325 lines
12 KiB
Markdown
325 lines
12 KiB
Markdown
# Lab 02 - Certificates
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## Create Working Environment
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```sh
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mkdir -p /root/ca
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cd /root/ca
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mkdir certs crl newcerts private
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chmod 700 private
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```
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## Create Private Key
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```sh
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openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out private/ca.key.pem
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```
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## Create Public Key
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```sh
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openssl pkey -in private/ca.key.pem -out ca.key.pem.pub -pubout
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```
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## Create Certificate Authority
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Run using `sudo -i`:
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```sh
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touch index.txt
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echo 1000 > serial
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```
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Create OpenSSL config:
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```sh
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vi /root/ca/openssl.cnf
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```
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***`/root/ca/openssl.cnf`:***
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```ini
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# OpenSSL root CA configuration file.
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# Copy to `/root/ca/openssl.cnf`.
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[ ca ]
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# `man ca`
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default_ca = CA_default
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[ CA_default ]
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# Directory and file locations.
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dir = /root/ca
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certs = $dir/certs
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crl_dir = $dir/crl
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new_certs_dir = $dir/newcerts
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database = $dir/index.txt
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serial = $dir/serial
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RANDFILE = $dir/private/.rand
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# The root key and root certificate.
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private_key = $dir/private/ca.key.pem
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certificate = $dir/certs/ca.cert.pem
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# For certificate revocation lists.
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crlnumber = $dir/crlnumber
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crl = $dir/crl/ca.crl.pem
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crl_extensions = crl_ext
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default_crl_days = 30
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# SHA-1 is deprecated, so use SHA-2 instead.
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default_md = sha256
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name_opt = ca_default
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cert_opt = ca_default
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default_days = 375
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preserve = no
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policy = policy_strict
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[ policy_strict ]
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# The root CA should only sign intermediate certificates that match.
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# See the POLICY FORMAT section of `man ca`.
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countryName = match
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stateOrProvinceName = match
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organizationName = match
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organizationalUnitName = optional
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commonName = supplied
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emailAddress = optional
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[ policy_loose ]
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# Allow the intermediate CA to sign a more diverse range of certificates.
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# See the POLICY FORMAT section of the `ca` man page.
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countryName = optional
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stateOrProvinceName = optional
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localityName = optional
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organizationName = optional
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organizationalUnitName = optional
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commonName = supplied
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emailAddress = optional
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[ req ]
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# Options for the `req` tool (`man req`).
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default_bits = 2048
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distinguished_name = req_distinguished_name
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string_mask = utf8only
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# SHA-1 is deprecated, so use SHA-2 instead.
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default_md = sha256
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# Extension to add when the -x509 option is used.
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x509_extensions = v3_ca
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[ req_distinguished_name ]
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# See <https://en.wikipedia.org/wiki/Certificate_signing_request>.
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countryName = Country Name (2 letter code)
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stateOrProvinceName = State or Province Name
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localityName = Locality Name
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0.organizationName = Organization Name
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organizationalUnitName = Organizational Unit Name
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commonName = Common Name
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emailAddress = Email Address
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# Optionally, specify some defaults.
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countryName_default = GB
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stateOrProvinceName_default = England
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localityName_default =
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0.organizationName_default = Alice Ltd
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organizationalUnitName_default =
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emailAddress_default =
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[ v3_ca ]
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# Extensions for a typical CA (`man x509v3_config`).
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subjectKeyIdentifier = hash
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authorityKeyIdentifier = keyid:always,issuer
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basicConstraints = critical, CA:true
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keyUsage = critical, digitalSignature, cRLSign, keyCertSign
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[ v3_intermediate_ca ]
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# Extensions for a typical intermediate CA (`man x509v3_config`).
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subjectKeyIdentifier = hash
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authorityKeyIdentifier = keyid:always,issuer
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basicConstraints = critical, CA:true, pathlen:0
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keyUsage = critical, digitalSignature, cRLSign, keyCertSign
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[ usr_cert ]
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# Extensions for client certificates (`man x509v3_config`).
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basicConstraints = CA:FALSE
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nsCertType = client, email
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nsComment = "OpenSSL Generated Client Certificate"
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subjectKeyIdentifier = hash
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authorityKeyIdentifier = keyid,issuer
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keyUsage = critical, nonRepudiation, digitalSignature, keyEncipherment
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extendedKeyUsage = clientAuth, emailProtection
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[ server_cert ]
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# Extensions for server certificates (`man x509v3_config`).
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basicConstraints = CA:FALSE
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nsCertType = server
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nsComment = "OpenSSL Generated Server Certificate"
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subjectKeyIdentifier = hash
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authorityKeyIdentifier = keyid,issuer:always
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keyUsage = critical, digitalSignature, keyEncipherment
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extendedKeyUsage = serverAuth
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[ crl_ext ]
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# Extension for CRLs (`man x509v3_config`).
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authorityKeyIdentifier=keyid:always
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[ ocsp ]
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# Extension for OCSP signing certificates (`man ocsp`).
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basicConstraints = CA:FALSE
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subjectKeyIdentifier = hash
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authorityKeyIdentifier = keyid,issuer
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keyUsage = critical, digitalSignature
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extendedKeyUsage = critical, OCSPSigning
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```
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Create root certificate:
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```sh
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openssl req -config openssl.cnf -key private/ca.key.pem -new -x509 -days 7300 -sha256 -extensions v3_ca -out certs/ca.cert.pem
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```
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## Create Certificate Signing Request
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```sh
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openssl req -new -newkey rsa:2048 -nodes -keyout server.key -out server.csr
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```
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## Create Certificate Chain
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### Preparation
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```sh
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mkdir -p /root/intermediate
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echo 1000 > /root/intermediate/serial
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echo 0100 > /root/intermediate/crlnumber
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```
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Configure OpenSSL:
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```sh
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vi /root/intermediate/openssl_intermediate.cnf
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```
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***`openssl_intermediate.cnf`:***
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```ini
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[ ca ] # The default CA section
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default_ca = CA_default # The default CA name
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[ CA_default ] # Default settings for the intermediate CA
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dir = /root/intermediate # Intermediate CA directory
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certs = $dir/certs # Certificates directory
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crl_dir = $dir/crl # CRL directory
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new_certs_dir = $dir/newcerts # New certificates directory
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database = $dir/index.txt # Certificate index file
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serial = $dir/serial # Serial number file
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RANDFILE = $dir/private/.rand # Random number file
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private_key = $dir/private/intermediate.key.pem # Intermediate CA private key
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certificate = $dir/certs/intermediate.cert.pem # Intermediate CA certificate
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crl = $dir/crl/intermediate.crl.pem # Intermediate CA CRL
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crlnumber = $dir/crlnumber # Intermediate CA CRL number
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crl_extensions = crl_ext # CRL extensions
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default_crl_days = 30 # Default CRL validity days
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default_md = sha256 # Default message digest
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preserve = no # Preserve existing extensions
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email_in_dn = no # Exclude email from the DN
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name_opt = ca_default # Formatting options for names
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cert_opt = ca_default # Certificate output options
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policy = policy_loose # Certificate policy
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[ policy_loose ] # Policy for less strict validation
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countryName = optional # Country is optional
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stateOrProvinceName = optional # State or province is optional
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localityName = optional # Locality is optional
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organizationName = optional # Organization is optional
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organizationalUnitName = optional # Organizational unit is optional
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commonName = supplied # Must provide a common name
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emailAddress = optional # Email address is optional
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[ req ] # Request settings
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default_bits = 2048 # Default key size
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distinguished_name = req_distinguished_name # Default DN template
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string_mask = utf8only # UTF-8 encoding
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default_md = sha256 # Default message digest
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x509_extensions = v3_intermediate_ca # Extensions for intermediate CA certificate
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[ req_distinguished_name ] # Template for the DN in the CSR
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countryName = Country Name (2 letter code)
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stateOrProvinceName = State or Province Name
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localityName = Locality Name
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0.organizationName = Organization Name
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organizationalUnitName = Organizational Unit Name
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commonName = Common Name
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emailAddress = Email Address
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[ v3_intermediate_ca ] # Intermediate CA certificate extensions
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subjectKeyIdentifier = hash # Subject key identifier
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authorityKeyIdentifier = keyid:always,issuer # Authority key identifier
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basicConstraints = critical, CA:true, pathlen:0 # Basic constraints for a CA
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keyUsage = critical, digitalSignature, cRLSign, keyCertSign # Key usage for a CA
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[ crl_ext ] # CRL extensions
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authorityKeyIdentifier=keyid:always # Authority key identifier
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[ server_cert ] # Server certificate extensions
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basicConstraints = CA:FALSE # Not a CA certificate
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nsCertType = server # Server certificate type
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keyUsage = critical, digitalSignature, keyEncipherment # Key usage for a server cert
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extendedKeyUsage = serverAuth # Extended key usage for server authentication purposes (e.g., TLS/SSL servers).
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authorityKeyIdentifier = keyid,issuer # Authority key identifier linking the certificate to the issuer's public key.
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```
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```sh
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openssl genrsa -out /root/intermediate/intermediate.key.pem 4096
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```
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### Requesting an Intermediate Certificate
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Be sure to specify a fantasy domain name as "Common Name" while generating the request.
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```sh
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cd /root/intermediate
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# Create Request
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openssl req -new -newkey rsa:2048 -nodes -key intermediate.key.pem -out intermediate.req
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```
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### Signing the Intermediate Certificate
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```sh
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openssl ca -config /root/ca/openssl.cnf -extensions v3_intermediate_ca -days 3650 -notext -md sha256 -in intermediate.req -out intermediate.cer
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```
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You might notice, that - probably due to an error in the lab's paper - signing the certificate is not working.
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This is caused by the `policy_strict` policy which requires the country, city and company of certificate requests to equal with the corresponding fields of the CA's certificate.
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Change the CA's `policy` configuration to `policy_loose` in order to address the issue:
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```sh
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sed -i 's/^\(policy *= policy_\)strict/\1loose/' /root/ca/openssl.cnf
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```
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After that, signing works properly:
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```sh
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openssl ca -config /root/ca/openssl.cnf -extensions v3_intermediate_ca -days 3650 -notext -md sha256 -in intermediate.req -out intermediate.cer
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```
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Check the output:
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```sh
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openssl x509 -in intermediate.cer -noout -text
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```
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# Signing Data
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Create a file with secret content:
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```sh
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cd /root
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vi secret.txt
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```
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## Create Signature
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```sh
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# Create and encrypt hash of file
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openssl dgst -sha256 -sign /root/ca/private/ca.key.pem -out /tmp/hash.sha256 secret.txt
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# Convert hash file to base64
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openssl base64 -in /tmp/hash.sha256 -out secret.sig
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```
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## Verify Signature
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Under normal circumstances:
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```sh
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# Re-create hash file from base64
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openssl base64 -d -in secret.sig -out /tmp/hash.sha256
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# Check integrity of `secret.txt`
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openssl dgst -sha256 -verify /root/ca/ca.key.pem.pub -signature /tmp/hash.sha256 secret.txt
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```
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