fv:      defaultFormVals.Clone().Set(http.CanonicalHeaderKey(xhttp.AmzChecksumAlgo), "algo-val"),
			wantErr: `Each form field that you specify in a form must appear in the list of policy conditions. "X-Amz-Checksum-Algorithm" not specified in the policy.`,
		},
		{
			name:    "unknown key XAmzChecksumCRC32 is error as it does not appear in policy",
			fv:      defaultFormVals.Clone().Set(http.CanonicalHeaderKey(xhttp.AmzChecksumCRC32), "crc32-val"),

	nv := make(textproto.MIMEHeader, len(v))
	for k, kv := range v {
		// Canonicalize all headers, to remove any duplicates.
		nv[http.CanonicalHeaderKey(k)] = kv
	}

	// Save all supported headers.
	for _, supportedHeader := range supportedHeaders {
		value, ok := nv[http.CanonicalHeaderKey(supportedHeader)]
		if ok {
			if v, ok := replicationToInternalHeaders[supportedHeader]; ok {
				m[v] = strings.Join(value, ",")

		// Form fields names are in canonical format, convert conditions names
		// to canonical for simplification purpose, so `$key` will become `Key`
		formCanonicalName := http.CanonicalHeaderKey(strings.TrimPrefix(policy.Key, "$"))

		// Operator for the current policy condition
		op := policy.Operator

		// Multiple values are not allowed for a single form field