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<a href="https://gitlab.com/dkg">Daniel Kahn Gillmor</a> created an issue: <a href="https://gitlab.com/gnutls/libtasn1/-/issues/36">#36</a>
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<a id="user-content-description-of-problem" class="anchor" href="#description-of-problem" aria-hidden="true"></a>Description of problem:</h2>
<p dir="auto">Over in <a href="https://gitlab.com/gnutls/gnutls/-/issues/1238" data-original="https://gitlab.com/gnutls/gnutls/-/issues/1238" data-link="false" data-link-reference="true" data-project="179611" data-issue="87111762" data-reference-type="issue" data-container="body" data-placement="top" title="certtool: adding a policy without qualifiers results in empty sequence" class="gfm gfm-issue has-tooltip">gnutls#1238</a>, I noted that <code>certtool</code> was emitting an empty sequence of policyQualifiers even though the ASN.1 specification for <code>policyQualifiers</code> clearly says <code>(1..MAX) OPTIONAL</code>.</p>
<p dir="auto">If libtasn1 knows that a given <code>SEQUENCE</code> is <code>OPTIONAL</code> and it has a minimum length (e.g. <code>(1..MAX)</code>, or, regardless of the upper limit, even <code>(1..2)</code> really), and the data structure to be written is an <em>empty</em> sequence, then libtasn1 should be clever enough to omit the member entirely.</p>
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<a id="user-content-version-of-libtasn1-used" class="anchor" href="#version-of-libtasn1-used" aria-hidden="true"></a>Version of libtasn1 used:</h2>
<p dir="auto">4.16.0-2</p>
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<a id="user-content-distributor-of-libtasn1-eg-ubuntu-fedora-rhel" class="anchor" href="#distributor-of-libtasn1-eg-ubuntu-fedora-rhel" aria-hidden="true"></a>Distributor of libtasn1 (e.g., Ubuntu, Fedora, RHEL)</h2>
<p dir="auto">Debian</p>
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<a id="user-content-how-reproducible" class="anchor" href="#how-reproducible" aria-hidden="true"></a>How reproducible:</h2>
<p dir="auto">Steps to Reproduce:</p>
<pre class="code highlight js-syntax-highlight language-plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext">printf 'policy1=1.2.3.4\ncn="test"' > foo.template</span>
<span id="LC2" class="line" lang="plaintext">certtool --generate-privkey > foo.key</span>
<span id="LC3" class="line" lang="plaintext">certtool --generate-self-signed --template foo.template --load-privkey foo.key --outder | dumpasn1 </span></code></pre>
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<a id="user-content-actual-results" class="anchor" href="#actual-results" aria-hidden="true"></a>Actual results:</h2>
<pre class="code highlight js-syntax-highlight language-plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext">556 18: SEQUENCE {</span>
<span id="LC2" class="line" lang="plaintext"> 558 3: OBJECT IDENTIFIER certificatePolicies (2 5 29 32)</span>
<span id="LC3" class="line" lang="plaintext"> 563 11: OCTET STRING 30 09 30 07 06 03 2A 03 04 30 00</span>
<span id="LC4" class="line" lang="plaintext"> : }</span></code></pre>
<p dir="auto">The payload of the extension converts to:</p>
<pre class="code highlight js-syntax-highlight language-plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext">$ xxd -r -c 256 <<<"0000 30 09 30 07 06 03 2A 03 04 30 00" | dumpasn1 -</span>
<span id="LC2" class="line" lang="plaintext"> 0 9: SEQUENCE {</span>
<span id="LC3" class="line" lang="plaintext"> 2 7: SEQUENCE {</span>
<span id="LC4" class="line" lang="plaintext"> 4 3: OBJECT IDENTIFIER '1 2 3 4'</span>
<span id="LC5" class="line" lang="plaintext"> 9 0: SEQUENCE {}</span>
<span id="LC6" class="line" lang="plaintext"> : }</span>
<span id="LC7" class="line" lang="plaintext"> : }</span>
<span id="LC8" class="line" lang="plaintext">$</span></code></pre>
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<a id="user-content-expected-results" class="anchor" href="#expected-results" aria-hidden="true"></a>Expected results:</h2>
<p dir="auto">The payload of the extension should be <code>30 07 30 05 06 03 2A 03 04</code>, which is:</p>
<pre class="code highlight js-syntax-highlight language-plaintext" lang="plaintext" v-pre="true"><code><span id="LC1" class="line" lang="plaintext"> 0 7: SEQUENCE {</span>
<span id="LC2" class="line" lang="plaintext"> 2 5: SEQUENCE {</span>
<span id="LC3" class="line" lang="plaintext"> 4 3: OBJECT IDENTIFIER '1 2 3 4'</span>
<span id="LC4" class="line" lang="plaintext"> : }</span>
<span id="LC5" class="line" lang="plaintext"> : }</span></code></pre>
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