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Class java.security.cert.X509Certificate

java.lang.Object
    |
    +----java.security.cert.Certificate
            |
            +----java.security.cert.X509Certificate

public abstract class X509Certificate

extends Certificate

implements X509Extension

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.

A good decription and profiling is provided in the IETF PKIX WG draft, Part I: X.509 Certificate and CRL Profile, <draft-ietf-pkix-ipki-part1-06.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
     }
 

Here is sample code to instantiate an X.509 certificate:

 
 InputStream inStream = new FileInputStream("fileName-of-cert");
 X509Certificate cert = X509Certificate.getInstance(inStream);
 inStream.close();
 

 byte[] certData = <certificate read from a file, say>
 X509Certificate cert = X509Certificate.getInstance(certData);
 

In either case, the code that instantiates an X.509 certificate consults the Java security properties file to locate the actual implementation. The default implementation for the java.security.cert package is the Sun X.509 v3 implementation, from what is known to the java.security APIs as the "SUN" provider.

The Java security properties file is located in the file named <JAVA_HOME>/lib/security/java.security, where <JAVA_HOME> refers to the directory where the JDK was installed. In the Security properties file, the default implementation for X.509 v3 is given as:

 cert.provider.x509=sun.security.x509.X509CertImpl
 

The value of this cert.provider.x509 property has to be changed to instatiate another implementation.

See Also:

Certificate, X509Extension

X509Certificate()

checkValidity()

Checks that the certificate is currently valid.

checkValidity(Date)

Checks that the specified date is within the certificate's validity period.

getBasicConstraints()

Gets the certificate constraints path length from the critical BasicConstraints extension, (OID = 2.5.29.19).

getInstance(byte[])

Instantiates an X509Certificate object, and initializes it with the specified byte array.

getInstance(InputStream)

Instantiates an X509Certificate object, and initializes it with the data read from the input stream inStream.

getIssuerDN()

Gets the issuer (issuer distinguished name) value from the certificate.

getIssuerUniqueID()

Gets the issuerUniqueID value from the certificate.

getKeyUsage()

Gets a boolean array representing bits of the KeyUsage extension, (OID = 2.5.29.15).

getNotAfter()

Gets the notAfter date from the validity period of the certificate.

getNotBefore()

Gets the notBefore date from the validity period of the certificate.

getSerialNumber()

Gets the serialNumber value from the certificate.

getSigAlgName()

Gets the signature algorithm name for the certificate signature algorithm.

getSigAlgOID()

Gets the signature algorithm OID string from the certificate.

getSigAlgParams()

Gets the DER-encoded signature algorithm parameters from this certificate's signature algorithm.

getSignature()

Gets the signature value (the raw signature bits) from the certificate.

getSubjectDN()

Gets the subject (subject distinguished name) value from the certificate.

getSubjectUniqueID()

Gets the subjectUniqueID value from the certificate.

getTBSCertificate()

Gets the DER-encoded certificate information, the tbsCertificate from this certificate.

getVersion()

Gets the version (version number) value from the certificate.

public X509Certificate()

public static final X509Certificate getInstance(InputStream inStream) throws CertificateException

Instantiates an X509Certificate object, and initializes it with the data read from the input stream inStream. The implementation (X509Certificate is an abstract class) is provided by the class specified as the value of the cert.provider.x509 property in the security properties file.

Note: Only one DER-encoded certificate is expected to be in the input stream. Also, all X509Certificate subclasses must provide a constructor of the form:

 public <subClass>(InputStream inStream) ...
 

Parameters:

inStream - an input stream with the data to be read to initialize the certificate.

Returns:

an X509Certificate object initialized with the data from the input stream.

Throws: CertificateException

if a class initialization or certificate parsing error occurs.

public static final X509Certificate getInstance(byte[] certData) throws CertificateException

Instantiates an X509Certificate object, and initializes it with the specified byte array. The implementation (X509Certificate is an abstract class) is provided by the class specified as the value of the cert.provider.x509 property in the security properties file.

Note: All X509Certificate subclasses must provide a constructor of the form:

 public <subClass>(InputStream inStream) ...
 

Parameters:

certData - a byte array containing the DER-encoded certificate.

Returns:

an X509Certificate object initialized with the data from certData.

Throws: CertificateException

if a class initialization or certificate parsing error occurs.

public abstract void checkValidity() throws CertificateExpiredException, CertificateNotYetValidException

Checks that the certificate is currently valid. It is if the current date and time are within the validity period given in the certificate.

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             Validity

 Validity ::= SEQUENCE {
     notBefore      CertificateValidityDate,
     notAfter       CertificateValidityDate }

 CertificateValidityDate ::= CHOICE {
     utcTime        UTCTime,
     generalTime    GeneralizedTime }
 

Throws: CertificateExpiredException

if the certificate has expired.

Throws: CertificateNotYetValidException

if the certificate is not yet valid.

public abstract void checkValidity(Date date) throws CertificateExpiredException, CertificateNotYetValidException

Checks that the specified date is within the certificate's validity period. In other words, this determines whether the certificate would be valid at the specified date/time.

Parameters:

date - the Date to check against to see if this certificate is valid at that date/time.

Throws: CertificateExpiredException

if the certificate has expired with respect to the date supplied.

Throws: CertificateNotYetValidException

if the certificate is not yet valid with respect to the date supplied.

See Also:

checkValidity

public abstract int getVersion()

Gets the version (version number) value from the certificate. The ASN.1 definition for this is:

 version         [0]  EXPLICIT Version DEFAULT v1

 Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
 

Returns:

the version number.

public abstract BigInteger getSerialNumber()

Gets the 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     CertificateSerialNumber

 
 CertificateSerialNumber  ::=  INTEGER
 

Returns:

the serial number.

public abstract Principal getIssuerDN()

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    Name


 Name ::= CHOICE { RDNSequence }
 RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
 RelativeDistinguishedName ::=
     SET OF AttributeValueAssertion

 AttributeValueAssertion ::= SEQUENCE {
                               AttributeType,
                               AttributeValue }
 AttributeType ::= OBJECT IDENTIFIER
 AttributeValue ::= ANY
 

The 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.

Returns:

a Principal whose name is the issuer distinguished name.

public abstract Principal getSubjectDN()

Gets the subject (subject distinguished name) value from the certificate. The ASN.1 definition for this is:

 subject    Name
 

See getIssuerDN for Name and other relevant definitions.

Returns:

a Principal whose name is the subject name.

public abstract Date getNotBefore()

Gets the notBefore date from the validity period of the certificate. The relevant ASN.1 definitions are:

 validity             Validity

 
 Validity ::= SEQUENCE {
     notBefore      CertificateValidityDate,
     notAfter       CertificateValidityDate }

 CertificateValidityDate ::= CHOICE {
     utcTime        UTCTime,
     generalTime    GeneralizedTime }
 

Returns:

the start date of the validity period.

See Also:

checkValidity

public abstract Date getNotAfter()

Gets the notAfter date from the validity period of the certificate. See getNotBefore for relevant ASN.1 definitions.

Returns:

the end date of the validity period.

See Also:

checkValidity

public abstract byte[] getTBSCertificate() throws CertificateEncodingException

Gets the DER-encoded certificate information, the tbsCertificate from this certificate. This can be used to verify the signature independently.

Returns:

the DER-encoded certificate information.

Throws: CertificateEncodingException

if an encoding error occurs.

public abstract byte[] getSignature()

Gets the signature value (the raw signature bits) from the certificate. The ASN.1 definition for this is:

 signature     BIT STRING  
 

Returns:

the signature.

public abstract String getSigAlgName()

Gets the signature algorithm name for the certificate signature algorithm. An example is the string "SHA-1/DSA". The ASN.1 definition for this is:

 signatureAlgorithm   AlgorithmIdentifier

 AlgorithmIdentifier  ::=  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.

Returns:

the signature algorithm name.

public abstract String getSigAlgOID()

Gets the signature algorithm OID string from the certificate. An OID is represented by a set of positive whole numbers separated by periods. For example, the string "1.2.840.10040.4.3" identifies the SHA-1 with DSA signature algorithm, as per the PKIX part I.

See getSigAlgName for relevant ASN.1 definitions.

Returns:

the signature algorithm OID string.

public abstract byte[] getSigAlgParams()

Gets the DER-encoded signature algorithm parameters from this certificate's signature algorithm. In most cases, the signature algorithm parameters are null; the parameters are usually supplied with the certificate's public key. If access to individual parameter values is needed then use AlgorithmParameters and instantiate with the name returned by getSigAlgName.

See getSigAlgName for relevant ASN.1 definitions.

Returns:

the DER-encoded signature algorithm parameters, or null if no parameters are present.

public abstract boolean[] getIssuerUniqueID()

Gets the 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. The PKIX Part I 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 OPTIONAL

 UniqueIdentifier  ::=  BIT STRING
 

Returns:

the issuer unique identifier or null if it is not present in the certificate.

public abstract boolean[] getSubjectUniqueID()

Gets the subjectUniqueID value from the certificate.

The ASN.1 definition for this is:

 subjectUniqueID  [2]  IMPLICIT UniqueIdentifier OPTIONAL

 UniqueIdentifier  ::=  BIT STRING
 

Returns:

the subject unique identifier or null if it is not present in the certificate.

public abstract boolean[] getKeyUsage()

Gets a boolean array representing bits of the 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) }
 

The PKIX part I draft recommends that when used, this be marked as a critical extension.

Returns:

the bit values of the KeyUsage extension as an array of booleans, or null if the KeyUsage extension is not present in the certificate.

public abstract int getBasicConstraints()

Gets the certificate constraints path length from the critical 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 the PKIX profile 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 }
 

Returns:

the length of the constraint if the BasicConstraints extension is present in the certificate and the cA value is TRUE. Otherwise returns -1.

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