Probably no impact wrt to the http/2 ack DoS that dependabot complained
about, but I'lll do the bump anyway. I also turned dependabot off,
because the signal to noise ratio isn't amazing.
The Elligator inverse map uses the least significant bits of the private
key, which clamping sets to 0, to choose a random low-order point to add
to the public key, to ensure uniformity of representatives.
The other ways that the private key is used, namely in calls to
curve25519.ScalarMult and curve25519.ScalarBaseMult, do their own
clamping when necessary and are documented to accept a uniformly random
scalar.
While this was a good idea back when I did it:
* People don't like the fact that it requires a fork of utls to fix
compatibility issues, and would rather spend 3 years complaining
about it instead of spending a weekend to fix the issues in
upstream.
* Tor over meek is trivially identifiable regardless of utls or not.
* Malware asshats ruined domain fronting for everybody.
Replace agl's Elligator2 implementation with a different one, that fixes
the various distinguishers stemming from bugs in the original
implementation and "The Elligator paper is extremely hard to read".
All releases prior to this commit are trivially distinguishable with
simple math, so upgrading is strongly recommended. The upgrade is fully
backward-compatible with existing implementations, however the
non-upgraded side will emit traffic that is trivially distinguishable
from random.
Special thanks to Loup Vaillant for his body of work on this primitive,
and for motivating me to fix it.
Microsoft recently updated the root CA certificates that are served to
Azure clients. See the following article for more details:
https://docs.microsoft.com/en-us/azure/security/fundamentals/tls-certificate-changes
This change broke meek-lite because none of its pins work anymore. That
means that Tor Browser users can no longer use meek-azure or moat as
both rely on meek-lite.
This patch fixes the problem by updating the certificate pins.
Signed-off-by: Yawning Angel <yawning@schwanenlied.me>
The old behavior closed the connection on handshake failure after:
* The first N bytes (random on a per-server basis).
* The first M seconds (random on a per-server basis).
Whichever came first. As Sergey Frolov kindly points out, depending on
which conditions cause termination, the server will send either a FIN or
a RST. This change will remove the "amount read" based termination
threshold, so that connections that cause failed handshakes will discard
all data received until the teardown time is reached.
Thanks to Sergey Frolov for bringing this issue to my attention.
* Bump the module import to a new tag
* Bump the rest of the dependencies while I'm here
* Add some new fingerprints from upstream
* Disable my fork's AES timing sidechannel defenses
HPKP is effectively dead as far as a standard goes, but the idea has
merit in certain use cases, this being one of them.
As a TLS MITM essentially will strip whatever obfuscation that the
transport may provide, the digests of the SubjectPublicKeyInfo fields
of the Tor Browser Azure meek host are now hardcoded.
The behavior can be disabled by passing `disableHPKP=true` on the bridge
line, for cases where comaptibility is prefered over security.
Changes:
* Use a fork of utls with some compatibility improvements.
* Switch the default ClientHello profile to `HelloFirefox_Auto`.
* Add the `HelloChrome_71` profile.
The existing `HelloFirefox_Auto` profile that points to
`HelloFirefox_63` also matches the (common) behavior of Firefox 65,
assuming that 3DES ciphersuites are not disabled.
Per dcf:
> As for the TODO, my plan was was to expose a "utls" SOCKS arg
> to make it configurable per bridge, and just reuse the utls
> Client Hello ID names:
> utls=HelloChrome_Auto
This adds support for all currently supported utls ClientHello IDs
with the following caveats/differences:
* `none` - Disables using utls entirely, forces `crypto/tls`.
* `HelloGolang` - Alias of `none`, since using utls is pointless.
* `HelloCustom` - Omitted as pointless.
There's still some interesting oddities depending on remote server and
what fingerprint is chosen, but I can watch videos online with the
chosen settings and the TBB Azure bridge.
Note: Despite what people are claiming in the Tor Browser bug tracker
it isn't all that hard to use the built in http client with utls. And
yes, the `transport.go` code does negotiate correctly in a standalone
test case (apart from compatibility related oddities).
Yawning Angel
David Fifield
Philipp Winter