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Change description:
Remove ECDHE_ECDSA_WITH_AES_128_CBC_SHA and ECDHE_ECDSA_WITH_AES_256_CBC_SHA TLS cipher suites.

TLS's CBC-mode construction is flawed, making it fragile and very difficult to implement securely. Although CBC-mode ciphers are still widely used with RSA, they are virtually nonexistent with ECDSA (0.00% in UMA).

Changes to API surface:
- Our ClientHello will no longer advertise the above ciphers.

Links:
Public standards discussion:
No discussion of this removal, but CBC-mode ciphers are extremely problematic and were removed in TLS 1.3:
https://tlswg.github.io/tls13-spec/#rfc.appendix.A.4
The upcoming TLS registry updates document also adds a "Recommended" column which will set all CBC-mode ciphers to "No".
https://tools.ietf.org/html/draft-sandj-tls-iana-registry-updates-01#section-6

Support in other browsers:
Internet Explorer: still offered
Firefox: still offered
Safari: still offered

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