Root-CA

Für meine Zertifikate erstelle ich mir eine eigene Certificate Authority. Server-Zertifikate und User-Zertifikate werden jeweils von einer eigenen CA erstellt.

Es ergibt sich folgende Struktur:

        Root-CA
        /     \
Server-CA     User-CA
   |            |
 SCert 1      UCert 1
 SCert 2      UCert 2
  ...          ...
 SCert n      UCert m

Es wird das Paket openssl benötigt:

apt-get install openssl

Folgendes Script legt in einem beliebigen Verzeichnis obige CA-Struktur an. Es benötigt eine angepasste openssl.cnf.tpl Datei, welche im gleichen Verzeichnis wie das Script selbst liegen muss: ./scripts

scx:~/ca/scripts# ls
mk_ca_struct*  mk_cert_server*  mk_cert_user*  openssl.cnf.tpl 

./scripts/openssl.cnf.tpl

# OpenSSL configuration file for certificates.
# 2007 by neobiker
#
# $Id: openssl.cnf.tpl,v 1.1 2008/06/26 20:35:28 root Exp root $
#
# $Log: openssl.cnf.tpl,v $
# Revision 1.1  2008/06/26 20:35:28  root
# Initial revision
#

[ new_oids]

####################################################################
[ ca ]
default_ca      = Server_CA                     # The default ca section

####################################################################
[ Root_CA ]

dir             = $path/RootCA                  # Where everything is kept
certs           = $dir/certs                    # Where the issued certs are kept
crl_dir         = $dir/crls                     # Where the issued crl are kept
database        = $dir/index.txt                # database index file.
new_certs_dir   = $dir/newcerts                 # default place for new certs.

certificate     = $dir/private/RCAcert.pem      # The CA certificate
serial          = $dir/serial                   # The current serial number
crl             = $dir/crls/crl.pem             # The current CRL
private_key     = $dir/private/RCAkey.pem       # The private key

default_days    = 1825                          # how long to certify for
default_crl_days= 365                           # how long before next CRL
default_md      = md5                           # which md to use.

x509_extensions = RCA_cert                      # The extentions to add to the cert
preserve        = no

policy          = policy_match                  # default policy

[ Server_CA ]

dir             = $path/ServerCA                # Where everything is kept
certs           = $dir/certs                    # Where the issued certs are kept
crl_dir         = $dir/crls                     # Where the issued crl are kept
database        = $dir/index.txt                # database index file.
new_certs_dir   = $dir/newcerts                 # default place for new certs.

certificate     = $dir/private/SCAcert.pem      # The CA certificate
serial          = $dir/serial                   # The current serial number
crl             = $dir/crls/crl.pem             # The current CRL
private_key     = $dir/private/SCAkey.pem       # The private key

default_days    = 1825                          # how long to certify for
default_crl_days= 30                            # how long before next CRL
default_md      = md5                           # which md to use.

x509_extensions = SCA_cert                      # The extentions to add to the cert
preserve        = no

policy          = policy_anything               # default policy

[ User_CA ]

dir             = $path/UserCA                  # Where everything is kept
certs           = $dir/certs                    # Where the issued certs are kept
crl_dir         = $dir/crls                     # Where the issued crl are kept
database        = $dir/index.txt                # database index file.
new_certs_dir   = $dir/newcerts                 # default place for new certs.

certificate     = $dir/private/UCAcert.pem      # The CA certificate
serial          = $dir/serial                   # The current serial number
crl             = $dir/crls/crl.pem             # The current CRL
private_key     = $dir/private/UCAkey.pem       # The private key

default_days    = 730                           # how long to certify for
default_crl_days= 30                            # how long before next CRL
default_md      = md5                           # which md to use.

x509_extensions = UCA_cert                      # The extentions to add to the cert
preserve        = no

policy          = policy_match                  # default policy

[ policy_match ]

countryName             = match
stateOrProvinceName     = supplied
localityName            = optional
organizationName        = supplied
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

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

####################################################################
[ req ]

default_bits                    = 2048
distinguished_name              = req_distinguished_name
attributes                      = req_attributes

x509_extensions                 = v3_ca         # The extentions to add to the self signed cert

string_mask                     = nombstr

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

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

localityName                    = Locality Name (eg, city)
localityName_default            = Nuernberg

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

organizationalUnitName          = Organizational Unit Name (eg, section or website)
organizationalUnitName_default  = OrganisationUnit

commonName                      = Common Name (SERVER / USER name)
#commonName_default             = server.company.de
commonName_max                  = 64

emailAddress                    = Email Address (eg, YOUR email)
emailAddress_default            = webmaster@company.de

[ req_attributes ]
        # Das Challenge Password dient dazu, sich bei Verlust des geheimen
        # Schluessels gegenueber der Herausgeber-CA fuer einen
        # Zertifikatswiderruf auszuweisen. Wird bei der Erstellung der
        # Zeritifikatsanforderung erfragt.

challengePassword               = A challenge password
challengePassword_min           = 4
challengePassword_max           = 20

unstructuredName                = company.de

##################################################################
[ RCA_cert ]

basicConstraints        = critical, CA:TRUE
keyUsage                = cRLSign, keyCertSign
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid,issuer:always
subjectAltName          = email:copy
issuerAltName           = issuer:copy
#crlDistributionPoints  = URI:http://company.homeip.net/RCA.crl
nsCertType              = sslCA, emailCA, objCA
#nsBaseUrl              = https://company.de/
nsComment               = "issued by company.de CA"


[ SCA_cert ]

# basicConstraints      = critical, CA:FALSE
keyUsage                = digitalSignature, keyEncipherment
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid,issuer:always
subjectAltName          = email:copy
issuerAltName           = issuer:copy
#crlDistributionPoints  = URI:http://company.homeip.net/SCA.crl
nsCertType              = server
nsBaseUrl               = https://company.de/
nsComment               = "issued by company.de (Server CA)"


[ UCA_cert ]

# basicConstraints      = critical, CA:FALSE
keyUsage                = digitalSignature, keyEncipherment, keyAgreement
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid,issuer:always
subjectAltName          = email:copy
issuerAltName           = issuer:copy
#crlDistributionPoints  = URI:http://company.homeip.net/UCA.crl
nsCertType              = client, email
#nsBaseUrl              = https://company.de/
nsComment               = "issued by company.de (User CA)"


#################################################################
[ v3_ca ]

basicConstraints        = critical, CA:true
keyUsage                = cRLSign, keyCertSign
subjectKeyIdentifier    = hash
authorityKeyIdentifier  = keyid,issuer:always
subjectAltName          = email:copy
issuerAltName           = issuer:copy
#crlDistributionPoints  = URI:http://company.de/RCA.crl
nsCertType              = sslCA, emailCA, objCA
#nsBaseUrl              = https://company.de/
nsComment               = "issued by company.de CA"

[ crl_ext ]

issuerAltName           = issuer:copy
authorityKeyIdentifier  = keyid:always,issuer:always

./scripts/mk_ca_struct

#!/bin/sh
# RootCA + Server-CA + UserCA erstellen
#
# $Id: mk_ca_struct,v 1.2 2008/06/26 20:49:58 root Exp root $
#
# $Log: mk_ca_struct,v $
# Revision 1.2  2008/06/26 20:49:58  root
# *** empty log message ***
#
# Revision 1.1  2008/06/26 20:35:28  root
# Initial revision
#
#

absolute_dir ()
{
    [ -d "$1" ] || exit 1
    pushd "$1" >/dev/null
    pwd
    popd >/dev/null
}

bdir=`dirname $0`
pwd=`pwd`

echo -n "Where to install the CA directories [$pwd] "
read a

if [ -z "$a" ]; then
    CA_DIR=$pwd
else
    [ -d "$1" ] || mkdir $a
    CA_DIR=`absolute_dir $a`
fi

if [ -d $CA_DIR/certs ]; then
    echo -n "Warning: $CA_DIR/certs found - delete all [n] "
    read b

    if [ -z "$b" -o "$b" == "n" -o "$b" == "N" ]; then
        echo "OK, exiting"
        exit 0
    fi

else
    [ -d $CA_DIR ] || mkdir $CA_DIR
fi

cp -r $bdir $CA_DIR
pushd $CA_DIR

rm -rf certs private RootCA ServerCA UserCA 2>/dev/null
mkdir certs private

cat <<EOF > openssl.cnf
# openssl.cnf by neobiker

HOME = .
RANDFILE = $ENV::HOME/.rnd

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

path = $CA_DIR

EOF

cat scripts/openssl.cnf.tpl >> openssl.cnf

cat <<EOF

----------------------
Erstelle eine Root CA:

EOF

mkdir RootCA
cd RootCA
mkdir certs newcerts private
chmod go-rwx private
echo "01" > serial
touch index.txt
cd ..

openssl req -config openssl.cnf \
            -newkey rsa:2048 -x509 -days 1825 \
            -out    RootCA/private/RCAcert.pem -outform PEM \
            -keyout RootCA/private/RCAkey.pem

cp RootCA/private/RCAcert.pem certs/00.pem
cd certs
c_rehash .
cd ..

cat <<EOF


----------------------------------------------
Erstelle eine Server CA (signiert von Root CA):

EOF

cd $CA_DIR
mkdir ServerCA
cd ServerCA
mkdir certs newcerts private
chmod go-rwx private
echo "01" > serial
touch index.txt
cd ..

openssl req -config openssl.cnf \
            -newkey rsa:2048 -days 1825 \
            -out    ServerCA/private/SCAreq.pem -outform PEM \
            -keyout ServerCA/private/SCAkey.pem

openssl ca -config openssl.cnf \
           -name Root_CA \
           -in  ServerCA/private/SCAreq.pem \
           -out ServerCA/private/SCAcert.pem

cp ServerCA/private/SCAcert.pem certs/01.pem
cd certs
c_rehash .
cd ..

cat <<EOF


---------------------------------------------
Erstelle eine User CA (signiert von Root CA):

EOF

cd $CA_DIR
mkdir UserCA
cd UserCA
mkdir certs newcerts private
chmod go-rwx private
echo "01" > serial
touch index.txt
cd ..

openssl req -config openssl.cnf \
            -newkey rsa:2048 -days 1825 \
            -out    UserCA/private/UCAreq.pem -outform PEM \
            -keyout UserCA/private/UCAkey.pem

openssl ca -config openssl.cnf \
           -name Root_CA \
           -in  UserCA/private/UCAreq.pem \
           -out UserCA/private/UCAcert.pem

cp UserCA/private/UCAcert.pem certs/02.pem
cd certs
c_rehash .
cd ..

popd

./scripts/mk_cert_server

#!/bin/sh
#
# $Id: mk_cert_server,v 1.1 2008/06/26 20:35:28 root Exp root $
#
# $Log: mk_cert_server,v $
# Revision 1.1  2008/06/26 20:35:28  root
# Initial revision
#

absolute_dir ()
{
    pushd `dirname $0` >/dev/null
    cd $1
    pwd
    popd >/dev/null
}

dir=`absolute_dir dirname $0\..`
pushd $dir

echo ""
echo -n "Server-Cert Name: "
read cert

[ -z "$cert" ] && popd && exit 1

if [ -e private/${cert}Key.pem ]; then
    echo "Error: private/${cert}Key.pem exists!"
    ls -l */${cert}*
    exit 1
fi

echo "--------"
echo "${cert}Key.pem & ${cert}Req.pem ..."
echo ""

openssl req -config openssl.cnf \
            -newkey rsa:1024 \
            -keyout ${cert}Key.pem -keyform PEM \
            -out    ${cert}Req.pem -outform PEM

echo ""
echo -n "Passwort aus ${cert}Key.pem entfernen [y] ? "
read a

if [ -z "$a" -o "$a" == "y" -o "$a" == "Y" ]; then

    openssl rsa < ${cert}Key.pem \
                > ${cert}-Key.pem

    chmod go-rwx ${cert}-Key.pem ${cert}Key.pem
    cp ${cert}-Key.pem private
    mv ${cert}-Key.pem ServerCA/private
fi
cp ${cert}Key.pem private
mv ${cert}Key.pem ServerCA/private

echo "===================="
echo "${cert}Cert.pem  ..."
echo "===================="

openssl ca -config openssl.cnf \
           -name Server_CA \
           -in   ${cert}Req.pem \
           -out  ${cert}Cert.pem

chmod go-rwx ${cert}Cert.pem
cp ${cert}Cert.pem certs
mv ${cert}Cert.pem ServerCA/certs
mv ${cert}Req.pem  ServerCA/private

echo "----------------------------------------------"
echo ""
ls -l certs private
echo ""

popd

Zuerst lege ich die CA Struktur mit den entsprechenden Zertifikaten an:

scx:/root/ca# ./scripts/mk_ca_struct
...

Im Anschluss erzeuge ich mir für z.B. Cyrus-Imap-Server mein erstes Server-Zertifikat mit folgendem Script:

scx:/root/ca# ./scripts/mk_cert_server

Server-Cert Name: imap
...

Ein Test sieht so aus:

scx:/root/ca# openssl s_client -CApath /root/ca/certs -port 993 -host imap > /tmp/foo
...