Starting in the Solaris 10 1/06 release, SMTP can use Transport Layer Security (TLS) in version 8.13 of sendmail. This service to SMTP servers and clients provides private, authenticated communications over the Internet, as well as protection from eavesdroppers and attackers. Note that this service is not enabled by default.
The following procedure uses sample data to show you how to set up the certificates that enable sendmail to use TLS. For more information, see Support for Running SMTP With TLS in Version 8.13 of sendmail.
Become superuser or assume an equivalent role.
Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services. To configure a role with the Primary Administrator profile, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.
Stop sendmail.
# svcadm disable -t network/smtp:sendmail |
Set up the certificates that enable sendmail to use TLS.
Complete the following:
# cd /etc/mail # mkdir -p certs/CA # cd certs/CA # mkdir certs crl newcerts private # echo "01" > serial # cp /dev/null index.txt # cp /etc/sfw/openssl/openssl.cnf . |
Use your preferred text editor to change the dir value in the openssl.cnf file from /etc/sfw/openssl to /etc/mail/certs/CA.
Use the openssl command-line tool to implement TLS.
Note that the following command line generates interactive text.
# openssl req -new -x509 -keyout private/cakey.pem -out cacert.pem -days 365 \ -config openssl.cnf Generating a 1024 bit RSA private key .....................................++++++ .....................................++++++ writing new private key to 'private/cakey.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) []:US State or Province Name (full name) []:California Locality Name (eg, city) []:Menlo Park Organization Name (eg, company) [Unconfigured OpenSSL Installation]:Sun Microsystems Organizational Unit Name (eg, section) []:Solaris Common Name (eg, YOUR name) []:somehost.somedomain.example.com Email Address []:someuser@example.com |
This command creates and processes certificate requests.
This req option generates a new certificate request.
This req option creates a self-signed certificate.
This req option enables you to assign private/cakey.pem as the file name for your newly created private key.
This req option enables you to assign cacert.pem as your output file.
This req option enables you to certify the certificate for 365 days. The default value is 30.
This req option enables you to specify openssl.cnf as the configuration file.
Note that this command requires that you provide the following:
Country Name, such as US.
State or Province Name, such as California.
Locality Name, such as Menlo Park.
Organization Name, such as Sun Microsystems.
Organizational Unit Name, such as Solaris.
Common Name, which is the machine's fully qualified host name. For more information, see the check-hostname(1M) man page.
Email Address, such as someuser@example.com.
(Optional) If you need a new secure connection, make a new certificate and sign the new certificate with the certificate authority.
Make a new certificate.
# cd /etc/mail/certs/CA # openssl req -nodes -new -x509 -keyout newreq.pem -out newreq.pem -days 365 \ -config openssl.cnf Generating a 1024 bit RSA private key ..............++++++ ..............++++++ writing new private key to 'newreq.pem' ----- 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) []:US State or Province Name (full name) []:California Locality Name (eg, city) []:Menlo Park Organization Name (eg, company) [Unconfigured OpenSSL Installation]:Sun Microsystems Organizational Unit Name (eg, section) []:Solaris Common Name (eg, YOUR name) []:somehost.somedomain.example.com Email Address []:someuser@example.com |
This command requires that you provide the same information that you provided in step 3c.
Note that in this example, the certificate and private key are in the file newreq.pem.
Sign the new certificate with the certificate authority.
# cd /etc/mail/certs/CA # openssl x509 -x509toreq -in newreq.pem -signkey newreq.pem -out tmp.pem Getting request Private Key Generating certificate request # openssl ca -config openssl.cnf -policy policy_anything -out newcert.pem -infiles tmp.pem Using configuration from openssl.cnf Enter pass phrase for /etc/mail/certs/CA/private/cakey.pem: Check that the request matches the signature Signature ok Certificate Details: Serial Number: 1 (0x1) Validity Not Before: Jun 23 18:44:38 2005 GMT Not After : Jun 23 18:44:38 2006 GMT Subject: countryName = US stateOrProvinceName = California localityName = Menlo Park organizationName = Sun Microsystems organizationalUnitName = Solaris commonName = somehost.somedomain.example.com emailAddress = someuser@example.com X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Comment: OpenSSL Generated Certificate X509v3 Subject Key Identifier: 93:D4:1F:C3:36:50:C5:97:D7:5E:01:E4:E3:4B:5D:0B:1F:96:9C:E2 X509v3 Authority Key Identifier: keyid:99:47:F7:17:CF:52:2A:74:A2:C0:13:38:20:6B:F1:B3:89:84:CC:68 DirName:/C=US/ST=California/L=Menlo Park/O=Sun Microsystems/OU=Solaris/\ CN=someuser@example.com/emailAddress=someuser@example.com serial:00 Certificate is to be certified until Jun 23 18:44:38 2006 GMT (365 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 # rm -f tmp.pem |
In this example the file newreq.pem contains the unsigned certificate and private key. The file newcert.pem contains the signed certificate.
Displays certificate information, converts certificates to various forms, and signs certificate requests
Used to sign certificate requests in a variety of forms and to generate CRLs (certificate revocation lists)
Enable sendmail to use the certificates by adding the following lines to your .mc file.
define(`confCACERT_PATH', `/etc/mail/certs')dnl define(`confCACERT', `/etc/mail/certs/CAcert.pem')dnl define(`confSERVER_CERT', `/etc/mail/certs/MYcert.pem')dnl define(`confSERVER_KEY', `/etc/mail/certs/MYkey.pem')dnl define(`confCLIENT_CERT', `/etc/mail/certs/MYcert.pem')dnl define(`confCLIENT_KEY', `/etc/mail/certs/MYkey.pem')dnl |
For more information, see Configuration File Options for Running SMTP With TLS.
Rebuild and install your sendmail.cf file in your /etc/mail directory.
For detailed instructions, see Building the sendmail.cf Configuration File.
Create symbolic links from the files you created with openssl to the files you defined in your .mc file.
# cd /etc/mail/certs # ln -s CA/cacert.pem CAcert.pem # ln -s CA/newcert.pem MYcert.pem # ln -s CA/newreq.pem MYkey.pem |
For added security, deny read permission to group and others for MYkey.pem.
# chmod go-r MYkey.pem |
Use a symbolic link to install CA certs in the directory assigned to confCACERT_PATH.
# C=CAcert.pem # ln -s $C `openssl x509 -noout -hash < $C`.0 |
For secure mail with other hosts, install their host certificates.
Copy the file defined by the other host's confCACERT option to /etc/mail/certs/host.domain.cert.pem.
Replace host.domain with the other host's fully qualified host name.
Use a symbolic link to install CA certs in the directory assigned to confCACERT_PATH.
# C=host.domain.cert.pem # ln -s $C `openssl x509 -noout -hash < $C`.0 |
Replace host.domain with the other host's fully qualified host name.
Restart sendmail.
# svcadm enable network/smtp:sendmail |
The following is an example of a Received: header for secure mail with TLS.
Received: from his.example.com ([IPv6:2001:db8:3c4d:15::1a2f:1a2b]) by her.example.com (8.13.4+Sun/8.13.4) with ESMTP id j2TNUB8i242496 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for <janepc@her.example.com>; Tue, 29 Mar 2005 15:30:11 -0800 (PST) Received: from her.example.com (her.city.example.com [192.168.0.0]) by his.example.com (8.13.4+Sun/8.13.4) with ESMTP id j2TNU7cl571102 version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for <janepc@her.example.com>; Tue, 29 Mar 2005 15:30:07 -0800 (PST) |
Note that the value for verify is OK, which means that the authentication was successful. For more information, see Macros for Running SMTP With TLS.
The following OpenSSL man pages: