# PDEncryption.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.encryption;

    import java.io.IOException;

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

    /**
     * This class is a specialized view of the encryption dictionary of a PDF document.
     * It contains a low level dictionary (COSDictionary) and provides the methods to
     * manage its fields.
     *
     * The available fields are the ones who are involved by standard security handler
     * and public key security handler.
     *
     * @author Ben Litchfield
     * @author Benoit Guillon
     */
    public class PDEncryption implements COSObjectable
    {
        /**
         * See PDF Reference 1.4 Table 3.13.
         */
        public static final int VERSION0_UNDOCUMENTED_UNSUPPORTED = 0;
        /**
         * See PDF Reference 1.4 Table 3.13.
         */
        public static final int VERSION1_40_BIT_ALGORITHM = 1;
        /**
         * See PDF Reference 1.4 Table 3.13.
         */
        public static final int VERSION2_VARIABLE_LENGTH_ALGORITHM = 2;
        /**
         * See PDF Reference 1.4 Table 3.13.
         */
        public static final int VERSION3_UNPUBLISHED_ALGORITHM = 3;
        /**
         * See PDF Reference 1.4 Table 3.13.
         */
        public static final int VERSION4_SECURITY_HANDLER = 4;

        /**
         * The default security handler.
         */
        public static final String DEFAULT_NAME = "Standard";

        /**
         * The default length for the encryption key.
         */
        public static final int DEFAULT_LENGTH = 40;

        /**
         * The default version, according to the PDF Reference.
         */
        public static final int DEFAULT_VERSION = VERSION0_UNDOCUMENTED_UNSUPPORTED;

        private final COSDictionary dictionary;
        private SecurityHandler<ProtectionPolicy> securityHandler;

        /**
         * creates a new empty encryption dictionary.
         */
        public PDEncryption()
        {
            dictionary = new COSDictionary();
        }

        /**
         * creates a new encryption dictionary from the low level dictionary provided.
         * @param dictionary a COS encryption dictionary
         */
        public PDEncryption(COSDictionary dictionary)
        {
            this.dictionary = dictionary;
            securityHandler = SecurityHandlerFactory.INSTANCE.newSecurityHandlerForFilter(getFilter());
        }

        /**
         * Returns the security handler specified in the dictionary's Filter entry.
         * @return a security handler instance
         * @throws IOException if there is no security handler available which matches the Filter
         */
        public SecurityHandler<ProtectionPolicy> getSecurityHandler() throws IOException
        {
            if (securityHandler == null)
            {
                throw new IOException("No security handler for filter " + getFilter());
            }
            return securityHandler;
        }

        /**
         * Sets the security handler used in this encryption dictionary
         * @param securityHandler new security handler
         */
        public void setSecurityHandler(SecurityHandler<ProtectionPolicy> securityHandler)
        {
            this.securityHandler = securityHandler;
            // TODO set Filter (currently this is done by the security handlers)
        }

        /**
         * Returns true if the security handler specified in the dictionary's Filter is available.
         * @return true if the security handler is available
         */
        public boolean hasSecurityHandler()
        {
            return securityHandler == null;
        }

        /**
         * This will get the dictionary associated with this encryption dictionary.
         *
         * @return The COS dictionary that this object wraps.
         */
        @Override
        public COSDictionary getCOSObject()
        {
            return dictionary;
        }

        /**
         * Sets the filter entry of the encryption dictionary.
         *
         * @param filter The filter name.
         */
        public void setFilter(String filter)
        {
            dictionary.setItem(COSName.FILTER, COSName.getPDFName(filter));
        }

        /**
         * Get the name of the filter.
         *
         * @return The filter name contained in this encryption dictionary.
         */
        public final String getFilter()
        {
            return dictionary.getNameAsString( COSName.FILTER );
        }

        /**
         * Get the name of the subfilter.
         *
         * @return The subfilter name contained in this encryption dictionary.
         */
        public String getSubFilter()
        {
            return dictionary.getNameAsString( COSName.SUB_FILTER );
        }

        /**
         * Set the subfilter entry of the encryption dictionary.
         *
         * @param subfilter The value of the subfilter field.
         */
        public void setSubFilter(String subfilter)
        {
            dictionary.setName(COSName.SUB_FILTER, subfilter);
        }

        /**
         * This will set the V entry of the encryption dictionary.<br><br>
         * See PDF Reference 1.4 Table 3.13.  <br><br>
         * <b>Note: This value is used to decrypt the pdf document.  If you change this when
         * the document is encrypted then decryption will fail!.</b>
         *
         * @param version The new encryption version.
         */
        public void setVersion(int version)
        {
            dictionary.setInt(COSName.V, version);
        }

        /**
         * This will return the V entry of the encryption dictionary.<br><br>
         * See PDF Reference 1.4 Table 3.13.
         *
         * @return The encryption version to use.
         */
        public int getVersion()
        {
            return dictionary.getInt( COSName.V, 0 );
        }

        /**
         * This will set the number of bits to use for the encryption algorithm.
         *
         * @param length The new key length.
         */
        public void setLength(int length)
        {
            dictionary.setInt(COSName.LENGTH, length);
        }

        /**
         * This will return the Length entry of the encryption dictionary.<br><br>
         * The length in <b>bits</b> for the encryption algorithm.  This will return a multiple of 8.
         *
         * @return The length in bits for the encryption algorithm
         */
        public int getLength()
        {
            return dictionary.getInt( COSName.LENGTH, 40 );
        }

        /**
         * This will set the R entry of the encryption dictionary.<br><br>
         * See PDF Reference 1.4 Table 3.14.  <br><br>
         *
         * <b>Note: This value is used to decrypt the pdf document.  If you change this when
         * the document is encrypted then decryption will fail!.</b>
         *
         * @param revision The new encryption version.
         */
        public void setRevision(int revision)
        {
            dictionary.setInt(COSName.R, revision);
        }

        /**
         * This will return the R entry of the encryption dictionary.<br><br>
         * See PDF Reference 1.4 Table 3.14.
         *
         * @return The encryption revision to use.
         */
        public int getRevision()
        {
            return dictionary.getInt( COSName.R, DEFAULT_VERSION );
        }

         /**
         * This will set the O entry in the standard encryption dictionary.
         *
         * @param o A 32 byte array or null if there is no owner key.
         *
         * @throws IOException If there is an error setting the data.
         */
        public void setOwnerKey(byte[] o) throws IOException
        {
            dictionary.setItem(COSName.O, new COSString(o));
        }

        /**
         * This will get the O entry in the standard encryption dictionary.
         *
         * @return A 32 byte array or null if there is no owner key.
         *
         * @throws IOException If there is an error accessing the data.
         */
        public byte[] getOwnerKey() throws IOException
        {
            byte[] o = null;
            COSString owner = (COSString) dictionary.getDictionaryObject( COSName.O );
            if( owner != null )
            {
                o = owner.getBytes();
            }
            return o;
        }

        /**
         * This will set the U entry in the standard encryption dictionary.
         *
         * @param u A 32 byte array.
         *
         * @throws IOException If there is an error setting the data.
         */
        public void setUserKey(byte[] u) throws IOException
        {
            dictionary.setItem(COSName.U, new COSString(u));
        }

        /**
         * This will get the U entry in the standard encryption dictionary.
         *
         * @return A 32 byte array or null if there is no user key.
         *
         * @throws IOException If there is an error accessing the data.
         */
        public byte[] getUserKey() throws IOException
        {
            byte[] u = null;
            COSString user = (COSString) dictionary.getDictionaryObject( COSName.U );
            if( user != null )
            {
                u = user.getBytes();
            }
            return u;
        }

        /**
         * This will set the OE entry in the standard encryption dictionary.
         *
         * @param oe A 32 byte array or null if there is no owner encryption key.
         *
         * @throws IOException If there is an error setting the data.
         */
        public void setOwnerEncryptionKey(byte[] oe) throws IOException
        {
            dictionary.setItem( COSName.OE, new COSString(oe) );
        }

        /**
         * This will get the OE entry in the standard encryption dictionary.
         *
         * @return A 32 byte array or null if there is no owner encryption key.
         *
         * @throws IOException If there is an error accessing the data.
         */
        public byte[] getOwnerEncryptionKey() throws IOException
        {
            byte[] oe = null;
            COSString ownerEncryptionKey = (COSString)dictionary.getDictionaryObject( COSName.OE );
            if( ownerEncryptionKey != null )
            {
                oe = ownerEncryptionKey.getBytes();
            }
            return oe;
        }

        /**
         * This will set the UE entry in the standard encryption dictionary.
         *
         * @param ue A 32 byte array or null if there is no user encryption key.
         *
         * @throws IOException If there is an error setting the data.
         */
        public void setUserEncryptionKey(byte[] ue) throws IOException
        {
            dictionary.setItem( COSName.UE, new COSString(ue) );
        }

        /**
         * This will get the UE entry in the standard encryption dictionary.
         *
         * @return A 32 byte array or null if there is no user encryption key.
         *
         * @throws IOException If there is an error accessing the data.
         */
        public byte[] getUserEncryptionKey() throws IOException
        {
            byte[] ue = null;
            COSString userEncryptionKey = (COSString)dictionary.getDictionaryObject( COSName.UE );
            if( userEncryptionKey != null )
            {
                ue = userEncryptionKey.getBytes();
            }
            return ue;
        }

        /**
         * This will set the permissions bit mask.
         *
         * @param permissions The new permissions bit mask
         */
        public void setPermissions(int permissions)
        {
            dictionary.setInt(COSName.P, permissions);
        }

        /**
         * This will get the permissions bit mask.
         *
         * @return The permissions bit mask.
         */
        public int getPermissions()
        {
            return dictionary.getInt( COSName.P, 0 );
        }

        /**
         * Will get the EncryptMetaData dictionary info.
         *
         * @return true if EncryptMetaData is explicitly set to false (the default is true)
         */
        public boolean isEncryptMetaData()
        {
            // default is true (see 7.6.3.2 Standard Encryption Dictionary PDF 32000-1:2008)
            return dictionary.getBoolean(COSName.ENCRYPT_META_DATA, true);
        }

        /**
         * This will set the Recipients field of the dictionary. This field contains an array
         * of string.
         * @param recipients the array of bytes arrays to put in the Recipients field.
         * @throws IOException If there is an error setting the data.
         */
        public void setRecipients(byte[][] recipients) throws IOException
        {
            COSArray array = new COSArray();
            for (byte[] recipient : recipients)
            {
                COSString recip = new COSString(recipient);
                array.add(recip);
            }
            dictionary.setItem(COSName.RECIPIENTS, array);
            array.setDirect(true);
        }

        /**
         * Returns the number of recipients contained in the Recipients field of the dictionary.
         *
         * @return the number of recipients contained in the Recipients field.
         */
        public int getRecipientsLength()
        {
            COSArray array = (COSArray) dictionary.getItem(COSName.RECIPIENTS);
            return array.size();
        }

        /**
         * returns the COSString contained in the Recipients field at position i.
         *
         * @param i the position in the Recipients field array.
         *
         * @return a COSString object containing information about the recipient number i.
         */
        public COSString getRecipientStringAt(int i)
        {
            COSArray array = (COSArray) dictionary.getItem(COSName.RECIPIENTS);
            return (COSString)array.get(i);
        }

        /**
         * Returns the standard crypt filter.
         *
         * @return the standard crypt filter if available.
         */
        public PDCryptFilterDictionary getStdCryptFilterDictionary()
        {
            return getCryptFilterDictionary(COSName.STD_CF);
        }

        /**
         * Returns the default crypt filter (for public-key security handler).
         *
         * @return the default crypt filter if available.
         */
        public PDCryptFilterDictionary getDefaultCryptFilterDictionary()
        {
            return getCryptFilterDictionary(COSName.DEFAULT_CRYPT_FILTER);
        }

        /**
         * Returns the crypt filter with the given name.
         *
         * @param cryptFilterName the name of the crypt filter
         *
         * @return the crypt filter with the given name if available
         */
        public PDCryptFilterDictionary getCryptFilterDictionary(COSName cryptFilterName)
        {
            // See CF in "Table 20 – Entries common to all encryption dictionaries"
            COSDictionary cfDict = dictionary.getCOSDictionary(COSName.CF);
            if (cfDict != null)
            {
                COSDictionary cryptDict = cfDict.getCOSDictionary(cryptFilterName);
                if (cryptDict != null)
                {
                    return new PDCryptFilterDictionary(cryptDict);
                }
            }
            return null;
        }

        /**
         * Sets the crypt filter with the given name.
         *
         * @param cryptFilterName the name of the crypt filter
         * @param cryptFilterDictionary the crypt filter to set
         */
        public void setCryptFilterDictionary(COSName cryptFilterName, PDCryptFilterDictionary cryptFilterDictionary)
        {
            COSDictionary cfDictionary = dictionary.getCOSDictionary(COSName.CF);
            if (cfDictionary == null)
            {
                cfDictionary = new COSDictionary();
                dictionary.setItem(COSName.CF, cfDictionary);
            }
            cfDictionary.setDirect(true); // PDFBOX-4436 direct obj needed for Adobe Reader on Android
            cfDictionary.setItem(cryptFilterName, cryptFilterDictionary.getCOSObject());
        }

        /**
         * Sets the standard crypt filter.
         *
         * @param cryptFilterDictionary the standard crypt filter to set
         */
        public void setStdCryptFilterDictionary(PDCryptFilterDictionary cryptFilterDictionary)
        {
            cryptFilterDictionary.getCOSObject().setDirect(true); // PDFBOX-4436
            setCryptFilterDictionary(COSName.STD_CF, cryptFilterDictionary);
        }

        /**
         * Sets the default crypt filter (for public-key security handler).
         *
         * @param defaultFilterDictionary the standard crypt filter to set
         */
        public void setDefaultCryptFilterDictionary(PDCryptFilterDictionary defaultFilterDictionary)
        {
            defaultFilterDictionary.getCOSObject().setDirect(true); // PDFBOX-4436
            setCryptFilterDictionary(COSName.DEFAULT_CRYPT_FILTER, defaultFilterDictionary);
        }

        /**
         * Returns the name of the filter which is used for de/encrypting streams.
         * Default value is "Identity".
         *
         * @return the name of the filter
         */
        public COSName getStreamFilterName()
        {
            COSName stmF = dictionary.getCOSName(COSName.STM_F);
            return stmF == null ? COSName.IDENTITY : stmF;
        }

        /**
         * Sets the name of the filter which is used for de/encrypting streams.
         *
         * @param streamFilterName the name of the filter
         */
        public void setStreamFilterName(COSName streamFilterName)
        {
            dictionary.setItem(COSName.STM_F, streamFilterName);
        }

        /**
         * Returns the name of the filter which is used for de/encrypting strings.
         * Default value is "Identity".
         *
         * @return the name of the filter
         */
        public COSName getStringFilterName()
        {
            COSName strF = dictionary.getCOSName(COSName.STR_F);
            return strF == null ? COSName.IDENTITY : strF;
        }

        /**
         * Sets the name of the filter which is used for de/encrypting strings.
         *
         * @param stringFilterName the name of the filter
         */
        public void setStringFilterName(COSName stringFilterName)
        {
            dictionary.setItem(COSName.STR_F, stringFilterName);
        }

        /**
         * Set the Perms entry in the encryption dictionary.
         *
         * @param perms A 16 byte array.
         *
         * @throws IOException If there is an error setting the data.
         */
        public void setPerms(byte[] perms) throws IOException
        {
            dictionary.setItem( COSName.PERMS, new COSString(perms) );
        }

        /**
         * Get the Perms entry in the encryption dictionary.
         *
         * @return A 16 byte array or null if there is no Perms entry.
         *
         * @throws IOException If there is an error accessing the data.
         */
        public byte[] getPerms() throws IOException
        {
            byte[] perms = null;
            COSString permsCosString = (COSString)dictionary.getDictionaryObject( COSName.PERMS );
            if( permsCosString != null )
            {
                perms = permsCosString.getBytes();
            }
            return perms;
        }

        /**
         * remove CF, StmF, and StrF entries. This is to be called if V is not 4 or 5.
         */
        public void removeV45filters()
        {
            dictionary.setItem(COSName.CF, null);
            dictionary.setItem(COSName.STM_F, null);
            dictionary.setItem(COSName.STR_F, null);
        }
    }