path: root/share/man/man8/ssl.8

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.Dd $Mdocdate: March 7 2013 $
.Dt SSL 8
.Os
.Sh NAME
.Nm ssl
.Nd details for libssl and libcrypto
.Sh DESCRIPTION
This document describes some of the issues relating to the use of
the OpenSSL libssl and libcrypto libraries.
This document is intended as an overview of what the libraries do,
and what uses them.
.Pp
The SSL libraries (libssl and libcrypto) implement the SSL version 2,
SSL version 3, and TLS version 1 protocols.
SSL version 2 and 3 are most commonly used by the HTTPS protocol for
encrypted web transactions, as can be done with
.Xr httpd 8 .
The libcrypto library is also used by various programs such as
.Xr ssh 1 ,
.Xr sshd 8 ,
and
.Xr isakmpd 8 .
.Sh RANDOM DATA SOURCE
.Ox
uses the
.Xr arandom 4
device as the default source for random data when needed by the routines in
libcrypto and libssl.
If the
.Xr arandom 4
device does not exist or is not readable, many of the routines will fail.
This is most commonly seen by users as the RSA routines failing in
applications such as
.Xr ssh 1
and
.Xr httpd 8 .
.Pp
It is important to remember when using a random data source for certificate
and key generation that the random data source should not be visible by
people who could duplicate the process and come up with the same result.
You should ensure that nobody who you don't trust is in a position to read
the same random data used by you to generate keys and certificates.
The
.Xr arandom 4
device ensures that no two users on the same machine will see the same
data.
See
.Xr openssl 1
for more information on how to use different sources of random data.
.Sh SERVER CERTIFICATES
The most common uses of SSL/TLS will require you to generate a server
certificate, which is provided by your host as evidence of its identity
when clients make new connections.
The certificates reside in the
.Pa /etc/ssl
directory, with the keys in the
.Pa /etc/ssl/private
directory.
.Pp
Private keys can be encrypted using AES and a passphrase to protect their
integrity should the encrypted file be disclosed.
However, it is important to note that encrypted server keys mean that the
passphrase needs to be typed in every time the server is started.
If a passphrase is not used, you will need to be absolutely sure your
key file is kept secure.
.Sh GENERATING RSA SERVER CERTIFICATES FOR WEB SERVERS
To support HTTPS transactions in
.Xr httpd 8
you will need to generate an RSA certificate.
.Bd -literal -offset indent
# openssl genrsa -out /etc/ssl/private/server.key 2048
.Ed
.Pp
Or, if you wish the key to be encrypted with a passphrase that you will
have to type in when starting servers
.Bd -literal -offset indent
# openssl genrsa -aes256 -out /etc/ssl/private/server.key 2048
.Ed
.Pp
The next step is to generate a Certificate Signing Request (CSR) which is
used to get a Certificate Authority (CA) to sign your certificate.
To do this use the command:
.Bd -literal -offset indent
# openssl req -new -key /etc/ssl/private/server.key \e
  -out /etc/ssl/private/server.csr
.Ed
.Pp
This
.Pa server.csr
file can then be given to a Certificate Authority who will sign the key.
.Pp
You can also sign the key yourself, using the command:
.Bd -literal -offset indent
# openssl x509 -sha256 -req -days 365 \e
  -in /etc/ssl/private/server.csr \e
  -signkey /etc/ssl/private/server.key \e
  -out /etc/ssl/server.crt
.Ed
.Pp
With
.Pa /etc/ssl/server.crt
and
.Pa /etc/ssl/private/server.key
in place, you should be able to start
.Xr httpd 8
with the
.Ar -DSSL
flag, enabling HTTPS transactions with your machine on port 443.
.Pp
You will most likely want to generate a self-signed certificate in the
manner above along with your certificate signing request to test your
server's functionality even if you are going to have the certificate
signed by another Certificate Authority.
Once your Certificate Authority returns the signed certificate to you,
you can switch to using the new certificate by replacing the self-signed
.Pa /etc/ssl/server.crt
with the certificate signed by your Certificate Authority, and then
restarting
.Xr httpd 8 .
.Sh GENERATING DSA SERVER CERTIFICATES
Generating a DSA certificate involves several steps.
First, generate parameters for DSA keys.
The following command will generate 1024-bit keys:
.Bd -literal -offset indent
# openssl dsaparam 1024 -out dsa1024.pem
.Ed
.Pp
Once you have the DSA parameters generated, you can generate a
CSR and unencrypted private key using the command:
.Bd -literal -offset indent
# openssl req -nodes -newkey dsa:dsa1024.pem \e
  -out /etc/ssl/dsacert.csr -keyout /etc/ssl/private/dsakey.pem
.Ed
.Pp
To generate an encrypted private key, you would use:
.Bd -literal -offset indent
# openssl req -newkey dsa:dsa1024.pem \e
  -out /etc/ssl/dsacert.csr -keyout /etc/ssl/private/dsakey.pem
.Ed
.Pp
This
.Pa server.csr
file can then be given to a CA who will sign the key.
.Pp
You can also sign the key yourself, using the command:
.Bd -literal -offset indent
# openssl x509 -sha256 -req -days 365 \e
  -in /etc/ssl/private/dsacert.csr \e
  -signkey /etc/ssl/private/dsacert.key \e
  -out /etc/ssl/dsacert.crt
.Ed
.Sh GENERATING ECDSA SERVER CERTIFICATES
First, generate parameters for ECDSA keys.
The following command will use a NIST/SECG curve over a 384-bit
prime field:
.Bd -literal -offset indent
# openssl ecparam -out ec-secp384r1.pem -name secp384r1
.Ed
.Pp
Once you have the ECDSA parameters generated, you can generate a
CSR and unencrypted private key using the command:
.Bd -literal -offset indent
# openssl req -nodes -newkey ec:ec-secp384r1.pem \e
  -keyout /etc/ssl/private/eccert.key -new \e
  -out /etc/ssl/private/eccert.csr
.Ed
.Pp
To generate an encrypted private key, you would use:
.Bd -literal -offset indent
# openssl req -newkey ec:ec-secp384r1.pem \e
  -keyout /etc/ssl/private/eccert.key -new \e
  -out /etc/ssl/private/eccert.csr
.Ed
.Pp
This
.Pa eccert.csr
file can then be given to a CA who will sign the key.
.Pp
You can also sign the key yourself, using the command:
.Bd -literal -offset indent
# openssl x509 -sha256 -req -days 365 \e
  -in /etc/ssl/private/eccert.csr \e
  -signkey /etc/ssl/private/eccert.key \e
  -out /etc/ssl/eccert.crt
.Ed
.Sh USING SSL/TLS WITH SENDMAIL
By default,
.Xr sendmail 8
expects both the keys and certificates to reside in
.Pa /etc/mail/certs ,
not in the
.Pa /etc/ssl
directory.
The default paths may be overridden in the sendmail.cf file.
See
.Xr starttls 8
for information on configuring
.Xr sendmail 8
to use SSL/TLS.
.Sh SEE ALSO
.Xr openssl 1 ,
.Xr ssh 1 ,
.Xr ssl 3 ,
.Xr arandom 4 ,
.Xr httpd 8 ,
.Xr isakmpd 8 ,
.Xr rc 8 ,
.Xr sendmail 8 ,
.Xr sshd 8 ,
.Xr starttls 8
.Sh HISTORY
Prior to Sept 21, 2000,
there were problems shipping fully functional implementations of these
protocols, as such shipment would include shipping
.Em into
the United States.
RSA Data Security Inc (RSADSI) held the patent on the RSA algorithm in the
United States, and because of this, free implementations of RSA were
difficult to distribute and propagate.
(The RSA patent was probably more effective at preventing the adoption of
widespread international integrated crypto than the much maligned ITAR
restrictions were.)
Prior to
.Ox 2.8 ,
these libraries shipped without the RSA algorithm -- all such functions
were stubbed to fail.
Since RSA is a key component of SSL version 2, this meant that SSL version
2 would not work at all.
SSL version 3 and TLS version 1 allow for the exchange of keys via
mechanisms that do not involve RSA, and would work with the shipped version
of the libraries, assuming both ends could agree to a cipher suite and key
exchange that did not involve RSA.
Likewise, the SSH1 protocol in
.Xr ssh 1
uses RSA, so it was similarly encumbered.
.Pp
For instance, another typical alternative is DSA, which is not encumbered
by commercial patents (and lawyers).
.Pp
The HTTPS protocol used by web browsers (in modern incarnations) allows for
the use of SSL version 3 and TLS version 1, which in theory allows for
encrypted web transactions without using RSA.
Unfortunately, all the popular web browsers buy their cryptographic code
from RSADSI.
Predictably, RSADSI would prefer that web browsers used their patented
algorithm, and thus their libraries do not implement any non-RSA cipher and
keying combination.
The result of this was that while the HTTPS protocol allowed for many
cipher suites that did not require the use of patented algorithms, it was
very difficult to use these with the popular commercially available
software.
Prior to version 2.8,
.Ox
allowed users to download RSA enabled versions of the shared libssl and
libcrypto libraries which allowed users to enable full function without
recompiling the applications.
This method is now no longer needed, as the fully functional
libraries ship with the system.
However, this entire debacle is worth remembering when choosing
software and vendors.
.Pp
This document first appeared in
.Ox 2.5 .