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PDFBox : Signature fails "Can't write signature, not enough space"

I implemented a signature feature in JAVA using PDFBox.
The signing part of my code is :
ExternalSigningSupport externalSigning = document.saveIncrementalForExternalSigning(output);
byte[] cmsSignature = new byte[0];
try {
Certificate[] certificationChain = SignatureUtils.getCertificateChain(alias);
X509Certificate certificate = (X509Certificate) certificationChain[0];
PrivateKey privateKey = SignatureUtils.getSignaturePrivateKey(alias, password);
CMSSignedDataGenerator gen = new CMSSignedDataGenerator();
ContentSigner sha1Signer = new JcaContentSignerBuilder("SHA256WithRSA").build(privateKey);
gen.addSignerInfoGenerator(new JcaSignerInfoGeneratorBuilder(new JcaDigestCalculatorProviderBuilder().build())
.build(sha1Signer, certificate));
gen.addCertificates(new JcaCertStore(Arrays.asList(certificationChain)));
CMSProcessableInputStream msg = new CMSProcessableInputStream(externalSigning.getContent());
CMSSignedData signedData = gen.generate(msg, false);
if (tsaUrl != null && !tsaUrl.isEmpty()) {
ValidationTimeStamp validation;
validation = new ValidationTimeStamp(tsaUrl);
signedData = validation.addSignedTimeStamp(signedData);
}
cmsSignature = signedData.getEncoded();
if (logger.isDebugEnabled()) {
logger.debug("signature length = " + cmsSignature.length);
logger.debug("certificate = " + certificate.toString());
}
} catch (GeneralSecurityException | CMSException | OperatorCreationException | IOException e) {
throw new SignatureException(e.getMessage());
}
externalSigning.setSignature(cmsSignature);
Everything works fine if I use my testing auto-signed certificate I generated with the keytool command.
The problem is, when I try this code with an existing certificate which is truly certified, I get the exeption :
Caused by: java.io.IOException: Can't write signature, not enough space
at org.apache.pdfbox.pdfwriter.COSWriter.writeExternalSignature(COSWriter.java:797)
at org.apache.pdfbox.pdmodel.interactive.digitalsignature.SigningSupport.setSignature(SigningSupport.java:48)
I have no idea why this doesn't work...
Any help would be appreciated ! =)

In a comment you mention that you get
signature length = 10721
in the log files and that you
didn't set any preferred size
By default PDFBox reserves 0x2500 bytes for the signature. That's 9472 bytes decimally. Thus, just like the exception says, there's not enough space.
You can set the size PDFBox reserves for the signature by using a SignatureOptions object during document.addSignature:
SignatureOptions signatureOptions = new SignatureOptions();
signatureOptions.setPreferredSignatureSize(20000);
document.addSignature(signature, signatureOptions);

Generate valid CMS Signature file adding external PKCS#1 with Java

I'm generating CMS signature files with external PKCS#1 based on this thread.
The first step is obtain the signed attributes from the original file to be signed in external application which is returning PKCS#1 byte array.
Then build standard org.bouncycastle.cms.SignerInfoGenerator with original file hash, signed data (PKCS#1) and certificate to add to CMS, and finally create the attached signature.
But when i'd tried to validate it using this code:
String originalFile = "aG9sYQ0KYXNkYXMNCg0KYWZzDQo=";
String cmsSignedFile = "MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBg...j2Dwytp6kzQNwtXGO8QbWty1lOo8oYm+6LR8EWba3ikO/m9ol/G808vit9gAAAAAAAA==";
byte[] signedByte = DatatypeConverter.parseBase64Binary(cmsSignedFile);
Security.addProvider(new BouncyCastleProvider());
CMSSignedData s = new CMSSignedData(new CMSProcessableByteArray(DatatypeConverter.parseBase64Binary(originalFile)), signedByte);
SignerInformationStore signers = s.getSignerInfos();
SignerInformation signerInfo = (SignerInformation)signers.getSigners().iterator().next();
FileInputStream fis = new FileInputStream("C:/myCertificate.cer");
CertificateFactory cf = CertificateFactory.getInstance("X.509");
X509Certificate cert = (X509Certificate)cf.generateCertificates(fis).iterator().next();
boolean result = signerInfo.verify(new JcaSimpleSignerInfoVerifierBuilder().setProvider("BC").build(cert.getPublicKey()));
System.out.println("Verified: "+result);
I get Verified: false
I'm adding Content Type, Signing time, Message digest and OCSP as signed attributes and TSP Token as unsigned attribute (I'm not sure if this is right).
I'm also trying to recover data from CMS signature, using the code below:
//load cms signed file with attached data
CMSSignedData cms = new CMSSignedData(FileUtils.readFileToByteArray(new File("C:/tmp/tempFile1864328163858309463.cms")));
System.out.println(cms.getSignerInfos().getSigners().iterator().next().getDigestAlgorithmID().getAlgorithm().getId());
System.out.println(Hex.encodeHexString(cms.getSignerInfos().getSigners().iterator().next().getSignature()));
//recover signer certificate info
Store certs = cms.getCertificates();
Collection<X509CertificateHolder> col = certs.getMatches(null);
X509CertificateHolder []h1 = col.toArray(new X509CertificateHolder[col.size()]);
X509CertificateHolder firmante = h1[0];
System.out.println(firmante.getSubject());
System.out.println(h1[1].getSubject());
SignerInformation sinfo = cms.getSignerInfos().getSigners().iterator().next();
//recover OCSP information
//THIS FAILS :(
// Store infocspbasic = cms.getOtherRevocationInfo(OCSPObjectIdentifiers.id_pkix_ocsp_basic);
// Object basic = infocspbasic.getMatches(null).iterator().next();
//recover signing time
if (sinfo.getSignedAttributes() != null) {
Attribute timeStampAttr = sinfo.getSignedAttributes().get(PKCSObjectIdentifiers.pkcs_9_at_signingTime);
ASN1Encodable attrValue = timeStampAttr.getAttrValues().getObjectAt(0);
final Date signingDate;
if (attrValue instanceof ASN1UTCTime) {
ASN1UTCTime time = ASN1UTCTime.getInstance(attrValue);
Date d = time.getDate();
System.out.println("ASN1UTCTime:" + d);
} else if (attrValue instanceof Time) {
signingDate = ((Time) attrValue).getDate();
} else if (attrValue instanceof ASN1GeneralizedTime) {
System.out.println("ASN1GeneralizedTimeASN1GeneralizedTime");
} else {
signingDate = null;
}
}
//recover timestamp TOken
//unsigned attributes are null :(
if (sinfo.getUnsignedAttributes() != null) {
Attribute timeStampAttr = sinfo.getUnsignedAttributes().get(PKCSObjectIdentifiers.id_aa_signatureTimeStampToken);
for (ASN1Encodable value : timeStampAttr.getAttrValues().toArray()) {
TimeStampToken token = new TimeStampToken(new CMSSignedData(value.toASN1Primitive().getEncoded()));
System.out.println(token.getTimeStampInfo().getGenTime());
}
}
But I can't retrieve OCSP response nor TSP Token information. Additionally I've downloaded this viewer software to help verify it:
Any help would be very appreciated.

I found a project named j4sign which implements CMS signature with external PKCS#1. The link goes to the project's forum where I posted the code sample using their classes and the final correction to make the validation works.

Verify Digital Signature on Android

I am developing an Android application that requires Digitally signing an html document.
The document resides in the DB, in a JSON form.
I'm signing the document locally using a BASH Script I found on some other SO question :
openssl dgst -sha1 someHTMLDoc.html > hash
openssl rsautl -sign -inkey privateKey.pem -keyform PEM -in hash > signature.bin
Private key was generated using :
openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -pkeyopt rsa_keygen_pubexp:3 -out privateKey.pem
Public key was generated using :
openssl pkey -in privateKey.pem -out publicKey.pem -pubout
I want to verify the signature created in Signature.bin together with the data in someHTMLDoc.html, back in the application.
I am sending both the html and signature as JSON Object ex:
{ "data" : "<html><body></body></html>", "signature":"6598 13a9 b12b 21a9 ..... " }
The android application holds the PublicKey in shared prefs as follows :
-----BEGIN PUBLIC KEY-----
MIIBIDANBgkqhkiG9w0AAAEFAAOCAQ0AvniCAKCAQEAvni/NSEX3Rhx91HkJl85
\nx1noyYET ......
Notice the "\n" (newline) in there (was automatically added when copying string from publicKey.pem to Android Gradle Config.
Ok, after all preparations, now the question.
I am trying to validate the key with no success.
I am using the following code :
private boolean verifySignature(String data, String signature) {
InputStream is = null;
try {
is = new ByteArrayInputStream(Config.getDogbarPublic().getBytes("UTF-8")); //Read DogBar Public key
BufferedReader br = new BufferedReader(new InputStreamReader(is));
List<String> lines = new ArrayList<String>();
String line;
while ((line = br.readLine()) != null)
lines.add(line);
// removes the first and last lines of the file (comments)
if (lines.size() > 1 && lines.get(0).startsWith("-----") && lines.get(lines.size() - 1).startsWith("-----")) {
lines.remove(0);
lines.remove(lines.size() - 1);
}
// concats the remaining lines to a single String
StringBuilder sb = new StringBuilder();
for (String aLine : lines)
sb.append(aLine);
String key = sb.toString();
byte[] keyBytes = Base64.decode(key.getBytes("utf-8"), Base64.DEFAULT);
X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey publicKey = keyFactory.generatePublic(spec);
Signature signCheck = Signature.getInstance("SHA1withRSA"); //Instantiate signature checker object.
signCheck.initVerify(publicKey);
signCheck.update(data.getBytes());
return signCheck.verify(signature.getBytes()); //verify signature with public key
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
Can anyone help ? what am i doing wrong ?
Am i missing some byte conversion ? maybe the JSON object is affecting the signature ?
Should a signature contain the \n (linebreak) that the original file contains or should it be without in the JSON file ?
Thanks in advance for all the help, its highly appreciated.

Digital signature is a process of computing digest (function H) of data (C) and encrypting it with asymmetric encryption algorithm (function E) to produce cypher text (S):
S = E(H(C))
Signature verification takes the signature decrypts the given signature (function D) - which results in H(C) only if the public key used in decryption is paired with private key used in encryption, and computes the digest of data to check if the two digests match:
H(C) == D(E(H(C)))
It's clear from this that the bytes given to the hash function (C) must be exactly the same in order for the signature to validate.
In your case they are not, because when you're computing the digest using openssl dgst the output (H(C) on the right) is literally something like:
SHA1(someHTMLDoc.html)= 22596363b3de40b06f981fb85d82312e8c0ed511
And this is the input to the RSA encryption.
And when you're verifying the signature, the output of the digest (H(C) on the left) are the raw bytes, for instance in hex:
22596363b3de40b06f981fb85d82312e8c0ed511
So you end up encrypting bytes to produce (H(C) on the right):
0000000: 5348 4131 2873 6f6d 6548 746d 6c44 6f63 SHA1(someHtmlDoc
0000010: 2e68 746d 6c29 3d20 3232 3539 3633 3633 .html)= 22596363
0000020: 6233 6465 3430 6230 3666 3938 3166 6238 b3de40b06f981fb8
0000030: 3564 3832 3331 3265 3863 3065 6435 3131 5d82312e8c0ed511
0000040: 0a .
and comparing against bytes (H(C) on the left):
0000000: 2259 6363 b3de 40b0 6f98 1fb8 5d82 312e "Ycc..#.o...].1.
0000010: 8c0e d511 ....
Also you need to use -sign with openssl dgst in order to have proper output format (see Difference between openSSL rsautl and dgst).
So on the OpenSSL side do:
openssl dgst -sha1 -sign privateKey.pem someHTMLDoc.html > signature.bin
On the Java side do:
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.security.KeyFactory;
import java.security.Signature;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.X509EncodedKeySpec;
import org.spongycastle.util.io.pem.PemObject;
import org.spongycastle.util.io.pem.PemReader;
public class VerifySignature {
public static void main(final String[] args) throws Exception {
try (PemReader reader = publicKeyReader(); InputStream data = data(); InputStream signatureData = signature()) {
final PemObject publicKeyPem = reader.readPemObject();
final byte[] publicKeyBytes = publicKeyPem.getContent();
final KeyFactory keyFactory = KeyFactory.getInstance("RSA");
final X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyBytes);
final RSAPublicKey publicKey = (RSAPublicKey) keyFactory.generatePublic(publicKeySpec);
final Signature signature = Signature.getInstance("SHA1withRSA");
signature.initVerify(publicKey);
final byte[] buffy = new byte[16 * 1024];
int read = -1;
while ((read = data.read(buffy)) != -1) {
signature.update(buffy, 0, read);
}
final byte[] signatureBytes = new byte[publicKey.getModulus().bitLength() / 8];
signatureData.read(signatureBytes);
System.out.println(signature.verify(signatureBytes));
}
}
private static InputStream data() throws FileNotFoundException {
return new FileInputStream("someHTMLDoc.html");
}
private static PemReader publicKeyReader() throws FileNotFoundException {
return new PemReader(new InputStreamReader(new FileInputStream("publicKey.pem")));
}
private static InputStream signature() throws FileNotFoundException {
return new FileInputStream("signature.bin");
}
}
I've used Spongy Castle for PEM decoding of the public key to make things a bit more readable and easier to use.

If you have a digitally signed XML file (downloaded from the web) and a certificate (.cer file) and you want to verify the digital signature in an android app then here is the code:
You need two things xmlFilePath and certificateFilePath
boolean verifySignature() {
boolean valid = false;
try {
File file = new File("xmlFilePath");
DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
f.setNamespaceAware(true);
Document doc = f.newDocumentBuilder().parse(file);
NodeList nodes = doc.getElementsByTagNameNS(Constants.SignatureSpecNS, "Signature");
if (nodes.getLength() == 0) {
throw new Exception("Signature NOT found!");
}
Element sigElement = (Element) nodes.item(0);
XMLSignature signature = new XMLSignature(sigElement, "");
CertificateFactory cf = CertificateFactory.getInstance("X.509");
InputStream ims = new InputStream("certificateFilePath");
X509Certificate cert = (X509Certificate) cf.generateCertificate(ims);
if (cert == null) {
PublicKey pk = signature.getKeyInfo().getPublicKey();
if (pk == null) {
throw new Exception("Did not find Certificate or Public Key");
}
valid = signature.checkSignatureValue(pk);
} else {
valid = signature.checkSignatureValue(cert);
}
} catch (Exception e) {
e.printStackTrace();
Toast.makeText(this, "Failed signature " + e.getMessage(), Toast.LENGTH_SHORT).show();
}
return valid;
}
If you want to do it in java but not in android studio. Here is the code:
public static boolean isXmlDigitalSignatureValid(String signedXmlFilePath,
String pubicKeyFilePath) throws Exception {
boolean validFlag;
File file = new File(signedXmlFilePath);
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(file);
doc.getDocumentElement().normalize();
NodeList nl = doc.getElementsByTagNameNS(XMLSignature.XMLNS, "Signature");
if (nl.getLength() == 0) {
throw new Exception("No XML Digital Signature Found, document is discarded");
}
FileInputStream fileInputStream = new FileInputStream(pubicKeyFilePath);
CertificateFactory cf = CertificateFactory.getInstance("X.509");
X509Certificate cert = (X509Certificate) cf.generateCertificate(fileInputStream);
PublicKey publicKey = cert.getPublicKey();
DOMValidateContext valContext = new DOMValidateContext(publicKey, nl.item(0));
XMLSignatureFactory fac = XMLSignatureFactory.getInstance("DOM");
XMLSignature signature = fac.unmarshalXMLSignature(valContext);
validFlag = signature.validate(valContext);
return validFlag;
}
The reason is that you will need to add dependency if you use the same code in android studio, sometimes confusing also.
If you are interested in reading digital signature documents, you can read www.xml.com/post It is an interesting document for understanding the need for a digital signature.

Sign and encrypt a file using S/MIME

I am currently trying to adapt a few scripts we use to sign an encrypt/decrypt xml files using OpenSSL and S/MIME using Java and BouncyCastle.
The command to sign and encrypt our file:
openssl smime -sign -signer Pub1.crt -inkey Priv.key -in foo.xml | openssl smime -encrypt -out foo.xml.smime Pub2.crt Pub1.crt
This generates a signed and encrypted smime-file containing our xml file. Currently this happens using a set of shell scripts under linux using the OpenSSL library. In the future we want to integrate this process into our Java application.
I've found out that this should be possible using the BouncyCastle library (see this post). The answer there provides two Java classes showing how to sign and encrypt an email using BouncyCastle and S/MIME. Comparing this to our OpenSSL command it seems that many of the things needed to sign an encrypt an email is not needed in our approach.
Some more meta information from our generated files:
Signed file
MIME-Version: 1.0
Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg="sha-256"; boundary="----709621D94E0377688356FAAE5A2C1321"
Encrypted file
MIME-Version: 1.0
Content-Disposition: attachment; filename="smime.p7m"
Content-Type: application/x-pkcs7-mime; smime-type=enveloped-data; name="smime.p7m"
Content-Transfer-Encoding: base64
Is it even possible to sign and encrypt a simple file in the way we did it using OpenSSL? My current knowledge of signing and de/encryption is not very high at the moment so forgive me for not providing code samples. I guess what I am looking for is more input into what I need to do and maybe some expertise from people who have already done this. I hope this is the right place to ask this. If not, please correct me.

I had a similar question as you but I managed to solve it. I have to warn you, my knowledge about signing and encryption isn't that high either. But this code seemed to work for me.
In my case I used a personalsign pro 3 certificate from globalsign, Previously I just called openssl from within java. But the I wanted to clean my code and decided to use bouncy castle instead.
public static boolean signAllFiles(List<File> files) {
Boolean signingSucceeded = true;
KeyStore ks = null;
char[] password = null;
Security.addProvider(new BouncyCastleProvider());
try {
ks = KeyStore.getInstance("PKCS12");
password = "yourpass".toCharArray();
ks.load(new FileInputStream("full/path/to/your/original/certificate.pfx"), password);
} catch (Exception e) {
signingSucceeded = false;
}
// Get privatekey and certificate
X509Certificate cert = null;
PrivateKey privatekey = null;
try {
Enumeration<String> en = ks.aliases();
String ALIAS = "";
Vector<Object> vectaliases = new Vector<Object>();
while (en.hasMoreElements())
vectaliases.add(en.nextElement());
String[] aliases = (String[])(vectaliases.toArray(new String[0]));
for (int i = 0; i < aliases.length; i++)
if (ks.isKeyEntry(aliases[i]))
{
ALIAS = aliases[i];
break;
}
privatekey = (PrivateKey)ks.getKey(ALIAS, password);
cert = (X509Certificate)ks.getCertificate(ALIAS);
// publickey = ks.getCertificate(ALIAS).getPublicKey();
} catch (Exception e) {
signingSucceeded = false;
}
for (File source : files) {
String fileName = "the/path/andNameOfYourOutputFile";
try {
// Reading files which need to be signed
File fileToSign = source;
byte[] buffer = new byte[(int)fileToSign.length()];
DataInputStream in = new DataInputStream(new FileInputStream(fileToSign));
in.readFully(buffer);
in.close();
// Generate signature
ArrayList<X509Certificate> certList = new ArrayList<X509Certificate>();
certList.add(cert);
Store<?> certs = new JcaCertStore(certList);
CMSSignedDataGenerator signGen = new CMSSignedDataGenerator();
ContentSigner sha1signer = new JcaContentSignerBuilder("SHA1withRSA").setProvider("BC").build(
privatekey);
signGen.addSignerInfoGenerator(new JcaSignerInfoGeneratorBuilder(
new JcaDigestCalculatorProviderBuilder().build()).build(sha1signer, cert));
signGen.addCertificates(certs);
CMSTypedData content = new CMSProcessableByteArray(buffer);
CMSSignedData signedData = signGen.generate(content, false);
byte[] signeddata = signedData.getEncoded();
// Write signature to Fi File
FileOutputStream envfos = new FileOutputStream(fileName);
byte[] outputString = Base64.encode(signeddata);
int fullLines = (int)Math.floor(outputString.length / 64);
for (int i = 0; i < fullLines; i++) {
envfos.write(outputString, i * 64, 64);
envfos.write("\r\n".getBytes());
}
envfos.write(outputString, fullLines * 64, outputString.length % 64);
envfos.close();
} catch (Exception e) {
signingSucceeded = false;
}
}
return signingSucceeded;
}
This is only the code to sign a file, I hope it helps.

Use BouncyCastle to generate Signed File

I have a PDF file and I use this code to sign this file:
certificate = (X509Certificate) loadKeyStore(certificateFile, password).getCertificate(alias);
privateKey = (PrivateKey) loadKeyStore(certificateFile, password).getKey(alias, alias.toCharArray());
Security.addProvider(new BouncyCastleProvider());
BufferedInputStream inFile = new BufferedInputStream(new FileInputStream(origem));
byte[] dates = new byte[inFile.available()];
entrada.read(dates);
entrada.close();
CMSSignedDataGenerator genetateSign = new CMSSignedDataGenerator();
geradorAss.addSigner(privateKey, certificate, CMSSignedDataGenerator.DIGEST_SHA1);
List certList = new ArrayList();
certList.add(certificate);
CertStore certs = CertStore.getInstance("Collection", new CollectionCertStoreParameters(certList));
geradorAss.addCertificatesAndCRLs(certs);
// Efetivamente assinar os dados de entrada
CMSProcessable content = new CMSProcessableByteArray(dates);
String providerName;
if (ks.getType().equalsIgnoreCase("JKS")) {
providerName = BouncyCastleProvider.PROVIDER_NAME;
} else {
providerName = ks.getProvider().getName();
}
CMSSignedData signedDate = genetateSign.generate(content, providerName);
signedDate = new CMSSignedData(content, signedDate.getEncoded());
File f = Converter.converter("signedFile.pdf", signedDate.getEncoded());
But, the file f no open on reader. When I get the file f and run this code:
CMSSignedData data = new CMSSignedData(new FileInputStream(f));
Occur this error:
org.bouncycastle.cms.CMSException: Malformed content.
Someone can help me?
Summarizing:
I need to generate the final file after signing. For example, I have a test.pdf file, I want to sign and generate test_signed.pdf file. And this test_signed.pdf file must have the signature and should still be readable in your reader.
I'm waiting...

PDF has an embedded signature inside the document, while CMS is signature itself. To extract and verify signature from PDF use iText library. Here is an example.