crypto/tls: remove SSLv3 support

@rsc

SSLv3 has been irreparably broken since the POODLE attack 5 years ago.

RFC 7568 (f.k.a. draft-ietf-tls-sslv3-diediedie) prohibits its use in no uncertain terms, and proceeds to list everything that's broken with it.

SSLv3 MUST NOT be used.

Negotiation of SSLv3 from any version of TLS MUST NOT be permitted.

Major CDNs dropped support immediately upon the disclosure of POODLE. Google frontends followed in 2015. Mozilla called the end of SSL 3.0 in 2014.

In crypto/tls, SSLv3 is only supported on the server side, and is disabled by default. It's time we remove it entirely, as it's not just obsolete, but insecure.

I would like to mark it as deprecated in Go 1.13 and announce it in the release notes, also to get feedback on the impact, and then remove it in Go 1.14.

/cc @rsc @agl

Out of curiosity, this is the diffstat of a very straightforward removal of SSLv3, without touching tests or refactoring.

 src/crypto/tls/auth_test.go             |  7 -------
 src/crypto/tls/cipher_suites.go         | 48 ------------------------------------------------
 src/crypto/tls/common.go                |  9 ++-------
 src/crypto/tls/conn.go                  | 22 +---------------------
 src/crypto/tls/handshake_server_test.go |  1 -
 src/crypto/tls/key_agreement.go         | 11 ++++-------
 src/crypto/tls/prf.go                   | 98 ++++----------------------------------------------------------------------------------------------
 src/crypto/tls/prf_test.go              | 16 ----------------
 src/crypto/tls/tls_test.go              |  1 -
 9 files changed, 11 insertions(+), 202 deletions(-)

I'm certainly in favor of doing this but it would be nice to know more about the impact.

It seems clear from the links in the top message above that SSLv3 has not been a concern for HTTPS since 2014-2015. What's less clear is whether there are other SSL servers (especially on company-internal networks) that have not yet migrated to TLS. That seems very unlikely, but we simply don't know.

Marking it deprecated in Go 1.13 sounds like a reasonable tentative plan. I suggest we:

consider this issue tentatively accepted
add text to the Go 1.13 release notes about the removal and pointing back here for feedback
remove support at the start of the Go 1.14 dev cycle
leave this issue open to collect that feedback until the end of the Go 1.14 dev cycle
accept the issue at the end of the Go 1.14 dev cycle assuming no showstopper feedback arrives

Change https://golang.org/cl/184102 mentions this issue: crypto/tls: deprecate SSLv3 support

crypto/tls: deprecate SSLv3 support

Change https://golang.org/cl/191976 mentions this issue: crypto/tls: remove SSLv3 support

This has now landed. We'll keep this open to collect feedback until the freeze, at which point we'll make a final decision.

crypto/tls: remove SSLv3 support

This was tentatively accepted in June - see #32716 (comment).
This issue was left open to collect feedback about problems after the change landed.
There have been no reported problems, so this is now a likely accept.

Leaving open for a week for final comments.

No final comments, so accepting.

This was implemented by CL 191976. Closing.

CCC-4304 Update Openssl To Support Unsecure Protocol

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crypto/tls: remove SSLv3 support #32716

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crypto/tls: remove SSLv3 support #32716

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FiloSottile commented on Jun 21, 2019

rsc commented on Jun 26, 2019

gopherbot commented on Jun 27, 2019

gopherbot commented on Aug 27, 2019

FiloSottile commented on Aug 27, 2019

7 remaining items

rsc commented on Dec 11, 2019

rsc commented on Jan 8, 2020

FiloSottile commented on Jan 8, 2020

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