Allow passing custom get query params (#1905)

Allow checking if a query param starts with "x-" which is documented by
Amazon as a parameter S3 will ignore and recommended as a way to add
custom info to server access logs.

Allow GetObject calls to set custom query parameters if they want.

api-get-options.go

@@ -87,10 +87,10 @@ func (o *GetObjectOptions) Set(key, value string) {
 }
 
 // SetReqParam - set request query string parameter
-// supported key: see supportedQueryValues.
+// supported key: see supportedQueryValues and allowedCustomQueryPrefix.
 // If an unsupported key is passed in, it will be ignored and nothing will be done.
 func (o *GetObjectOptions) SetReqParam(key, value string) {
-	if !isStandardQueryValue(key) {
+	if !isCustomQueryValue(key) && !isStandardQueryValue(key) {
 		// do nothing
 		return
 	}
@@ -101,10 +101,10 @@ func (o *GetObjectOptions) SetReqParam(key, value string) {
 }
 
 // AddReqParam - add request query string parameter
-// supported key: see supportedQueryValues.
+// supported key: see supportedQueryValues and allowedCustomQueryPrefix.
 // If an unsupported key is passed in, it will be ignored and nothing will be done.
 func (o *GetObjectOptions) AddReqParam(key, value string) {
-	if !isStandardQueryValue(key) {
+	if !isCustomQueryValue(key) && !isStandardQueryValue(key) {
 		// do nothing
 		return
 	}

get-options_test.go

@@ -57,3 +57,45 @@ func TestSetHeader(t *testing.T) {
 		}
 	}
 }
+
+func TestCustomQueryParameters(t *testing.T) {
+	var (
+		paramKey   = "x-test-param"
+		paramValue = "test-value"
+
+		invalidParamKey   = "invalid-test-param"
+		invalidParamValue = "invalid-test-param"
+	)
+
+	testCases := []struct {
+		setParamsFunc func(o *GetObjectOptions)
+	}{
+		{func(o *GetObjectOptions) {
+			o.AddReqParam(paramKey, paramValue)
+			o.AddReqParam(invalidParamKey, invalidParamValue)
+		}},
+		{func(o *GetObjectOptions) {
+			o.SetReqParam(paramKey, paramValue)
+			o.SetReqParam(invalidParamKey, invalidParamValue)
+		}},
+	}
+
+	for i, testCase := range testCases {
+		opts := GetObjectOptions{}
+		testCase.setParamsFunc(&opts)
+
+		// This and the following checks indirectly ensure that only the expected
+		// valid header is added.
+		if len(opts.reqParams) != 1 {
+			t.Errorf("Test %d: Expected 1 kv-pair in query parameters, got %v", i+1, len(opts.reqParams))
+		}
+
+		if v, ok := opts.reqParams[paramKey]; !ok {
+			t.Errorf("Test %d: Expected query parameter with key %s missing", i+1, paramKey)
+		} else if len(v) != 1 {
+			t.Errorf("Test %d: Expected 1 value for query parameter with key %s, got %d values", i+1, paramKey, len(v))
+		} else if v[0] != paramValue {
+			t.Errorf("Test %d: Expected query value %s for key %s, got %s", i+1, paramValue, paramKey, v[0])
+		}
+	}
+}

utils.go

@@ -528,6 +528,14 @@ func isStandardQueryValue(qsKey string) bool {
 	return supportedQueryValues[qsKey]
 }
 
+// Per documentation at https://docs.aws.amazon.com/AmazonS3/latest/userguide/LogFormat.html#LogFormatCustom, the
+// set of query params starting with "x-" are ignored by S3.
+const allowedCustomQueryPrefix = "x-"
+
+func isCustomQueryValue(qsKey string) bool {
+	return strings.HasPrefix(qsKey, allowedCustomQueryPrefix)
+}
+
 var (
 	md5Pool    = sync.Pool{New: func() interface{} { return md5.New() }}
 	sha256Pool = sync.Pool{New: func() interface{} { return sha256.New() }}

utils_test.go

@@ -408,3 +408,24 @@ func TestIsAmzHeader(t *testing.T) {
 		}
 	}
 }
+
+// Tests if query parameter starts with "x-" and will be ignored by S3.
+func TestIsCustomQueryValue(t *testing.T) {
+	testCases := []struct {
+		// Input.
+		queryParamKey string
+		// Expected result.
+		expectedValue bool
+	}{
+		{"x-custom-key", true},
+		{"xcustom-key", false},
+		{"random-header", false},
+	}
+
+	for i, testCase := range testCases {
+		actual := isCustomQueryValue(testCase.queryParamKey)
+		if actual != testCase.expectedValue {
+			t.Errorf("Test %d: Expected to pass, but failed", i+1)
+		}
+	}
+}