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<a href="https://gitlab.com/tatsuhiro-t" style="color: #1068bf;">Tatsuhiro Tsujikawa</a> created an issue: <a href="https://gitlab.com/gnutls/gnutls/-/issues/1403" style="color: #1068bf;">#1403</a>
</p>
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<h2 dir="auto" style="font-size: 1.5em; font-weight: 600; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-color: #eaeaea; border-bottom-style: solid; color: #303030; margin: 0 0 16px;" align="initial">
<a id="user-content-description-of-problem" class="anchor" href="#description-of-problem" aria-hidden="true" style="color: #1068bf; margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Description of problem:</h2>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">I often observed that boringssl early data got rejected by gnutls server due to ticket age:</p>
<blockquote dir="auto" style="font-size: inherit; color: #525252; padding-top: 0.5rem; padding-bottom: 0.5rem; padding-left: 1.5rem; box-shadow: inset 4px 0 0 0 #dbdbdb; border-top-width: 0; border-bottom-width: 0; border-right-width: 0; margin: 0.5rem 0;" align="initial">
<p style="color: inherit; line-height: 1.5; margin: 0;">gnutls[3]: ASSERT: tls13/anti_replay.c[_gnutls_anti_replay_check]:152
gnutls[4]: EXT[0x...]: replay detected; rejecting early data</p>
</blockquote>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">That is <a href="https://gitlab.com/gnutls/gnutls/-/blob/84546da2c30d84a7aaeaf82af1f6d0b101b54d81/lib/tls13/anti_replay.c#L147-151" style="color: #1068bf; margin-top: 0;">https://gitlab.com/gnutls/gnutls/-/blob/84546da2c30d84a7aaeaf82af1f6d0b101b54d81/lib/tls13/anti_replay.c#L147-151</a></p>
<div class="gl-relative markdown-code-block js-markdown-code">
<pre class="code highlight js-syntax-highlight language-c" lang="c" v-pre="true" style='display: block; font-size: 13px; color: #303030; line-height: 1.6em; overflow-x: auto; border-radius: 4px; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; margin: 0 0 16px; padding: 12px; border: 1px solid #dbdbdb;'><code style='font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; background-color: inherit; border-radius: 4px; white-space: pre; margin-top: 0; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; overflow-wrap: normal; padding: unset;'><span id="LC1" class="line" lang="c" style="margin-top: 0;"> <span class="cm" style="margin-top: 0;">/* It shouldn't be possible that the server's view of ticket</span></span>
<span id="LC2" class="line" lang="c"><span class="cm" style="margin-top: 0;"> * age is smaller than the client's view.</span></span>
<span id="LC3" class="line" lang="c"><span class="cm" style="margin-top: 0;"> */</span></span></code></pre>
<copy-code></copy-code>
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<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">Whey does this happen? Because boringssl drops sub-second when calculating obfuscated_ticket_age:</p>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial"><a href="https://boringssl.googlesource.com/boringssl/+/refs/heads/master/ssl/extensions.cc#1982" rel="nofollow noreferrer noopener" target="_blank" style="color: #1068bf; margin-top: 0;">https://boringssl.googlesource.com/boringssl/+/refs/heads/master/ssl/extensions.cc#1982</a></p>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">It looks like RFC 8446 only says that "a server MUST validate
that the ticket age for the selected PSK identity ... is within a small tolerance of the time since the ticket
was issued". This particular check done by gnutls might be too strict.</p>
<h2 dir="auto" style="font-size: 1.5em; font-weight: 600; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-color: #eaeaea; border-bottom-style: solid; color: #303030; margin: 24px 0 16px;" align="initial">
<a id="user-content-version-of-gnutls-used" class="anchor" href="#version-of-gnutls-used" aria-hidden="true" style="color: #1068bf; margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Version of gnutls used:</h2>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">master branch</p>
<h2 dir="auto" style="font-size: 1.5em; font-weight: 600; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-color: #eaeaea; border-bottom-style: solid; color: #303030; margin: 24px 0 16px;" align="initial">
<a id="user-content-distributor-of-gnutls-eg-ubuntu-fedora-rhel" class="anchor" href="#distributor-of-gnutls-eg-ubuntu-fedora-rhel" aria-hidden="true" style="color: #1068bf; margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Distributor of gnutls (e.g., Ubuntu, Fedora, RHEL)</h2>
<h2 dir="auto" style="font-size: 1.5em; font-weight: 600; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-color: #eaeaea; border-bottom-style: solid; color: #303030; margin: 24px 0 16px;" align="initial">
<a id="user-content-how-reproducible" class="anchor" href="#how-reproducible" aria-hidden="true" style="color: #1068bf; margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>How reproducible:</h2>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">Send early data from boringssl client to gnutls server.
Do this several times and see the early data rejection by gnutls server.</p>
<h2 dir="auto" style="font-size: 1.5em; font-weight: 600; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-color: #eaeaea; border-bottom-style: solid; color: #303030; margin: 24px 0 16px;" align="initial">
<a id="user-content-actual-results" class="anchor" href="#actual-results" aria-hidden="true" style="color: #1068bf; margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Actual results:</h2>
<p dir="auto" style="color: #303030; margin: 0 0 16px;" align="initial">Early data from boringssl client is often rejected.</p>
<h2 dir="auto" style="font-size: 1.5em; font-weight: 600; padding-bottom: 0.3em; border-bottom-width: 1px; border-bottom-color: #eaeaea; border-bottom-style: solid; color: #303030; margin: 24px 0 16px;" align="initial">
<a id="user-content-expected-results" class="anchor" href="#expected-results" aria-hidden="true" style="color: #1068bf; margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Expected results:</h2>
<p dir="auto" style="color: #303030; margin: 0;" align="initial">Early data from boringssl client should be accepted if the ticket age is within the acceptable range.</p>
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