diff --git a/vendor/github.com/jcmturner/gofork/encoding/asn1/marshal.go b/vendor/github.com/jcmturner/gofork/encoding/asn1/marshal.go
new file mode 100644
index 0000000..f52eee9
--- /dev/null
+++ b/vendor/github.com/jcmturner/gofork/encoding/asn1/marshal.go
@@ -0,0 +1,659 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package asn1
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+	"reflect"
+	"time"
+	"unicode/utf8"
+)
+
+// A forkableWriter is an in-memory buffer that can be
+// 'forked' to create new forkableWriters that bracket the
+// original. After
+//    pre, post := w.fork()
+// the overall sequence of bytes represented is logically w+pre+post.
+type forkableWriter struct {
+	*bytes.Buffer
+	pre, post *forkableWriter
+}
+
+func newForkableWriter() *forkableWriter {
+	return &forkableWriter{new(bytes.Buffer), nil, nil}
+}
+
+func (f *forkableWriter) fork() (pre, post *forkableWriter) {
+	if f.pre != nil || f.post != nil {
+		panic("have already forked")
+	}
+	f.pre = newForkableWriter()
+	f.post = newForkableWriter()
+	return f.pre, f.post
+}
+
+func (f *forkableWriter) Len() (l int) {
+	l += f.Buffer.Len()
+	if f.pre != nil {
+		l += f.pre.Len()
+	}
+	if f.post != nil {
+		l += f.post.Len()
+	}
+	return
+}
+
+func (f *forkableWriter) writeTo(out io.Writer) (n int, err error) {
+	n, err = out.Write(f.Bytes())
+	if err != nil {
+		return
+	}
+
+	var nn int
+
+	if f.pre != nil {
+		nn, err = f.pre.writeTo(out)
+		n += nn
+		if err != nil {
+			return
+		}
+	}
+
+	if f.post != nil {
+		nn, err = f.post.writeTo(out)
+		n += nn
+	}
+	return
+}
+
+func marshalBase128Int(out *forkableWriter, n int64) (err error) {
+	if n == 0 {
+		err = out.WriteByte(0)
+		return
+	}
+
+	l := 0
+	for i := n; i > 0; i >>= 7 {
+		l++
+	}
+
+	for i := l - 1; i >= 0; i-- {
+		o := byte(n >> uint(i*7))
+		o &= 0x7f
+		if i != 0 {
+			o |= 0x80
+		}
+		err = out.WriteByte(o)
+		if err != nil {
+			return
+		}
+	}
+
+	return nil
+}
+
+func marshalInt64(out *forkableWriter, i int64) (err error) {
+	n := int64Length(i)
+
+	for ; n > 0; n-- {
+		err = out.WriteByte(byte(i >> uint((n-1)*8)))
+		if err != nil {
+			return
+		}
+	}
+
+	return nil
+}
+
+func int64Length(i int64) (numBytes int) {
+	numBytes = 1
+
+	for i > 127 {
+		numBytes++
+		i >>= 8
+	}
+
+	for i < -128 {
+		numBytes++
+		i >>= 8
+	}
+
+	return
+}
+
+func marshalBigInt(out *forkableWriter, n *big.Int) (err error) {
+	if n.Sign() < 0 {
+		// A negative number has to be converted to two's-complement
+		// form. So we'll subtract 1 and invert. If the
+		// most-significant-bit isn't set then we'll need to pad the
+		// beginning with 0xff in order to keep the number negative.
+		nMinus1 := new(big.Int).Neg(n)
+		nMinus1.Sub(nMinus1, bigOne)
+		bytes := nMinus1.Bytes()
+		for i := range bytes {
+			bytes[i] ^= 0xff
+		}
+		if len(bytes) == 0 || bytes[0]&0x80 == 0 {
+			err = out.WriteByte(0xff)
+			if err != nil {
+				return
+			}
+		}
+		_, err = out.Write(bytes)
+	} else if n.Sign() == 0 {
+		// Zero is written as a single 0 zero rather than no bytes.
+		err = out.WriteByte(0x00)
+	} else {
+		bytes := n.Bytes()
+		if len(bytes) > 0 && bytes[0]&0x80 != 0 {
+			// We'll have to pad this with 0x00 in order to stop it
+			// looking like a negative number.
+			err = out.WriteByte(0)
+			if err != nil {
+				return
+			}
+		}
+		_, err = out.Write(bytes)
+	}
+	return
+}
+
+func marshalLength(out *forkableWriter, i int) (err error) {
+	n := lengthLength(i)
+
+	for ; n > 0; n-- {
+		err = out.WriteByte(byte(i >> uint((n-1)*8)))
+		if err != nil {
+			return
+		}
+	}
+
+	return nil
+}
+
+func lengthLength(i int) (numBytes int) {
+	numBytes = 1
+	for i > 255 {
+		numBytes++
+		i >>= 8
+	}
+	return
+}
+
+func marshalTagAndLength(out *forkableWriter, t tagAndLength) (err error) {
+	b := uint8(t.class) << 6
+	if t.isCompound {
+		b |= 0x20
+	}
+	if t.tag >= 31 {
+		b |= 0x1f
+		err = out.WriteByte(b)
+		if err != nil {
+			return
+		}
+		err = marshalBase128Int(out, int64(t.tag))
+		if err != nil {
+			return
+		}
+	} else {
+		b |= uint8(t.tag)
+		err = out.WriteByte(b)
+		if err != nil {
+			return
+		}
+	}
+
+	if t.length >= 128 {
+		l := lengthLength(t.length)
+		err = out.WriteByte(0x80 | byte(l))
+		if err != nil {
+			return
+		}
+		err = marshalLength(out, t.length)
+		if err != nil {
+			return
+		}
+	} else {
+		err = out.WriteByte(byte(t.length))
+		if err != nil {
+			return
+		}
+	}
+
+	return nil
+}
+
+func marshalBitString(out *forkableWriter, b BitString) (err error) {
+	paddingBits := byte((8 - b.BitLength%8) % 8)
+	err = out.WriteByte(paddingBits)
+	if err != nil {
+		return
+	}
+	_, err = out.Write(b.Bytes)
+	return
+}
+
+func marshalObjectIdentifier(out *forkableWriter, oid []int) (err error) {
+	if len(oid) < 2 || oid[0] > 2 || (oid[0] < 2 && oid[1] >= 40) {
+		return StructuralError{"invalid object identifier"}
+	}
+
+	err = marshalBase128Int(out, int64(oid[0]*40+oid[1]))
+	if err != nil {
+		return
+	}
+	for i := 2; i < len(oid); i++ {
+		err = marshalBase128Int(out, int64(oid[i]))
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}
+
+func marshalPrintableString(out *forkableWriter, s string) (err error) {
+	b := []byte(s)
+	for _, c := range b {
+		if !isPrintable(c) {
+			return StructuralError{"PrintableString contains invalid character"}
+		}
+	}
+
+	_, err = out.Write(b)
+	return
+}
+
+func marshalIA5String(out *forkableWriter, s string) (err error) {
+	b := []byte(s)
+	for _, c := range b {
+		if c > 127 {
+			return StructuralError{"IA5String contains invalid character"}
+		}
+	}
+
+	_, err = out.Write(b)
+	return
+}
+
+func marshalUTF8String(out *forkableWriter, s string) (err error) {
+	_, err = out.Write([]byte(s))
+	return
+}
+
+func marshalTwoDigits(out *forkableWriter, v int) (err error) {
+	err = out.WriteByte(byte('0' + (v/10)%10))
+	if err != nil {
+		return
+	}
+	return out.WriteByte(byte('0' + v%10))
+}
+
+func marshalFourDigits(out *forkableWriter, v int) (err error) {
+	var bytes [4]byte
+	for i := range bytes {
+		bytes[3-i] = '0' + byte(v%10)
+		v /= 10
+	}
+	_, err = out.Write(bytes[:])
+	return
+}
+
+func outsideUTCRange(t time.Time) bool {
+	year := t.Year()
+	return year < 1950 || year >= 2050
+}
+
+func marshalUTCTime(out *forkableWriter, t time.Time) (err error) {
+	year := t.Year()
+
+	switch {
+	case 1950 <= year && year < 2000:
+		err = marshalTwoDigits(out, year-1900)
+	case 2000 <= year && year < 2050:
+		err = marshalTwoDigits(out, year-2000)
+	default:
+		return StructuralError{"cannot represent time as UTCTime"}
+	}
+	if err != nil {
+		return
+	}
+
+	return marshalTimeCommon(out, t)
+}
+
+func marshalGeneralizedTime(out *forkableWriter, t time.Time) (err error) {
+	year := t.Year()
+	if year < 0 || year > 9999 {
+		return StructuralError{"cannot represent time as GeneralizedTime"}
+	}
+	if err = marshalFourDigits(out, year); err != nil {
+		return
+	}
+
+	return marshalTimeCommon(out, t)
+}
+
+func marshalTimeCommon(out *forkableWriter, t time.Time) (err error) {
+	_, month, day := t.Date()
+
+	err = marshalTwoDigits(out, int(month))
+	if err != nil {
+		return
+	}
+
+	err = marshalTwoDigits(out, day)
+	if err != nil {
+		return
+	}
+
+	hour, min, sec := t.Clock()
+
+	err = marshalTwoDigits(out, hour)
+	if err != nil {
+		return
+	}
+
+	err = marshalTwoDigits(out, min)
+	if err != nil {
+		return
+	}
+
+	err = marshalTwoDigits(out, sec)
+	if err != nil {
+		return
+	}
+
+	_, offset := t.Zone()
+
+	switch {
+	case offset/60 == 0:
+		err = out.WriteByte('Z')
+		return
+	case offset > 0:
+		err = out.WriteByte('+')
+	case offset < 0:
+		err = out.WriteByte('-')
+	}
+
+	if err != nil {
+		return
+	}
+
+	offsetMinutes := offset / 60
+	if offsetMinutes < 0 {
+		offsetMinutes = -offsetMinutes
+	}
+
+	err = marshalTwoDigits(out, offsetMinutes/60)
+	if err != nil {
+		return
+	}
+
+	err = marshalTwoDigits(out, offsetMinutes%60)
+	return
+}
+
+func stripTagAndLength(in []byte) []byte {
+	_, offset, err := parseTagAndLength(in, 0)
+	if err != nil {
+		return in
+	}
+	return in[offset:]
+}
+
+func marshalBody(out *forkableWriter, value reflect.Value, params fieldParameters) (err error) {
+	switch value.Type() {
+	case flagType:
+		return nil
+	case timeType:
+		t := value.Interface().(time.Time)
+		if params.timeType == TagGeneralizedTime || outsideUTCRange(t) {
+			return marshalGeneralizedTime(out, t)
+		} else {
+			return marshalUTCTime(out, t)
+		}
+	case bitStringType:
+		return marshalBitString(out, value.Interface().(BitString))
+	case objectIdentifierType:
+		return marshalObjectIdentifier(out, value.Interface().(ObjectIdentifier))
+	case bigIntType:
+		return marshalBigInt(out, value.Interface().(*big.Int))
+	}
+
+	switch v := value; v.Kind() {
+	case reflect.Bool:
+		if v.Bool() {
+			return out.WriteByte(255)
+		} else {
+			return out.WriteByte(0)
+		}
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return marshalInt64(out, v.Int())
+	case reflect.Struct:
+		t := v.Type()
+
+		startingField := 0
+
+		// If the first element of the structure is a non-empty
+		// RawContents, then we don't bother serializing the rest.
+		if t.NumField() > 0 && t.Field(0).Type == rawContentsType {
+			s := v.Field(0)
+			if s.Len() > 0 {
+				bytes := make([]byte, s.Len())
+				for i := 0; i < s.Len(); i++ {
+					bytes[i] = uint8(s.Index(i).Uint())
+				}
+				/* The RawContents will contain the tag and
+				 * length fields but we'll also be writing
+				 * those ourselves, so we strip them out of
+				 * bytes */
+				_, err = out.Write(stripTagAndLength(bytes))
+				return
+			} else {
+				startingField = 1
+			}
+		}
+
+		for i := startingField; i < t.NumField(); i++ {
+			var pre *forkableWriter
+			pre, out = out.fork()
+			err = marshalField(pre, v.Field(i), parseFieldParameters(t.Field(i).Tag.Get("asn1")))
+			if err != nil {
+				return
+			}
+		}
+		return
+	case reflect.Slice:
+		sliceType := v.Type()
+		if sliceType.Elem().Kind() == reflect.Uint8 {
+			bytes := make([]byte, v.Len())
+			for i := 0; i < v.Len(); i++ {
+				bytes[i] = uint8(v.Index(i).Uint())
+			}
+			_, err = out.Write(bytes)
+			return
+		}
+
+		// jtasn1 Pass on the tags to the members but need to unset explicit switch and implicit value
+		//var fp fieldParameters
+		params.explicit = false
+		params.tag = nil
+		for i := 0; i < v.Len(); i++ {
+			var pre *forkableWriter
+			pre, out = out.fork()
+			err = marshalField(pre, v.Index(i), params)
+			if err != nil {
+				return
+			}
+		}
+		return
+	case reflect.String:
+		switch params.stringType {
+		case TagIA5String:
+			return marshalIA5String(out, v.String())
+		case TagPrintableString:
+			return marshalPrintableString(out, v.String())
+		default:
+			return marshalUTF8String(out, v.String())
+		}
+	}
+
+	return StructuralError{"unknown Go type"}
+}
+
+func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters) (err error) {
+	if !v.IsValid() {
+		return fmt.Errorf("asn1: cannot marshal nil value")
+	}
+	// If the field is an interface{} then recurse into it.
+	if v.Kind() == reflect.Interface && v.Type().NumMethod() == 0 {
+		return marshalField(out, v.Elem(), params)
+	}
+
+	if v.Kind() == reflect.Slice && v.Len() == 0 && params.omitEmpty {
+		return
+	}
+
+	if params.optional && params.defaultValue != nil && canHaveDefaultValue(v.Kind()) {
+		defaultValue := reflect.New(v.Type()).Elem()
+		defaultValue.SetInt(*params.defaultValue)
+
+		if reflect.DeepEqual(v.Interface(), defaultValue.Interface()) {
+			return
+		}
+	}
+
+	// If no default value is given then the zero value for the type is
+	// assumed to be the default value. This isn't obviously the correct
+	// behaviour, but it's what Go has traditionally done.
+	if params.optional && params.defaultValue == nil {
+		if reflect.DeepEqual(v.Interface(), reflect.Zero(v.Type()).Interface()) {
+			return
+		}
+	}
+
+	if v.Type() == rawValueType {
+		rv := v.Interface().(RawValue)
+		if len(rv.FullBytes) != 0 {
+			_, err = out.Write(rv.FullBytes)
+		} else {
+			err = marshalTagAndLength(out, tagAndLength{rv.Class, rv.Tag, len(rv.Bytes), rv.IsCompound})
+			if err != nil {
+				return
+			}
+			_, err = out.Write(rv.Bytes)
+		}
+		return
+	}
+
+	tag, isCompound, ok := getUniversalType(v.Type())
+	if !ok {
+		err = StructuralError{fmt.Sprintf("unknown Go type: %v", v.Type())}
+		return
+	}
+	class := ClassUniversal
+
+	if params.timeType != 0 && tag != TagUTCTime {
+		return StructuralError{"explicit time type given to non-time member"}
+	}
+
+	// jtasn1 updated to allow slices of strings
+	if params.stringType != 0 && !(tag == TagPrintableString || (v.Kind() == reflect.Slice && tag == 16 && v.Type().Elem().Kind() == reflect.String)) {
+		return StructuralError{"explicit string type given to non-string member"}
+	}
+
+	switch tag {
+	case TagPrintableString:
+		if params.stringType == 0 {
+			// This is a string without an explicit string type. We'll use
+			// a PrintableString if the character set in the string is
+			// sufficiently limited, otherwise we'll use a UTF8String.
+			for _, r := range v.String() {
+				if r >= utf8.RuneSelf || !isPrintable(byte(r)) {
+					if !utf8.ValidString(v.String()) {
+						return errors.New("asn1: string not valid UTF-8")
+					}
+					tag = TagUTF8String
+					break
+				}
+			}
+		} else {
+			tag = params.stringType
+		}
+	case TagUTCTime:
+		if params.timeType == TagGeneralizedTime || outsideUTCRange(v.Interface().(time.Time)) {
+			tag = TagGeneralizedTime
+		}
+	}
+
+	if params.set {
+		if tag != TagSequence {
+			return StructuralError{"non sequence tagged as set"}
+		}
+		tag = TagSet
+	}
+
+	tags, body := out.fork()
+
+	err = marshalBody(body, v, params)
+	if err != nil {
+		return
+	}
+
+	bodyLen := body.Len()
+
+	var explicitTag *forkableWriter
+	if params.explicit {
+		explicitTag, tags = tags.fork()
+	}
+
+	if !params.explicit && params.tag != nil {
+		// implicit tag.
+		tag = *params.tag
+		class = ClassContextSpecific
+	}
+
+	err = marshalTagAndLength(tags, tagAndLength{class, tag, bodyLen, isCompound})
+	if err != nil {
+		return
+	}
+
+	if params.explicit {
+		err = marshalTagAndLength(explicitTag, tagAndLength{
+			class:      ClassContextSpecific,
+			tag:        *params.tag,
+			length:     bodyLen + tags.Len(),
+			isCompound: true,
+		})
+	}
+
+	return err
+}
+
+// Marshal returns the ASN.1 encoding of val.
+//
+// In addition to the struct tags recognised by Unmarshal, the following can be
+// used:
+//
+//	ia5:		causes strings to be marshaled as ASN.1, IA5 strings
+//	omitempty:	causes empty slices to be skipped
+//	printable:	causes strings to be marshaled as ASN.1, PrintableString strings.
+//	utf8:		causes strings to be marshaled as ASN.1, UTF8 strings
+func Marshal(val interface{}) ([]byte, error) {
+	var out bytes.Buffer
+	v := reflect.ValueOf(val)
+	f := newForkableWriter()
+	err := marshalField(f, v, fieldParameters{})
+	if err != nil {
+		return nil, err
+	}
+	_, err = f.writeTo(&out)
+	return out.Bytes(), err
+}