Building a Secure RedHat Apache Server HOWTO
Richard Sigle, Richard.sigle@equifax.com
0.1, 2001-02-06
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The guide is designed to explain how PKI and SSL work together. It is essential
to understand how the SSL protocol works to successfully deploy a secure
server.
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1. Purpose/Scope of this Guide
The purpose of this guide is to assist RedHat Linux users with the installation
of server (SSL) certificates using the Apache web server. The goal is to
provide a clear procedure that will save time and, in many cases, money!
First, I will cover what you need to know about the SSL protocol and digital
certificates. In my experience, building an Apache web server with ModSSL and
OpenSSL is the most beneficial software combination. OpenSSL is a general-
purpose cryptography library that supports the SSL v2/v3 and TLS v1 protocols.
ModSSL is an Apache API module designed to act as an interface between Apache
and OpenSSL. The biggest advantage is that all three packages are free.
Then, beginning with Section 4, I will go through the step-by-step procedures
for generating keys and installing certificates on a RedHat-Apache server
compiled with ModSSL and OpenSSL. The procedures in Section 4 will also work
with commercial SSL-server packages such as Stronghold and Raven that are
closely related to Apache.
Disclaimer: I am a technical support engineer for Equifax Secure Inc., a
Certificate Authority. Therefore, I use Equifax Secure certificates and
examples geared towards installing Equifax Secure certificates. However, the
instructions will also work with certificates issued by other Certificate
Authorities. Since this document was written at my own initiative, Equifax
Secure Inc. is neither liable nor accountable for any consequences resulting
from the use of these procedures.
My comments to the reader is in this style (emphasized).
Example lines are in plain roman style.
Note that extra comments and advice is found in comments within the SGML
source.
1.1 About Secure Sockets Layer (SSL)
SSL is a presentation layer service, located between the TCP and the
application layer. It is platform and application independent. SSL is
responsible for the management of a secure communications channel between the
client and server. SSL provides a strong mechanism for encrypting data
transferred between a client and a server.
1.2 FeedBack
Comments on this guide may be directed to the author
(richard.sigle@equifax.com).
1.3 Copyrights and Trademarks
Copyright (c) 2001 by Richard L. Sigle
Please freely copy and distribute this document in any format. It's requested
that corrections and/or comments be forwarded to the document maintainer. You
may create a derivative work and distribute it provided that you:
* Send your derivative work (in the most suitable format such as sgml) to the
LDP (Linux Documentation Project) or the like for posting on the Internet. If
not the LDP, then let the LDP know where it is available.
* License the derivative work with this same license or use GPL. Include a
copyright notice and at least a pointer to the license used.
* Give due credit to previous authors and major contributors.
If you're considering making a derived work other than a translation, it's
requested that you discuss your plans with the current maintainer.
1.4 Acknowledgements and Thanks
I would like to thank Tony Villasenor for tirelessly reading my drafts and
offering his input and advice. Without Tony, this document would never have
been finished.
2. Introduction to Secure Sockets Layer/Private Key Infrastructure
PKI is an asymmetric key system which consists of a public key (which is sent
to clients) and a private key (stays local on the server). PKI differs from a
symmetric key system in which both the client and server use the same key for
encryption/decryption.
2.1 Responsibilities of SSL/PKI
SSL sets out to fulfill requirements that make it acceptable for use in the
transmission of even the most sensitive of transactions, such as credit card
information, medical records, legal documents, and e-commerce applications.
Each application can choose to utilize some or all of the following criteria
depending on the sensitivity and value of the transactions it will be
processing.
Privacy
Let's say that a message is to be coded for transmission from A to B. A
uses B's public key to encrypt the message. In this way B will be the
only person who can decode and read this message using his private key.
We cannot however be sure that A is the person who he claims to be.
Authenticity
In order to be sure that A is the person who he claims to be, we want
guaranteed authenticity. This requires a slightly more complex coding
process. In this case, A's message to B is first encrypted with A's
private key and then with B's public key. B now has to decrypt it first
with his private key and then with A's public key. Now B can be sure that
A is who he claims to be as nobody else could create a message encrypted
with his private key. SSL achieves this with the use of certificates
(PKI). A certificate is issued by a neutral third party - such as a
certificate authority (CA) - and includes a digital signature and/or a
time stamp in addition to the public key of the certified party. A self-
signed digital certificate can be created by anyone with the correct SSL
tools, but self-signed certificates lack the weight of validation
performed by a mutually respected neutral third party.
integrity
In SSL, integrity is guaranteed by using a MAC (Message Authentication
Code) with the necessary hash table functions. Upon generation of a
message, the MAC is obtained by applying a hash function and the result
is then added to the message. After the message has been received,
validity is then checked by comparing the message's embedded MAC with a
new MAC computed from the received message. This would immediately reveal
messages that have been altered by a third party.
Non-Repudiation
Non-repudiation protects both parties from each other during online
transactions. It prevents one or the other from saying that they did not
send a particular piece of information. Non-repudiation does not allow
either party to alter the transaction after it has been made. Digital
non-repudiation is the equivalent of signing a contract, in the
traditional sense.
2.2 How SSL Works
The SSL protocol includes two sub-protocols: the SSL record protocol and the
SSL handshake protocol. The SSL record protocol defines the format used to
transmit data. The SSL handshake protocol involves using the SSL record
protocol to exchange a series of messages between an SSL-enabled server and an
SSL-enabled client when they first establish an SSL connection. This exchange
of messages is designed to facilitate the following actions:
* Authenticate the server to the client. The server certificate is signed by a
Certificate Authority to insure that it is not corrupted and establishes a
chain of trust.
* Allow the client and server to select the cryptographic algorithms, or
ciphers, that they both support.
* Optionally authenticate the client to the server.
* Use public-key encryption techniques to generate shared secrets.
* Establish an encrypted SSL connection.
SSL Handshake Protocol
The Handshake Protocol is used to co-ordinate the state of the client and the
server. During the handshake, the following events take place:
* Certificates are exchanged between the client and server (asymmetric keys).
The server sends its public key to the client. If the server is set to verify
client authentication via a certificate, the client sends its public key to
the server. The validity dates on the certificates are verified and they are
checked for the digital signature of a trusted certificate authority. If the
validity date and/or digital signature are not correct, the browser will
issue a warning to the user. The user is then given the option to trust the
certificate holder.
* The client then generates a random key (symmetric key). These will be used
for encryption and for calculating MACs. They are encrypted using the
server's public key and sent to the server. Only the server has the ability
to decrypt the new random key. The new symmetric key is used for encrypting
the data that is sent between client and server.
Note: The use of a symmetric key after server-browser authentication greatly
enhances subsequent throughput performance.
* A message encryption algorithm and a hash function for integrity are
negotiated. This negotiation process could be carried out such that the
client presents a list of supported algorithms to the server, which, in turn,
selects the strongest cipher available to both of them. Identifiers for the
chosen encryption algorithm and hash function are stored in the cipher spec
field of the current state for use by the record protocol.
* All of the following fields are set during handshaking: Protocol Version,
Session ID, Cipher Suite, Compression Method and two random values
ClientHello.random and ServerHello.random.
Note: An IP address is required for each SSL connection. Name based virtual
hosts are resolved during the application layer. Remember Secure Sockets Layer
resides below the application layer.
Session Key(Symmetric Code)
* 40-bit, originally used only for export purposes
* 56-bit, used by DES
* 64-bit key - used by CAST, 256 times stronger than 56-bit
* 80-bit key - used by CAST, 16 million times stronger than 56-bit (infeasible
to break with current technology)
* 128-bit key - used by CAST or RC2, exhaustive key search impossible now and
for the foreseeable future
Public/Private Key Pair(Asymmetric Code)
* 512-bit
* 768-bit
* 1024-bit
* 2048-bit
2.3 How PKI Works
The client and the server each have a public key and a private key (the
client's browser randomly creates a key pair for the SSL session, unless, a
client certificate is held by the client and requested by the server).
The sender uses their private key to encrypt a message. This act authenticates
the source of the message. The resulting cipher is encrypted once more with the
receiving party's public key. This action provides confidentiality because only
the receiving party is able to do the initial decryption of the message using
their private key. The receiver uses the sender's public key to further decrypt
the encrypted message. Because only the sender has access to their private key,
the receiver is assured that the encrypted message originated from the sender.
A message digest is used to verify that neither party or a third party has
tampered with or changed the message in any way. A message digest is obtained
by applying a hash function (part of the private key known as the fingerprint)
to the message. The digest (which is now known as the signature) is attached or
appended to the message. The signature's length is constant (no matter how
large the file is) and depends on what type of message digest the private key
contains (md5 - 128 bit, sha1 - 160 bit, etc). Changing even one bit in the
message will change the length of the signature and thus prove that the message
has been tampered with.
2.4 Certificates(x509 Standard)
Digital certificates make it possible to trust an entity on the Internet. A
digital certificate contains the user's credentials, which have been verified
by a neutral third-party certificate authority.
A mathematical algorithm and a value (key) are used to encrypt data into an
unreadable form. A second key is used to decrypt the data, using a
complementary algorithm and a related value. The two keys must contain a
related value and are known as a key pair.
Note: ITU-T Recommendation X.509 [CCI88c] specifies the authentication service
for X.500 directories, as well as the X.509 certificate syntax. The certificate
is signed by the issuer to authenticate the binding between the subject
(user's) name and the user's public key. SSLv3 was adopted in 1994. The major
difference between versions 2 and 3 is the addition of the extensions field.
This field grants more flexibility as it can convey additional information
beyond just the key and name binding. Standard extensions include subject and
issuer attributes, certification policy information, and key usage
restrictions.
An X.509 certificate consists of the following fields:
* Version
* serial number
* signature algorithm ID
* issuer name
* validity period
* subject (user) name
* subject public key information
* issuer unique identifier (version 2 and 3 only)
* subject unique identifier (version 2 and 3 only)
* extensions (version 3 only)
* signature on the above fields
2.5 Digital Certificate Private Key
The private key is not embedded within a digital certificate. The private key
does not include any server information. It contains encryption information and
a fingerprint. It is generated locally on your system and should remain in a
secure environment. If the private key is compromised, a perpetrator
essentially has the code to your security system. The transmissions between
client and server can be intercepted and decrypted. This type of vulnerability
is why it is recommended to create a private key that is encrypted using triple
DES technology. The file is then encrypted and password protected making it all
but impossible to use without the correct pass phrase.
The security of a transaction is dependent on its private key. Should this key
fall into the wrong hands then anyone can easily duplicate it and use it to
compromise security. A compromised key could lead to messages meant for the
server to be intercepted and manipulated by unscrupulous hackers. A fully
secure system must be able to detect impostors and prevent the duplication of
keys.
2.6 Digital Certificate Public Key
The public key is embedded in a digital certificate, which is sent by the
server to a client when a secure connection is requested. This process
identifies the server using the certificate. The public key validates the
integrity, authenticity, and is also used to encrypt data to create a private
data transmission.
2.7 Certificate Signing Request(CSR)
A CSR contains the information required by a certificate authority to create
the certificate. The CSR contains an encrypted version of the private key's
complimentary algorithm, common value, and information that identifies the
server. This information includes, but is not limited to, country, state,
organization, common name (domain name), and contact information.
3. Working with Certificates
The following section covers the steps involved in creating the private key
file, certificate signing request, and a self-signed certificate. If you plan
to obtain a certificate signed by a certificate authority, you will need to
create a certificate signing request (CSR). Otherwise, you can create a self-
signed certificate.
3.1 Create a Private Key
To create a private key, you must have the OpenSSL toolkit installed and
configured with Apache. The following examples use the OpenSSL command line
tool which is located in the /usr/local/ssl/bin directory by default. The
examples assume that the directory containing the OpenSSL command line tool has
been added to the $PATH.
To create a private key using the triple des encryption standard (recommended),
use the following command:
openssl genrsa -des3 -out filename.key 1024
You will be prompted to enter and re-enter a pass phrase. If you choose to use
triple des encryption, you will be prompted for the password each time you
start the SSL server from a cold start. (When using the restart command, you
will not be prompted for the password). Some of you may find this password
prompt to be a nuisance, especially if you need to boot the system during off-
hours. Or, you may believe that your system is already sufficiently secure. So,
if you choose not to have a password prompt (hence no triple des encryption),
use the command below. If you would rather create just a 512-bit key, then omit
the 1024 at the end of the command and OpenSSL will default to 512 bits. Using
the smaller key is slightly faster, but it is also less secure.
To create a private key without triple des encryption, use the following
command:
openssl genrsa -out filename.key 1024
To add a password to an existing private key, use the following command:
openssl -in filename.key -des3 -out newfilename.key
To remove a password from an existing private key, use the following command:
openssl -in filename.key -out newfilename.key
Note: Your private key will be created in the current directory unless
otherwise specified. There are 3 easy ways to deal with this. If OpenSSL is in
your path, you can run it from the directory that you have designated to store
your key files in (default is /etc/httpd/conf/ssl.key if you installed Apache
using the RPM or /usr/local/apache/conf/ssl.key if you installed Apache using
the source files). Another solution is to copy the files from the directory
where they were created to the correct directory. And, last but not least, you
can specify the path when running the command (eg. openssl genrsa -out /etc/
httpd/conf/ssl.key/filename.key 1024). Doesn't matter how you do it as long as
it gets done before you proceed.
For more information on the OpenSSL toolkit check out: OpenSSL_Website.
3.2 Create a Certificate Signing Request
To obtain a certificate signed by a certificate authority, you will need to
create a Certificate Signing Request (CSR). The purpose is to send the
certificate authority enough information to create the certificate without
sending the entire private key or compromising any sensitive information. The
CSR also contains the information that will be included in the certificate,
such as, domain name, locality information, etc.
* Locate the private key that you would like to creat a CSR from. Enter the
following command:
openssl req -new -key filename.key -out filename.csr
You will be prompted for Locality information, common name (domain name),
organizational information, etc. Check with the CA that you are applying to for
information on required fields and invalid entries.
Send the CSR to the CA per their instructions.
Wait for your new certificate and/or create a self-signed certificate. A self-
signed certificate can be used until you receive your certificate from the
certificate authority.
Note: Use the following command to create a private key and request at the same
time.
openssl genrsa -des3 -out filename.key 1024
3.3 Creating a Self-Signed Certificate
It is not necessary to create a self-signed certificate if you are obtaining a
CA-signed certificate. However, creating a self-signed certificate is very
simple. All you need is a private key and the name of the server (fully
qualified domain name) that you want to secure. You will be prompted for
information such as locality information, common name (domain name),
organizational information, etc. OpenSSL gives you a great deal of freedom
here. The only required field for the certificate to function correctly is the
common name (domain name) field. If this is not present or incorrect, you will
receive a Certificate Name Check warning from your browser.
To create a self-signed certificate:
openssl req -new -key filename.key -x509 -out filename.crt
3.4 Installing your Web Server Certificate
If you followed these instructions so far you shouldn't have any problems at
this point. If you sent your CSR to a certificate authority and you have not
gotten your certificate back yet, you can take a break now! If you are using a
self-signed certificate, or you have received your certificate, you may
continue.
* Ensure that the private key file is in the directory that you have chosen to
use. The following examples will be based on the RedHat RPM installation
default of /etc/httpd/conf/ssl.key.
* Ensure that the CA-signed or self-signed certificate is in its designated
location. Again, I will be using the RPM default of /etc/httpd/conf/ssl.crt.
If it is not there already, put it there.
* If there is an intermediate (root) certificate to be installed, copy it to
the /etc/httpd/conf/ssl.crt directory, also.
* Now, you will be required to edit the httpd.conf file. Make a back-up of this
file before you proceed to the next step, Configuring_your_Apache_Server.
4. Configuring your Apache Server
The Apache server must be configured with supplementary API modules in order to
support SSL. There are many SSL software packages available. My examples are
based on Apache configured with ModSSL and OpenSSL. There are countless mailing
lists and newsgroups available to support these products. You may find these
instructions helpful for some commercial SSL software packages that are based
on the Apache web server.
A few things to keep in mind: You can have multiple virtual hosts on the same
server. You can have numerous name-based virtual hosts on the same IP address.
You can also have numerous name-based virtual hosts and one (1) secure virtual
host on the same IP. But - you cannot have multiple secure virtual hosts on the
same IP. The question that so many ask: Why? The answer is: SSL works below the
application layer. Name based hosts are not defined until the application
layer.
Specifically, you cannot have multiple secure virtual hosts on the same SOCKET
(IP address + port). By default, a secure host will use port 443. You can
change configure your virtual host to use a different port number with the same
IP, thus creating another socket. There are many disadvantages to this
approach. The most obvious disadvantage is that if you are not using the
default port, your URL must also contain the port number to access the secure
site.
Example:
* Site using default port - www.something.com - would be accessed as https://
www.something.com
* A site using port 8888 would be accessed as https://www.something.com:8888
Another disadvantage is that if you introduce more ports, you will be providing
more opportunities for port sniffing hackers. Last, if you select a port that
is used by something else, you will create conflict problem.
4.1 Define a Secure Virtual Host
Setting up virtual hosts is fairly straightforward. I will go through the
basics of setting up a secure virtual host.
In these examples, I use the .crt and .key file extensions. That is my personal
way of avoiding confusion with the various files. With Apache, you can use any
extension you choose - or no extension at all.
All of your secure virtual hosts should be contained within and
, usually located towards the end of the httpd.conf file.
An example of a secure virtual host:
DocumentRoot /etc/httpd/htdocs
ServerName www.somewhere.com
ServerAdmin someone@somewhere.com
ErrorLog /etc/httpd/logs/error_log
TransferLog /etc/httpd/logs/access_log
SSLEngine on
SSLCertificateFile /etc/httpd/conf/ssl.crt/server.crt
SSLCertificateKeyFile /etc/httpd/conf/ssl.key/server.key
SSLCACertificateFile /etc/httpd/conf/ssl.crt/ca-bundle.crt
SSLOptions +StdEnvVars
SSLOptions +StdEnvVars
SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown
CustomLog /etc/httpd/logs/ssl_request_log \
"%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
The directives that are the most important for SSL are the SSLEngine on,
SSLCertificateFile, SSLCertificateKeyFile, and in many cases
SSLCACertificateFile directives.
SSL Engine
"SSLEngine on" - this is ModSSL's command to start SSL.
SSLCertificateFile
SSLCertificateFile Tells Apache where to find the certificate file and what it
is named. The example above shows "server.crt" as the certificate file name.
This is the default that is added when you configure ModSSL with Apache. I
personally don't recommend using the default names. Save yourself some
frustration and name your certificates as servername.crt (domainname.crt). You
may also decide to use an alternative directory than the default /etc/httpd/
conf/ssl.crt or /usr/local/apache/conf/ssl.crt. Just remember to make the
necessary changes to the path.
SSLCertificateKeyFile
SSLCertificateKeyFile tells Apache the name of the private key and where to
find it. The directory defined here should have read/write permissions for root
only. No one else should have access to this directory.
SSLCACertificateFile
The SSLCACertificateFile directive tells Apache where to find the Intermediate
(root) certificate. This directive may or may not be necessary depending on the
CA that you are using. This certificate is essentially a ring of trust.
Intermediate Certificate - A Certificate Authority obtains a certificate in
much the same way as you. This is known as an intermediate certificate. It
basically says that the holder of the intermediate certificate is whom they say
they are and is authorized to issue certificates to customers. Web browsers
have a list of "trusted" certificate authorities that is updated with each
release. If a Certificate authority is fairly new, its intermediate certificate
may not be in the browser's list of trusted CA's. Combine this with the fact
that most people don't update their browsers very often; it could take years
before a CA is recognized as trusted automatically. The solution is to install
the intermediate certificate on the server using the SSLCACertificateFile
directive. Usually, a "trusted" CA issues the intermediate certificate. If it
is not, then you may need to use the SSLCertificateChainFile directive,
although this is unlikely.
4.2 Certificate Examples
Server Certificate File
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
Contents of the Certificate File
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 1516 (0x5ec)
Signature Algorithm: md5WithRSAEncryption
Issuer: C=US, O=Equifax Secure Inc, CN=Equifax Secure E-
Business CA
Validity
Not Before: Jul 12 15:21:01 2000 GMT
Not After : Jun 2 22:42:34 2001 GMT
Subject: C=us, ST=ga, L=atlanta, O=Equifax, OU=Rick,
CN=172.18.116.44/Email=richard.sigle@equifax.com
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public Key: (1024 bit)
Modulus (1024 bit):
00:c8:eb:93:26:97:ca:00:ce:4c:e4:f3:fd:43:31:
cd:53:ed:b4:8a:ad:93:84:dc:7a:48:39:b5:28:57:
03:7f:a9:ac:3e:58:6a:7a:e3:52:3e:1e:52:58:a2:
6f:23:ad:bb:84:d8:88:ed:6d:a5:da:08:6b:c8:6c:
a5:4c:34:67:d8:46:1c:ca:20:50:b0:e8:54:7f:ca:
5e:ef:09:ff:6e:8d:a6:2b:02:f5:54:0f:c2:d0:45:
12:ad:66:e7:8b:dd:68:be:64:a4:9b:69:bd:a4:1a:
5e:ef:09:ff:6e:8d:a6:2b:02:f5:54:0f:c2:d0:45:
12:ad:66:e7:8b:dd:68:be:64:a4:9b:69:bd:a4:1a:
5a:2f:3b:6e:73:84:d8:d6:17:bd:12:39:34:fa:3d:
d8:a9:e8:59:3c:c2:61:c5:b3
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Key Usage: critical
Digital Signature, Non Repudiation, Key Encipherment,
Data Encipherment
Netscape Cert Type:
SSL Server
X509v3 Authority Key Identifier:
keyid:5B:E0:A8:75:1C:78:02:47:71:AB:CE:27:32:E7:24:88:42:
28:48:56
Signature Algorithm: md5WithRSAEncryption
87:53:74:e9:e1:a6:10:56:8c:fa:63:0e:7b:72:ff:76:4b:79:
0e:49:2a:58:ed:71:7a:bf:77:61:fa:e8:74:04:37:8c:d3:6a:
9a:3d:80:76:7a:c3:64:30:e7:1b:40:25:4e:2a:81:8b:e5:ac:
76:a4:38:67:cc:3f:93:43:e1:1d:c3:8d:ba:ed:cc:d7:aa:a4:
ab:d3:84:77:7c:8f:26:f6:dd:ba:3b:6a:99:81:e1:9e:7e:0f:
ca:a6:ff:c0:c3:59:6e:dc:a6:03:23:bf:8f:24:ff:15:ad:ac:
0d:85:fc:38:bf:d1:24:2d:1a:d3:72:55:12:95:5f:65:f0:60:
df:b1
Private Key File
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: DES-EDE3-CBC,124F61450D85A480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-----END RSA PRIVATE KEY-----
Contents of the Private Key
read RSA key
Enter PEM pass phrase:
Private-Key: (1024 bit)
modulus:
00:c8:eb:93:26:97:ca:00:ce:4c:e4:f3:fd:43:31:
cd:53:ed:b4:8a:ad:93:84:dc:7a:48:39:b5:28:57:
03:7f:a9:ac:3e:58:6a:7a:e3:52:3e:1e:52:58:a2:
6f:23:ad:bb:84:d8:88:ed:6d:a5:da:08:6b:c8:6c:
a5:4c:34:67:d8:46:1c:ca:20:50:b0:e8:54:7f:ca:
5e:ef:09:ff:6e:8d:a6:2b:02:f5:54:0f:c2:d0:45:
12:ad:66:e7:8b:dd:68:be:64:a4:9b:69:bd:a4:1a:
5a:2f:3b:6e:73:84:d8:d6:17:bd:12:39:34:fa:3d:
d8:a9:e8:59:3c:c2:61:c5:b3
publicExponent: 65537 (0x10001)
privateExponent:
00:b6:57:7d:3b:58:24:1e:a9:1b:85:e9:9c:9e:5f:
d3:3d:69:0c:21:93:37:bf:2b:2c:da:e1:6c:74:48:
cb:c7:0f:60:5f:50:74:8a:44:45:be:54:5c:5d:4e:
45:58:f6:f1:a8:b5:af:46:f2:ec:c2:bc:43:bd:28:
44:b7:ad:13:d3:ca:de:59:24:e8:fa:f8:e5:5f:45:
38:2c:a0:a3:de:98:13:d8:80:38:e1:47:53:4c:ea:
e4:66:c3:82:93:89:c3:90:83:44:e1:13:4f:74:76:
e2:c0:89:97:77:5f:33:d8:7d:27:21:52:55:c2:d7:
dc:01:f9:bc:21:8d:a3:f5:c1
prime1:
00:e3:2d:6b:5e:05:6b:e1:46:e6:ab:ae:f3:8b:d0:
5f:94:5c:6f:f5:47:46:1d:4e:66:d3:7e:98:18:e0:
2c:0d:08:ca:b7:29:72:af:53:62:30:ec:be:26:1f:
cc:5a:ed:65:62:65:70:1e:18:19:61:e3:77:00:a7:
3a:9e:4e:12:93
prime2:
00:e2:69:56:78:e8:39:ff:17:db:cc:39:d7:7f:70:
41:dc:c5:59:43:16:c1:84:4c:ae:e7:5d:8a:c5:4b:
da:88:8e:03:99:7c:88:f2:8a:13:31:57:44:e0:b5:
c8:0a:60:b0:05:de:f6:9e:f2:00:ec:37:21:8d:3b:
dc:8e:c9:d4:61
exponent1:
1a:ad:6a:be:4f:c4:ab:5f:b8:16:d1:24:a8:76:7f:
c2:dc:58:09:65:a5:46:2b:be:c7:77:46:45:25:8e:
06:b9:d1:94:50:b9:b6:fd:03:ba:db:12:39:47:e2:
a7:8a:d9:2d:04:dc:75:ac:3e:ce:cf:f7:59:8c:49:
c5:ed:45:21
exponent2:
2d:4e:fd:32:06:ef:0c:40:7f:08:d8:8e:6a:7f:51:
7e:d7:b3:6c:3c:92:8f:62:35:22:31:d3:02:76:92:
8d:ff:35:73:32:bb:c9:25:9e:7f:a2:42:33:61:cd:
5d:5e:49:fb:72:ca:11:b6:c6:3e:7f:2d:e4:b0:95:
0b:b2:12:21
coefficient:
50:52:09:22:cb:fb:b2:b8:58:85:ab:1d:82:b9:6e:
d0:f6:dc:e8:ce:a6:5d:a1:ff:c8:4d:3b:2b:1c:19:
64:f0:c4:4a:bc:b2:1d:2b:2d:09:59:83:a3:9a:89:
f8:db:2c:2c:8a:bd:fd:a3:16:51:76:aa:ce:ea:85:
6b:1c:9f:f7
4.3 Restart the Web Server
The script to restart the webserver may be located in /usr/local/sbin, /usr/
sbin, (where the script is called httpd) or /usr/local/apache/bin (where the
script is called apachectl). If you are not running the server with SSL
enabled, you will need to stop and start the server. You may also write your
own customized scripts to start, restart, and stop your server. As long as it
starts the SSL engine, you should be OK.
The commands are:
httpd stop
httpd startssl
httpd restart
or
apachectl stop
apachectl startssl
apachectl restart
5. Troubleshooting
Here are some common problems that may arise.
5.1 Server Appears to start, but you cannot access the secure site
Check the error_log file. If you did not set your virtual host to write to an
error log, you may want to reconsider. The example SSL virtual host writes to
an error log file. Most likely you will have a few warnings and an error at the
end of the log that basically say that the private key does not match the
certificate.
Example:
[Tue Nov 21 09:09:02 2000] [notice] Apache/1.3.14 (Unix) mod_ssl/
2.7.1
OpenSSL/0.9.6 configured -- resuming normal operations
[Tue Nov 21 09:09:16 2000] [notice] caught SIGTERM, shutting down
[Tue Nov 21 14:39:54 2000] [notice] Apache/1.3.14 (Unix) mod_ssl/
2.7.1
OpenSSL/0.9.6 configured -- resuming normal operations
[Tue Nov 21 14:40:31 2000] [notice] caught SIGTERM, shutting down
[Tue Nov 21 14:43:53 2000] [error] mod_ssl: Init:
(esi.fin.equifax.com:443)
Unable to configure RSA server private key (OpenSSL library error
follows)
[Tue Nov 21 14:43:53 2000] [error] OpenSSL: error:0B080074:x509
certificate
routines:X509_check_private_key:key values mismatch
If you get the error messages above, chances are the key and certificate do not
match. Make sure you aren't using the default server.key file. You should also
check the httpd.conf file to make sure that the directives are pointing to the
correct private key and certificate.
You can check to make sure that you your private key and certificate are in the
correct format and match each other. To do this, give the commands below to
decrypt the private key in one terminal window and decrypt the certificate in
the other. What you will be comparing are the Modulus and the Exponent of each
key. If the modulus and exponent from the key matches the set from the
certificate, you have just confirmed that your certificate and key are
correctly paired.
If all else fails, create a new private key, CSR or self-signed certificate.
Before you do this, check your CA's re-issue policy. You may be charged for a
re-issue.
To view the contents of the certificate:
openssl x509 -noout -text -in filename.crt
To view the contents of the private key:
openssl rsa -noout -text -in filename.key
5.2 Certificate Name Check Warning is issued by the client's browser
The most common cause for this is omitting the "www" at the beginning of the
domain name when creating the CSR. The name defined by the "ServerName"
directive for that virtual host must match the domain name presented by the
certificate exactly or the browser will let the client know. The exception is a
wild card certificate. A wild card certificate's domain name field would look
like *.somedomain.com. This enables you to use one certificate for any number
of sub-domains of somedomain.com (e.g. host1.somedomain.com and
host2.somedomain.com).
5.3 Certificate was Signed by an Untrusted Certificate Authority Warning is
issued by the client's browser
If you are using a self-signed certificate, you will get this warning. Your
clients will be given the option to trust your certificate or not. If you have
a CA signed certificate and are getting the untrusted warning, you probably
need to install their intermediate (root) certificate.
5.4 SSLEngine on is an un-recognized command (when starting Apache)
This error message is issued if you do not have ModSSL compiled with Apache.
Some SSL packages use a different directive to start SSL within a virtual host.
If you are using a package that does use a different directive, you will also
receive this error message.
5.5 You have forgotten your "PEM Passphrase" and you would like to know how to
reset it
There is no way to reset this passphrase. The only solution is to remember the
passphrase or create a new private key. You will then need to obtain a new
certificate or create a new self-signed certificate.
6. Glossary
Authentication
The positive identification of a network entity such as a server, a
client, or a user. In SSL context, authentication represents the server
and client Certificate verification process.
Access Control
The restriction of access to network realms. In Apache context usually
the restriction of access to certain URLs.
Algorithm
An unambiguous formula or set of rules for solving a problem in a finite
number of steps. Algorithms for encryption are usually called Ciphers.
Certificate
A data record used for authenticating network entities such as a server
or a client. A certificate contains X.509 information pieces about its
owner (called the subject) and the signing Certificate Authority (called
the issuer), plus the owner's public key and the signature made by the
CA. Network entities verify these signatures using CA certificates.
Certificate Authority (CA)
A trusted third party whose purpose is to sign certificates for network
entities that it has authenticated using secure means. Other network
entities can check the signature to verify that a CA has authenticated
the bearer of a certificate.
Certificate Signing Request (CSR)
An unsigned certificate for submission to a Certification Authority,
which signs it with the Private Key of their CA Certificate. Once the CSR
is signed, it becomes a real certificate. Cipher An algorithm or system
for data encryption. Examples are DES, IDEA, RC4, etc.
Ciphertext
The result after a Plaintext passed a Cipher.
Configuration Directive
A configuration command that controls one or more aspects of a program's
behavior. In Apache context these are all the command names in the first
column of the configuration files.
Cryptography - Symmetric
The client and server use the same key to encrypt and to decrypt data.
Cryptography - Asymmetric
Consists of a key pair (public and private). PKI is Asymmetric
Cryptography
Digital Signatures
A piece of data that is sent with an encrypted message that identifies
the originator and verifies that it has not been altered.
HTTPS
The HyperText Transport Protocol (Secure), the standard encrypted
communication mechanism on the World Wide Web. This is actually just HTTP
over SSL.
Message Digest
A hash of a message, which can be used to verify that the contents of the
message have not been altered in transit.
Non-repudiation
A service that provides proof of the integrity and origin of data, both
in an non-forgeable relationship, which can be verified by any third
party at any time, or, an authentication that with high assurance can be
asserted to be genuine.
A property achieved through cryptographic methods which prevents an
individual or entity from denying having performed a particular action
related to data (such as mechanisms for non-rejection or authority
(origin); for proof of obligation, intent, or commitment, or for proof of
ownership).
OpenSSL
The Open Source toolkit for SSL/TLS; see http://www.openssl.org/
Pass Phrase
The word or phrase that protects private key files. It prevents
unauthorized users from encrypting them. Usually it's just the secret
encryption/decryption key used for Ciphers.
Plaintext
The unencrypted text.
Private Key
The secret key in a Public Key Cryptography system, used to decrypt
incoming messages and sign outgoing ones.
Public Key
The publicly available key in a Public Key Cryptography system, used to
encrypt messages bound for its owner and to decrypt signatures made by
its owner.
Public Key Cryptography
The study and application of asymmetric encryption systems, which use one
key for encryption and another for decryption. A corresponding pair of
such keys constitutes a key pair. Also called Asymmetric Cryptography.
Secure Sockets Layer (SSL)
A protocol created by Netscape Communications Corporation for general
communication authentication and encryption over TCP/IP networks. The
most popular usage is HTTPS, i.e. the HyperText Transfer Protocol (HTTP)
over SSL.
Session
The context information of an SSL communication.
SSLeay
The original SSL/TLS implementation library developed by Eric A. Young
; see http://www.ssleay.org/
Symmetric Cryptography
The study and application of Ciphers that use a single secret key for
both encryption and decryption operations.
Transport Layer Security (TLS)
The successor protocol to SSL, created by the Internet Engineering Task
Force (IETF) for general communication authentication and encryption over
TCP/IP networks. TLS version 1 and is nearly identical with SSL version
3.
Uniform Resource Locator (URL)
The formal identifier to locate various resources on the World Wide Web.
The most popular URL scheme is http. SSL uses the scheme https
X.509
An authentication certificate scheme recommended by the International
Telecommunication Union (ITU-T) and used for SSL/TLS authentication.
ITU-T
Recommendation X.509 [CCI88c] specifies the authentication service for
X.500 directories, as well as the X.509 certificate syntax. Directory
authentication in X.509 can be carried out using either secret-key
techniques or public-key techniques; the latter is based on public-key
certificates. The standard does not specify a particular cryptographic
algorithm, although an informative annex of the standard describes the
RSA algorithm.