Test (and fix) handling of dangling references

10 files changed, 140 insertions, 79 deletions

diff --git a/libqpdf/QPDF_json.cc b/libqpdf/QPDF_json.cc
index b7fe4368..18631114 100644
--- a/libqpdf/QPDF_json.cc
+++ b/libqpdf/QPDF_json.cc
@@ -147,6 +147,7 @@ QPDF::JSONReactor::arrayStart()
 void
 QPDF::JSONReactor::containerEnd(JSON const& value)
 {
+    auto from_state = state;
     state = state_stack.back();
     state_stack.pop_back();
     if (state == st_initial) {
@@ -215,10 +216,13 @@ QPDF::JSONReactor::containerEnd(JSON const& value)
         if (!parse_error) {
             object_stack.pop_back();
         }
-    } else if (state == st_qpdf) {
+    } else if ((state == st_top) && (from_state == st_qpdf)) {
         for (auto const& og: this->reserved) {
-            // QXXXQ
-            // QTC::TC("qpdf", "QPDF_json non-trivial null reserved");
+            // Handle dangling indirect object references which the
+            // PDF spec says to treat as nulls. It's tempting to make
+            // this an error, but that would be wrong since valid
+            // input files may have these.
+            QTC::TC("qpdf", "QPDF_json non-trivial null reserved");
             this->pdf.replaceObject(og, QPDFObjectHandle::newNull());
         }
         this->reserved.clear();
diff --git a/qpdf/qpdf.testcov b/qpdf/qpdf.testcov
index 9b1910fb..65aa421a 100644
--- a/qpdf/qpdf.testcov
+++ b/qpdf/qpdf.testcov
@@ -675,3 +675,4 @@ QPDF_json ignore second-level key 0
 QPDF_json ignore unknown key in object_top 0
 QPDF_json ignore unknown key in trailer 0
 QPDF_json ignore unknown key in stream 0
+QPDF_json non-trivial null reserved 0
diff --git a/qpdf/qtest/qpdf/good13.out b/qpdf/qtest/qpdf/good13.out
index 6df4bd7d..e6cb1d32 100644
--- a/qpdf/qtest/qpdf/good13.out
+++ b/qpdf/qtest/qpdf/good13.out
@@ -1,10 +1,11 @@
 /QTest is indirect and has type dictionary (9)
 /QTest is a dictionary
+  /dangling-ref-for-json-test is direct
   /hex strings is direct
   /indirect is indirect
   /names is direct
   /nesting is direct
   /strings is direct
 unparse: 7 0 R
-unparseResolved: << /hex#20strings [ (Potato) <01020300040560> (AB) ] /indirect 8 0 R /names [ /nesting /hex#20strings /text#2fplain ] /nesting << /a [ 1 2 << /x (y) >> [ (z) ] ] /b << / (legal) /a [ 1 2 ] >> >> /strings [ (one) <24a2> () (\(\)) (\() (\)) (a\f\b\t\r\nb) (") ("") ("\("\)") <410042> (a\nb) (a b) <efbbbfcf80> <efbbbff09fa594> ] >>
+unparseResolved: << /dangling-ref-for-json-test [ 9 0 R ] /hex#20strings [ (Potato) <01020300040560> (AB) ] /indirect 8 0 R /names [ /nesting /hex#20strings /text#2fplain ] /nesting << /a [ 1 2 << /x (y) >> [ (z) ] ] /b << / (legal) /a [ 1 2 ] >> >> /strings [ (one) <24a2> () (\(\)) (\() (\)) (a\f\b\t\r\nb) (") ("") ("\("\)") <410042> (a\nb) (a b) <efbbbfcf80> <efbbbff09fa594> ] >>
 test 1 done
diff --git a/qpdf/qtest/qpdf/good13.pdf b/qpdf/qtest/qpdf/good13.pdf
index 89953222..0c97b89f 100644
--- a/qpdf/qtest/qpdf/good13.pdf
+++ b/qpdf/qtest/qpdf/good13.pdf
@@ -74,6 +74,7 @@ b) (π) (🥔)]
     /b <</a [1 2] / (legal)>>
   >>
   /names [/n#65sting /hex#20strings /text#2fplain]
+  /dangling-ref-for-json-test [9 0 R]
 >>
 endobj
 
@@ -81,6 +82,12 @@ endobj
 (hello)
 endobj
 
+% NOTE:
+%
+% If adding a new object, update /dangling-ref-for-json-test to point
+% to something that's not here.
+%
+
 xref
 0 9
 0000000000 65535 f 
@@ -91,12 +98,12 @@ xref
 0000000403 00000 n 
 0000000438 00000 n 
 0000000556 00000 n 
-0000000908 00000 n 
+0000000946 00000 n 
 trailer <<
   /Size 9
   /Root 1 0 R
   /QTest 7 0 R
 >>
 startxref
-932
+1085
 %%EOF
diff --git a/qpdf/qtest/qpdf/good13.qdf b/qpdf/qtest/qpdf/good13.qdf
index 297c35f3..236ee585 100644
--- a/qpdf/qtest/qpdf/good13.qdf
+++ b/qpdf/qtest/qpdf/good13.qdf
@@ -13,12 +13,15 @@ endobj
 %% Original object ID: 7 0
 2 0 obj
 <<
+  /dangling-ref-for-json-test [
+    4 0 R
+  ]
   /hex#20strings [
     (Potato)
     <01020300040560>
     (AB)
   ]
-  /indirect 4 0 R
+  /indirect 5 0 R
   /names [
     /nesting
     /hex#20strings
@@ -68,22 +71,27 @@ endobj
 <<
   /Count 1
   /Kids [
-    5 0 R
+    6 0 R
   ]
   /Type /Pages
 >>
 endobj
 
-%% Original object ID: 8 0
+%% Original object ID: 9 0
 4 0 obj
+null
+endobj
+
+%% Original object ID: 8 0
+5 0 obj
 (hello)
 endobj
 
 %% Page 1
 %% Original object ID: 3 0
-5 0 obj
+6 0 obj
 <<
-  /Contents 6 0 R
+  /Contents 7 0 R
   /MediaBox [
     0
     0
@@ -93,9 +101,9 @@ endobj
   /Parent 3 0 R
   /Resources <<
     /Font <<
-      /F1 8 0 R
+      /F1 9 0 R
     >>
-    /ProcSet 9 0 R
+    /ProcSet 10 0 R
   >>
   /Type /Page
 >>
@@ -103,9 +111,9 @@ endobj
 
 %% Contents for page 1
 %% Original object ID: 4 0
-6 0 obj
+7 0 obj
 <<
-  /Length 7 0 R
+  /Length 8 0 R
 >>
 stream
 BT
@@ -116,12 +124,12 @@ ET
 endstream
 endobj
 
-7 0 obj
+8 0 obj
 44
 endobj
 
 %% Original object ID: 6 0
-8 0 obj
+9 0 obj
 <<
   /BaseFont /Helvetica
   /Encoding /WinAnsiEncoding
@@ -132,7 +140,7 @@ endobj
 endobj
 
 %% Original object ID: 5 0
-9 0 obj
+10 0 obj
 [
   /PDF
   /Text
@@ -140,23 +148,24 @@ endobj
 endobj
 
 xref
-0 10
+0 11
 0000000000 65535 f 
 0000000052 00000 n 
 0000000133 00000 n 
-0000000710 00000 n 
-0000000809 00000 n 
-0000000870 00000 n 
-0000001112 00000 n 
-0000001211 00000 n 
-0000001257 00000 n 
-0000001402 00000 n 
+0000000756 00000 n 
+0000000855 00000 n 
+0000000903 00000 n 
+0000000964 00000 n 
+0000001207 00000 n 
+0000001306 00000 n 
+0000001352 00000 n 
+0000001497 00000 n 
 trailer <<
   /QTest 2 0 R
   /Root 1 0 R
-  /Size 10
+  /Size 11
   /ID [<31415926535897932384626433832795><31415926535897932384626433832795>]
 >>
 startxref
-1437
+1533
 %%EOF
diff --git a/qpdf/qtest/qpdf/json-changed-good13.pdf b/qpdf/qtest/qpdf/json-changed-good13.pdf
index b8240b18..2c25334c 100644
--- a/qpdf/qtest/qpdf/json-changed-good13.pdf
+++ b/qpdf/qtest/qpdf/json-changed-good13.pdf
@@ -13,12 +13,15 @@ endobj
 %% Original object ID: 7 0
 2 0 obj
 <<
+  /dangling-ref-for-json-test [
+    4 0 R
+  ]
   /hex#20strings [
     (Potato)
     <01020300040560>
     (AB)
   ]
-  /indirect 4 0 R
+  /indirect 5 0 R
   /names [
     /nesting
     /hex#20strings
@@ -68,22 +71,27 @@ endobj
 <<
   /Count 1
   /Kids [
-    5 0 R
+    6 0 R
   ]
   /Type /Pages
 >>
 endobj
 
-%% Original object ID: 8 0
+%% Original object ID: 9 0
 4 0 obj
+null
+endobj
+
+%% Original object ID: 8 0
+5 0 obj
 (hello)
 endobj
 
 %% Page 1
 %% Original object ID: 3 0
-5 0 obj
+6 0 obj
 <<
-  /Contents 6 0 R
+  /Contents 7 0 R
   /MediaBox [
     0
     0
@@ -93,9 +101,9 @@ endobj
   /Parent 3 0 R
   /Resources <<
     /Font <<
-      /F1 8 0 R
+      /F1 9 0 R
     >>
-    /ProcSet 9 0 R
+    /ProcSet 10 0 R
   >>
   /Type /Page
 >>
@@ -103,9 +111,9 @@ endobj
 
 %% Contents for page 1
 %% Original object ID: 4 0
-6 0 obj
+7 0 obj
 <<
-  /Length 7 0 R
+  /Length 8 0 R
 >>
 stream
 BT
@@ -116,12 +124,12 @@ ET
 endstream
 endobj
 
-7 0 obj
+8 0 obj
 44
 endobj
 
 %% Original object ID: 6 0
-8 0 obj
+9 0 obj
 <<
   /BaseFont /Helvetica
   /Encoding /WinAnsiEncoding
@@ -132,7 +140,7 @@ endobj
 endobj
 
 %% Original object ID: 5 0
-9 0 obj
+10 0 obj
 [
   /PDF
   /Text
@@ -140,23 +148,24 @@ endobj
 endobj
 
 xref
-0 10
+0 11
 0000000000 65535 f 
 0000000052 00000 n 
 0000000133 00000 n 
-0000000706 00000 n 
-0000000805 00000 n 
-0000000866 00000 n 
-0000001108 00000 n 
-0000001207 00000 n 
-0000001253 00000 n 
-0000001398 00000 n 
+0000000752 00000 n 
+0000000851 00000 n 
+0000000899 00000 n 
+0000000960 00000 n 
+0000001203 00000 n 
+0000001302 00000 n 
+0000001348 00000 n 
+0000001493 00000 n 
 trailer <<
   /QTest 2 0 R
   /Root 1 0 R
-  /Size 10
+  /Size 11
   /ID [<31415926535897932384626433832795><31415926535897932384626433832795>]
 >>
 startxref
-1433
+1529
 %%EOF
diff --git a/qpdf/qtest/qpdf/manual-qpdf-json-out.json b/qpdf/qtest/qpdf/manual-qpdf-json-out.json
index a04c98ae..877351dd 100644
--- a/qpdf/qtest/qpdf/manual-qpdf-json-out.json
+++ b/qpdf/qtest/qpdf/manual-qpdf-json-out.json
@@ -1,7 +1,7 @@
 {
   "qpdf-v2": {
     "pdfversion": "2.0",
-    "maxobjectid": 8,
+    "maxobjectid": 100,
     "objects": {
       "obj:1 0 R": {
         "value": {
@@ -119,7 +119,15 @@
         }
       },
       "obj:8 0 R": {
-        "value": "u:hello"
+        "value": {
+          "/dangling": [
+            "100 0 R"
+          ],
+          "/k1": "u:hello"
+        }
+      },
+      "obj:100 0 R": {
+        "value": null
       },
       "trailer": {
         "value": {
diff --git a/qpdf/qtest/qpdf/manual-qpdf-json-pdf.json b/qpdf/qtest/qpdf/manual-qpdf-json-pdf.json
index a27f551f..6e9520d4 100644
--- a/qpdf/qtest/qpdf/manual-qpdf-json-pdf.json
+++ b/qpdf/qtest/qpdf/manual-qpdf-json-pdf.json
@@ -1,7 +1,7 @@
 {
   "qpdf-v2": {
     "pdfversion": "2.0",
-    "maxobjectid": 9,
+    "maxobjectid": 10,
     "objects": {
       "obj:1 0 R": {
         "value": {
@@ -79,11 +79,16 @@
         }
       },
       "obj:4 0 R": {
-        "value": "u:hello"
+        "value": {
+          "/dangling": [
+            "6 0 R"
+          ],
+          "/k1": "u:hello"
+        }
       },
       "obj:5 0 R": {
         "value": {
-          "/Contents": "6 0 R",
+          "/Contents": "7 0 R",
           "/MediaBox": [
             0,
             0,
@@ -93,23 +98,26 @@
           "/Parent": "3 0 R",
           "/Resources": {
             "/Font": {
-              "/F1": "8 0 R"
+              "/F1": "9 0 R"
             },
-            "/ProcSet": "9 0 R"
+            "/ProcSet": "10 0 R"
           },
           "/Type": "/Page"
         }
       },
       "obj:6 0 R": {
+        "value": null
+      },
+      "obj:7 0 R": {
         "stream": {
           "data": "QlQKICAvRjEgMjQgVGYKICA3MiA3MjAgVGQKICAoUG90YXRvKSBUagpFVAo=",
           "dict": {}
         }
       },
-      "obj:7 0 R": {
+      "obj:8 0 R": {
         "value": 44
       },
-      "obj:8 0 R": {
+      "obj:9 0 R": {
         "value": {
           "/BaseFont": "/Helvetica",
           "/Encoding": "/WinAnsiEncoding",
@@ -118,7 +126,7 @@
           "/Type": "/Font"
         }
       },
-      "obj:9 0 R": {
+      "obj:10 0 R": {
         "value": [
           "/PDF",
           "/Text"
@@ -132,7 +140,7 @@
           ],
           "/QTest": "2 0 R",
           "/Root": "1 0 R",
-          "/Size": 10
+          "/Size": 11
         }
       }
     }
diff --git a/qpdf/qtest/qpdf/manual-qpdf-json.json b/qpdf/qtest/qpdf/manual-qpdf-json.json
index 579c88f9..4a7a3f4e 100644
--- a/qpdf/qtest/qpdf/manual-qpdf-json.json
+++ b/qpdf/qtest/qpdf/manual-qpdf-json.json
@@ -134,7 +134,10 @@
         }
       },
       "obj:8 0 R": {
-        "value": "u:hello"
+        "value": {
+          "/k1": "u:hello",
+          "/dangling": ["100 0 R"]
+        }
       }
     }
   }
diff --git a/qpdf/qtest/qpdf/manual-qpdf-json.pdf b/qpdf/qtest/qpdf/manual-qpdf-json.pdf
index d8a40eed..0611bae0 100644
--- a/qpdf/qtest/qpdf/manual-qpdf-json.pdf
+++ b/qpdf/qtest/qpdf/manual-qpdf-json.pdf
@@ -85,14 +85,19 @@ endobj
 
 %% Original object ID: 8 0
 4 0 obj
-(hello)
+<<
+  /dangling [
+    6 0 R
+  ]
+  /k1 (hello)
+>>
 endobj
 
 %% Page 1
 %% Original object ID: 3 0
 5 0 obj
 <<
-  /Contents 6 0 R
+  /Contents 7 0 R
   /MediaBox [
     0
     0
@@ -102,19 +107,24 @@ endobj
   /Parent 3 0 R
   /Resources <<
     /Font <<
-      /F1 8 0 R
+      /F1 9 0 R
     >>
-    /ProcSet 9 0 R
+    /ProcSet 10 0 R
   >>
   /Type /Page
 >>
 endobj
 
+%% Original object ID: 100 0
+6 0 obj
+null
+endobj
+
 %% Contents for page 1
 %% Original object ID: 4 0
-6 0 obj
+7 0 obj
 <<
-  /Length 7 0 R
+  /Length 8 0 R
 >>
 stream
 BT
@@ -125,12 +135,12 @@ ET
 endstream
 endobj
 
-7 0 obj
+8 0 obj
 44
 endobj
 
 %% Original object ID: 6 0
-8 0 obj
+9 0 obj
 <<
   /BaseFont /Helvetica
   /Encoding /WinAnsiEncoding
@@ -141,7 +151,7 @@ endobj
 endobj
 
 %% Original object ID: 5 0
-9 0 obj
+10 0 obj
 [
   /PDF
   /Text
@@ -149,23 +159,24 @@ endobj
 endobj
 
 xref
-0 10
+0 11
 0000000000 65535 f 
 0000000052 00000 n 
 0000000133 00000 n 
 0000000829 00000 n 
 0000000928 00000 n 
-0000000989 00000 n 
-0000001231 00000 n 
-0000001330 00000 n 
-0000001376 00000 n 
-0000001521 00000 n 
+0000001029 00000 n 
+0000001251 00000 n 
+0000001322 00000 n 
+0000001421 00000 n 
+0000001467 00000 n 
+0000001612 00000 n 
 trailer <<
   /QTest 2 0 R
   /Root 1 0 R
-  /Size 10
+  /Size 11
   /ID [<31415926535897932384626433832795><31415926535897932384626433832795>]
 >>
 startxref
-1556
+1648
 %%EOF