improvement: ARSN-36 handle duplicate query params

Handle duplicate references of query params by flattening the array
and picking the first occurence of the duplicate param

lib/s3routes/routesUtils.js

@@ -839,6 +839,21 @@ const routesUtils = {
         request.objectKey = resources.object;
         request.parsedHost = resources.host;
         request.path = resources.path;
+        /**
+         * Flatten duplicate query params
+         * Duplicate query params in url e.g. ?a=1&a=2&a=3&b=4&c=5 are parsed
+         * by the HTTP parser as { a: [1, 2, 3], b: 4, c: 5}. Since duplicate
+         * params are invalid in AWS S3 it's reduced to the value of the first
+         * occurence of the duplicate query param
+         * */
+        const queryParams = request.query;
+        Object.keys(queryParams).forEach(key => {
+            const param = queryParams[key];
+            if (Array.isArray(param)) {
+                queryParams[key] = param.reduce(prev => prev);
+            }
+        });
+
         // For streaming v4 auth, the total body content length
         // without the chunk metadata is sent as
         // the x-amz-decoded-content-length

tests/unit/s3routes/routesUtils/normalizeRequest.js

@@ -76,4 +76,16 @@ describe('routesUtils.normalizeRequest', () => {
         assert.strictEqual(result.objectKey, objName);
         assert.strictEqual(result.parsedHost, 's3.amazonaws.com');
     });
+
+    it('should pick the first occurence of the query param when duplicates ' +
+        'are present ', () => {
+        const request = {
+            url: `/${bucketName}/${objName}?a=1&a=2&a=3&b=4&c=5`,
+            headers: { host: 's3.amazonaws.com' },
+        };
+        const result = routesUtils.normalizeRequest(request, validHosts);
+        assert.strictEqual(result.query.a, '1');
+        assert.strictEqual(result.query.b, '4');
+        assert.strictEqual(result.query.c, '5');
+    });
 });