JFI: MLS Retiring (Mozilla Location Service)

General
15

I don’t think so. Their website states:

supl.grapheneos.org - TLS reverse proxy to supl.google.com

A reverse proxy hides the user’s IP (which on IPv4 an operator’s NAT renders mostly useless anyhow) but the supl requests contain the IMSI as session id making tracking as easy as possible. Here are a few loglines from my instance of supl-proxy (the IMSI passed to supl.google.com is random and only used for that session):

2024-07-07 20:39:21,775 [INFO] __main__: Packet from mobile
{
  "length": 36,
  "version": {
    "maj": 1,
    "min": 0,
    "servind": 0
  },
  "sessionID": {
    "setSessionID": {
      "sessionId": 0,
      "setId": [
        "imsi",
        "62 02 21 27 61 48 19 f4"
      ]
    },
    "slpSessionID": {
      "sessionID": "d9 0a 6c 1f",
      "slpId": [
        "fQDN",
        "supl.google.com"
      ]
    }
  },
  "message": [
    "msSUPLPOS",
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