| // 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 ( |
| "big" |
| "bytes" |
| "fmt" |
| "io" |
| "os" |
| "reflect" |
| "time" |
| ) |
| |
| // 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{bytes.NewBuffer(nil), 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 os.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 os.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 os.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 os.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 os.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 os.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 os.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 os.Error) { |
| if len(oid) < 2 || oid[0] > 6 || oid[1] >= 40 { |
| return StructuralError{"invalid object identifier"} |
| } |
| |
| err = out.WriteByte(byte(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 os.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 os.Error) { |
| b := []byte(s) |
| for _, c := range b { |
| if c > 127 { |
| return StructuralError{"IA5String contains invalid character"} |
| } |
| } |
| |
| _, err = out.Write(b) |
| return |
| } |
| |
| func marshalTwoDigits(out *forkableWriter, v int) (err os.Error) { |
| err = out.WriteByte(byte('0' + (v/10)%10)) |
| if err != nil { |
| return |
| } |
| return out.WriteByte(byte('0' + v%10)) |
| } |
| |
| func marshalUTCTime(out *forkableWriter, t *time.Time) (err os.Error) { |
| switch { |
| case 1950 <= t.Year && t.Year < 2000: |
| err = marshalTwoDigits(out, int(t.Year-1900)) |
| case 2000 <= t.Year && t.Year < 2050: |
| err = marshalTwoDigits(out, int(t.Year-2000)) |
| default: |
| return StructuralError{"Cannot represent time as UTCTime"} |
| } |
| |
| if err != nil { |
| return |
| } |
| |
| err = marshalTwoDigits(out, t.Month) |
| if err != nil { |
| return |
| } |
| |
| err = marshalTwoDigits(out, t.Day) |
| if err != nil { |
| return |
| } |
| |
| err = marshalTwoDigits(out, t.Hour) |
| if err != nil { |
| return |
| } |
| |
| err = marshalTwoDigits(out, t.Minute) |
| if err != nil { |
| return |
| } |
| |
| err = marshalTwoDigits(out, t.Second) |
| if err != nil { |
| return |
| } |
| |
| switch { |
| case t.ZoneOffset/60 == 0: |
| err = out.WriteByte('Z') |
| return |
| case t.ZoneOffset > 0: |
| err = out.WriteByte('+') |
| case t.ZoneOffset < 0: |
| err = out.WriteByte('-') |
| } |
| |
| if err != nil { |
| return |
| } |
| |
| offsetMinutes := t.ZoneOffset / 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 os.Error) { |
| switch value.Type() { |
| case timeType: |
| return marshalUTCTime(out, value.Interface().(*time.Time)) |
| 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)) |
| 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 params fieldParameters |
| 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: |
| if params.stringType == tagIA5String { |
| return marshalIA5String(out, v.String()) |
| } else { |
| return marshalPrintableString(out, v.String()) |
| } |
| return |
| } |
| |
| return StructuralError{"unknown Go type"} |
| } |
| |
| func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters) (err os.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 params.optional && reflect.DeepEqual(v.Interface(), reflect.Zero(v.Type()).Interface()) { |
| return |
| } |
| |
| if v.Type() == rawValueType { |
| rv := v.Interface().(RawValue) |
| 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 { |
| if tag != tagPrintableString { |
| return StructuralError{"Explicit string type given to non-string member"} |
| } |
| tag = params.stringType |
| } |
| |
| 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. |
| func Marshal(val interface{}) ([]byte, os.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 |
| } |
