Creating SSL Certificate with Custom CA

July 4, 2021 · updated May 6, 2022

Creating Default OpenSSL Config File

INI

#
# OpenSSL example configuration file.
# This is mostly being used for generation of certificate requests.
#

# Note that you can include other files from the main configuration
# file using the .include directive.
#.include filename

# This definition stops the following lines choking if HOME isn't
# defined.
HOME                    = .
SAN                     = CN:copy

# Extra OBJECT IDENTIFIER info:
#oid_file               = $ENV::HOME/.oid
oid_section             = new_oids

# To use this configuration file with the "-extfile" option of the
# "openssl x509" utility, name here the section containing the
# X.509v3 extensions to use:
# extensions        =
# (Alternatively, use a configuration file that has only
# X.509v3 extensions in its main [= default] section.)

[ new_oids ]

# We can add new OIDs in here for use by 'ca', 'req' and 'ts'.
# Add a simple OID like this:
# testoid1=1.2.3.4
# Or use config file substitution like this:
# testoid2=${testoid1}.5.6

# Policies used by the TSA examples.
tsa_policy1             = 1.2.3.4.1
tsa_policy2             = 1.2.3.4.5.6

[ tsa ]
default_tsa             = tsa_config1

[ tsa_config1 ]

# These are used by the TSA reply generation only.
crypto_device           = builtin        # OpenSSL engine to use for signing
signer_digest           = sha256            # Signing digest to use. (Optional)
default_policy          = tsa_policy1
other_policies          = tsa_policy2, tsa_policy3    # acceptable policies (optional)
digests                 = sha1, sha256, sha384, sha512  # Acceptable message digests (mandatory)
accuracy                = secs:1, millisecs:500, microsecs:100    # (optional)
clock_precision_digits  = 0    # number of digits after dot. (optional)
# Is ordering defined for timestamps?
# (optional, default: no)
ordering                = yes
# Must the TSA name be included in the reply?
# (optional, default: no)
tsa_name                = yes
# Must the ESS cert id chain be included?
# (optional, default: no)
ess_cert_id_chain       = no
# algorithm to compute certificate
# identifier (optional, default: sha1)
ess_cert_id_alg         = sha256

[ ca ]
default_ca              = CA_default

[ CA_default ]
x509_extensions         = web_cert
default_days            = 365
policy                  = default_policy

[ default_policy ]
countryName             = match
stateOrProvinceName     = match
organizationName        = match
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ ca_policy ]
countryName             = match
stateOrProvinceName     = optional
organizationName        = match
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ optional_policy ]
countryName             = optional
stateOrProvinceName     = optional
localityName            = optional
organizationName        = optional
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ smime_policy ]
countryName             = optional
stateOrProvinceName     = optional
localityName            = optional
organizationName        = optional
organizationalUnitName  = optional
commonName              = optional
emailAddress            = match

[ req ]
default_bits            = 2048
distinguished_name      = req_distinguished_name
attributes              = req_attributes
x509_extensions         = web_cert    # The extensions to add to the self signed cert
# req_extensions        = v3_req

# Passwords for private keys if not present they will be prompted for
# input_password = secret
# output_password = secret

# This sets a mask for permitted string types. There are several options.
# default: PrintableString, T61String, BMPString.
# pkix     : PrintableString, BMPString (PKIX recommendation before 2004)
# utf8only: only UTF8Strings (PKIX recommendation after 2004).
# nombstr : PrintableString, T61String (no BMPStrings or UTF8Strings).
# MASK:XXXX a literal mask value.
# WARNING: ancient versions of Netscape crash on BMPStrings or UTF8Strings.
string_mask = utf8only

[ req_attributes ]
challengePassword       = A challenge password
challengePassword_min   = 4
challengePassword_max   = 20

[ req_distinguished_name ]
countryName             = Country Name (2 letter code)
countryName_default     = ID
countryName_min         = 2
countryName_max         = 2

stateOrProvinceName     = State or Province Name (full name)
stateOrProvinceName_default    = Jakarta

localityName            = Locality Name (eg, city)

0.organizationName      = Organization Name (eg, company)
0.organizationName_default = Personal Company

# we can do this but it is not needed normally :-)
#1.organizationName     = Second Organization Name (eg, company)
#1.organizationName_default = World Wide Web Pty Ltd

organizationalUnitName  = Organizational Unit Name (eg, section)
#organizationalUnitName_default =

commonName              = Common Name (e.g. server FQDN or YOUR name)
commonName_max          = 64

emailAddress            = Email Address
emailAddress_max        = 64

#######################################################################
# Signing cert: certificate for non CA
#######################################################################
[ web_cert ]
# This goes against PKIX guidelines but some CAs do it and some software
# requires this to avoid interpreting an end user certificate as a CA.
basicConstraints        = critical, CA:FALSE
# This is typical in keyUsage for a client certificate.
keyUsage                = nonRepudiation, digitalSignature, keyEncipherment
extendedKeyUsage        = serverAuth, clientAuth

# PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer:always

# optional: create separate config file, execute with -extfile file.cnf
# signing multiple domains/IPs
#subjectAltName = DNS:*.dev.lab, DNS:dev.lab, IP:127.0.0.1
subjectAltName          = $ENV::SAN
# Special certificate for ASP.NET development
# TODO: find exact value for version in byte, not in BER format
1.3.6.1.4.1.311.84.1.1  = ASN1:INT:2

#######################################################################
# Signing cert: certificate for intermedia CA
#######################################################################
[ ica_cert ]
basicConstraints        = critical, CA:TRUE, pathlen:0
keyUsage                = cRLSign, keyCertSign, digitalSignature
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer:always

#######################################################################
# Signing cert: self signed for CA's cert
#######################################################################
[ ca_cert ]
basicConstraints        = critical, CA:TRUE
keyUsage                = cRLSign, keyCertSign, digitalSignature
extendedKeyUsage        = critical, serverAuth, clientAuth, codeSigning, emailProtection, timeStamping
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer:always

#######################################################################
# Signing cert: code signing
#######################################################################
[ codesign_cert ]
basicConstraints        = critical, CA:FALSE
keyUsage                = critical, nonRepudiation, digitalSignature
extendedKeyUsage        = critical, codeSigning, msCodeInd, msCodeCom, msCTLSign, timeStamping
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer:always

#######################################################################
# Signing cert: for S/MIME certificate
#######################################################################
[ smime_cert ]
# https://tools.ietf.org/html/rfc3850
# digitalSignature is required, used for signing email
keyUsage                = digitalSignature, nonRepudiation, keyEncipherment
# emailProtection is used for encrpyting message
extendedKeyUsage        = emailProtection
subjectAltName          = email:copy
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid:always, issuer:always

#######################################################################
# Read config from environment variable with shorten of key name
#######################################################################
[ env ]
subjectAltName          = $ENV::SAN

Creating Custom Root CA

Creating the CA key: openssl genrsa -des3 -out root-CA.key 4096 Note: remove -des option to create key without password

Creating self sign CA certificate

PowerShell

openssl req -x509 -new -nodes -key root-CA.key -sha256 -days 3650 -out root-CA.crt `
	-subj "/C=ID/O=Dev lab/CN=Dev lab Root CA" `
	-addext 'keyUsage = cRLSign, keyCertSign, digitalSignature' `
	-addext 'extendedKeyUsage = critical, serverAuth, clientAuth, codeSigning, emailProtection, timeStamping' `
	-addext 'subjectKeyIdentifier=hash' `
	-addext 'authorityKeyIdentifier=keyid:always,issuer:always' `
	-addext "basicConstraints = critical, CA:TRUE"

Explanations:

subj create unattended answer subject
basicConstraints CA:TRUE means it’s issuer
keyUsage determine what’s this cert for: certificate signing (keyCertSign), CRL signing (cRLSign), digital signature
extendedKeyUsage an extended version of keyUsage: server authentication (serverAuth), client authentication (clientAuth), file/code signing (codeSigning), S/MIME signing (emailProtection), time stamping
subjectKeyIdentifier identifier of this cert
authoritykKeyIdentifier

the identifier which signs the cert, if it’s root cert, then it should be itself

Shorter version

openssl req -config openssl.cnf -x509 -new -nodes -key root-CA.key -out root-CA.crt -days 3650 -extensions ca_cert -subj "/C=ID/O=Dev Lab/CN=Dev Lab Root CA"

Reference: OpenSSL man page

Inspect root CA certificate openssl x509 -noout -text -in root-CA.crt

Convert into PKCS12 (.pfx) format openssl pkcs12 -export -name "Root CA" -out root-CA.pfx -inkey root-CA.key -in root-CA.crt Then import the pfx file into local machine placed under Trusted Root Certification Authorities

Creating Intermediate CA

Creating the intermedia CA key openssl genrsa -out server-CA.key 4096

Creating intermediate certificate request

openssl req -new -key server-CA.key -out server-CA.csr -subj "/C=ID/O=Dev Lab/OU=Development/CN=Dev Lab Server CA"

Sign the intermedia CA certificate’s request with CA’s key and cert: openssl x509 -extfile openssl.cnf -req -in server-CA.csr -CA root-CA.crt -CAkey root-CA.key -CAcreateserial -out server-CA.crt -extensions ica_cert -days 3650

Inspect root CA certificate openssl x509 -noout -text -in server-CA.crt

Convert into PKCS12 format openssl pkcs12 -export -name "Dev lab Server CA" -inkey server-CA.key -in server-CA.crt -out server-CA.pfx Then import the pfx file into local machine placed under Intermediate Certification Authorities

Creating User Certificate

Creating the certificate key openssl genrsa -out dev.lab.key 2048

Before moving on, the openssl config is configured to accept subject alternate name from environment variable named SAN (see line 176), so you need to configure first, otherwise, it will fail: $Env:SAN = 'DNS:*.dev.lab, DNS:dev.lab'. You can set it to the same as CN if you don’t want to assign it to wilcard domain. We can also assign it to IP address as follows: $Env:SAN = 'DNS:*.dev.lab,DNS:dev.lab,DNS:localhost,IP:127.0.0.1'. After that, we can continue to create certificate request

PowerShell

openssl req -new -key dev.lab.key -out dev.lab.csr -subj "/C=ID/ST=Jakarta/O=Dev Home/OU=Development/CN=*.dev.lab"

Sign the certificate request using server CA’s key and certificate

PowerShell

openssl x509 -extfile openssl.cnf -extensions web_cert -req -CA server-CA.crt `
	-CAkey server-CA.key -CAcreateserial -days 365 `
	-in dev.lab.csr -out dev.lab.crt

Convert into PKCS12 format openssl pkcs12 -export -name "dev.lab Certificate" -inkey dev.lab.key -in dev.lab.crt -out dev.lab.pfx

Import the .pfx file into local machine using default location.

Creating S/MIME Certificate

Creating the certificate key

openssl genrsa -out iroel-email.key 2048

Creating certificate request openssl req -new -key iroel-email.key -out iroel-email.csr -subj "/C=ID/ST=Jakarta/CN=Fakhrulhilal Maktum/emailAddress=iroel@dev.lab" -addext "subjectAltName = email:iroel@dev.lab, email:iroel@other.lab"

Sign the certificate request using server CA’s key and certificate

PowerShell

$Env:SAN = 'email:iroel@dev.lab, email:iroel@dev.test'
openssl x509 -extfile openssl.cnf -extensions smime_cert -req -CA server-CA.crt `
	-CAkey server-CA.key -CAcreateserial -setalias "Dev email certificate" `
	-in iroel-email.csr -out iroel-email.crt -trustout -days 365

Convert into PKCS12 format openssl pkcs12 -export -name "wilcard.dev.lab Certificate" -inkey dev.lab.key -in dev.lab.crt -out dev.lab.pfx

Import the .pfx file into local machine using default location.

Installing Certificates

Installing CAs’ Certificate

Install root certificate (root-CA.crt) to Trusted Root Certification Authorities in machine level
Install intermediate certificate (server-CA.crt) to Intermediate Certification Authorities

Install IIS Express Certificate

Install the certificate in Local Machine wide and in default location (Personal). Run this powershell with administrator privilege. Friendly name is -name parameter value when converting into PKCS12 format.

PowerShell

$PfxPassword = 'pfx_password'
#$Certificate = Get-ChildItem Cert:\LocalMachine\My | ?{ $_.FriendlyName -eq 'localhost' }
$Certificate = Get-PfxCertificate -FilePath .\dev.lab.pfx -Password (ConvertTo-SecureString -String $PfxPassword -AsPlainText)
$IisExpress = Get-CimInstance Win32_Product -Filter 'Name like "IIS%Express%"'
for ($Port = 44300; $Port -lt 44400; $Port++) {
    netsh http delete sslcert ipport=0.0.0.0:$Port
    netsh http add sslcert ipport=0.0.0.0:$Port  certhash="$($Certificate.Thumbprint)"  appid="$($IisExpress.IdentifyingNumber)"
}

Installing Kestrel Certificate

Using environment variable ASPNETCORE_Kestrel__Certificates__Default__Path = path to pfx file ASPNETCORE_Kestrel__Certificates__Default__Password = pfx’s password
Using appsettings.json

JSON

{
  "Kestrel": {
    "Certificates": {
      "Default": {
        "Path": "path/to/pfx/file",
        "Password": "pfx's password",
        /* or using .crt and key file */
        /*
        "Path": "path/to/crt/file",
        "KeyPath": "path/to/key/file"
        */
      }
    }
  }
}

Reference: Configure endpoints for the ASP.NET Core Kestrel web server

Using dotnet tool: dotnet dev-certs https --clean -i .\dev.lab.pfx -p the_password

Installing remote desktop certificate

PowerShell

$PfxPassword = 'pfx_password'
#$Certificate = Get-ChildItem Cert:\LocalMachine\My | ?{ $_.FriendlyName -eq 'localhost' }
$Certificate = Get-PfxCertificate -FilePath .\dev.lab.pfx -Password (ConvertTo-SecureString -String $PfxPassword -AsPlainText)
wmic /namespace:\\root\cimv2\TerminalServices PATH Win32_TSGeneralSetting Set SSLCertificateSHA1Hash="$($Certificate.Thumbprint)"