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feat: restrict obfuscation to font core media types
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EPUB 3.3 explicitly restricts the font obfuscation algorithm to resources
being declared as dont Core Media Types.

This commit:
- registers obfuscated resources to the OCFPackage when parsing the
  `encyrption.xml` file (with parsing location)
- checks that if obfuscated resources are declared in Package Documents,
  they have a font core media type
- add and tweak tests

Fix #1291
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rdeltour committed Jan 24, 2022
1 parent 73fe57c commit a229edf
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Showing 29 changed files with 141 additions and 23 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -302,6 +302,7 @@ private void initialize()
severities.put(MessageId.PKG_023, Severity.USAGE);
severities.put(MessageId.PKG_024, Severity.INFO);
severities.put(MessageId.PKG_025, Severity.ERROR);
severities.put(MessageId.PKG_026, Severity.ERROR);

// Resources
severities.put(MessageId.RSC_001, Severity.ERROR);
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1 change: 1 addition & 0 deletions src/main/java/com/adobe/epubcheck/messages/MessageId.java
Original file line number Diff line number Diff line change
Expand Up @@ -296,6 +296,7 @@ public enum MessageId implements Comparable<MessageId>
PKG_023("PKG-023"),
PKG_024("PKG-024"),
PKG_025("PKG-025"),
PKG_026("PKG-026"),

// Messages relating to resources
RSC_001("RSC-001"),
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8 changes: 5 additions & 3 deletions src/main/java/com/adobe/epubcheck/ocf/EncryptionHandler.java
Original file line number Diff line number Diff line change
Expand Up @@ -22,14 +22,15 @@

package com.adobe.epubcheck.ocf;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;

import com.adobe.epubcheck.api.EPUBLocation;
import com.adobe.epubcheck.util.HandlerUtil;
import com.adobe.epubcheck.xml.XMLElement;
import com.adobe.epubcheck.xml.XMLHandler;
import com.adobe.epubcheck.xml.XMLParser;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;

public class EncryptionHandler implements XMLHandler
{
private final OCFPackage ocf;
Expand Down Expand Up @@ -83,6 +84,7 @@ public void startElement()
if (algorithm.equals("http://www.idpf.org/2008/embedding"))
{
ocf.setEncryption(entryName, new IDPFFontManglingFilter(null));
ocf.setObfuscated(entryName, parser.getLocation());
}
else if (algorithm.equals("http://ns.adobe.com/pdf/enc#RC"))
{
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26 changes: 25 additions & 1 deletion src/main/java/com/adobe/epubcheck/ocf/OCFChecker.java
Original file line number Diff line number Diff line change
Expand Up @@ -51,9 +51,11 @@
import com.adobe.epubcheck.api.Report;
import com.adobe.epubcheck.messages.MessageId;
import com.adobe.epubcheck.opf.OPFChecker;
import com.adobe.epubcheck.opf.OPFChecker30;
import com.adobe.epubcheck.opf.OPFData;
import com.adobe.epubcheck.opf.OPFHandler;
import com.adobe.epubcheck.opf.OPFHandler30;
import com.adobe.epubcheck.opf.OPFItem;
import com.adobe.epubcheck.opf.ValidationContext;
import com.adobe.epubcheck.opf.ValidationContext.ValidationContextBuilder;
import com.adobe.epubcheck.util.CheckUtil;
Expand All @@ -64,6 +66,7 @@
import com.adobe.epubcheck.xml.XMLParser;
import com.adobe.epubcheck.xml.XMLValidator;
import com.adobe.epubcheck.xml.XMLValidators;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
Expand Down Expand Up @@ -349,7 +352,7 @@ else if (!normalizedEntriesSet.add(Normalizer.normalize(entry, Form.NFC)))
for (final String entry : ocf.getFileEntries())
{
ocf.reportMetadata(entry, report);

// if the entry is not in the whitelist (META-INF/* + mimetype)
// and not declared in (one of) the OPF document(s)
if (!entry.startsWith("META-INF/") && !entry.startsWith("META-INF\\")
Expand All @@ -371,6 +374,27 @@ public boolean apply(OPFHandler opfHandler)
report.message(MessageId.OPF_003, EPUBLocation.create(ocf.getName()), entry);
}
OCFFilenameChecker.checkCompatiblyEscaped(entry, report, validationVersion);

// check obfuscated resource are Font Core Media Types
if (ocf.isObfuscatedFont(entry))
{
for (OPFHandler opf : opfHandlers)
{
// try to find the first Package Document where the entry is
// declared
Optional<OPFItem> item = opf.getItemByPath(entry);
if (item.isPresent())
{
// report if it is not a font core media type
if (!OPFChecker30.isBlessedFontType(item.get().getMimeType()))
{
report.message(MessageId.PKG_026, ocf.getObfuscationDeclarationLocation(entry),
item.get().getMimeType(), opf.getPath());
}
break;
}
}
}
}

// check all directory entries without duplicates
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34 changes: 28 additions & 6 deletions src/main/java/com/adobe/epubcheck/ocf/OCFPackage.java
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,6 @@
import java.io.InputStream;
import java.util.Collections;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.Set;
Expand All @@ -26,7 +25,8 @@

public abstract class OCFPackage implements GenericResourceProvider
{
final Hashtable<String, EncryptionFilter> enc;
final Map<String, EncryptionFilter> enc = new HashMap<>();
final Map<String, EPUBLocation> obfuscated = new HashMap<>();
String uniqueIdentifier;
private Report reporter;
private final Supplier<OCFData> ocfData = Suppliers.memoize(new Supplier<OCFData>()
Expand Down Expand Up @@ -72,16 +72,17 @@ public Map<String, OPFData> get()
}
});

public OCFPackage()
{
this.enc = new Hashtable<String, EncryptionFilter>();
}

public void setEncryption(String name, EncryptionFilter encryptionFilter)
{
enc.put(name, encryptionFilter);
}

public void setObfuscated(String name, EPUBLocation location)
{
obfuscated.put(name, location);
}

/**
* @param name
* the name of a relative file that is possibly in the container
Expand Down Expand Up @@ -133,6 +134,27 @@ public boolean canDecrypt(String fileName)
return filter == null || filter.canDecrypt();
}

/**
* @param path path of the resource to test
* @return true if that resource is encrypted with the font obfuscation algorithm
*/
public boolean isObfuscatedFont(String path)
{
return obfuscated.containsKey(path);
}

/**
* Returns the location in META-INF/encryption.xml where the given resource
* is declared as an obfuscated font, or <code>null</code> if it is not.
*
* @param path path of the resource to test
* @return the location in META-INF/encryption.xml, or null
*/
public EPUBLocation getObfuscationDeclarationLocation(String path)
{
return obfuscated.get(path);
}

/**
* This method parses the container entry and stores important data, but does
* /not/ validate the container against a schema definition.
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4 changes: 4 additions & 0 deletions src/main/java/com/adobe/epubcheck/opf/OPFHandler.java
Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,10 @@ public OPFHandler(ValidationContext context, XMLParser parser)
this.report = context.report;
this.parser = parser;
}

public String getPath() {
return path;
}

public boolean getOpf12PackageFile()
{
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Original file line number Diff line number Diff line change
Expand Up @@ -313,7 +313,8 @@ PKG_022=Wrong file extension for image. The image is a "%1$s" file but has the f
PKG_023=Validating the EPUB against version 2.0, default validation profile will be used.
PKG_024=Uncommon EPUB file extension.
PKG_024_SUG=For maximum compatibility, use ".epub".
PKG_025=Publication resource must not be located in the META-INF directory
PKG_025=Publication resource must not be located in the META-INF directory
PKG_026=Obfuscated resource must be a Font Core Media Type (was declared as "%1$s" in "%2$s").

#Resources
RSC_001=File "%1$s" could not be found.
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22 changes: 14 additions & 8 deletions src/test/resources/epub3/container-publication.feature
Original file line number Diff line number Diff line change
Expand Up @@ -119,9 +119,10 @@ Feature: EPUB 3 ▸ Open Container Format ▸ Full Publication Checks
And the message contains 'expected element "encryption"'
And no other errors or warnings are reported

Scenario: Report an unknown encryption scheme
Scenario: Verify encryption can be used
(but file will not be parsed)
Given the reporting level is set to INFO
When checking EPUB 'ocf-encryption-unknown-error'
When checking EPUB 'ocf-encryption-unknown-valid'
Then info RSC-004 is reported
And no other errors or warnings are reported

Expand Down Expand Up @@ -180,16 +181,21 @@ Feature: EPUB 3 ▸ Open Container Format ▸ Full Publication Checks


## 5. Resource Obfuscation
Scenario: Verify a publication with obfuscated resource (here a font file)

Scenario: Verify a publication with obfuscated font
When checking EPUB 'ocf-obfuscation-valid'
Then no errors or warnings are reported

Scenario: Verify a publication with obfuscation of a usually-parsed resource (here an SVG image)
When checking EPUB 'ocf-obfuscation-svg-valid'
Then info RSC-004 is reported
Scenario: Report an obfuscated font that is not a Core Media Type
When checking EPUB 'ocf-obfuscation-not-cmt-error'
Then error PKG-026 is reported
And no errors or warnings are reported


Scenario: Report an obfuscated font that is not a font
When checking EPUB 'ocf-obfuscation-not-font-error'
Then error PKG-026 is reported
And no errors or warnings are reported


## C. the 'application/epub+zip' Media Type

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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta charset="utf-8"/>
<title>Minimal EPUB</title>
</head>
<body>
<h1>Loomings</h1>
<p>Call me Ishmael.</p>
</body>
</html>
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" xml:lang="en" lang="en">
<head>
<meta charset="utf-8"/>
<title>Minimal Nav</title>
</head>
<body>
<nav epub:type="toc">
<ol>
<li><a href="content_001.xhtml">content 001</a></li>
</ol>
</nav>
</body>
</html>
Binary file not shown.
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
<?xml version="1.0" encoding="UTF-8"?>
<package xmlns="http://www.idpf.org/2007/opf" version="3.0" xml:lang="en" unique-identifier="q">
<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
<dc:title id="title">Minimal EPUB 3.0</dc:title>
<dc:language>en</dc:language>
<dc:identifier id="q">NOID</dc:identifier>
<meta property="dcterms:modified">2017-06-14T00:00:01Z</meta>
</metadata>
<manifest>
<item id="content_001" href="content_001.xhtml" media-type="application/xhtml+xml"/>
<item id="nav" href="nav.xhtml" media-type="application/xhtml+xml" properties="nav"/>
<item id="font" href="obfuscated-font.otf" media-type="font/opentype"/>
</manifest>
<spine>
<itemref idref="content_001" />
</spine>
</package>
Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
<?xml version="1.0" encoding="UTF-8" ?>
<container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
<rootfiles>
<rootfile full-path="EPUB/package.opf" media-type="application/oebps-package+xml"/>
</rootfiles>
</container>
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
<?xml version="1.0" encoding="UTF-8"?>
<encryption xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
<EncryptedData xmlns="http://www.w3.org/2001/04/xmlenc#">
<EncryptionMethod Algorithm="http://www.idpf.org/2008/embedding"/>
<CipherData>
<CipherReference URI="EPUB/obfuscated-font.otf"/>
</CipherData>
</EncryptedData>
</encryption>
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,5 @@
<body epub:type="bodymatter">
<h1>Loomings</h1>
<p>Call me Ishmael.</p>
<img src="emoji.svg" alt="a smiling emoji" />
</body>
</html>
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@
<manifest>
<item id="content_001" href="content_001.xhtml" media-type="application/xhtml+xml"/>
<item id="nav" href="nav.xhtml" media-type="application/xhtml+xml" properties="nav"/>
<item id="emoji" href="emoji.svg" media-type="image/svg+xml"/>
<item id="doc" href="doc.xml" media-type="application/xml"/>
</manifest>
<spine>
<itemref idref="content_001" />
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
<enc:EncryptedData>
<enc:EncryptionMethod Algorithm="http://www.idpf.org/2008/embedding"/>
<enc:CipherData>
<enc:CipherReference URI="EPUB/emoji.svg"/>
<enc:CipherReference URI="EPUB/doc.xml"/>
</enc:CipherData>
</enc:EncryptedData>
</encryption>
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
application/epub+zip
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@
<manifest>
<item id="content_001" href="content_001.xhtml" media-type="application/xhtml+xml"/>
<item id="nav" href="nav.xhtml" media-type="application/xhtml+xml" properties="nav"/>
<item id="font" href="obfuscated-font.otf" media-type="font/opentype"/>
<item id="font" href="obfuscated-font.otf" media-type="font/otf"/>
</manifest>
<spine>
<itemref idref="content_001" />
Expand Down

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