firestuff/2016-03-27-ec-ca-redux-now-with-more-nitrokey.html

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<p>This is a revisit on my doc on <a href="2016-03-21-elliptic-curve-certificate-authority.html">how to set up an EC CA</a>. In this version, we’re using the <a href="https://shop.nitrokey.com/shop/product/nitrokey-hsm-7">Nitrokey HSM</a> for key generation, storage, and operations. You’ll need two Nitrokey HSMs. You can get away with one, but there’s not a lot of point to splitting root and intermediate certs if you then keep them on the same device. You’ll also need a <a href="2016-03-26-nitrokey-hsm-ec-setup.html">system set up</a> to talk to the Nitrokey, which is a bit tricky.</p>

<p>If you do this right, you can set up a CA where the keys never touched computer that you’re using to host the CA; they only ever reside protected in the Nitrokey.</p>

<p>You have a choice between making the keys unexportable, or supporting a <a href="https://github.com/OpenSC/OpenSC/wiki/SmartCardHSM#using-key-backup-and-restore">backup scheme</a>. Choose wisely, because you can’t change later. If you’re choosing the former, make sure you can answer “what is my plan if the Nitrokey breaks?”.</p>

<p>There’s one material difference from the other instructions: the Nitrokey HSM only supports up to 320-bit EC keys, so we can’t use P-384 (secp384r1) as we did in the other instructions. We’ll be using P-256 (prime256v1) instead.</p>

<p>XXXX is still our placeholder of choice.</p>

<h3>Create directory structure</h3>

<pre><code>mkdir ca
cd ca
mkdir -p {root,intermediate}/{certs,crl,csr,newcerts}
mkdir -p {client,server}/{certs,csr,pfx,private}
touch {root,intermediate}/database
echo 1000 | tee {root,intermediate}/{serial,crlnumber}
chmod 700 {client,server}/private
</code></pre>

<h3>Create openssl.cnf</h3>

<pre><code>cat &gt; openssl.cnf &amp;lt;&amp;lt;'END'
openssl_conf = openssl_init
[ openssl_init ]
engines = engines
[ ca ]
default_ca = ca_intermediate
[ ca_root ]
dir               = root
certs             = $dir/certs
crl_dir           = $dir/crl
new_certs_dir     = $dir/newcerts
database          = $dir/database
serial            = $dir/serial
crlnumber         = $dir/crlnumber
private_key       = label_root
certificate       = $dir/certs/root.cert.pem
crl               = $dir/crl/root.crl.pem
crl_extensions    = ext_crl
default_md        = sha256
name_opt          = ca_default
cert_opt          = ca_default
default_crl_days  = 30
default_days      = 3650
preserve          = no
policy            = policy_strict
[ ca_intermediate ]
dir               = intermediate
certs             = $dir/certs
crl_dir           = $dir/crl
new_certs_dir     = $dir/newcerts
database          = $dir/database
serial            = $dir/serial
crlnumber         = $dir/crlnumber
private_key       = label_intermediate
certificate       = $dir/certs/intermediate.cert.pem
crl               = $dir/crl/intermediate.crl.pem
crl_extensions    = ext_crl
default_md        = sha256
name_opt          = ca_default
cert_opt          = ca_default
default_crl_days  = 30
default_days      = 375
preserve          = no
policy            = policy_loose
[ policy_strict ]
countryName             = match
stateOrProvinceName     = match
organizationName        = match
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional
[ policy_loose ]
countryName             = optional
stateOrProvinceName     = optional
localityName            = optional
organizationName        = optional
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional
[ req ]
default_bits        = 2048
string_mask         = utf8only
default_md          = sha256
distinguished_name  = req_distinguished_name
[ req_distinguished_name ]
countryName                     = Country Name (2 letter code)
stateOrProvinceName             = State or Province Name
localityName                    = Locality Name
0.organizationName              = Organization Name
organizationalUnitName          = Organizational Unit Name
commonName                      = Common Name
emailAddress                    = Email Address
[ ext_root ]
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer
basicConstraints        = critical, CA:true
keyUsage                = critical, digitalSignature, cRLSign, keyCertSign
[ ext_intermediate ]
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer
basicConstraints        = critical, CA:true, pathlen:0
keyUsage                = critical, digitalSignature, cRLSign, keyCertSign
[ ext_client ]
basicConstraints        = CA:FALSE
nsCertType              = client, email
nsComment               = "OpenSSL Generated Client Certificate"
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid, issuer
keyUsage                = critical, nonRepudiation, digitalSignature, keyEncipherment
extendedKeyUsage        = clientAuth, emailProtection
[ ext_server ]
basicConstraints        = CA:FALSE
nsCertType              = server
nsComment               = "OpenSSL Generated Server Certificate"
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid, issuer:always
keyUsage                = critical, digitalSignature, keyEncipherment
extendedKeyUsage        = serverAuth
[ ext_crl ]
authorityKeyIdentifier  = keyid:always
[ ext_ocsp ]
basicConstraints        = CA:FALSE
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid, issuer
keyUsage                = critical, digitalSignature
extendedKeyUsage        = critical, OCSPSigning
[ engines ]
pkcs11 = engine_pkcs11
[ engine_pkcs11 ]
engine_id     = pkcs11
dynamic_path  = /usr/lib/arm-linux-gnueabihf/openssl-1.0.0/engines/libpkcs11.so
MODULE_PATH   = /usr/local/lib/pkcs11/opensc-pkcs11.so
init          = 0
END
</code></pre>

<h3>Tell future commands to use your new conf file</h3>

<pre><code>export OPENSSL_CONF=openssl.cnf
</code></pre>

<h3>Create a root key</h3>

<p>Insert your root HSM.</p>

<pre><code>/usr/local/bin/pkcs11-tool --module /usr/local/lib/opensc-pkcs11.so --login --keypairgen --key-type EC:prime256v1 --label root
# Enter PIN
</code></pre>

<h3>Create a self-signed root cert</h3>

<pre><code>openssl req -engine pkcs11 -keyform engine -key label_root -new -extensions ext_root -out root/certs/root.cert.pem -x509 -subj '/C=US/ST=California/O=XXXX/OU=XXXX Certificate Authority/CN=XXXX Root CA' -days 7300
# Enter PIN
chmod 444 root/certs/root.cert.pem
</code></pre>

<h3>Verify root cert</h3>

<pre><code>openssl x509 -noout -text -in root/certs/root.cert.pem
</code></pre>

<p>Check:</p>

<ul>
<li>Expiration date (20 years in future)</li>
<li>Signature algorithm (ecdsa-with-SHA256)</li>
<li>Public key size (256 bit)</li>
<li>CA:TRUE</li>
</ul>

<h3>Import root cert onto HSM</h3>

<pre><code>openssl x509 -in root/certs/root.cert.pem -out root/certs/root.cert.der -outform der
/usr/local/bin/pkcs11-tool --module /usr/local/lib/opensc-pkcs11.so --login --write-object root/certs/root.cert.der --type cert --label root
# Enter PIN
</code></pre>

<h3>Create an intermediate key</h3>

<p>Insert your intermediate HSM</p>

<pre><code>/usr/local/bin/pkcs11-tool --module /usr/local/lib/opensc-pkcs11.so --login --keypairgen --key-type EC:prime256v1 --label intermediate
# Enter PIN
</code></pre>

<h3>Create an intermediate certificate signing request (CSR)</h3>

<pre><code>openssl req -engine pkcs11 -keyform engine -new -key label_intermediate -out intermediate/csr/intermediate.csr.pem  -subj '/C=US/ST=California/O=XXXX/OU=XXXX Certificate Authority/CN=XXXX Intermediate'
# Enter PIN
</code></pre>

<h3>Sign intermediate cert with root key</h3>

<p>Insert your root HSM</p>

<pre><code>openssl ca -engine pkcs11 -keyform engine -name ca_root -extensions ext_intermediate -notext -in intermediate/csr/intermediate.csr.pem -out intermediate/certs/intermediate.cert.pem
# Enter PIN
chmod 444 intermediate/certs/intermediate.cert.pem
</code></pre>

<h3>Verify intermediate cert</h3>

<pre><code>openssl x509 -noout -text -in intermediate/certs/intermediate.cert.pem
openssl verify -CAfile root/certs/root.cert.pem intermediate/certs/intermediate.cert.pem
</code></pre>

<p>Check:</p>

<ul>
<li>Expiration date (10 years in future)</li>
<li>Signature algorithm (ecdsa-with-SHA256)</li>
<li>Public key size (256 bit)</li>
<li>CA:TRUE</li>
<li>OK</li>
</ul>

<h3>Import root &amp; intermediate certs onto HSM</h3>

<p>Insert your intermediate HSM</p>

<pre><code>openssl x509 -in intermediate/certs/intermediate.cert.pem -out intermediate/certs/intermediate.cert.der -outform der
/usr/local/bin/pkcs11-tool --module /usr/local/lib/opensc-pkcs11.so --login --write-object root/certs/root.cert.der --type cert --label root
# Enter PIN
/usr/local/bin/pkcs11-tool --module /usr/local/lib/opensc-pkcs11.so --login --write-object intermediate/certs/intermediate.cert.der --type cert --label intermediate
# Enter PIN
</code></pre>

<h3>Create a chain certificate file</h3>

<pre><code>cat intermediate/certs/intermediate.cert.pem root/certs/root.cert.pem &gt; intermediate/certs/chain.cert.pem
chmod 444 intermediate/certs/chain.cert.pem
</code></pre>

<h3>CA setup done!</h3>

<p>Take your root HSM, if you have a separate one, and lock it in a safe somewhere; you won’t need it for regular use.</p>

<p>The following steps are examples of how to use your new CA.</p>

<h3>Create a client key</h3>

<p>You can substitute “server” for “client” for a server cert.</p>

<pre><code>openssl ecparam -name secp384r1 -genkey | openssl ec -aes-256-cbc -out client/private/test1.key.pem
# Create client key password
chmod 400 client/private/test1.key.pem
</code></pre>

<h3>Create a client certificate signing request (CSR)</h3>

<pre><code>openssl req -new -key client/private/test1.key.pem -out client/csr/test1.csr.pem  -subj '/C=US/ST=California/O=XXXX/OU=XXXX Test/CN=XXXX Test 1'
</code></pre>

<h3>Sign client cert with intermediate key</h3>

<pre><code>openssl ca -engine pkcs11 -keyform engine -extensions ext_client -notext -in client/csr/test1.csr.pem -out client/certs/test1.cert.pem
# Enter PIN
chmod 444 client/certs/test1.cert.pem
</code></pre>

<h3>Verify client cert</h3>

<pre><code>openssl x509 -noout -text -in client/certs/test1.cert.pem
openssl verify -CAfile intermediate/certs/chain.cert.pem client/certs/test1.cert.pem
</code></pre>

<p>Check:</p>

<ul>
<li>Expiration date (1 year in future)</li>
<li>Signature algorithm (ecdsa-with-SHA256)</li>
<li>Public key size (384 bit)</li>
<li>CA:FALSE</li>
<li>OK</li>
</ul>

<h3>Create a PKCS#12 bundle for the client</h3>

<p>This is an easy(er) way to get all the necessary keys &amp; certs to the client in one package.</p>

<pre><code>openssl pkcs12 -export -out client/pfx/test1.pfx -inkey client/private/test1.key.pem -in client/certs/test1.cert.pem -certfile intermediate/certs/chain.cert.pem
# Enter both the client key password, and a new password for the export; you'll need to give the latter to the client
</code></pre>

<h3>Generate a certificate revocation list (CRL)</h3>

<p>Initially empty. You can also do this for your root CA (with its HSM inserted).</p>

<pre><code>openssl ca -engine pkcs11 -keyform engine -gencrl -out intermediate/crl/intermediate.crl.pem
</code></pre>

<h3>Verify certificate revocation list</h3>

<pre><code>openssl crl -in intermediate/crl/intermediate.crl.pem -noout -text
</code></pre>

<p>Check:</p>

<ul>
<li>Expiration date (30 days in future)</li>
<li>Signature algorithm (ecdsa-with-SHA256)</li>
</ul>

<h3>Revoke a certificate</h3>

<p>Only do this if you need to. Find the certificate:</p>

<pre><code>cat intermediate/database
# You'll need the hex-formatted serial number, in the third field.
# Substitute serial number for YYYY below.
</code></pre>

<p>Revoke it:</p>

<pre><code>openssl ca -engine pkcs11 -keyform engine -revoke intermediate/newcerts/YYYY.pem
# Enter PIN
</code></pre>

<p>Generate a new CRL file:</p>

<pre><code>openssl ca -engine pkcs11 -keyform engine -gencrl -out intermediate/crl/intermediate.crl.pem
# Enter PIN
</code></pre>

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