Abstract class for X.509 certificates. This provides a standard way to access all the attributes of an X.509 certificate.
In June of 1996, the basic X.509 v3 format was completed by ISO/IEC and ANSI X9, which is described below in ASN.1:
Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING }
These certificates are widely used to support authentication and other functionality in Internet security systems. Common applications include Privacy Enhanced Mail (PEM), Transport Layer Security (SSL), code signing for trusted software distribution, and Secure Electronic Transactions (SET).
These certificates are managed and vouched for by Certificate Authorities (CAs). CAs are services which create certificates by placing data in the X.509 standard format and then digitally signing that data. CAs act as trusted third parties, making introductions between principals who have no direct knowledge of each other. CA certificates are either signed by themselves, or by some other CA such as a "root" CA.
More information can be found in RFC 2459, "Internet X.509 Public Key Infrastructure Certificate and CRL Profile" at http://www.ietf.org/rfc/rfc2459.txt .
The ASN.1 definition of tbsCertificate is:
TBSCertificate ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version must be v2 or v3
subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version must be v2 or v3
extensions [3] EXPLICIT Extensions OPTIONAL
-- If present, version must be v3
}
Certificates are instantiated using a certificate factory. The following is an example of how to instantiate an X.509 certificate:
InputStream inStream = new FileInputStream("fileName-of-cert");
CertificateFactory cf = CertificateFactory.getInstance("X.509");
X509Certificate cert = (X509Certificate)cf.generateCertificate(inStream);
inStream.close();
The validity period consists of two date/time values: the first and last dates (and times) on which the certificate is valid. It is defined in ASN.1 as:
validity ValidityValidity ::= SEQUENCE { notBefore CertificateValidityDate, notAfter CertificateValidityDate }
CertificateValidityDate ::= CHOICE { utcTime UTCTime, generalTime GeneralizedTime }
other object is an
instanceof Certificate, then
its encoded form is retrieved and compared with the
encoded form of this certificate.BasicConstraints extension, (OID = 2.5.29.19).
The basic constraints extension identifies whether the subject
of the certificate is a Certificate Authority (CA) and
how deep a certification path may exist through that CA. The
pathLenConstraint field (see below) is meaningful
only if cA is set to TRUE. In this case, it gives the
maximum number of CA certificates that may follow this certificate in a
certification path. A value of zero indicates that only an end-entity
certificate may follow in the path.
Note that for RFC 2459 this extension is always marked
critical if cA is TRUE, meaning this certificate belongs
to a Certificate Authority.
The ASN.1 definition for this is:
BasicConstraints ::= SEQUENCE {
cA BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL }
InputStream inStrm = new FileInputStream("DER-encoded-Cert");
CertificateFactory cf = CertificateFactory.getInstance("X.509");
X509Certificate cert = (X509Certificate)cf.generateCertificate(inStrm);
inStrm.close();
Set critSet = cert.getCriticalExtensionOIDs();
if (critSet != null && !critSet.isEmpty()) {
System.out.println("Set of critical extensions:");
for (Iterator i = critSet.iterator(); i.hasNext();) {
String oid = (String)i.next();
System.out.println(oid);
}
}
ExtKeyUsageSyntax field of the
extended key usage extension, (OID = 2.5.29.37). It indicates
one or more purposes for which the certified public key may be
used, in addition to or in place of the basic purposes
indicated in the key usage extension field. The ASN.1
definition for this is:
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeIdKey purposes may be defined by any organization with a need. Object identifiers used to identify key purposes shall be assigned in accordance with IANA or ITU-T Rec. X.660 | ISO/IEC/ITU 9834-1.KeyPurposeId ::= OBJECT IDENTIFIER
This method was added to version 1.4 of the Java 2 Platform Standard
Edition. In order to maintain backwards compatibility with existing
service providers, this method is not abstract
and it provides a default implementation. Subclasses
should override this method with a correct implementation.
oid
String.
The oid string is
represented by a set of nonnegative whole numbers separated
by periods.
For example:
| OID (Object Identifier) | Extension Name |
|---|---|
| 2.5.29.14 | SubjectKeyIdentifier |
| 2.5.29.15 | KeyUsage |
| 2.5.29.16 | PrivateKeyUsage |
| 2.5.29.17 | SubjectAlternativeName |
| 2.5.29.18 | IssuerAlternativeName |
| 2.5.29.19 | BasicConstraints |
| 2.5.29.30 | NameConstraints |
| 2.5.29.33 | PolicyMappings |
| 2.5.29.35 | AuthorityKeyIdentifier |
| 2.5.29.36 | PolicyConstraints |
IssuerAltName extension, (OID = 2.5.29.18).
The ASN.1 definition of the IssuerAltName extension is:
IssuerAltName ::= GeneralNamesThe ASN.1 definition of
GeneralNames is defined
in getSubjectAlternativeNames
.
If this certificate does not contain an IssuerAltName
extension, null is returned. Otherwise, a
Collection is returned with an entry representing each
GeneralName included in the extension. Each entry is a
List whose first entry is an Integer
(the name type, 0-8) and whose second entry is a String
or a byte array (the name, in string or ASN.1 DER encoded form,
respectively). For more details about the formats used for each
name type, see the getSubjectAlternativeNames method.
Note that the Collection returned may contain more
than one name of the same type. Also, note that the returned
Collection is immutable and any entries containing byte
arrays are cloned to protect against subsequent modifications.
This method was added to version 1.4 of the Java 2 Platform Standard
Edition. In order to maintain backwards compatibility with existing
service providers, this method is not abstract
and it provides a default implementation. Subclasses
should override this method with a correct implementation.
issuer
as an implementation specific Principal object, which should not be
relied upon by portable code.
Gets the issuer (issuer distinguished name) value from
the certificate. The issuer name identifies the entity that signed (and
issued) the certificate.
The issuer name field contains an X.500 distinguished name (DN). The ASN.1 definition for this is:
issuer NameTheName ::= CHOICE { RDNSequence } RDNSequence ::= SEQUENCE OF RelativeDistinguishedName RelativeDistinguishedName ::= SET OF AttributeValueAssertion AttributeValueAssertion ::= SEQUENCE { AttributeType, AttributeValue } AttributeType ::= OBJECT IDENTIFIER AttributeValue ::= ANY
Name describes a hierarchical name composed of
attributes,
such as country name, and corresponding values, such as US.
The type of the AttributeValue component is determined by
the AttributeType; in general it will be a
directoryString. A directoryString is usually
one of PrintableString,
TeletexString or UniversalString.issuerUniqueID value from the certificate.
The issuer unique identifier is present in the certificate
to handle the possibility of reuse of issuer names over time.
RFC 2459 recommends that names not be reused and that
conforming certificates not make use of unique identifiers.
Applications conforming to that profile should be capable of
parsing unique identifiers and making comparisons.
The ASN.1 definition for this is:
issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONALUniqueIdentifier ::= BIT STRING
X500Principal.
It is recommended that subclasses override this method.
KeyUsage extension, (OID = 2.5.29.15).
The key usage extension defines the purpose (e.g., encipherment,
signature, certificate signing) of the key contained in the
certificate.
The ASN.1 definition for this is:
KeyUsage ::= BIT STRING {
digitalSignature (0),
nonRepudiation (1),
keyEncipherment (2),
dataEncipherment (3),
keyAgreement (4),
keyCertSign (5),
cRLSign (6),
encipherOnly (7),
decipherOnly (8) }
RFC 2459 recommends that when used, this be marked
as a critical extension.
InputStream inStrm = new FileInputStream("DER-encoded-CRL");
CertificateFactory cf = CertificateFactory.getInstance("X.509");
X509CRL crl = (X509CRL)cf.generateCRL(inStrm);
inStrm.close();
byte[] certData = <DER-encoded certificate data>
ByteArrayInputStream bais = new ByteArrayInputStream(certData);
X509Certificate cert = (X509Certificate)cf.generateCertificate(bais);
bais.close();
X509CRLEntry badCert =
crl.getRevokedCertificate(cert.getSerialNumber());
if (badCert != null) {
Set nonCritSet = badCert.getNonCriticalExtensionOIDs();
if (nonCritSet != null)
for (Iterator i = nonCritSet.iterator(); i.hasNext();) {
String oid = (String)i.next();
System.out.println(oid);
}
}
notAfter date from the validity period of
the certificate. See getNotBefore
for relevant ASN.1 definitions.notBefore date from the validity period of
the certificate.
The relevant ASN.1 definitions are:
validity ValidityValidity ::= SEQUENCE { notBefore CertificateValidityDate, notAfter CertificateValidityDate }
CertificateValidityDate ::= CHOICE { utcTime UTCTime, generalTime GeneralizedTime }
serialNumber value from the certificate.
The serial number is an integer assigned by the certification
authority to each certificate. It must be unique for each
certificate issued by a given CA (i.e., the issuer name and
serial number identify a unique certificate).
The ASN.1 definition for this is:
serialNumber CertificateSerialNumberCertificateSerialNumber ::= INTEGER
signatureAlgorithm AlgorithmIdentifierAlgorithmIdentifier ::= SEQUENCE { algorithm OBJECT IDENTIFIER, parameters ANY DEFINED BY algorithm OPTIONAL } -- contains a value of the type -- registered for use with the -- algorithm object identifier value
The algorithm name is determined from the algorithm
OID string.
See getSigAlgName for relevant ASN.1 definitions.
See getSigAlgName for relevant ASN.1 definitions.
signature value (the raw signature bits) from
the certificate.
The ASN.1 definition for this is:
signature BIT STRING
SubjectAltName extension, (OID = 2.5.29.17).
The ASN.1 definition of the SubjectAltName extension is:
SubjectAltName ::= GeneralNames
GeneralNames :: = SEQUENCE SIZE (1..MAX) OF GeneralName
GeneralName ::= CHOICE {
otherName [0] OtherName,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] EDIPartyName,
uniformResourceIdentifier [6] IA5String,
iPAddress [7] OCTET STRING,
registeredID [8] OBJECT IDENTIFIER}
If this certificate does not contain a SubjectAltName
extension, null is returned. Otherwise, a
Collection is returned with an entry representing each
GeneralName included in the extension. Each entry is a
List whose first entry is an Integer
(the name type, 0-8) and whose second entry is a String
or a byte array (the name, in string or ASN.1 DER encoded form,
respectively).
RFC 822, DNS, and URI names are returned as Strings,
using the well-established string formats for those types (subject to
the restrictions included in RFC 2459). IPv4 address names are
returned using dotted quad notation. IPv6 address names are returned
in the form "a1:a2:...:a8", where a1-a8 are hexadecimal values
representing the eight 16-bit pieces of the address. OID names are
returned as Strings represented as a series of nonnegative
integers separated by periods. And directory names (distinguished names)
are returned in RFC 2253 string format. No standard string format is
defined for otherNames, X.400 names, EDI party names, or any
other type of names. They are returned as byte arrays
containing the ASN.1 DER encoded form of the name.
Note that the Collection returned may contain more
than one name of the same type. Also, note that the returned
Collection is immutable and any entries containing byte
arrays are cloned to protect against subsequent modifications.
This method was added to version 1.4 of the Java 2 Platform Standard
Edition. In order to maintain backwards compatibility with existing
service providers, this method is not abstract
and it provides a default implementation. Subclasses
should override this method with a correct implementation.
subject
as an implementation specific Principal object, which should not be
relied upon by portable code.
Gets the subject (subject distinguished name) value
from the certificate. If the subject value is empty,
then the getName() method of the returned
Principal object returns an empty string ("").
The ASN.1 definition for this is:
subject Name
See getIssuerDN
for Name
and other relevant definitions.
subjectUniqueID value from the certificate.
The ASN.1 definition for this is:
subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONALUniqueIdentifier ::= BIT STRING
X500Principal. If the subject value
is empty, then the getName() method of the returned
X500Principal object returns an empty string ("").
It is recommended that subclasses override this method.
tbsCertificate from this certificate.
This can be used to verify the signature independently.version (version number) value from the
certificate.
The ASN.1 definition for this is:
version [0] EXPLICIT Version DEFAULT v1Version ::= INTEGER { v1(0), v2(1), v3(2) }
wait methods.
The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways:
synchronized statement
that synchronizes on the object.
Class, by executing a
synchronized static method of that class.
Only one thread at a time can own an object's monitor.
wait methods.
The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.
The current thread must own this object's monitor. The thread
releases ownership of this monitor and waits until another thread
notifies threads waiting on this object's monitor to wake up
either through a call to the notify method or the
notifyAll method. The thread then waits until it can
re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait();
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.The current thread must own this object's monitor.
This method causes the current thread (call it T) to place itself in the wait set for this object and then to relinquish any and all synchronization claims on this object. Thread T becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:
A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops, like this one:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout);
... // Perform action appropriate to condition
}
(For more information on this topic, see Section 3.2.3 in Doug Lea's
"Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
2000), or Item 50 in Joshua Bloch's "Effective Java Programming
Language Guide" (Addison-Wesley, 2001).
If the current thread is interrupted by another thread while it is waiting, then an InterruptedException is thrown. This exception is not thrown until the lock status of this object has been restored as described above.
Note that the wait method, as it places the current thread into the wait set for this object, unlocks only this object; any other objects on which the current thread may be synchronized remain locked while the thread waits.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.
This method is similar to the wait method of one
argument, but it allows finer control over the amount of time to
wait for a notification before giving up. The amount of real time,
measured in nanoseconds, is given by:
1000000*timeout+nanos
In all other respects, this method does the same thing as the method of one argument. In particular, wait(0, 0) means the same thing as wait(0).
The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until either of the following two conditions has occurred:
notify method
or the notifyAll method.
timeout
milliseconds plus nanos nanoseconds arguments, has
elapsed.
The thread then waits until it can re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout, nanos);
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.