Apache™ FOP: PDF encryption.¶
Apache™ FOP supports encryption of PDF output, thanks to Patrick C. Lankswert. This feature is commonly used to prevent unauthorized viewing, printing, editing, copying text from the document and doing annotations. It is also possible to ask the user for a password in order to view the contents. Note that there already exist third party applications which can decrypt an encrypted PDF without effort and allow the aforementioned operations, therefore the degree of protection is limited.
For further information about features and restrictions regarding PDF encryption, look at the documentation coming with Adobe Acrobat or the technical documentation on the Adobe web site.
Usage (command line)¶
Encryption is enabled by supplying any of the encryption related options.
An owner password is set with the
-o option. This password is actually used as encryption key. Many tools for PDF processing ask for this password to disregard any restriction imposed on the PDF document.
If no owner password has been supplied but FOP was asked to apply some restrictions, a random password is used. In this case it is obviously impossiible to disregard restrictions in PDF processing tools.
A user password, supplied with the
-u option, will cause the PDF display software to ask the reader for this password in order to view the contents of the document. If no user password was supplied, viewing the content is not restricted.
Further restrictions can be imposed by using the following command-line options:
||disable copy/paste of content|
||disable editing in Adobe Acrobat|
||disable editing of annotations|
||disable filling in forms|
||disable text and graphics extraction for accessibility purposes|
||disable assembling documents|
||disable high quality printing|
When FOP is embedded in another Java application you need to set an options map on the renderer. These are the supported options:
|encryption-length||The encryption length in bit||Any multiple of 8 between 40 and 128||40|
|ownerPassword||The owner password||String|
|userPassword||The user password||String|
|allowPrint||Allows/disallows printing of the PDF||"TRUE" or "FALSE"||"TRUE"|
|allowCopyContent||Allows/disallows copy/paste of content||"TRUE" or "FALSE"||"TRUE"|
|allowEditContent||Allows/disallows editing in Adobe Acrobat||"TRUE" or "FALSE"||"TRUE"|
|allowEditAnnotations||Allows/disallows editing of annotations||"TRUE" or "FALSE"||"TRUE"|
|allowFillInForms||Allows/disallows filling in forms||"TRUE" or "FALSE"||"TRUE"|
|allowAccessContent||Allows/disallows text and graphics extraction for accessibility purposes||"TRUE" or "FALSE"||"TRUE"|
|allowAssembleDocument||Allows/disallows assembling document||"TRUE" or "FALSE"||"TRUE"|
|allowPrintHq||Allows/disallows high quality printing||"TRUE" or "FALSE"||"TRUE"|
An example to enable PDF encryption in Java code:
import org.apache.fop.pdf.PDFEncryptionParams; [..] FOUserAgent userAgent = fopFactory.newFOUserAgent(); useragent.getRendererOptions().put("encryption-params", new PDFEncryptionParams( null, "password", false, false, true, true)); Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, userAgent); [..]
The parameters for the constructor of PDFEncryptionParams are:
userPassword: String, may be null
ownerPassword: String, may be null
allowPrint: true if printing is allowed
allowCopyContent: true if copying content is allowed
allowEditContent: true if editing content is allowed
allowEditAnnotations: true if editing annotations is allowed
allowFillInForms: true if filling in forms is allowed.
allowAccessContent: true if extracting text and graphics is allowed
allowAssembleDocument: true if assembling document is allowed
allowPrintHq: true if printing to high quality is allowed
Alternatively, you can set each value separately in the Map provided by FOUserAgent.getRendererOptions() by using the following keys:
noprint: Boolean or "true"/"false"
nocopy: Boolean or "true"/"false"
noedit: Boolean or "true"/"false"
noannotations: Boolean or "true"/"false"
nofillinforms: Boolean or "true"/"false"
noaccesscontent: Boolean or "true"/"false"
noassembledoc: Boolean or "true"/"false"
noprinthq: Boolean or "true"/"false"
In order to use PDF encryption, FOP has to be compiled with cryptography support. Currently, only JCE is supported. JCE is part of JDK 1.4. For earlier JDKs, it can be installed separately. The build process automatically detects JCE presence and installs PDF encryption support if possible, otherwise a stub is compiled in.
Cryptography support must also be present at run time. In particular, a provider for the RC4 cipher is needed. Unfortunately, the sample JCE provider in Sun's JDK 1.4 does not provide RC4. If you get a message saying "Cannot find any provider supporting RC4" then you don't have the needed infrastructure.
There are several commercial and a few Open Source packages which provide RC4. A pure Java implementation is produced by The Legion of the Bouncy Castle. Mozilla JSS is an interface to a native implementation.
Installing a crypto provider¶
The pure Java implementation from Bouncy Castle is easy to install.
Download the binary distribution for your JDK version.
Unpack the distribution. Add the jar file to your classpath. A convenient way to use the jar on Linux is to simply drop it into the FOP lib directory, it will be automatically picked up by
java.securityfile and add
preferably at the end of the block defining the other crypto providers. For JDK 1.4 this is detailed on Sun's web site.
If you have any experience with Mozilla JSS or any other cryptography provider, please post it to the fop-user list.