[jira] [Created] (PDFBOX-2082) signing corrupts PDF when signature exactly fits allocated space

[Koloom (JIRA)]

Koloom created PDFBOX-2082:
------------------------------

             Summary: signing corrupts PDF when signature exactly fits 
allocated space
                 Key: PDFBOX-2082
                 URL: https://issues.apache.org/jira/browse/PDFBOX-2082
             Project: PDFBox
          Issue Type: Bug
          Components: Writing
            Reporter: Koloom
            Priority: Critical


The current check does not take "<>" into account, so if you are (un)lucky, the 
signature overwrites ">" and corrupts the PDF.

Fix for 1.8:

diff --git a/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/COSWriter.java 
b/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/COSWriter.java
index 3165589..755e849 100644
--- a/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/COSWriter.java
+++ b/pdfbox/src/main/java/org/apache/pdfbox/pdfwriter/COSWriter.java
@@ -779,12 +779,14 @@ public class COSWriter implements ICOSVisitor, Closeable
             SignatureInterface signatureInterface = 
doc.getSignatureInterface();
             byte[] sign = signatureInterface.sign(new 
ByteArrayInputStream(pdfContent));
             String signature = new COSString(sign).getHexString();
+            ++signaturePosition[0]; // move past "<"
+            --signaturePosition[1]; // move in front of ">"
             int leftSignaturerange = 
signaturePosition[1]-signaturePosition[0]-signature.length();
             if(leftSignaturerange<0)
             {
                 throw new IOException("Can't write signature, not enough 
space");
             }
-            getStandardOutput().setPos(signaturePosition[0]+1);
+            getStandardOutput().setPos(signaturePosition[0]);
             getStandardOutput().write(signature.getBytes());
         }
     }

Another thing is that pdfbox now allocates (2 * preferedSize + 2) for a 
signature. It quite confused me to see 16k+4 bytes allocated when I called 
setPreferedSignatureSize(4k) - it should have allocated 8k (each signature byte 
takes 2 bytes in the pdf). 

Fix for 1.8:

diff --git a/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java 
b/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java
index 358364a..23dd3ab 100644
--- a/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java
+++ b/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java
@@ -309,7 +309,7 @@ public class PDDocument implements Pageable, Closeable
         int preferedSignatureSize = options.getPreferedSignatureSize();
         if (preferedSignatureSize > 0)
         {
-            sigObject.setContents(new byte[preferedSignatureSize * 2 + 2]);
+            sigObject.setContents(new byte[preferedSignatureSize]);
         }
         else
         {




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