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.
(cherry picked from commit 7306f0668125ecbd1cb9d704f570fbb492a76fb8)
The auth proxy was only given the user and their password or public
key, so a proxy program had no way to restrict logins to particular
networks, or to record where an authentication attempt came from.
The JSON sent to the program now has a client_ip key holding the bare
IP the client connected from, with the port stripped so IPv6 arrives
as 2001:db8::1 rather than [2001:db8::1]:52344. An IPv4-mapped IPv6
address is reported as plain IPv4 so that a client arriving over a
dual-stack listener still matches IPv4 networks. The key is omitted
when the client has no IP address.
The IP is also mixed into the backend cache key. That is needed as the
program is only run on a cache miss, so a client from a
non-allowlisted address presenting valid credentials within the 5
minute cache lifetime would get a cache hit and be let in without the
program being consulted at all.
(cherry picked from commit 5dd34275dc)
Before this change, if the user changed their password or public-key
and the auth proxy script returned updated config parameters for the
backend (eg a rotated api_key) rclone would continue to re-use the old
backend with the old config parameters out of the fscache.
This was because both the VFS cache and the fs/cache key were derived
from the user name only, so a change in the user's password or
public-key did not invalidate the cached backend.
Fix this by deriving the cache key from the user plus a hash of the
password/public-key, so a credential change forces a fresh backend.
The hash uses a per-process random HMAC key so the fragment that
appears in logs cannot be brute-forced offline.
This changes log statements from log to fs package, which is required for --use-json-log
to properly make log output in JSON format. The recently added custom linting rule,
handled by ruleguard via gocritic via golangci-lint, warns about these and suggests
the alternative. Fixing was therefore basically running "golangci-lint run --fix",
although some manual fixup of mainly imports are necessary following that.
This adds a context.Context parameter to NewFs and related calls.
This is necessary as part of reading config from the context -
backends need to be able to read the global config.
Unfortunately bcrypt only hashes the first 72 bytes of a given input
which meant that using it on ssh keys which are longer than 72 bytes
was incorrect.
This swaps over to using sha256 which should be adequate for the
purpose of protecting in memory passwords where the unencrypted
password is likely in memory too.
Nick Craig-Wood