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<a href="https://gitlab.com/maciejsszmigiero">Maciej S. Szmigiero</a> created an issue: <a href="https://gitlab.com/gnutls/gnutls/-/issues/1658">#1658</a>
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<a href="#description-of-the-feature" aria-hidden="true" class="anchor" id="user-content-description-of-the-feature" style="margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Description of the feature:</h2>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">The built <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; margin-top: 0; font-weight: inherit; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>libgnutls.so.30.40.2</code> library lacks CET/shadow stack markings:</p>
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<pre class="code highlight js-syntax-highlight language-plaintext" v-pre="true" style='display: block; font-size: 14px; color: #3a383f; line-height: 1.6em; overflow-x: auto; border-radius: .25rem; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; margin: 0 0 1rem; padding: 12px; border: 1px solid #dcdcde;'><code style='font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; border-radius: .25rem; background-color: inherit; white-space: pre; margin-top: 0; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; overflow-wrap: normal; padding: unset;'><span id="LC1" class="line" lang="plaintext" style="margin-top: 0;">$ readelf -n /usr/lib64/libgnutls.so.30.40.2 | grep -a SHSTK</span>
<span id="LC2" class="line" lang="plaintext">(empty)</span></code></pre>
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<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">Now that shadow stack-enabled CPUs are getting more common each program which links to <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; margin-top: 0; font-weight: inherit; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>libgnutls</code> cannot benefit from shadow stack enforcement, since such enforcement requires that <em>all</em> of its library dependencies carry appropriate markings.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">Tested on a distribution which enables <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; margin-top: 0; font-weight: inherit; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>-fcf-protection</code> by default in GCC (Gentoo). This causes most of other libraries to get build with proper CET support.</p>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">I think the most likely reason that <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; margin-top: 0; font-weight: inherit; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>libgnutls</code> is missing CET markings is that assembly source files in <code style='font-size: 90%; color: #18171d; word-wrap: break-word; border-radius: .25rem; background-color: #ececef; font-weight: inherit; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; white-space: pre-wrap; overflow-wrap: break-word; word-break: keep-all; padding: 0.125rem 0.25rem;'>lib/accelerated/x86/elf</code> are missing them.</p>
<h2 dir="auto" style="margin-top: 1.5rem; margin-bottom: 1rem; border-bottom-style: solid; border-bottom-color: #dcdcde; font-weight: 600; font-size: 1.3125rem; letter-spacing: -0.01em; line-height: 1.25; color: #18171d; border-bottom-width: 1px; padding-bottom: 0.25rem;" align="initial">
<a href="#is-this-feature-implemented-in-other-libraries-and-which" aria-hidden="true" class="anchor" id="user-content-is-this-feature-implemented-in-other-libraries-and-which" style="margin-top: 0; float: left; margin-left: -20px; text-decoration: none; outline: none;"></a>Is this feature implemented in other libraries (and which)</h2>
<p dir="auto" style="color: #3a383f; margin: 0 0 1rem;" align="initial">OpenSSL 3 has proper CET support:</p>
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<pre class="code highlight js-syntax-highlight language-plaintext" v-pre="true" style='display: block; font-size: 14px; color: #3a383f; line-height: 1.6em; overflow-x: auto; border-radius: .25rem; position: relative; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; word-break: break-all; word-wrap: break-word; background-color: #fbfafd; margin: 0 0 1rem; padding: 12px; border: 1px solid #dcdcde;'><code style='font-size: inherit; color: inherit; word-wrap: normal; word-break: keep-all; border-radius: .25rem; background-color: inherit; white-space: pre; margin-top: 0; font-family: "GitLab Mono", "JetBrains Mono", "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; font-variant-ligatures: none; overflow-wrap: normal; padding: unset;'><span id="LC1" class="line" lang="plaintext" style="margin-top: 0;">$ readelf -n /usr/lib64/libssl.so.3 | grep -a SHSTK</span>
<span id="LC2" class="line" lang="plaintext"> Properties: x86 feature: IBT, SHSTK</span></code></pre>
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