CERTTOOL(1)CERTTOOL(1)NAMEcerttool - create key pairs, certificates and certificate signing
requests for use with Keychains
SYNOPSIScerttool command [command-args] [options]
certtool c [options]
certtool r outFileName [options]
certtool v infileName [options]
certtool i inFileName [options]
certtool d inFileName [options]
certtool I inFileName [options]
certtool D inFileName [options]
certtool y [options]
CERTTOOL COMMAND SUMMARY
c Create keypair and Certificate
r Create CSR
v Verify CSR
i Import Certificate
d Display Certificate
I Import CRL
D Display CRL
I Import a CRL
y Display all certs and CRLs in keychain
CERTTOOL OPTION SUMMARY
c Create the keychain, if one is needed.
d Create a CSR in DER format; default is PEM
k=keychainName
Specify the Keychain to use for the operation. If keychainName
starts with a '/', an absolute path is assumed; otherwise, the
specified filename is relative to the user's Library/Keychains
directory.
p=passphrase
Specify the keychain passphrase when creating
r=privateKeyFileName
Optional private key, for Import Certificate only
f=[18f]
Private Key Format = PKCS1/PKCS8/FIPS186; default is PKCS1
(openssl)
a Generate private key with default ACL
h Print usage message
v Execute in verbose mode.
DESCRIPTION
Certtool is a UNIX command-line program which is used to create key
pairs, certificates, and certificate signing requests; to import exter‐
nally generated certificates and Certificate Revocation Lists (CRLs)
into a Keychain, and to display the contents of certificates and CRLs.
Currently, the primary use of CertTool is to perform the certificate-
related administration required to configure an SSL server based on Mac
OS X's SecureTransport library.
EXAMPLES
Generating a Self-Signed Certificate
This command generates a key pair and a self-signed (root) certificate
and places them in a keychain. The root cert is signed by the private
key generated during this command. The cert generated by this command
is totally untrustworthy and cannot be used in the "real world"; the
primary use of this command is to facilitate early development of SSL
server applications based on SecureTransport. In particular, "real
world" SSL clients (e.g., web browsers) will complain to varying
degrees when they attempt to connect to an SSL server which presents a
cert which is generated by this command. Some broswers, after a fair
amount of handholding, will allow you to conditionally "trust" this
cert.
# CertTool c [options]
The available options are:
k=keyChainName
Where "keyChainName" is the name of the keychain into which keys and
the cert will be added. If no keychain is specified, keys and certs are
added to the default keychain. The specified keychain must exist unless
you specify the 'c' option.
c
Specifies that the designated keychain is to be created.
This an interactive command; you will be prompted for a number of dif‐
ferent items which are used to generate the keypair and the cert. A
sample session follows.
# CertTool k=certkc
Enter key and certificate label: testCert
Please specify parameters for the key pair you will generate.
r RSA
d DSA
f FEE
Select key algorithm by letter: r
Valid key sizes for RSA are 512..2048; default is 512
Enter key size in bits or CR for default: 512
You have selected algorithm RSA, key size 512 bits.
OK (y/anything)? y
Enter cert/key usage (s=signing, b=signing AND encrypting): b
...Generating key pair...
Note: you will be prompted for the Keychain's passphrase by the Key‐
chain system at this point if the specified keychain is not open and
you have not specified the passphrase via the 'p' option.
Please specify the algorithm with which your certificate will be signed.
5 RSA with MD5
s RSA with SHA1
Select signature algorithm by letter: s
You have selected algorithm RSA with SHA1.
OK (y/anything)? y
You will now specify the various components of the certificate's Rela‐
tive Distinguished Name (RDN). An RDN has a number of components, all
of which are optional, but at least one of which must be present.
Note that if you are creating a certificate for use in an SSL/TLS
server, the Common Name component of the RDN must match exactly the
host name of the server. This must not be an IP address, but the actual
domain name, e.g. www.apple.com. Entering a CR for a given RDN compo‐
nent results in no value for that component.
Common Name (e.g, www.apple.com) : 10.0.61.5
Country (e.g, US) :
Organization (e.g, Apple Computer, Inc.) : Apple
Organization Unit (e.g, Apple Data Security) :
State/Province (e.g., California) : California
You have specified:
Common Name : 10.0.61.5
Organization : Apple
State/Province : California
Is this OK (y/anything)? y
#
The "Common Name" portion of the RDN - in the above case, "10.0.61.5" -
MUST match the host name of the machine you'll running sslServer on.
(In this case the test machine doesn't have an actual hostname; it's
DHCP'd behind a firewall which is why "10.0.61.5" was specified for
Common Name.) This is part of SSL's certificate verification; it pre‐
vents an attack using DNS spoofing.
A brief note about cert/key usage: the normal configuration of Secure‐
Transport is that the server cert specified in SSLSetCertificate() is
capable of both signing and encryption. If this cert is only capable of
signing, then you must create a second keychain ontaining a cert which
is capable of encryption, and pass that to SSLSetEncryptionCertifi‐
cate().
Generating a Certificate Signing Request (CSR)
A CSR is the standard means by which an administrator of a web server
provides information to a Certificate Authority (CA) in order to obtain
a valid certificate which is signed by the CA. This type of cert is
used in the real world; certs signed by CAs such as Verisign or Thawte
are recognized by all web browsers when performing SSL transactions.
The general procedure for obtaining a "real" cert is:
· Generate a key pair
· Generate a CSR
· Provide the CSR and some other information and/or documentation
to the CA
· CA sends you a certificate which is signed by the CA.
· You import that certificate, obtained from the CA, into your
keychain.
The items in that keychain can now be used in SecureTransport's
SSLSetCertificate() call.
This command performs the first two steps in the above procedure. See
the section below entitled "Importing a Certificate" for information on
importing the resulting certificate into your keychain. The format of
this command is
# CertTool r outFileName [options]
The resulting CSR will be written to "outFileName". The available
options are:
k=keyChainName
Where "KeyChainName" is the name of the keychain into which keys and
the cert will be added. If no keychain is specified, keys and certs are
added to the default keychain. The specified keychain must exist unless
you specify the 'c' option.
d
The 'd' option tells CertTool to create the CSR in DER-encoded format.
The default is PEM-encoded, which is what most CAs expect. PEM encoded
data consists of printable ASCII text which can, for example, be pasted
into an email message. DER-encoded data is nonprintable binary data.
c
Specifies that the designated keychain is to be created.
This an interactive command; you will be prompted for a number of dif‐
ferent items which are used to generate the keypair and the CSR. The
prompts given, and the format of the data you must supply, are identi‐
cal to the data shown in the sample session in Section 2.
Verifying a CSR
A CSR contains, among other things, the public key which was generated
in as described above. The CSR is signed with the associated private
key. Thus the integrity of a CSR can be verified by extracting its pub‐
lic key and verifying the signature of the CSR. This command performs
this integrity check. The format of this command is
# CertTool v inFileName [options]
The only available option is the 'd' flag, which as described above in
the section entitled "Generating a Certificate Signing Request", indi‐
ciates that the CSR is in DER format rather than the default PEM for‐
mat. A typical (successful) run of this command is like so:
# CertTool v myCsr.pem
...CSR verified successfully.
A large number of things can go wrong if the verification fails; suf‐
fice it to say that if you see anything other than the above success
message, you have a bad or corrupted CSR.
Importing a Certificate from a Certificate Authority
Once you have negotiated with your CA, and provided them with the CSR
generated as described above as well as any other information, documen‐
tation, and payment they require, the CA will provide you with a cer‐
tificate. Use this command to add that certificate to the keychain con‐
taining the keypair you generated previously.
The format of this command is
# CertTool i inFileName [options]
The cert to import is obtained from "inFileName". The available options
are:
k=keyChainName
Where "keyChainName" is the name of the keychain to which the cert will
be added. If no keychain is specified, the cert is added to the default
keychain. The specified keychain typically contains the keypair you
generated previously. (Note you can import a certificate into a key‐
chain which does not contain keys you generated but there will be no
linkage between the imported certificate and a private key if you do
this.) If the keychain is not open when this command is executed, you
will be prompted by the Keychain system for its passphrase.
r=privateKeyFileName
Where "privateKeyFileName" is the name of the optional private key file
to imported along with the certificate. This option is used to import
cert/key pairs which are generated by other means, such as OpenSSL.
f=privateKeyFormat
Where "privateKeyFormat" is the format of the private key specified
with the 'r' option. The formats are: '1' for PKCS1 (OpenSSL format),
'8' (PKCS8), and 'f' (FIPS186, BSAFE format). The default is OpenSSL
format for both RSA and DSA keys.
d
Specifies DER format as described above. The default is PEM format.
c
Specifies that the designated keychain is to be created.
Displaying a Certificate
This displays the contents of an existing certificate, obtained from a
file. The format of this command is
# CertTool d inFileName [options]
The cert to display is obtained from "inFileName". The only available
option is the 'd' flag, specifying DER format as described above. The
default is PEM format. Actually, in the absence of this option, cert‐
tool will correctly determine the format of the certificate (PEM or
DER).
Importing a CRL
This command is used to add a Certificate Revocation List (CRL) to a
keychain. The format of this command is
# CertTool I inFileName [options]
The CRL to import is obtained from "inFileName". The available options
are:
k=keyChainName
Where "KeyChainName" is the name of the keychain to which the CRL will
be added. If no keychain is specified, the cert is added to the
default keychain. If the keychain is not open when this command is
executed, you will be prompted by the Keychain system for its
passphrase.
d
Specifies DER format as described above. The default is PEM format.
c
Specifies that the designated keychain is to be created.
Displaying a CRL
This displays the contents of an existing Certificate Revocation List
(CRL), obtained from a file. The format of this command is
# CertTool D inFileName [options]
The cert to display is obtained from "inFileName". The only available
option is the 'd' flag, specifying DER format as described above. The
default is PEM format.
Displaying Certificates and CRLs in a keychain
This displays the contents of all certificates and CRLs in a keychain.
The format of this command is
# CertTool y [options]
The available options are:
k=keyChainName
Where "KeyChainName" is the name of the keychain to display.
v
Specifies verbose mode.
Certificate Authorities and CSRs
As mentioned above, the general procedure for obtaining a "real" cert
is:
· Generate a key pair
· Generate a CSR
· Provide the CSR and some other information and/or documentation
to the CA
· CA sends you a certificate which is signed by the CA.
· You import that certificate, obtained from the CA, into your
keychain.
The items in that keychain can now be used in SecureTranspoert's
SSLSetCertificate() call.
One CA with an excellent web-based interface for obtaining a cert is
Verisign (http://www.verisign.com/products/site/index.html). You can
get a free 14-day trial certificate using nothing but CertTool,
Verisign's web site, and email. You need to provide some personal
information; then you paste in the CSR generated as described in the
section entitled "Generating a Certificate Signing Request" into a form
on the web site. A few minutes later Verisign emails you a certificate,
which you import into your keychain. The whole process takes less than
10 minutes. The free certificate obtained in this manner is signed by a
temporary root cert which is not recognized by any browsers, but
Verisign also provides a means of installing this temporary root cert
into your browser, directly from their web site. Typically one would
use the free, temporary cert to perform initial configuration of a
server and to ring out the general SSL infrastructure. Once you feel
comfortable with the operation of the server, then it's time to buy a
"real" certificate which will allow your web server to be recognized by
any browser.
Thawte has a similar, very friendly service at http://www.thawte.com/.
Note that, for early web server development and/or testing, you can
skip the entire procedure described above and just generate your own
self-signed root cert as described above. No CA is involved; no CSR is
generated; no cert needs to be imported - CertTool generates a cert for
you and immediately adds it to your keychain. Bear in mind that this
option requires tolerance of the various SSL clients you'll be testing
with, none of whom recognize your root cert.
FILES
/System/Library/Keychains/X509Anchors System root certificate database
SEE ALSOopenssl(1)Apple Computer, Inc. March 19, 2003 CERTTOOL(1)
