org.apache.poi.poifs.crypt.dsig
Class SignatureInfo

java.lang.Object
  org.apache.poi.poifs.crypt.dsig.SignatureInfo

All Implemented Interfaces:

SignatureConfig.SignatureConfigurable

public class SignatureInfo
extends java.lang.Object
implements SignatureConfig.SignatureConfigurable

This class is the default entry point for XML signatures and can be used for validating an existing signed office document and signing a office document.

Validating a signed office document

 OPCPackage pkg = OPCPackage.open(..., PackageAccess.READ);
 SignatureConfig sic = new SignatureConfig();
 sic.setOpcPackage(pkg);
 SignatureInfo si = new SignatureInfo();
 si.setSignatureConfig(sic);
 boolean isValid = si.validate();
 ...
 

Signing an office document

 // loading the keystore - pkcs12 is used here, but of course jks & co are also valid
 // the keystore needs to contain a private key and it's certificate having a
 // 'digitalSignature' key usage
 char password[] = "test".toCharArray();
 File file = new File("test.pfx");
 KeyStore keystore = KeyStore.getInstance("PKCS12");
 FileInputStream fis = new FileInputStream(file);
 keystore.load(fis, password);
 fis.close();
 
 // extracting private key and certificate
 String alias = "xyz"; // alias of the keystore entry
 Key key = keystore.getKey(alias, password);
 X509Certificate x509 = (X509Certificate)keystore.getCertificate(alias);
 
 // filling the SignatureConfig entries (minimum fields, more options are available ...)
 SignatureConfig signatureConfig = new SignatureConfig();
 signatureConfig.setKey(keyPair.getPrivate());
 signatureConfig.setSigningCertificateChain(Collections.singletonList(x509));
 OPCPackage pkg = OPCPackage.open(..., PackageAccess.READ_WRITE);
 signatureConfig.setOpcPackage(pkg);
 
 // adding the signature document to the package
 SignatureInfo si = new SignatureInfo();
 si.setSignatureConfig(signatureConfig);
 si.confirmSignature();
 // optionally verify the generated signature
 boolean b = si.verifySignature();
 assert (b);
 // write the changes back to disc
 pkg.close();
 

Implementation notes:

Although there's a XML signature implementation in the Oracle JDKs 6 and higher, compatibility with IBM JDKs is also in focus (... but maybe not thoroughly tested ...). Therefore we are using the Apache Santuario libs (xmlsec) instead of the built-in classes, as the compatibility seems to be provided there.

To use SignatureInfo and its sibling classes, you'll need to have the following libs in the classpath:

• BouncyCastle bcpkix and bcprov (tested against 1.54)
• Apache Santuario "xmlsec" (tested against 2.0.5)
• and slf4j-api (tested against 1.7.12)

SignatureInfo

public SignatureInfo()

Constructor initializes xml signature environment, if it hasn't been initialized before

getSignatureConfig

public SignatureConfig getSignatureConfig()

Returns:

the signature config

setSignatureConfig

public void setSignatureConfig(SignatureConfig signatureConfig)

Specified by:

setSignatureConfig in interface SignatureConfig.SignatureConfigurable

Parameters:

signatureConfig - the signature config, needs to be set before a SignatureInfo object is used

verifySignature

public boolean verifySignature()

Returns:

true, if first signature part is valid

confirmSignature

public void confirmSignature()
                      throws javax.xml.crypto.dsig.XMLSignatureException,
                             javax.xml.crypto.MarshalException

add the xml signature to the document

Throws:

javax.xml.crypto.dsig.XMLSignatureException

javax.xml.crypto.MarshalException

signDigest

public byte[] signDigest(byte[] digest)

Sign (encrypt) the digest with the private key. Currently only rsa is supported.

Parameters:

digest - the hashed input

Returns:

the encrypted hash

getSignatureParts

public java.lang.Iterable<SignatureInfo.SignaturePart> getSignatureParts()

Returns:

a signature part for each signature document. the parts can be validated independently.

initXmlProvider

protected static void initXmlProvider()

Initialize the xml signing environment and the bouncycastle provider

preSign

public DigestInfo preSign(org.w3c.dom.Document document,
                          java.util.List<DigestInfo> digestInfos)
                   throws javax.xml.crypto.dsig.XMLSignatureException,
                          javax.xml.crypto.MarshalException

Helper method for adding informations before the signing. Normally confirmSignature() is sufficient to be used.

Throws:

javax.xml.crypto.dsig.XMLSignatureException

javax.xml.crypto.MarshalException

postSign

public void postSign(org.w3c.dom.Document document,
                     byte[] signatureValue)
              throws javax.xml.crypto.MarshalException

Helper method for adding informations after the signing. Normally confirmSignature() is sufficient to be used.

Throws:

javax.xml.crypto.MarshalException

writeDocument

protected void writeDocument(org.w3c.dom.Document document)
                      throws javax.xml.crypto.MarshalException

Write XML signature into the OPC package

Parameters:

document - the xml signature document

Throws:

javax.xml.crypto.MarshalException