Hi Andreas,
On Jul 10, 2012, at 7:27 AM, Andreas Petersson wrote:
The first statement above gets at this, but it seems to me that the
middle ground between random generation per request and permanent
unique token is worth emphasizing if there will be proxies that want
to keep per-client identifiers around for some limited amount of time
that isn't forever.
It's also worth noting that the second statement above is equally true for
statically provisioned client IP addresses.
Also, this statement in 8.3 is not really true and probably better left out:
"Proxies using this extension will preserve the information of a
direct connection, which has an end-user privacy impact, if the end-
user or deployer does not know or expect that this is the case."
There can certainly be a privacy impact whether the user or deployer has
awareness/expectation or not.
Can you give some proof or at least some arguments for this statement?
If the deployer has awareness/expectation but users do not, then users'
expectations that their client addresses will not be shared will be violated.
But even if users have awareness/expectation that their client addresses will
be shared, the implications of that sharing may not be obvious, and there is
nothing preventing remote servers that receive the information from abusing it.
Examples: a user who doesn't know that his address is static and can be used by
a remote server to track and correlate all of his activity; a user who doesn't
know that his ISP maintains records of customer identity tied to client
addresses that may become subject to law enforcement request; a service that
combines static addresses or tokens received via the header with other
collected identifiers and shares them with other servers to enable more
pervasive tracking.
The first half of the statement is basically a refinement of the previous
sentence in the section ("The Forwarded HTTP header field, by design, exposes
information that some users consider privacy sensitive"), so I don't see what
is lost by eliminating it.
Alissa
Cheers,
Andreas