SERVER-119317 Improve object lifecycle of MD5 hash state (#47996)

GitOrigin-RevId: 28927c60881a488fcbc5fd4d925b410f33258827

etc/backports_required_for_multiversion_tests.yml

@@ -23,6 +23,8 @@ last-continuous:
   all:
   - test_file: jstests/core/index/elemmatch_index.js
     ticket: SERVER-108945
+  - test_file: jstests/core/filemd5.js
+    ticket: SERVER-119317
   - test_file: jstests/core/json_schema/json_schema.js
     ticket: SERVER-98676
   - test_file: jstests/core/query/explain/explain_plan_cache.js
@@ -902,6 +904,8 @@ last-lts:
   all:
   - test_file: jstests/core/index/elemmatch_index.js
     ticket: SERVER-108945
+  - test_file: jstests/core/filemd5.js
+    ticket: SERVER-119317
   - test_file: jstests/core/json_schema/json_schema.js
     ticket: SERVER-98676
   - test_file: jstests/core/query/explain/explain_plan_cache.js

jstests/core/filemd5.js

@@ -20,4 +20,24 @@ assert.commandFailedWithCode(db.runCommand({filemd5: 1, root: "fs", partialOk: 1
 assert.commandWorked(db.fs.chunks.insert({files_id: 2, n: 0}));
 assert.commandFailedWithCode(db.runCommand({filemd5: 2, root: "fs"}), 50848);
 assert.commandWorked(db.fs.chunks.update({files_id: 2, n: 0}, {$set: {data: 5}}));
-assert.commandFailedWithCode(db.runCommand({filemd5: 2, root: "fs"}), 50849);
+assert.commandFailedWithCode(db.runCommand({filemd5: 2, root: "fs"}), 50849);
+
+{
+    const result = assert.commandWorked(
+        db.runCommand({
+            filemd5: ObjectId("000000000000000000000000"),
+            root: "fs",
+            partialOk: true,
+        }),
+    );
+
+    assert(result.md5state !== undefined, "Expected md5state in filemd5 response with partialOk: true");
+    const hex = result.md5state.hex();
+    const totalBytes = hex.length / 2;
+    assert.gt(totalBytes, 72, "md5state expected to be larger than 72 bytes");
+
+    const checkFromByte = 72;
+    const paddingHex = hex.substring(checkFromByte * 2);
+    const allZeros = "0".repeat(paddingHex.length);
+    assert.eq(paddingHex, allZeros, "md5state expected to be zero padded");
+}

src/mongo/util/md5.cpp

@@ -309,6 +309,8 @@ static void md5_process(md5_state_t* pms, const md5_byte_t* data /*[64]*/) {
 }
 
 void md5_init(md5_state_t* pms) {
+    memset(pms, 0, sizeof(md5_state_t));
+
     pms->count[0] = pms->count[1] = 0;
     pms->abcd[0] = 0x67452301;
     pms->abcd[1] = /*0xefcdab89*/ T_MASK ^ 0x10325476;