Add a recoveryMode that suppresses errors from the Parser, and utilize it when searching for the main trailer in XRef_indexObjects (bug 1250079)

Instead of having `Parser_getObj` fail unconditionally for the referenced PDF file, this patch attempts to let searching for the main trailer continue even if there are errors.

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1250079.

src/core/obj.js

@@ -970,13 +970,15 @@ var XRef = (function XRefClosure() {
       var dict;
       for (i = 0, ii = trailers.length; i < ii; ++i) {
         stream.pos = trailers[i];
-        var parser = new Parser(new Lexer(stream), true, this);
+        var parser = new Parser(new Lexer(stream), /* allowStreams = */ true,
+                                /* xref = */ this, /* recoveryMode = */ true);
         var obj = parser.getObj();
         if (!isCmd(obj, 'trailer')) {
           continue;
         }
         // read the trailer dictionary
-        if (!isDict(dict = parser.getObj())) {
+        dict = parser.getObj();
+        if (!isDict(dict)) {
           continue;
         }
         // taking the first one with 'ID'

src/core/parser.js

@@ -66,10 +66,11 @@ function isEOF(v) {
 var MAX_LENGTH_TO_CACHE = 1000;
 
 var Parser = (function ParserClosure() {
-  function Parser(lexer, allowStreams, xref) {
+  function Parser(lexer, allowStreams, xref, recoveryMode) {
     this.lexer = lexer;
     this.allowStreams = allowStreams;
     this.xref = xref;
+    this.recoveryMode = recoveryMode || false;
     this.imageCache = Object.create(null);
     this.refill();
   }
@@ -115,7 +116,10 @@ var Parser = (function ParserClosure() {
               array.push(this.getObj(cipherTransform));
             }
             if (isEOF(this.buf1)) {
-              error('End of file inside array');
+              if (!this.recoveryMode) {
+                error('End of file inside array');
+              }
+              return array;
             }
             this.shift();
             return array;
@@ -136,7 +140,10 @@ var Parser = (function ParserClosure() {
               dict.set(key, this.getObj(cipherTransform));
             }
             if (isEOF(this.buf1)) {
-              error('End of file inside dictionary');
+              if (!this.recoveryMode) {
+                error('End of file inside dictionary');
+              }
+              return dict;
             }
 
             // Stream objects are not allowed inside content streams or

test/pdfs/.gitignore

@@ -99,6 +99,7 @@
 !bug911034.pdf
 !bug1108301.pdf
 !bug1157493.pdf
+!bug1250079.pdf
 !pdfjsbad1586.pdf
 !freeculture.pdf
 !issue6006.pdf

test/test_manifest.json

@@ -730,6 +730,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "bug1250079",
+       "file": "pdfs/bug1250079.pdf",
+       "md5": "a1dd21a70ae7097d96273e85a80b26ef",
+       "rounds": 1,
+       "link": false,
+       "type": "load"
+    },
     {  "id": "hudsonsurvey",
        "file": "pdfs/hudsonsurvey.pdf",
        "md5": "bf0e6576a7b6c2fe7485bce1b78e006f",