SERVER-42067 Ensure key Ordering offset does not exceed the maximum number of compound index keys

2 files changed, 17 insertions, 0 deletions

diff --git a/src/mongo/bson/ordering.h b/src/mongo/bson/ordering.h
index 793e14820f5..c1052e36a90 100644
--- a/src/mongo/bson/ordering.h
+++ b/src/mongo/bson/ordering.h
@@ -57,6 +57,9 @@ public:
         get(1) == -1
     */
     int get(int i) const {
+        uassert(ErrorCodes::Overflow,
+                str::stream() << "Ordering offset is out of bounds: " << i,
+                i >= 0 && static_cast<size_t>(i) < kMaxCompoundIndexKeys);
         return ((1 << i) & bits) ? -1 : 1;
     }
 
diff --git a/src/mongo/db/storage/key_string_test.cpp b/src/mongo/db/storage/key_string_test.cpp
index 0a4df927404..826b3130684 100644
--- a/src/mongo/db/storage/key_string_test.cpp
+++ b/src/mongo/db/storage/key_string_test.cpp
@@ -212,6 +212,20 @@ TEST(TypeBitsTest, AppendLotsOfZeroTypeBits) {
     ASSERT(!typeBits.isLongEncoding());
 }
 
+TEST_F(KeyStringBuilderTest, TooManyElementsInCompoundKey) {
+    // Construct an illegal KeyString with more than the limit of 32 elements in a compound index
+    // key. Encode 33 kBoolTrue ('o') values.
+    const char* data = "ooooooooooooooooooooooooooooooooo";
+    const size_t size = 33;
+
+    KeyString::Builder ks(KeyString::Version::V1);
+    ks.resetFromBuffer(data, size);
+
+    ASSERT_THROWS_CODE(KeyString::toBsonSafe(data, size, ALL_ASCENDING, ks.getTypeBits()),
+                       AssertionException,
+                       ErrorCodes::Overflow);
+}
+
 TEST_F(KeyStringBuilderTest, Simple1) {
     BSONObj a = BSON("" << 5);
     BSONObj b = BSON("" << 6);