com.itextpdf.signatures

Class SignatureUtil

java.lang.Object

com.itextpdf.signatures.SignatureUtil

public class SignatureUtil
extends Object

Utility class that provides several convenience methods concerning digital signatures.

Constructor Summary

Constructors

Constructor and Description
SignatureUtil(PdfDocument document) Creates a SignatureUtil instance.

Method Summary

Modifier and Type	Method and Description
boolean	doesSignatureFieldExist(String name) Checks whether a name exists as a signature field or not.
InputStream	extractRevision(String field) Extracts a revision from the document.
List<String>	getBlankSignatureNames() Gets the field names that have blank signatures.
int	getRevision(String field)
PdfSignature	getSignature(String name)
PdfDictionary	getSignatureDictionary(String name) Gets the signature dictionary, the one keyed by /V.
List<String>	getSignatureNames() Gets the field names that have signatures and are signed.
int	getTotalRevisions()
String	getTranslatedFieldName(String name)
PdfPKCS7	readSignatureData(String signatureFieldName) Prepares an PdfPKCS7 instance for the given signature.
PdfPKCS7	readSignatureData(String signatureFieldName, String securityProvider) Prepares an PdfPKCS7 instance for the given signature.
boolean	signatureCoversWholeDocument(String name) Checks if the signature covers the entire document (except for signature's Contents) or just a part of it.

Methods inherited from class java.lang.Object

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

Constructor Detail

SignatureUtil

public SignatureUtil(PdfDocument document)

Creates a SignatureUtil instance. Sets the acroForm field to the acroForm in the PdfDocument. iText will create a new AcroForm if the PdfDocument doesn't contain one.

Parameters:

document - PdfDocument to be inspected

Method Detail

readSignatureData

public PdfPKCS7 readSignatureData(String signatureFieldName)

Prepares an PdfPKCS7 instance for the given signature. This method handles signature parsing and might throw an exception if signature is malformed.

The returned PdfPKCS7 can be used to fetch additional info about the signature and also to perform integrity check of data signed by the given signature field.

In order to validate the signature it is required to check if it covers the entire file, otherwise one cannot be sure that signature in question indeed signs the data that constitutes current PdfDocument with all its contents. In order to check that given signature covers the current PdfDocument please use signatureCoversWholeDocument(String) method.

Parameters:

signatureFieldName - the signature field name

Returns:

a PdfPKCS7 instance which can be used to fetch additional info about the signature and also to perform integrity check of data signed by the given signature field.

readSignatureData

public PdfPKCS7 readSignatureData(String signatureFieldName,
                                  String securityProvider)

Prepares an PdfPKCS7 instance for the given signature. This method handles signature parsing and might throw an exception if signature is malformed.

The returned PdfPKCS7 can be used to fetch additional info about the signature and also to perform integrity check of data signed by the given signature field.

Prepared PdfPKCS7 instance calculates digest based on signature's /ByteRange entry. In order to check that /ByteRange is properly defined and given signature indeed covers the current PDF document revision please use signatureCoversWholeDocument(String) method.

Parameters:

signatureFieldName - the signature field name

securityProvider - the security provider or null for the default provider

Returns:

a PdfPKCS7 instance which can be used to fetch additional info about the signature and also to perform integrity check of data signed by the given signature field.

getSignature

public PdfSignature getSignature(String name)

getSignatureDictionary

public PdfDictionary getSignatureDictionary(String name)

Gets the signature dictionary, the one keyed by /V.

Parameters:

name - the field name

Returns:

the signature dictionary keyed by /V or null if the field is not a signature

getSignatureNames

public List<String> getSignatureNames()

Gets the field names that have signatures and are signed.

Returns:

List containing the field names that have signatures and are signed

getBlankSignatureNames

public List<String> getBlankSignatureNames()

Gets the field names that have blank signatures.

Returns:

List containing the field names that have blank signatures

getTotalRevisions

public int getTotalRevisions()

getRevision

public int getRevision(String field)

getTranslatedFieldName

public String getTranslatedFieldName(String name)

extractRevision

public InputStream extractRevision(String field)

Extracts a revision from the document.

Parameters:

field - the signature field name

Returns:

an InputStream covering the revision. Returns null if it's not a signature field

signatureCoversWholeDocument

public boolean signatureCoversWholeDocument(String name)

Checks if the signature covers the entire document (except for signature's Contents) or just a part of it.

If this method does not return true it means that signature in question does not cover the entire contents of current PdfDocument. Such signatures cannot be considered as verifying the PDF document, because content that is not covered by signature might have been modified since the signature creation.

Parameters:

name - the signature field name

Returns:

true if the signature covers the entire document, false if it doesn't

doesSignatureFieldExist

public boolean doesSignatureFieldExist(String name)

Checks whether a name exists as a signature field or not. It checks both signed fields and blank signatures.

Parameters:

name - name of the field

Returns:

boolean does the signature field exist