proposal: encoding/asn1: support for generalstring by struct tag

[jcmturner]

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

go version go1.7.5 linux/amd64

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GORACE=""
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build372878858=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1

The issue

Using "encoding/asn1" it is not possible to marshal into a an asn1 general string. It is possible to unmarshal from one but it is only possible to marshal into one of ia5, printable or utf8.
https://play.golang.org/p/cwv9ZGV5K5

Suggestion

There should be an struct tag such as "generalstring" that works in the same way as the "ia5" tag but sets the asn1 tag value of 27.

[gopherbot]

Change https://golang.org/cl/134223 mentions this issue: encoding/asn1: add ability to marshal to general string

[agnivade]

/cc @FiloSottile

[johanbrandhorst]

I wanted to revive this issue as a proposal, would it be better to open a new issue or can we reuse this one? I believe the suggestion is pretty straightforward - add a new struct tag to the encoding/asn1 package, generalstring that will marshal a string field using the GeneralString ASN.1 tag (27). The GeneralString type is used extensively by protocols such as Kerberos (RFC 1510, RFC 4120).