After posting question I did a quick and dirty test to add bytes from path
manually to a new bytes array
byte[] digest = md.digest();
byte[] pBytes = path.getBytes();
int L = digest.length + pBytes.length;
byte[] message = new byte[L];
for (int i=0;i<pBytes.length;i++) {
message[i] = pBytes[i];
}
for (int i=pBytes.length,n=0; n<digest.length; n++) {
message[i+n] = digest[n];
}
String sign = new String(Base64.encodeToString(mac.doFinal(message), Base64.NO_WRAP));
And voilà; the hmac sign matches!
I have solved my problem but keeping question unanswered for some day to say if a better answer is provided that sheds light on this.