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CA Certificates and Extension Interactions
750
Red Hat Certificate System Administrator’s Guide • September 2005
A certificate chain generally consists of an entity certificate, zero or more intermediate CA
certificates, and a root CA certificate. Typically the root CA certificate is self-signed and is
loaded into Communicator's certificate database as a trusted CA.
An exchange of certificates takes place when performing an SSL handshake, when sending
an S/MIME message, or when sending a signed object. As part of the handshake, the sender
is expected to send the subject certificate and any intermediate CA certificates needed to
link the subject certificate to the trusted root. For certificate chaining to work properly the
certificates should have the following properties:
•
CA certificates must have either the
basicConstraints
extension, the
netscape-cert-type
extension with one or more CA bits set, or both, as described
above.
•
If CAs issue multiple certificates for the same identity, for example for separate signing
and encryption keys, they must include the
keyUsage
extension in the subject
certificates.
•
If CAs ever intend to generate new keys for their CA, they must add the
authorityKeyIdentifier
extension to all subject certificates. If the
key ID
is
anything other than the SHA-1 hash of the CA certificates
subjectPublicKeyInfo
field, then the CA certificate should contain the
subjectKeyIdentifier
extension.
This will allow for a smooth transition when the new issuing certificate becomes
active.
Both extensions
The certificate is a CA certificate if the
cA
component of
basicConstraints
is true. If one or more of the SSL CA (5),
S/MIME CA (6), or object-signing CA (7) bits are set in the
redhat-cert-type
extension, then the CA will be limited to
issuing certificates for the specified application areas; otherwise,
the CA can issue certificates for any application.
Extensions Present
Description
Summary of Contents for CERTIFICATE 7.1 ADMINISTRATOR
Page 1: ...Administrator s Guide Red Hat Certificate System Version7 1 September 2005 ...
Page 22: ...22 Red Hat Certificate System Administrator s Guide September 2005 ...
Page 128: ...Cloning a CA 128 Red Hat Certificate System Administrator s Guide September 2005 ...
Page 368: ...ACL Reference 368 Red Hat Certificate System Administrator s Guide September 2005 ...
Page 460: ...Constraints Reference 460 Red Hat Certificate System Administrator s Guide September 2005 ...
Page 592: ...CRL Extension Reference 592 Red Hat Certificate System Administrator s Guide September 2005 ...