With --auth-proxy set and --auth-key unset, serve s3 registered every client
supplied access key ID with an empty secret and verified the SigV4 signature
against that, so anyone could sign a request for an arbitrary access key ID with
an empty secret and be let in. The proxy program was only ever given the access
key ID (as both user and pass) so it had nothing with which to authenticate the
client either.
An S3 client never sends its secret, only a signature made with it, so the
server has to know the secret to check the request. The auth proxy protocol as
been changed to handle this. For serve s3 the proxy program is given just the
access key ID as the user (no pass or public_key) and must return the matching
secret as _secret_access_key in its output. rclone verifies the request's
signature against that secret, refusing the request if the proxy rejects the
access key ID, doesn't return a secret or returns an empty one, or the signature
doesn't match. The secret is only used for this server's own verification and is
never registered with gofakes3, so other serve s3 instances in the same process
don't honour it.
The proxy's answers are cached. If a signature fails against a cached secret the
proxy is consulted again so a rotated secret takes effect immediately - but only
for a signature mismatch, and at most once every 10 seconds per access key ID
and client IP, so a stream of bad signatures can't make the proxy program run
for every request. A rotation never shuts down the cached backend under requests
still using it. A cached answer is checked with the proxy again once it is 5
minutes old even if in constant use, so revoking an access key ID takes effect
within 5 minutes.
This means --auth-key is no longer needed with --auth-proxy: it is ignored and a
warning is given at startup if both are set. The proxy is the source of truth
for both the credentials and the backend they map to. Presigned URLs (credential
in the query string) are now recognised by the proxy middleware too. The auth
proxy docs are added to serve s3.
Note that the serve s3 auth proxy protocol has changed. The proxy program is now
given the access key ID as "user" (it was previously given an MD5 hash of it,
with the access key ID as "pass") and must return the matching secret as
"_secret_access_key".
This needs gofakes3 v0.0.9 for signature.V4SignVerifyWithSecret.
Run still uses a fresh local directory as the backing Fs that the
server wraps. RunWithBackend takes an extra remote name (e.g.
"TestS3Minio:") and uses a random subdirectory of that remote instead,
starting the matching fstest/testserver/init.d script on the way in
and tearing it down on the way out.
AuthProxy is only run for the local backend.
This implements --auth-proxy for serve s3. In addition it:
* add listbuckets tests with and without authProxy
* use auth proxy test framework
* servetest: implement workaround for #7454
* update github.com/rclone/gofakes3 to fix race condition
Nick Craig-Wood
Hakan İSMAİL
Sawjan Gurung
albertony
Ivan Andreev