crypto/tls: TLS_ECDHE_*_WITH_CHACHA20_POLY1305 constants are misnamed

[jrwren]

What version of Go are you using (go version)?

$ go version
1.12

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/jrwren/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/jrwren/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/dx/1319ml391vqcwyncfz2vf6t80000gn/T/go-build976546411=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Tried to use crypto/tls with RFC standard names.

What did you expect to see?

RFC & IANA standard names.

What did you see instead?

https://github.com/golang/go/blob/master/src/crypto/tls/cipher_suites.go#L461
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305 and TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305

Both https://www.iana.org/assignments/tls-parameters/tls-parameters.xml and RFC7905 refer to these as TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 and TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 respectfully.

Maybe this is too nit-picky, but I spent enough time double checking that they are the same. I'd like to spare the next person from any confusion.

Is it OK to send a patch to add the missing _SHA256 suffixes to those constants?

[FiloSottile]

Unfortunately, the Go 1 Compatibility Promise prevents us from updating the constant. I would accept a CL documenting the mistake though. Also, the API in #30325 should return the correct name.