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Allow an upper bound on the number of indirect objects #731

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36 changes: 36 additions & 0 deletions src/main/java/org/verapdf/cos/COSDocument.java
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,8 @@ public class COSDocument {

private static final Logger LOGGER = Logger.getLogger(COSDocument.class.getCanonicalName());

private static volatile int maxNumberOfObjects = -1;

private PDDocument doc;
private IReader reader;
private COSHeader header;
Expand Down Expand Up @@ -136,7 +138,39 @@ public void setHeader(String header) {
this.header.setHeader(header);
}

/**
* Sets an upper bound on the number of indirect objects the document may declare in its
* cross-reference table. Enumerating the objects materialises one entry per key, so a document that
* declares an extreme number of objects (a small compressed input can, via an object stream) can
* exhaust the heap; with a bound set it is rejected with a {@link VeraPDFParserException} before the
* objects are materialised, instead of failing with an OutOfMemoryError. A negative value (the
* default) removes the bound, keeping the historical behaviour.
*
* @param max maximum number of indirect objects, or a negative value for no bound
*/
public static void setMaxNumberOfObjects(int max) {
maxNumberOfObjects = max;
}

/**
* @return the current upper bound on the number of indirect objects, or {@code -1} if unbounded
*/
public static int getMaxNumberOfObjects() {
return maxNumberOfObjects;
}

private void checkObjectCountLimit() {
if (maxNumberOfObjects >= 0) {
int declared = this.xref.getAllKeys().size();
if (declared > maxNumberOfObjects) {
Comment on lines +163 to +165

@coderabbitai coderabbitai Bot Sep 5, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Snapshot the configured limit for each check.

checkObjectCountLimit() reads maxNumberOfObjects at Line 163 and again at Line 165. If another thread calls setMaxNumberOfObjects(int) between those reads, one invocation can compare against a different limit than the one that passed the guard. volatile does not make the two reads atomic.

Read the field once into a local variable and use that value for the complete check.

Proposed fix 
 private void checkObjectCountLimit() {
-    if (maxNumberOfObjects >= 0) {
+    final int max = maxNumberOfObjects;
+    if (max >= 0) {
         int declared = this.xref.getAllKeys().size();
-        if (declared > maxNumberOfObjects) {
+        if (declared > max) {
             throw new VeraPDFParserException("Number of indirect objects (" + declared
-                    + ") exceeds the configured maximum of " + maxNumberOfObjects);
+                    + ") exceeds the configured maximum of " + max);
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Suggested change
if (maxNumberOfObjects >= 0) {
int declared = this.xref.getAllKeys().size();
if (declared > maxNumberOfObjects) {
private void checkObjectCountLimit() {
final int max = maxNumberOfObjects;
if (max >= 0) {
int declared = this.xref.getAllKeys().size();
if (declared > max) {
throw new VeraPDFParserException("Number of indirect objects (" + declared
") exceeds the configured maximum of " + max);
}
}
}
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In `@src/main/java/org/verapdf/cos/COSDocument.java` around lines 163 - 165,
Update checkObjectCountLimit() to read maxNumberOfObjects once into a local
snapshot, then use that snapshot for both the nonnegative guard and
declared-count comparison, preserving the existing behavior while avoiding
inconsistent limits from concurrent setMaxNumberOfObjects(int) updates.

After applying the fix, consider running `coderabbit review --agent` for local
review. Visit https://docs.coderabbit.ai/cli.

throw new VeraPDFParserException("Number of indirect objects (" + declared
+ ") exceeds the configured maximum of " + maxNumberOfObjects);
}
}
}

public List<COSObject> getObjects() {
checkObjectCountLimit();
List<COSObject> result = new ArrayList<>();
for (COSKey key : this.xref.getAllKeys()) {
COSObject obj = this.body.get(key);
Expand All @@ -161,6 +195,7 @@ public List<COSObject> getObjects() {
}

public List<COSObject> getObjectsByType(ASAtom type) {
checkObjectCountLimit();
List<COSObject> result = new ArrayList<>();
for (COSKey key : this.xref.getAllKeys()) {
COSObject obj = this.body.get(key);
Expand Down Expand Up @@ -192,6 +227,7 @@ private static void addObjectWithTypeKeyCheck(List<COSObject> objects,
}

public Map<COSKey, COSObject> getObjectsMap() {
checkObjectCountLimit();
Map<COSKey, COSObject> result = new HashMap<>();
for (COSKey key : this.xref.getAllKeys()) {
COSObject obj = this.body.get(key);
Expand Down