iaik.pkcs.pkcs7
Class ContentInfo

java.lang.Object
  |
  +--iaik.pkcs.pkcs7.ContentInfo

public class ContentInfo

extends Object

This class represents the non-stream implemention of the PKCS#7 ContentInfo type.

The PKCS#7 standard describes a general syntax for data that may have cryptography applied to it, such as digital signatures and digital envelopes.

The ASN.1 type ContentInfo type associates a content type (data, signedData, envelopedData, signedAndEnvelopedData, digestedData, encryptedData) with some particular content for specifying a general syntax for content exchanged between entities according the PKCS#7 standard:

 ContentInfo ::= SEQUENCE {
    contentType ContentType,
    content
      [0] EXPLICIT ANY DEFINED BY contentType OPTIONAL }
 

 ContentType ::= OBJECT IDENTIFIER
 

If the optional content is not present, the content value has to be supplied by other means.

This class consists of two parts: the first static part implements a factory for registering all the non-stream implementations of the several PKCS#7 content types. And the second non-static part provides constructors and methods for creating, en- and decoding non-stream PKCS#7 content type objects in the usual way.

The stream-supporting equivalent to this class is implemented by the ContentInfoStream class.

When creating a new ContentInfo to be sent use the ContentInfo(Content) constructor and subsequently call the toASN1Object or writeTo method, e.g.:

 // create a PKCS#7 object, e.g. Data:
 Data data = ...;
 ...
 // create a ContentInfo for the PKCS#7 object and encode it to a stream:
 ContentInfo ci = new ContentInfo(data);
 OutputStream encoded_stream = ...;
 ci.writeTo(encoded_stream);
 

However, if you want to sent a ContentInfo without any content, you only have to supply the content type identifier when creating a ContentInfo object, e.g.:

 ContentInfo ci = new ContentInfo(ObjectID.pkcs7_data);
 ci.writeTo(encoded_stream);
 

After creating an ContentInfo instance for parsing an already existing ContentInfo object supplied as ASN.1 object or DER encoded from an input stream, you may use the getContentInputStream method for getting the unparsed content as input stream, or you may call the getContent method for getting the already parsed content as Content descendant.

The different usage may be illustrated by means of the two types of a SignedData message. When receiving a ContentInfo holding an implicit message the content is included in the SignedData object, and so the getContent method may be appropriate for getting the already parsed SignedData content, e.g.:

 // create a ContentInfo from the encoding:
 ContentInfo ci = new ContentInfo(encodedStream);
 // ask for the content type:
 if (ci.getContentType().equals(ObjectID.pkcs7_signedData)) {
    // get the SignedData content:
    SignedData signedData = (SignedData)ci.getContent()
    // proceed as usual for reading the data, getting the SignerInfos and
    // verifying the signatures
 } else {
    throw new PKCSParsingException("Error! Expected content type SignedData!");
 }
 

However, when receiving a ContentInfo holding an explicit message where the content is not included in the SignedData object, you may want to use the the SignedData(byte[] content, AlgorithmID[] hashAlgorithms) constructor for initializing a SignedData object with raw content and hash algorithms in the usual way, and subsequently decode the received SignedData object by feeding the decode method with the DER encoded SignedData object obtained from the ContentInfo by calling the getContentInputStream method, e.g.:

 // the raw data received by other means, supplied by a byte array:
 byte[] message = ...;
 // the hash algorithms (e.g. parsed from the headers of a S/MIME multipart/signed entity):
 AlgorithmID[] algIDs = { AlgorithmID.sha1, AlgorithmID.md5 };
 // the DER encoded content info, supplied from an input stream:
 InputStream encoded_stream = ...;
 // create a SignedData object from raw data and hash algorithms:
 SignedData signed_data = new SignedData(message, algIDs);
 // create a ContentInfo from the DER encoding:
 ContentInfo ci = new ContentInfo(encoded_stream);
 // check the content type:
 if (ci.getContentType().equals(ObjectID.pkcs7_signedData)) {
    // now decode the DER encoded SignedData obtained from the ContentInfo:
    signed_data.decode(ci.getContentInputStream());
 } else {
    throw new PKCSParsingException("Error! Expected a SignedData content!");
 }
 // proceed as usual for reading the content, getting SignerInfos and verifying signatures
 ...
 

Version:

File Revision 37

See Also:

Data, DigestedData, EncryptedData, EnvelopedData, SignedAndEnvelopedData, SignedData, Content

Constructor Summary

ContentInfo(ASN1Object obj)
Creates a PKCS#7 ContentInfo from an ASN1Object.

ContentInfo(Content content)
Creates a PKCS#7 ContentInfo from the given content value.

ContentInfo(InputStream is)
Creates a new ContentInfo where the DER encoded data is read from the given InputStream.

ContentInfo(ObjectID contentType)
Creates an empty PKCS#7 ContentInfo from the given content type.

Method Summary

static Content	create(ObjectID oid) Returns an instance of the specified PKCS#7 content type implementation, defined by its ASN.1 ObjectID.
static Content	create(ObjectID oid, ASN1Object obj) Returns an instance of the specified PKCS#7 content type implementation, defined by its ASN.1 ObjectID.
protected void	decode(DerInputStream is) Reads and decodes the ContentInfo from a DerInputStream.
void	destroyCriticalData() Destroys the critical data of this object.
Content	getContent() Returns the content of this PKCS#7 ContentInfo.
InputStream	getContentInputStream() Returns the unparsed content of this PKCS#7 ContentInfo as DER encoding.
ObjectID	getContentType() Returns the content type of this PKCS#7 ContentInfo.
boolean	hasContent() Returns true if this ContentInfo has a content.
static void	register(ObjectID oid, Class cls) Registers a new implementation for a Content defined through the given ObjectID.
void	setContent(Content content) Sets the content of this ContentInfo from the given content value.
ASN1Object	toASN1Object() Returns this PKCS#7 ContentInfo as ASN1Object.
byte[]	toByteArray() Returns this PKCS#7 ContentInfo as DER encoded byte array.
String	toString() Returns a string giving some information about this PKCS#7 ContentInfo.
String	toString(boolean detailed) Returns a string giving some - if requested - detailed information about this PKCS#7 ContentInfo.
void	writeTo(OutputStream os) Writes the DER encoding of this object to the given OutputStream.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ContentInfo

public ContentInfo(Content content)

Creates a PKCS#7 ContentInfo from the given content value.

The content type object identifier internally is derived from the given content object by using the getContentType method.

Parameters:

content - the content object as Content descendant.

ContentInfo

public ContentInfo(ObjectID contentType)

Creates an empty PKCS#7 ContentInfo from the given content type.

Since no content is specified, it is set to null. The content value may be supplied by other means.

Parameters:

contentType - the type of the content

ContentInfo

public ContentInfo(ASN1Object obj)
            throws PKCSParsingException

Creates a PKCS#7 ContentInfo from an ASN1Object. The given ASN1Object represents an alredy existing ContentInfo object which may have been created by using the toASN1Object method of this class.

Parameters:

obj - the PKCS#7 ContentInfo as an ASN1Object

Throws:

PKCSParsingException - if the ASN1Object could not be parsed

ContentInfo

public ContentInfo(InputStream is)
            throws IOException,
                   PKCSParsingException

Creates a new ContentInfo where the DER encoded data is read from the given InputStream. The given input stream represents the DER encoding of an alredy existing ContentInfo object which may have been written to a stream by using the writeTo method of this class.

Parameters:

is - the InputStream holding a DER encoded PKCS#7 ContentInfo object

Throws:

IOException - if an I/O error occurs during reading from the InputStream

PKCSParsingException - if an error occurs while parsing the object

Method Detail

create

public static Content create(ObjectID oid)
                      throws PKCSException

Returns an instance of the specified PKCS#7 content type implementation, defined by its ASN.1 ObjectID. This method belongs to the static part of this class.

Parameters:

oid - the ObjectID of the PKCS#7 content type

Returns:

the implementation of the content with this oid

Throws:

PKCSException - if an error occurs when creating the PKCS#7 content object

create

public static Content create(ObjectID oid,
                             ASN1Object obj)
                      throws PKCSParsingException

Returns an instance of the specified PKCS#7 content type implementation, defined by its ASN.1 ObjectID. The new instance will be initialized with the given ASN1Object. This method belongs to the static part of this class.

This method only calls the corresponding create method of the ExtensionFactory for obtaining a non-stream supporting implementation of the desired PKCS#7 content type implementation, specified by its object identifier.

Parameters:

oid - the ObjectID of the PKCS#7 content type

obj - an ASN1Object representing the PKCS#7 content object specified by the given oid

Returns:

the initialized implementation of the PKCS#7 content object identified by the given oid

Throws:

PKCSParsingException - if an error occurs while parsing the object

register

public static void register(ObjectID oid,
                            Class cls)

Registers a new implementation for a Content defined through the given ObjectID. This method registeres the given class as non-stream supporting implementation of the supplied PKCS#7 content type. The content type has to be specified by its ObjectID. This method belongs to the static part of this class.

Parameters:

oid - the object id of the PKCS#7 content to be registered

cls - the implementing class

decode

protected void decode(DerInputStream is)
               throws IOException,
                      PKCSParsingException

Reads and decodes the ContentInfo from a DerInputStream. If the supplied InputStream actually is not an instance of DerInputStream, internally a DerInputStream is created before parsing the data.

Parameters:

is - the InputStream holding a DER encoded PKCS#7 ContentInfo object

Throws:

IOException - if an I/O error occurs during reading from the InputStream

PKCSParsingException - if an error occurs while parsing the object

toASN1Object

public ASN1Object toASN1Object()
                        throws PKCSException

Returns this PKCS#7 ContentInfo as ASN1Object. The ASN1Object returned by this method may be used as parameter value when creating a PKCS#7 ContentInfo from an ASN1Object by calling the ContentInfo(ASN1Object obj) constructor.

Returns:

this PKCS#7 ContentInfo as ASN1Object

toByteArray

public byte[] toByteArray()
                   throws PKCSException

Returns this PKCS#7 ContentInfo as DER encoded byte array. The ContentInfo structure is encoded as ASN.1 SEQUENCE using the indefinite length encoding scheme:

 30 80
    ...
    ...
 00 00
 

Returns:

this PKCS#7 ContentInfo as DER encoded byte array

Throws:

PKCSException - if an error occurs while encoding the object

writeTo

public void writeTo(OutputStream os)
             throws IOException,
                    PKCSException

Writes the DER encoding of this object to the given OutputStream. The ContentInfo structure is encoded as ASN.1 SEQUENCE using the indefinite length encoding scheme:

 30 80
    ...
    ...
 00 00
 

Parameters:

os - the OutputStream where the encoding shall be written to

Throws:

IOException - if an I/O error occurs during writing to the OutputStream

PKCSException - if an error occurs while encoding the object

hasContent

public boolean hasContent()

Returns true if this ContentInfo has a content.

Returns:

true if this ContentInfo has a content

getContent

public Content getContent()

Returns the content of this PKCS#7 ContentInfo.

Returns:

the content value as Content descendant or null if there is no content

getContentInputStream

public InputStream getContentInputStream()

Returns the unparsed content of this PKCS#7 ContentInfo as DER encoding. This method may be used for getting the DER encoding of the content for further processing it by the corresponding content implementing class itself. In this way, this method only shall be used as part of the parsing process; otherwise it will return null.

This method may be useful for parsing an explicit SignedData object that has been wrapped into a ContentInfo. You can use the SignedData(byte[] content, AlgorithmID[] hashAlgorithms) in the normal way for initializing a SignedData object with raw content and hash algorithms, and subsequently decode the received SignedData object by feeding the decode method with the DER encoded SignedData object obtained from the ContentInfo by calling this getContentInputStream method, e.g.:

 // the raw data received by other means, supplied as byte array:
 byte[] message = ...;
 // the hash algorithms (e.g. parsed from the headers of a S/MIME multipart/signed entity):
 AlgorithmID[] algIDs = { AlgorithmID.sha1, AlgorithmID.md5 };
 // the DER encoded content info, supplied from an input stream:
 InputStream der_stream = ...;
 // create a SignedData object from raw data and hash algorithms:
 SignedData signed_data = new SignedData(message, algIDs);
 // create a ContentInfo from the DER encoding:
 ContentInfo ci = new ContentInfo(der_stream);
 // check the content type:
 if (ci.getContentType().equals(ObjectID.pkcs7_signedData)) {
    // now decode the DER encoded SignedData obtained from the ContentInfo:
    signed_data.decode(ci.getContentInputStream());
 } else {
    throw new PKCSParsingException("Error! Expected a SignedData content!");
 }
 // proceed as usual for getting SignerInfos and verifying signatures
 ...
 

Returns:

an input stream carrying the DER encoding of the inherent content or null if there is no content or this method is not called during the parsing (decoding) process

getContentType

public ObjectID getContentType()

Returns the content type of this PKCS#7 ContentInfo.

Returns:

the content type, as ObjectID

setContent

public void setContent(Content content)

Sets the content of this ContentInfo from the given content value.

The content type object identifier internally is derived from the given content object by using the getContentType method.

Parameters:

content - the content object as Content descendant.

destroyCriticalData

public void destroyCriticalData()

Destroys the critical data of this object.

toString

public String toString()

Returns a string giving some information about this PKCS#7 ContentInfo.

Overrides:

toString in class Object

Returns:

the string representation

toString

public String toString(boolean detailed)

Returns a string giving some - if requested - detailed information about this PKCS#7 ContentInfo.

Parameters:

detailed - - whether or not to give detailed information

Returns:

the string representation