreas!<br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Mar 9, 2017 at 7:54 PM, Andreas Schultz <span dir="ltr"><<a href="mailto:aschultz@tpip.net" target="_blank" data-mce-href="mailto:aschultz@tpip.net">aschultz@tpip.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;" data-mce-style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">Hi Ingela,<br><br> I tried to understand the fragment reassembler in dtls_handshake.erl<br> and it seems that it is assuming that retransmissions will always use<br> the same record size.<br><br></blockquote><br><div>No it is not assuming that. It just does not care what the size is, it suppose</div><div>to just fill in the gaps (in the merge) until it has reasemmbled a whole. </div><div>Of course I have not written any specific test for it yet so I am not saying it</div><div>may not have bugs. </div></div></div></div></blockquote><div><br></div><div>I'm staring at dtls_handshake:merge_fragments/2 and I can't convince<br>myself that it will merge overlapping fragments.</div><div><br></div><div>Let's assume we have <<0,1,2>> and <4,5,6>>, the new fragment is <<2,3,4>>.</div><div>This would mean the following fragment records:</div><div><div><br></div><div>1: #handshake_fragment{fragment_offset = 0, fragment_length = 3, fragment = <<0,1,2>>}</div></div><div><div style="orphans: 2; text-align: start; text-indent: 0px; widows: 2; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial;"><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">2: #handshake_fragment{fragment_offset =<span class="Apple-converted-space"> 2</span>, fragment_length = 3,<span class="Apple-converted-space"> </span>fragment = <<2,3,4>>}</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial;"><div>3: #handshake_fragment{fragment_offset =<span class="Apple-converted-space"> 4</span>, fragment_length = 3,<span class="Apple-converted-space"> </span>fragment = <<4,5,6>>}</div></div><br></div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">IMHO <span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">merge_fragments will not merge fragment #1 and #2 (none of the conditions match),<br></span><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">the same goes for fragment #2 and #3.</span></div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"></span><br></div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">The expected output would be a fragment:</span></div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"></span><br></div><div style=""><span style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; orphans: 2; text-align: start; text-indent: 0px; widows: 2; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; float: none; display: inline !important;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"><span style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;" data-mce-style="color: #000000; font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"><span class="Apple-converted-space"> </span>#handshake_fragment{fragment_offset = 0, fragment_length = 6, fragment = <<0,1,2,3,4,5,6>>}</span></span></span><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; clear: both;" data-mce-style="clear: both;"><br></div><div style="clear: both;" data-mce-style="clear: both;"><br><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">I think the following (untested) change is needed:</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br data-mce-bogus="1"></div><div><div>diff --git a/lib/ssl/src/dtls_handshake.erl b/lib/ssl/src/dtls_handshake.erl</div><div>index fd1f969..245dc6e 100644</div><div>--- a/lib/ssl/src/dtls_handshake.erl</div><div>+++ b/lib/ssl/src/dtls_handshake.erl</div><div>@@ -464,10 +464,28 @@ merge_fragments(#handshake_fragment{</div><div> #handshake_fragment{</div><div> fragment_offset = CurrentOffSet,</div><div> fragment_length = CurrentLen,</div><div>- fragment = CurrentData}) when PreviousOffSet + PreviousLen == CurrentOffSet-></div><div>- Previous#handshake_fragment{</div><div>- fragment_length = PreviousLen + CurrentLen,</div><div>- fragment = <<PreviousData/binary, CurrentData/binary>>};</div><div>+ fragment = CurrentData})</div><div>+ when PreviousOffSet + PreviousLen >= CurrentOffSet andalso</div><div>+ PreviousOffSet + PreviousLen < CurrentOffSet + CurrentLength -></div><div>+ CurrentStart = PreviousOffSet + PreviousLen - CurrentOffSet,</div><div>+ <<_:CurrentStart/bytes, Data/binary>> = CurrentData,</div><div>+ Previous#handshake_fragment{</div><div>+ fragment_length = PreviousLen + CurrentLen - CurrentStart,</div><div>+ fragment = <<PreviousData/binary, Data/binary>>};</div><div>+%% already fully contained fragment</div><div>+merge_fragments(#handshake_fragment{</div><div>+ fragment_offset = PreviousOffSet, </div><div>+ fragment_length = PreviousLen,</div><div>+ fragment = PreviousData</div><div>+ } = Previous, </div><div>+ #handshake_fragment{</div><div>+ fragment_offset = CurrentOffSet,</div><div>+ fragment_length = CurrentLen,</div><div>+ fragment = CurrentData})</div><div>+ when PreviousOffSet + PreviousLen >= CurrentOffSet andalso</div><div>+ PreviousOffSet + PreviousLen >= CurrentOffSet + CurrentLength -></div><div>+ Previous;</div><div>+</div></div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br></div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Andreas</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br data-mce-bogus="1"></div><blockquote class="gmail_quote" style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 0px 0px 0px 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;" data-mce-style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">RFC 6347, Sect. 4.3.2 states:<br><br> > When a DTLS implementation receives a handshake message fragment, it<br> > MUST buffer it until it has the entire handshake message. DTLS<br> > implementations MUST be able to handle overlapping fragment ranges.<br> > This allows senders to retransmit handshake messages with smaller<br> > fragment sizes if the PMTU estimate changes.<br><br> Last time I looked at OpenSSL's DTLS sending side, it did exactly that.<br> It refragmented the handshake on retransmit to the minimum IP MTU.<br><br> From my understanding of the fragment merging logic, it will not merge<br> overlapping fragments (it might even become confused).<br><br> Am I missing something there?<br><br></blockquote><br><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">It is suppose to merge overlapping fragments. I am currently trying to get</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">all the basic tests going. I acctually merged some new code this week</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">with a few fixes and a lot more tests activated, however I doubt that the nighlty</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">tests drops a lot of packages....</div><br><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">There are still a lot to do but now I think we are getting there. And I had a lot of</div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">use of your code even the parts I did not use. I hope to get some quick check </div><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">tests going too in the long run.</div><br><div style="color: rgb(0, 0, 0); font-family: arial, helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Regards Ingela </div><br></div></div></div></div><blockquote style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" data-mce-style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><div dir="ltr"><div class="gmail_extra"></div></div><br></blockquote></div></div></body></html>