[Pkg-javascript-commits] [pdf.js] 70/157: Subtract start offset for xrefs in recovery mode

[David Prévot]

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taffit pushed a commit to branch master
in repository pdf.js.

commit fd29bb0c575be5f5ac2d6732e4f01674e44be0d0
Author: Rob Wu <rob at robwu.nl>
Date:   Fri Jul 10 20:18:53 2015 +0200

    Subtract start offset for xrefs in recovery mode
    
    Xref offsets are relative to the start of the PDF data, not to the start
    of the PDF file. This is clear if you look at the other code:
    
    - In the XRef's readXRefTable and processXRefTable methods of XRef, the
      offset of a xref entry is set to the bytes as given by a PDF file.
      These values are always relative to the start of the PDF file (%PDF-).
    
    - The XRef's readXRef method adds the start offset of the stream to
      Xref entry's offset: "stream.pos = startXRef + stream.start".
      Clearly, this line assumes that the entry offset excludes the start
      offset.
    
    However, when the PDF is parsed in recovery mode, the xref table is
    filled with entries whose offset is relative to the start of the stream
    rather than the PDF file. This is incorrect, and the fix is to subtract
    the start offset of the stream from the entry's byte offset.
    
    The manually created PDF file serves as a regression test. It is a valid
    PDF, except:
    - The integer to point to the start of the xref table and the %%EOF
      trailer are missing. This will activate recovery mode in PDF.js
    - Some junk was added before the start of the PDF file. This exposes the
      bad offset bug.
---
 src/core/obj.js         |  6 +++---
 test/pdfs/.gitignore    |  1 +
 test/pdfs/issue6069.pdf | 28 ++++++++++++++++++++++++++++
 test/test_manifest.json |  6 ++++++
 4 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/src/core/obj.js b/src/core/obj.js
index 7e31929..8c618eb 100644
--- a/src/core/obj.js
+++ b/src/core/obj.js
@@ -1081,7 +1081,7 @@ var XRef = (function XRefClosure() {
         } else if ((m = /^(\d+)\s+(\d+)\s+obj\b/.exec(token))) {
           if (typeof this.entries[m[1]] === 'undefined') {
             this.entries[m[1]] = {
-              offset: position,
+              offset: position - stream.start,
               gen: m[2] | 0,
               uncompressed: true
             };
@@ -1094,8 +1094,8 @@ var XRef = (function XRefClosure() {
           var xrefTagOffset = skipUntil(content, 0, xrefBytes);
           if (xrefTagOffset < contentLength &&
               content[xrefTagOffset + 5] < 64) {
-            xrefStms.push(position);
-            this.xrefstms[position] = 1; // don't read it recursively
+            xrefStms.push(position - stream.start);
+            this.xrefstms[position - stream.start] = 1; // Avoid recursion
           }
 
           position += contentLength;
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index f500e35..d428da4 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -145,3 +145,4 @@
 !issue6010_2.pdf
 !issue6068.pdf
 !issue6081.pdf
+!issue6069.pdf
diff --git a/test/pdfs/issue6069.pdf b/test/pdfs/issue6069.pdf
new file mode 100644
index 0000000..3d148da
--- /dev/null
+++ b/test/pdfs/issue6069.pdf
@@ -0,0 +1,28 @@
+Some junk before the header
+
+%PDF-1.1
+1 0 obj
+<</Type/Catalog/Pages 2 0 R>>
+endobj
+2 0 obj
+<</Type/Pages/Count 1/Kids[3 0 R]/MediaBox [0 0 400 50]>>
+endobj
+3 0 obj
+<</Type/Page/Parent 2 0 R/Resources<</Font<</F1<</Type/Font/Subtype/Type1/BaseFont/Arial>>>>>>/Contents 4 0 R>>
+endobj
+4 0 obj
+<</Length 43>>
+stream
+BT/F1 14 Tf 20 20 Td(Missing value for startxref and junk before magic header) Tj ET
+endstream
+endobj
+xref
+0 5
+0000000000 65535 f 
+0000000008 00000 n 
+0000000054 00000 n 
+0000000128 00000 n 
+0000000254 00000 n 
+trailer
+<</Root 1 0 R/Size 5>>
+startxref
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 4b38c75..c303e9f 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -2278,5 +2278,11 @@
        "md5": "51a724136c0c10008bd061a78ea4b8fc",
        "rounds": 1,
        "type": "load"
+    },
+    {  "id": "issue6069",
+       "file": "pdfs/issue6069.pdf",
+       "md5": "d0ad8871f4116bca8e39513ffa8b7d8e",
+       "rounds": 1,
+       "type": "load"
     }
 ]

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