Root-CA

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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

Das Konfigurationsfile für alle 3 CAs liegt unter /etc/ssl/openssl.conf:

# OpenSSL configuration file for certificates.
# 2007 by neobiker
#
# $Id: openssl.cnf,v 1.3 2007/02/19 11:03:40 root Exp root $
#
# $Log: openssl.cnf,v $
# Revision 1.3  2007/02/19 11:03:40  root
# commented out crlDistributionPoints and nsBaseUrl
# deleted additional subjectAltNAme and issuerAltName
#
# Revision 1.2  2007/02/19 08:48:50  root
# initial configuration
#

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

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

path = /etc/ssl

[ 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     = Bavaria

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

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

organizationalUnitName          = Organizational Unit Name (eg, section or website)
organizationalUnitName_default  = Company XY CA

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

emailAddress                    = Email Address (eg, YOUR email)
emailAddress_default            = your-mail-account

[ 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                = neobiker.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://neobiker.de/RCA.crl
nsCertType              = sslCA, emailCA, objCA
nsBaseUrl               = https://neobiker.de/
nsComment               = "ausgegeben von neobiker's 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://neobiker.de/SCA.crl
nsCertType              = server
nsBaseUrl               = https://neobiker.de/
nsComment               = "ausgegeben von neobiker's CA (Server)"


[ 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://neobiker.de/UCA.crl
nsCertType              = client, email
nsBaseUrl               = https://friedrich-net.de/
nsComment               = "ausgegeben von neobiker's CA (User)"


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

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

[ crl_ext ]

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

Jetzt lege ich unter /etc/ssl die Verzeichnisse und die CAs an:

#!/bin/sh
# RootCA + Server-CA + UserCA erstellen
#
# $Id: mk_ca_struct,v 1.1 2007/02/19 11:44:22 root Exp root $
#
# $Log: mk_ca_struct,v $
# Revision 1.1  2007/02/19 11:44:22  root
# Initial revision
#

cd /etc/ssl
rm -i certs/* private/*
rm -rf RootCA ServerCA UserCA

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 -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 die von Root CA signiert wurde:

EOF

cd /etc/ssl
mkdir ServerCA
cd ServerCA
mkdir certs newcerts private
chmod go-rwx private
echo "01" > serial
touch index.txt
cd ..

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

openssl ca -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 die von Root CA signiert wurde:

EOF

cd /etc/ssl
mkdir UserCA
cd UserCA
mkdir certs newcerts private
chmod go-rwx private
echo "01" > serial
touch index.txt
cd ..

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

openssl ca -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 ..

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

#!/bin/sh
#
# $Id: mk_cert_server,v 1.4 2007/01/07 15:34:54 root Exp root $
#
# $Log: mk_cert_server,v $
# Revision 1.4  2007/01/07 15:34:54  root
# little beatifying
#
# Revision 1.3  2007/01/07 15:26:38  root
# chmod settings changed
#

pwd=`pwd`
dir=/etc/ssl
cd $dir

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

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

echo "Schluessel (Key) und Zertifikatanfrage (Req) ..."
echo ""
openssl req -newkey rsa:1024 -keyout ${cert}Key.pem -keyform PEM \
            -out ${cert}Req.pem -outform PEM

# Zum Start des Server's das Passwort aus dem Schluessel entfernen
echo ""
echo -n "Passwort aus Zertifikate-Schluessel 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
    mv ${cert}-Key.pem $dir/private
fi
mv ${cert}Key.pem $dir/private

echo ""
echo "Zertifikat erstellen / signieren ..."
echo ""
openssl ca -name Server_CA -in ${cert}Req.pem -out ${cert}Cert.pem
chmod go-rwx $dir/${cert}Cert.pem
mv ${cert}Cert.pem $dir/certs
mv ${cert}Req.pem $dir/private

echo ""
ls -l $dir/certs $dir/private
echo ""
xen1:/etc/ssl# ./scripts/mk_cert_server

Server-Cert Name: imap
Schluessel (Key) und Zertifikatanfrage (Req) ...

Generating a 1024 bit RSA private key
.................++++++
...................................++++++
writing new private key to 'imapKey.pem'
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [DE]:
State or Province Name (full name) [Bavaria]:
Locality Name (eg, city) [Nuremberg]:
Organization Name (eg, company) [neobiker.de]:
Organizational Unit Name (eg, section or website) [neobiker's CA]:
Common Name (SERVER / USER name) []:imap.fqdn
Email Address (eg, YOUR email) [yourmail]:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
neobiker.de []:

Passwort aus Zertifikate-Schluessel entfernen [y] ?
Enter pass phrase:
writing RSA key

Zertifikat erstellen / signieren ...

Using configuration from /usr/lib/ssl/openssl.cnf
Enter pass phrase for /etc/ssl/ServerCA/private/SCAkey.pem:
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
countryName           :PRINTABLE:'DE'
stateOrProvinceName   :PRINTABLE:'Bavaria'
localityName          :PRINTABLE:'Nuremberg'
organizationName      :PRINTABLE:'neobiker.de'
organizationalUnitName:PRINTABLE:'neobikers CA'
commonName            :PRINTABLE:'imap.fqdn'
emailAddress          :IA5STRING:'yourmail'
Certificate is to be certified until Feb 18 11:19:49 2012 GMT (1825 days)
Sign the certificate? [y/n]:y


1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated

/etc/ssl/certs:
total 28
-rw-r--r-- 1 root root 2061 2007-02-19 12:15 00.pem
-rw-r--r-- 1 root root 5917 2007-02-19 12:16 01.pem
-rw-r--r-- 1 root root 5911 2007-02-19 12:17 02.pem
lrwxrwxrwx 1 root root    6 2007-02-19 12:17 51c08bfb.0 -> 01.pem
lrwxrwxrwx 1 root root    6 2007-02-19 12:17 545678ed.0 -> 00.pem
lrwxrwxrwx 1 root root    6 2007-02-19 12:17 eb8ee7de.0 -> 02.pem
-rw------- 1 root root 5317 2007-02-19 12:19 imapCert.pem

/etc/ssl/private:
total 12
-rw------- 1 root root 891 2007-02-19 12:19 imap-Key.pem
-rw------- 1 root root 963 2007-02-19 12:19 imapKey.pem
-rw-r--r-- 1 root root 761 2007-02-19 12:19 imapReq.pem

Das File imap-Key-pem ist dabei der private Schlüssel ohne Passwort, damit der Server ohne Passwort-Eingabe den Cyrus starten kann. Die beiden Files private/imap-Key.pem und certs/imapCert-pem kopiere ich auf meinen Imap-Server nach /etc/ssl und trage diese Zertifikate in das Konfigfile /etc/imapd.cond auf dem Imap-Server ein:

scp certs/imap.Cert.pem imap:/etc/ssl/certs
scp private/imap-Key.pem imap:/etc/ssl/private

Ein Test sieht so aus:

xen1:/etc/ssl# openssl s_client -CApath /etc/ssl/certs -port 993 -host imap > /tmp/foo
depth=2 /C=DE/ST=Bavaria/L=Nuremberg/O=neobiker.de/OU=neobiker's User-CA/CN=imap.fqdn/emailAddress=yourmail
verify return:1
depth=1 /C=DE/ST=Bavaria/L=Nuremberg/O=neobiker.de/OU=neobiker's Server-CA/CN=imap.fqdn/emailAddress=yourmail
verify return:1
depth=0 /C=DE/ST=Bavaria/L=Nuremberg/O=neobiker.de/OU=neobiker's CA/CN=imap.fqdn/emailAddress=yourmail
verify return:1

CTRL-C