This makes us use TLS 1.3+ on sync connections by default. A new option
`insecureAllowOldTLSVersions` exists to allow communication with TLS
1.2-only clients (roughly Syncthing 1.2.2 and older). Even with that
option set you get a slightly simplified setup, with the cipher suite
order fixed instead of auto detected.
Our authentication is based on device ID (certificate fingerprint) but
we also check the certificate name for ... historical extra security
reasons. (I don't think this adds anything but it is what it is.) Since
that check breaks in Go 1.15 this change does two things:
- Adds a manual check for the peer certificate CommonName, and if they
are equal we are happy and don't call the more advanced
VerifyHostname() function. This allows our old style certificates to
still pass the check.
- Adds the cert name "syncthing" as a DNS SAN when generating the
certificate. This is the correct way nowadays and makes VerifyHostname()
happy in Go 1.15 as well, even without the above patch.
crypto/rand output is cryptographically secure by the Go library
documentation's promise. That, rather than strength (= passes randomness
tests) is the property that Syncthing needs).
- In the few places where we wrap errors, use the new Go 1.13 "%w"
construction instead of %s or %v.
- Where we create errors with constant strings, consistently use
errors.New and not fmt.Errorf.
- Remove capitalization from errors in the few places where we had that.
This adds a certificate lifetime parameter to our certificate generation
and hard codes it to twenty years in some uninteresting places. In the
main binary there are a couple of constants but it results in twenty
years for the device certificate and 820 days for the HTTPS one. 820 is
less than the 825 maximum Apple allows nowadays.
This also means we must be prepared for certificates to expire, so I add
some handling for that and generate a new certificate when needed. For
self signed certificates we regenerate a month ahead of time. For other
certificates we leave well enough alone.
* lib/tlsutil: Enable TLS 1.3 when available, on test builds (fixes#5065)
This enables TLS 1.3 negotiation on Go 1.12 by setting the GODEBUG
variable. For now, this just gets enabled on test versions (those with a
dash in the version number).
Users wishing to enable this on production builds can set GODEBUG
manually.
The string representation of connections now includes the TLS version
and cipher suite. This becomes part of the log output on connections.
That is, when talking to an old client:
Established secure connection .../TLS1.2-TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
and now potentially:
Established secure connection .../TLS1.3-TLS_AES_128_GCM_SHA256
(The cipher suite was there previously in the log output, but not the
TLS version.)
I also added this info as a new Crypto() method on the connection, and
propagate this out to the API and GUI, where it can be seen in the
connection address hover (although with bad word wrapping sometimes).
* wip
* wip
This changes the TLS and certificate handling in a few ways:
- We always use TLS 1.2, both for sync connections (as previously) and
the GUI/REST/discovery stuff. This is a tightening of the requirements
on the GUI. AS far as I can tell from caniusethis.com every browser from
2013 and forward supports TLS 1.2, so I think we should be fine.
- We always greate ECDSA certificates. Previously we'd create
ECDSA-with-RSA certificates for sync connections and pure RSA
certificates for the web stuff. The new default is more modern and the
same everywhere. These certificates are OK in TLS 1.2.
- We use the Go CPU detection stuff to choose the cipher suites to use,
indirectly. The TLS package uses CPU capabilities probing to select
either AES-GCM (fast if we have AES-NI) or ChaCha20 (faster if we
don't). These CPU detection things aren't exported though, so the tlsutil
package now does a quick TLS handshake with itself as part of init().
If the chosen cipher suite was AES-GCM we prioritize that, otherwise we
prefer ChaCha20. Some might call this ugly. I think it's awesome.
The intention for this package is to provide a combination of the
security of crypto/rand and the convenience of math/rand. It should be
the first choice of random data unless ultimate performance is required
and the usage is provably irrelevant from a security standpoint.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3186
This replaces the current 3072 bit RSA certificates with 384 bit ECDSA
certificates. The advantage is these certificates are smaller and
essentially instantaneous to generate. According to RFC4492 (ECC Cipher
Suites for TLS), Table 1: Comparable Key Sizes, ECC has comparable
strength to 3072 bit RSA at 283 bits - so we exceed that.
There is no compatibility issue with existing Syncthing code - this is
verified by the integration test ("h2" instance has the new
certificate).
There are browsers out there that don't understand ECC certificates yet,
although I think they're dying out. In the meantime, I've retained the
RSA code for the HTTPS certificate, but pulled it down to 2048 bits. I
don't think a higher security level there is motivated, is this matches
current industry standard for HTTPS certificates.
