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path: root/src/encoding/asn1/marshal.go
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Diffstat (limited to 'src/encoding/asn1/marshal.go')
-rw-r--r--src/encoding/asn1/marshal.go646
1 files changed, 646 insertions, 0 deletions
diff --git a/src/encoding/asn1/marshal.go b/src/encoding/asn1/marshal.go
new file mode 100644
index 000000000..b2f104b4c
--- /dev/null
+++ b/src/encoding/asn1/marshal.go
@@ -0,0 +1,646 @@
+// 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, int(year-1900))
+ case 2000 <= year && year < 2050:
+ err = marshalTwoDigits(out, int(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 timeType:
+ t := value.Interface().(time.Time)
+ if 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, int64(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
+ }
+
+ var fp fieldParameters
+ for i := 0; i < v.Len(); i++ {
+ var pre *forkableWriter
+ pre, out = out.fork()
+ err = marshalField(pre, v.Index(i), fp)
+ 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 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.stringType != 0 && tag != tagPrintableString {
+ 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 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 nil
+}
+
+// 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(), nil
+}
generated by cgit v1.2.3 (git 2.39.1) at 2025-06-05 13:53:33 +0000