Please, could someone point me in the right direction to digitally sign an MS-Office document (docx, xlsx, pptx) in Apache POI, or any other open source library?
I have already reviewed the classes under org.apache.poi.openxml4j.opc.signature but I cannot understand how I could add a signature to a document.
Check this sample code .. this sample code uses a file keystore PFX (PKCS12) .. Signs the Document and verify it.
// 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();
Here's the sample source : https://poi.apache.org/apidocs/org/apache/poi/poifs/crypt/dsig/SignatureInfo.html
I hope this could help!
