# PDSignature.java

    /*
     * Licensed to the Apache Software Foundation (ASF) under one or more
     * contributor license agreements.  See the NOTICE file distributed with
     * this work for additional information regarding copyright ownership.
     * The ASF licenses this file to You under the Apache License, Version 2.0
     * (the "License"); you may not use this file except in compliance with
     * the License.  You may obtain a copy of the License at
     *
     *      http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package org.apache.pdfbox.pdmodel.interactive.digitalsignature;

    import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Calendar;

    import org.apache.pdfbox.cos.COSArray;
    import org.apache.pdfbox.cos.COSBase;
    import org.apache.pdfbox.cos.COSDictionary;
    import org.apache.pdfbox.cos.COSInteger;
    import org.apache.pdfbox.cos.COSName;
    import org.apache.pdfbox.cos.COSString;
    import org.apache.pdfbox.pdmodel.common.COSObjectable;

    /**
     * This represents a digital signature that can be attached to a document. To learn more about
     * digital signatures, read
     * <a href="https://www.adobe.com/devnet-docs/acrobatetk/tools/DigSig/Acrobat_DigitalSignatures_in_PDF.pdf">Digital
     * Signatures in a PDF</a> by Adobe.
     *
     * @author Ben Litchfield
     * @author Thomas Chojecki
     */
    public class PDSignature implements COSObjectable
    {
        private final COSDictionary dictionary;

        /**
         * A signature filter value.
         */
        public static final COSName FILTER_ADOBE_PPKLITE = COSName.ADOBE_PPKLITE;

        /**
         * A signature filter value.
         */
        public static final COSName FILTER_ENTRUST_PPKEF = COSName.ENTRUST_PPKEF;

        /**
         * A signature filter value.
         */
        public static final COSName FILTER_CICI_SIGNIT = COSName.CICI_SIGNIT;

        /**
         * A signature filter value.
         */
        public static final COSName FILTER_VERISIGN_PPKVS = COSName.VERISIGN_PPKVS;

        /**
         * A signature subfilter value.
         */
        public static final COSName SUBFILTER_ADBE_X509_RSA_SHA1 = COSName.ADBE_X509_RSA_SHA1;

        /**
         * A signature subfilter value.
         */
        public static final COSName SUBFILTER_ADBE_PKCS7_DETACHED = COSName.ADBE_PKCS7_DETACHED;

        /**
         * A signature subfilter value.
         */
        public static final COSName SUBFILTER_ETSI_CADES_DETACHED = COSName.getPDFName("ETSI.CAdES.detached");

        /**
         * A signature subfilter value.
         */
        public static final COSName SUBFILTER_ADBE_PKCS7_SHA1 = COSName.ADBE_PKCS7_SHA1;

        /**
         * Default constructor.
         */
        public PDSignature()
        {
            dictionary = new COSDictionary();
            dictionary.setItem(COSName.TYPE, COSName.SIG);
        }

        /**
         * Constructor.
         *
         * @param dict The signature dictionary.
         */
        public PDSignature(COSDictionary dict)
        {
            dictionary = dict;
        }

        /**
         * Convert this standard java object to a COS dictionary.
         *
         * @return The COS dictionary that matches this Java object.
         */
        @Override
        public COSDictionary getCOSObject()
        {
            return dictionary;
        }

        /**
         * Set the dictionary type.
         *
         * @param type is the dictionary type.
         */
        public void setType(COSName type)
        {
            dictionary.setItem(COSName.TYPE, type);
        }

        /**
         * Set the filter.
         *
         * @param filter the filter to be used
         */
        public void setFilter(COSName filter)
        {
            dictionary.setItem(COSName.FILTER, filter);
        }

        /**
         * Set a subfilter that specify the signature that should be used.
         *
         * @param subfilter the subfilter that shall be used.
         */
        public void setSubFilter(COSName subfilter)
        {
            dictionary.setItem(COSName.SUB_FILTER, subfilter);
        }

        /**
         * Sets the name of the person or authority signing the document. According to the PDF
         * specification, this value should be used only when it is not possible to extract the name
         * from the signature.
         *
         * @param name the name to be used
         */
        public void setName(String name)
        {
            dictionary.setString(COSName.NAME, name);
        }

        /**
         * Sets the CPU host name or physical location of the signing.
         *
         * @param location the location to be used
         */
        public void setLocation(String location)
        {
            dictionary.setString(COSName.LOCATION, location);
        }

        /**
         * Sets the reason for the signing, such as (I agree...).
         *
         * @param reason the reason to be used
         */
        public void setReason(String reason)
        {
            dictionary.setString(COSName.REASON, reason);
        }

        /**
         * Sets the contact info provided by the signer to enable a recipient to contact the signer to
         * verify the signature, e.g. a phone number.
         *
         * @param contactInfo the contact info to be used
         */
        public void setContactInfo(String contactInfo)
        {
            dictionary.setString(COSName.CONTACT_INFO, contactInfo);
        }

        /**
         * Set the sign date.
         *
         * @param cal the date to be used as sign date
         */
        public void setSignDate(Calendar cal)
        {
            dictionary.setDate(COSName.M, cal);
        }

        /**
         * Returns the filter.
         * @return the filter
         */
        public String getFilter()
        {
            return dictionary.getNameAsString(COSName.FILTER);
        }

        /**
         * Returns the subfilter.
         *
         * @return the subfilter
         */
        public String getSubFilter()
        {
            return dictionary.getNameAsString(COSName.SUB_FILTER);
        }

        /**
         * Returns the name of the person or authority signing the document. According to the PDF
         * specification, this value should be used only when it is not possible to extract the name
         * from the signature.
         *
         * @return the name
         */
        public String getName()
        {
            return dictionary.getString(COSName.NAME);
        }

        /**
         * Returns the CPU host name or physical location of the signing.
         *
         * @return the location
         */
        public String getLocation()
        {
            return dictionary.getString(COSName.LOCATION);
        }

        /**
         * Returns the reason for the signing, such as (I agree...).
         *
         * @return the reason
         */
        public String getReason()
        {
            return dictionary.getString(COSName.REASON);
        }

        /**
         * Returns the contact info provided by the signer to enable a recipient to contact the signer
         * to verify the signature, e.g. a phone number.
         *
         * @return the contact info
         */
        public String getContactInfo()
        {
            return dictionary.getString(COSName.CONTACT_INFO);
        }

        /**
         * Returns the sign date.
         *
         * @return the sign date
         */
        public Calendar getSignDate()
        {
            return dictionary.getDate(COSName.M);
        }

        /**
         * Sets the byte range.
         *
         * @param range the byte range to be used
         */
        public void setByteRange(int[] range)
        {
            if (range.length!=4)
            {
                return;
            }
            COSArray ary = new COSArray();
            for ( int i : range )
            {
                ary.add(COSInteger.get(i));
            }

            dictionary.setItem(COSName.BYTERANGE, ary);
            ary.setDirect(true);
        }

        /**
         * Read out the byterange from the file.
         *
         * @return an integer array with the byterange, or an empty array if there is none.
         */
        public int[] getByteRange()
        {
            COSArray byteRange = dictionary.getCOSArray(COSName.BYTERANGE);
            if (byteRange == null)
            {
                return new int[0];
            }
            int[] ary = new int[byteRange.size()];
            for (int i = 0; i<ary.length;++i)
            {
                ary[i] = byteRange.getInt(i);
            }
            return ary;
        }

        /**
         * Returns the /Contents string as a byte array, i.e. the embedded signature between the
         * byterange gap.
         *
         * @return a byte array containing the signature, or an empty array if there isn't any.
         */
        public byte[] getContents()
        {
            COSBase base = dictionary.getDictionaryObject(COSName.CONTENTS);
            if (base instanceof COSString)
            {
                return ((COSString) base).getBytes();
            }
            return new byte[0];
        }

        /**
         * Will return the embedded signature between the byterange gap.
         *
         * @param pdfFile The signed pdf file as InputStream. It will be closed in this method.
         * @return a byte array containing the signature
         * @throws IOException if the pdfFile can't be read
         * @throws IndexOutOfBoundsException if the byterange array is not long enough
         */
        public byte[] getContents(InputStream pdfFile) throws IOException
        {
            int[] byteRange = getByteRange();
            int begin = byteRange[0]+byteRange[1]+1;
            int len = byteRange[2]-begin;

            return getConvertedContents(new COSFilterInputStream(pdfFile,new int[] {begin,len}));
        }

        /**
         * Will return the embedded signature between the byterange gap.
         *
         * @param pdfFile The signed pdf file as byte array
         * @return a byte array containing the signature
         * @throws IOException if the pdfFile can't be read
         * @throws IndexOutOfBoundsException if the byterange array is not long enough
         */
        public byte[] getContents(byte[] pdfFile) throws IOException
        {
            int[] byteRange = getByteRange();
            int begin = byteRange[0]+byteRange[1]+1;
            int len = byteRange[2]-begin-1;

            return getConvertedContents(new ByteArrayInputStream(pdfFile, begin, len));
        }

        private byte[] getConvertedContents(InputStream is) throws IOException
        {
            ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
            byte[] buffer = new byte[1024];
            int readLen;
            while ((readLen = is.read(buffer)) != -1)
            {
                int writeLen = readLen;
                int start = 0;
                // Filter < and (
                if(buffer[0]==0x3C || buffer[0]==0x28)
                {
                    ++start;
                    --writeLen;
                }
                // Filter > and ) at the end
                if(buffer[readLen-1]==0x3E || buffer[readLen-1]==0x29)
                {
                    --writeLen;
                }
                baos.write(buffer, start, writeLen);
            }
            is.close();

            return COSString.parseHex(baos.toString("ISO-8859-1")).getBytes();
        }

        /**
         * Sets the contents.
         *
         * @param bytes contents to be used
         */
        public void setContents(byte[] bytes)
        {
            COSString string = new COSString(bytes);
            string.setForceHexForm(true);
            dictionary.setItem(COSName.CONTENTS, string);
        }

        /**
         * Return the signed content of the document. This is not a PDF file, nor is it the PDF file
         * before signing, it is the byte sequence made of the input minus the area where the signature
         * bytes will be. See "The ByteRange and signature value" in the document
         * <a href="https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/DigitalSignaturesInPDF.pdf#page=5">Digital
         * Signatures in a PDF</a>.
         *
         * @param pdfFile The signed pdf file as InputStream. It will be closed in this method.
         * @return a byte array containing only the signed part of the content
         * @throws IOException if the pdfFile can't be read
         */
        public byte[] getSignedContent(InputStream pdfFile) throws IOException
        {
            try (COSFilterInputStream fis = new COSFilterInputStream(pdfFile, getByteRange()))
            {
                return fis.toByteArray();
            }
        }

        /**
         * Return the signed content of the document. This is not a PDF file, nor is it the PDF file
         * before signing, it is the byte sequence made of the input minus the area where the signature
         * bytes will be. See "The ByteRange and signature value" in the document
         * <a href="https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/DigitalSignaturesInPDF.pdf#page=5">Digital
         * Signatures in a PDF</a>.
         *
         * @param pdfFile The signed pdf file as byte array
         * @return a byte array containing only the signed part of the content
         * @throws IOException if the pdfFile can't be read
         */
        public byte[] getSignedContent(byte[] pdfFile) throws IOException
        {
            try (COSFilterInputStream fis = new COSFilterInputStream(pdfFile, getByteRange()))
            {
                return fis.toByteArray();
            }
        }

        /**
         * PDF signature build dictionary. Provides information about the signature handler.
         *
         * @return the pdf signature build dictionary.
         */
        public PDPropBuild getPropBuild()
        {
            PDPropBuild propBuild = null;
            COSDictionary propBuildDic = dictionary.getCOSDictionary(COSName.PROP_BUILD);
            if (propBuildDic != null)
            {
                propBuild = new PDPropBuild(propBuildDic);
            }
            return propBuild;
        }

        /**
         * PDF signature build dictionary. Provides information about the signature handler.
         *
         * @param propBuild the prop build
         */
        public void setPropBuild(PDPropBuild propBuild)
        {
            dictionary.setItem(COSName.PROP_BUILD, propBuild);
        }
    }