github.com/flyinox/gosm@v0.0.0-20171117061539-16768cb62077/src/encoding/asn1/marshal.go (about)

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package asn1
     6  
     7  import (
     8  	"errors"
     9  	"fmt"
    10  	"math/big"
    11  	"reflect"
    12  	"time"
    13  	"unicode/utf8"
    14  )
    15  
    16  var (
    17  	byte00Encoder encoder = byteEncoder(0x00)
    18  	byteFFEncoder encoder = byteEncoder(0xff)
    19  )
    20  
    21  // encoder represents a ASN.1 element that is waiting to be marshaled.
    22  type encoder interface {
    23  	// Len returns the number of bytes needed to marshal this element.
    24  	Len() int
    25  	// Encode encodes this element by writing Len() bytes to dst.
    26  	Encode(dst []byte)
    27  }
    28  
    29  type byteEncoder byte
    30  
    31  func (c byteEncoder) Len() int {
    32  	return 1
    33  }
    34  
    35  func (c byteEncoder) Encode(dst []byte) {
    36  	dst[0] = byte(c)
    37  }
    38  
    39  type bytesEncoder []byte
    40  
    41  func (b bytesEncoder) Len() int {
    42  	return len(b)
    43  }
    44  
    45  func (b bytesEncoder) Encode(dst []byte) {
    46  	if copy(dst, b) != len(b) {
    47  		panic("internal error")
    48  	}
    49  }
    50  
    51  type stringEncoder string
    52  
    53  func (s stringEncoder) Len() int {
    54  	return len(s)
    55  }
    56  
    57  func (s stringEncoder) Encode(dst []byte) {
    58  	if copy(dst, s) != len(s) {
    59  		panic("internal error")
    60  	}
    61  }
    62  
    63  type multiEncoder []encoder
    64  
    65  func (m multiEncoder) Len() int {
    66  	var size int
    67  	for _, e := range m {
    68  		size += e.Len()
    69  	}
    70  	return size
    71  }
    72  
    73  func (m multiEncoder) Encode(dst []byte) {
    74  	var off int
    75  	for _, e := range m {
    76  		e.Encode(dst[off:])
    77  		off += e.Len()
    78  	}
    79  }
    80  
    81  type taggedEncoder struct {
    82  	// scratch contains temporary space for encoding the tag and length of
    83  	// an element in order to avoid extra allocations.
    84  	scratch [8]byte
    85  	tag     encoder
    86  	body    encoder
    87  }
    88  
    89  func (t *taggedEncoder) Len() int {
    90  	return t.tag.Len() + t.body.Len()
    91  }
    92  
    93  func (t *taggedEncoder) Encode(dst []byte) {
    94  	t.tag.Encode(dst)
    95  	t.body.Encode(dst[t.tag.Len():])
    96  }
    97  
    98  type int64Encoder int64
    99  
   100  func (i int64Encoder) Len() int {
   101  	n := 1
   102  
   103  	for i > 127 {
   104  		n++
   105  		i >>= 8
   106  	}
   107  
   108  	for i < -128 {
   109  		n++
   110  		i >>= 8
   111  	}
   112  
   113  	return n
   114  }
   115  
   116  func (i int64Encoder) Encode(dst []byte) {
   117  	n := i.Len()
   118  
   119  	for j := 0; j < n; j++ {
   120  		dst[j] = byte(i >> uint((n-1-j)*8))
   121  	}
   122  }
   123  
   124  func base128IntLength(n int64) int {
   125  	if n == 0 {
   126  		return 1
   127  	}
   128  
   129  	l := 0
   130  	for i := n; i > 0; i >>= 7 {
   131  		l++
   132  	}
   133  
   134  	return l
   135  }
   136  
   137  func appendBase128Int(dst []byte, n int64) []byte {
   138  	l := base128IntLength(n)
   139  
   140  	for i := l - 1; i >= 0; i-- {
   141  		o := byte(n >> uint(i*7))
   142  		o &= 0x7f
   143  		if i != 0 {
   144  			o |= 0x80
   145  		}
   146  
   147  		dst = append(dst, o)
   148  	}
   149  
   150  	return dst
   151  }
   152  
   153  func makeBigInt(n *big.Int) (encoder, error) {
   154  	if n == nil {
   155  		return nil, StructuralError{"empty integer"}
   156  	}
   157  
   158  	if n.Sign() < 0 {
   159  		// A negative number has to be converted to two's-complement
   160  		// form. So we'll invert and subtract 1. If the
   161  		// most-significant-bit isn't set then we'll need to pad the
   162  		// beginning with 0xff in order to keep the number negative.
   163  		nMinus1 := new(big.Int).Neg(n)
   164  		nMinus1.Sub(nMinus1, bigOne)
   165  		bytes := nMinus1.Bytes()
   166  		for i := range bytes {
   167  			bytes[i] ^= 0xff
   168  		}
   169  		if len(bytes) == 0 || bytes[0]&0x80 == 0 {
   170  			return multiEncoder([]encoder{byteFFEncoder, bytesEncoder(bytes)}), nil
   171  		}
   172  		return bytesEncoder(bytes), nil
   173  	} else if n.Sign() == 0 {
   174  		// Zero is written as a single 0 zero rather than no bytes.
   175  		return byte00Encoder, nil
   176  	} else {
   177  		bytes := n.Bytes()
   178  		if len(bytes) > 0 && bytes[0]&0x80 != 0 {
   179  			// We'll have to pad this with 0x00 in order to stop it
   180  			// looking like a negative number.
   181  			return multiEncoder([]encoder{byte00Encoder, bytesEncoder(bytes)}), nil
   182  		}
   183  		return bytesEncoder(bytes), nil
   184  	}
   185  }
   186  
   187  func appendLength(dst []byte, i int) []byte {
   188  	n := lengthLength(i)
   189  
   190  	for ; n > 0; n-- {
   191  		dst = append(dst, byte(i>>uint((n-1)*8)))
   192  	}
   193  
   194  	return dst
   195  }
   196  
   197  func lengthLength(i int) (numBytes int) {
   198  	numBytes = 1
   199  	for i > 255 {
   200  		numBytes++
   201  		i >>= 8
   202  	}
   203  	return
   204  }
   205  
   206  func appendTagAndLength(dst []byte, t tagAndLength) []byte {
   207  	b := uint8(t.class) << 6
   208  	if t.isCompound {
   209  		b |= 0x20
   210  	}
   211  	if t.tag >= 31 {
   212  		b |= 0x1f
   213  		dst = append(dst, b)
   214  		dst = appendBase128Int(dst, int64(t.tag))
   215  	} else {
   216  		b |= uint8(t.tag)
   217  		dst = append(dst, b)
   218  	}
   219  
   220  	if t.length >= 128 {
   221  		l := lengthLength(t.length)
   222  		dst = append(dst, 0x80|byte(l))
   223  		dst = appendLength(dst, t.length)
   224  	} else {
   225  		dst = append(dst, byte(t.length))
   226  	}
   227  
   228  	return dst
   229  }
   230  
   231  type bitStringEncoder BitString
   232  
   233  func (b bitStringEncoder) Len() int {
   234  	return len(b.Bytes) + 1
   235  }
   236  
   237  func (b bitStringEncoder) Encode(dst []byte) {
   238  	dst[0] = byte((8 - b.BitLength%8) % 8)
   239  	if copy(dst[1:], b.Bytes) != len(b.Bytes) {
   240  		panic("internal error")
   241  	}
   242  }
   243  
   244  type oidEncoder []int
   245  
   246  func (oid oidEncoder) Len() int {
   247  	l := base128IntLength(int64(oid[0]*40 + oid[1]))
   248  	for i := 2; i < len(oid); i++ {
   249  		l += base128IntLength(int64(oid[i]))
   250  	}
   251  	return l
   252  }
   253  
   254  func (oid oidEncoder) Encode(dst []byte) {
   255  	dst = appendBase128Int(dst[:0], int64(oid[0]*40+oid[1]))
   256  	for i := 2; i < len(oid); i++ {
   257  		dst = appendBase128Int(dst, int64(oid[i]))
   258  	}
   259  }
   260  
   261  func makeObjectIdentifier(oid []int) (e encoder, err error) {
   262  	if len(oid) < 2 || oid[0] > 2 || (oid[0] < 2 && oid[1] >= 40) {
   263  		return nil, StructuralError{"invalid object identifier"}
   264  	}
   265  
   266  	return oidEncoder(oid), nil
   267  }
   268  
   269  func makePrintableString(s string) (e encoder, err error) {
   270  	for i := 0; i < len(s); i++ {
   271  		if !isPrintable(s[i]) {
   272  			return nil, StructuralError{"PrintableString contains invalid character"}
   273  		}
   274  	}
   275  
   276  	return stringEncoder(s), nil
   277  }
   278  
   279  func makeIA5String(s string) (e encoder, err error) {
   280  	for i := 0; i < len(s); i++ {
   281  		if s[i] > 127 {
   282  			return nil, StructuralError{"IA5String contains invalid character"}
   283  		}
   284  	}
   285  
   286  	return stringEncoder(s), nil
   287  }
   288  
   289  func makeUTF8String(s string) encoder {
   290  	return stringEncoder(s)
   291  }
   292  
   293  func appendTwoDigits(dst []byte, v int) []byte {
   294  	return append(dst, byte('0'+(v/10)%10), byte('0'+v%10))
   295  }
   296  
   297  func appendFourDigits(dst []byte, v int) []byte {
   298  	var bytes [4]byte
   299  	for i := range bytes {
   300  		bytes[3-i] = '0' + byte(v%10)
   301  		v /= 10
   302  	}
   303  	return append(dst, bytes[:]...)
   304  }
   305  
   306  func outsideUTCRange(t time.Time) bool {
   307  	year := t.Year()
   308  	return year < 1950 || year >= 2050
   309  }
   310  
   311  func makeUTCTime(t time.Time) (e encoder, err error) {
   312  	dst := make([]byte, 0, 18)
   313  
   314  	dst, err = appendUTCTime(dst, t)
   315  	if err != nil {
   316  		return nil, err
   317  	}
   318  
   319  	return bytesEncoder(dst), nil
   320  }
   321  
   322  func makeGeneralizedTime(t time.Time) (e encoder, err error) {
   323  	dst := make([]byte, 0, 20)
   324  
   325  	dst, err = appendGeneralizedTime(dst, t)
   326  	if err != nil {
   327  		return nil, err
   328  	}
   329  
   330  	return bytesEncoder(dst), nil
   331  }
   332  
   333  func appendUTCTime(dst []byte, t time.Time) (ret []byte, err error) {
   334  	year := t.Year()
   335  
   336  	switch {
   337  	case 1950 <= year && year < 2000:
   338  		dst = appendTwoDigits(dst, year-1900)
   339  	case 2000 <= year && year < 2050:
   340  		dst = appendTwoDigits(dst, year-2000)
   341  	default:
   342  		return nil, StructuralError{"cannot represent time as UTCTime"}
   343  	}
   344  
   345  	return appendTimeCommon(dst, t), nil
   346  }
   347  
   348  func appendGeneralizedTime(dst []byte, t time.Time) (ret []byte, err error) {
   349  	year := t.Year()
   350  	if year < 0 || year > 9999 {
   351  		return nil, StructuralError{"cannot represent time as GeneralizedTime"}
   352  	}
   353  
   354  	dst = appendFourDigits(dst, year)
   355  
   356  	return appendTimeCommon(dst, t), nil
   357  }
   358  
   359  func appendTimeCommon(dst []byte, t time.Time) []byte {
   360  	_, month, day := t.Date()
   361  
   362  	dst = appendTwoDigits(dst, int(month))
   363  	dst = appendTwoDigits(dst, day)
   364  
   365  	hour, min, sec := t.Clock()
   366  
   367  	dst = appendTwoDigits(dst, hour)
   368  	dst = appendTwoDigits(dst, min)
   369  	dst = appendTwoDigits(dst, sec)
   370  
   371  	_, offset := t.Zone()
   372  
   373  	switch {
   374  	case offset/60 == 0:
   375  		return append(dst, 'Z')
   376  	case offset > 0:
   377  		dst = append(dst, '+')
   378  	case offset < 0:
   379  		dst = append(dst, '-')
   380  	}
   381  
   382  	offsetMinutes := offset / 60
   383  	if offsetMinutes < 0 {
   384  		offsetMinutes = -offsetMinutes
   385  	}
   386  
   387  	dst = appendTwoDigits(dst, offsetMinutes/60)
   388  	dst = appendTwoDigits(dst, offsetMinutes%60)
   389  
   390  	return dst
   391  }
   392  
   393  func stripTagAndLength(in []byte) []byte {
   394  	_, offset, err := parseTagAndLength(in, 0)
   395  	if err != nil {
   396  		return in
   397  	}
   398  	return in[offset:]
   399  }
   400  
   401  func makeBody(value reflect.Value, params fieldParameters) (e encoder, err error) {
   402  	switch value.Type() {
   403  	case flagType:
   404  		return bytesEncoder(nil), nil
   405  	case timeType:
   406  		t := value.Interface().(time.Time)
   407  		if params.timeType == TagGeneralizedTime || outsideUTCRange(t) {
   408  			return makeGeneralizedTime(t)
   409  		}
   410  		return makeUTCTime(t)
   411  	case bitStringType:
   412  		return bitStringEncoder(value.Interface().(BitString)), nil
   413  	case objectIdentifierType:
   414  		return makeObjectIdentifier(value.Interface().(ObjectIdentifier))
   415  	case bigIntType:
   416  		return makeBigInt(value.Interface().(*big.Int))
   417  	}
   418  
   419  	switch v := value; v.Kind() {
   420  	case reflect.Bool:
   421  		if v.Bool() {
   422  			return byteFFEncoder, nil
   423  		}
   424  		return byte00Encoder, nil
   425  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   426  		return int64Encoder(v.Int()), nil
   427  	case reflect.Struct:
   428  		t := v.Type()
   429  
   430  		for i := 0; i < t.NumField(); i++ {
   431  			if t.Field(i).PkgPath != "" {
   432  				return nil, StructuralError{"struct contains unexported fields"}
   433  			}
   434  		}
   435  
   436  		startingField := 0
   437  
   438  		n := t.NumField()
   439  		if n == 0 {
   440  			return bytesEncoder(nil), nil
   441  		}
   442  
   443  		// If the first element of the structure is a non-empty
   444  		// RawContents, then we don't bother serializing the rest.
   445  		if t.Field(0).Type == rawContentsType {
   446  			s := v.Field(0)
   447  			if s.Len() > 0 {
   448  				bytes := s.Bytes()
   449  				/* The RawContents will contain the tag and
   450  				 * length fields but we'll also be writing
   451  				 * those ourselves, so we strip them out of
   452  				 * bytes */
   453  				return bytesEncoder(stripTagAndLength(bytes)), nil
   454  			}
   455  
   456  			startingField = 1
   457  		}
   458  
   459  		switch n1 := n - startingField; n1 {
   460  		case 0:
   461  			return bytesEncoder(nil), nil
   462  		case 1:
   463  			return makeField(v.Field(startingField), parseFieldParameters(t.Field(startingField).Tag.Get("asn1")))
   464  		default:
   465  			m := make([]encoder, n1)
   466  			for i := 0; i < n1; i++ {
   467  				m[i], err = makeField(v.Field(i+startingField), parseFieldParameters(t.Field(i+startingField).Tag.Get("asn1")))
   468  				if err != nil {
   469  					return nil, err
   470  				}
   471  			}
   472  
   473  			return multiEncoder(m), nil
   474  		}
   475  	case reflect.Slice:
   476  		sliceType := v.Type()
   477  		if sliceType.Elem().Kind() == reflect.Uint8 {
   478  			return bytesEncoder(v.Bytes()), nil
   479  		}
   480  
   481  		var fp fieldParameters
   482  
   483  		switch l := v.Len(); l {
   484  		case 0:
   485  			return bytesEncoder(nil), nil
   486  		case 1:
   487  			return makeField(v.Index(0), fp)
   488  		default:
   489  			m := make([]encoder, l)
   490  
   491  			for i := 0; i < l; i++ {
   492  				m[i], err = makeField(v.Index(i), fp)
   493  				if err != nil {
   494  					return nil, err
   495  				}
   496  			}
   497  
   498  			return multiEncoder(m), nil
   499  		}
   500  	case reflect.String:
   501  		switch params.stringType {
   502  		case TagIA5String:
   503  			return makeIA5String(v.String())
   504  		case TagPrintableString:
   505  			return makePrintableString(v.String())
   506  		default:
   507  			return makeUTF8String(v.String()), nil
   508  		}
   509  	}
   510  
   511  	return nil, StructuralError{"unknown Go type"}
   512  }
   513  
   514  func makeField(v reflect.Value, params fieldParameters) (e encoder, err error) {
   515  	if !v.IsValid() {
   516  		return nil, fmt.Errorf("asn1: cannot marshal nil value")
   517  	}
   518  	// If the field is an interface{} then recurse into it.
   519  	if v.Kind() == reflect.Interface && v.Type().NumMethod() == 0 {
   520  		return makeField(v.Elem(), params)
   521  	}
   522  
   523  	if v.Kind() == reflect.Slice && v.Len() == 0 && params.omitEmpty {
   524  		return bytesEncoder(nil), nil
   525  	}
   526  
   527  	if params.optional && params.defaultValue != nil && canHaveDefaultValue(v.Kind()) {
   528  		defaultValue := reflect.New(v.Type()).Elem()
   529  		defaultValue.SetInt(*params.defaultValue)
   530  
   531  		if reflect.DeepEqual(v.Interface(), defaultValue.Interface()) {
   532  			return bytesEncoder(nil), nil
   533  		}
   534  	}
   535  
   536  	// If no default value is given then the zero value for the type is
   537  	// assumed to be the default value. This isn't obviously the correct
   538  	// behavior, but it's what Go has traditionally done.
   539  	if params.optional && params.defaultValue == nil {
   540  		if reflect.DeepEqual(v.Interface(), reflect.Zero(v.Type()).Interface()) {
   541  			return bytesEncoder(nil), nil
   542  		}
   543  	}
   544  
   545  	if v.Type() == rawValueType {
   546  		rv := v.Interface().(RawValue)
   547  		if len(rv.FullBytes) != 0 {
   548  			return bytesEncoder(rv.FullBytes), nil
   549  		}
   550  
   551  		t := new(taggedEncoder)
   552  
   553  		t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{rv.Class, rv.Tag, len(rv.Bytes), rv.IsCompound}))
   554  		t.body = bytesEncoder(rv.Bytes)
   555  
   556  		return t, nil
   557  	}
   558  
   559  	tag, isCompound, ok := getUniversalType(v.Type())
   560  	if !ok {
   561  		return nil, StructuralError{fmt.Sprintf("unknown Go type: %v", v.Type())}
   562  	}
   563  	class := ClassUniversal
   564  
   565  	if params.timeType != 0 && tag != TagUTCTime {
   566  		return nil, StructuralError{"explicit time type given to non-time member"}
   567  	}
   568  
   569  	if params.stringType != 0 && tag != TagPrintableString {
   570  		return nil, StructuralError{"explicit string type given to non-string member"}
   571  	}
   572  
   573  	switch tag {
   574  	case TagPrintableString:
   575  		if params.stringType == 0 {
   576  			// This is a string without an explicit string type. We'll use
   577  			// a PrintableString if the character set in the string is
   578  			// sufficiently limited, otherwise we'll use a UTF8String.
   579  			for _, r := range v.String() {
   580  				if r >= utf8.RuneSelf || !isPrintable(byte(r)) {
   581  					if !utf8.ValidString(v.String()) {
   582  						return nil, errors.New("asn1: string not valid UTF-8")
   583  					}
   584  					tag = TagUTF8String
   585  					break
   586  				}
   587  			}
   588  		} else {
   589  			tag = params.stringType
   590  		}
   591  	case TagUTCTime:
   592  		if params.timeType == TagGeneralizedTime || outsideUTCRange(v.Interface().(time.Time)) {
   593  			tag = TagGeneralizedTime
   594  		}
   595  	}
   596  
   597  	if params.set {
   598  		if tag != TagSequence {
   599  			return nil, StructuralError{"non sequence tagged as set"}
   600  		}
   601  		tag = TagSet
   602  	}
   603  
   604  	t := new(taggedEncoder)
   605  
   606  	t.body, err = makeBody(v, params)
   607  	if err != nil {
   608  		return nil, err
   609  	}
   610  
   611  	bodyLen := t.body.Len()
   612  
   613  	if params.explicit {
   614  		t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{class, tag, bodyLen, isCompound}))
   615  
   616  		tt := new(taggedEncoder)
   617  
   618  		tt.body = t
   619  
   620  		tt.tag = bytesEncoder(appendTagAndLength(tt.scratch[:0], tagAndLength{
   621  			class:      ClassContextSpecific,
   622  			tag:        *params.tag,
   623  			length:     bodyLen + t.tag.Len(),
   624  			isCompound: true,
   625  		}))
   626  
   627  		return tt, nil
   628  	}
   629  
   630  	if params.tag != nil {
   631  		// implicit tag.
   632  		tag = *params.tag
   633  		class = ClassContextSpecific
   634  	}
   635  
   636  	t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{class, tag, bodyLen, isCompound}))
   637  
   638  	return t, nil
   639  }
   640  
   641  // Marshal returns the ASN.1 encoding of val.
   642  //
   643  // In addition to the struct tags recognised by Unmarshal, the following can be
   644  // used:
   645  //
   646  //	ia5:         causes strings to be marshaled as ASN.1, IA5String values
   647  //	omitempty:   causes empty slices to be skipped
   648  //	printable:   causes strings to be marshaled as ASN.1, PrintableString values
   649  //	utf8:        causes strings to be marshaled as ASN.1, UTF8String values
   650  //	utc:         causes time.Time to be marshaled as ASN.1, UTCTime values
   651  //	generalized: causes time.Time to be marshaled as ASN.1, GeneralizedTime values
   652  func Marshal(val interface{}) ([]byte, error) {
   653  	e, err := makeField(reflect.ValueOf(val), fieldParameters{})
   654  	if err != nil {
   655  		return nil, err
   656  	}
   657  	b := make([]byte, e.Len())
   658  	e.Encode(b)
   659  	return b, nil
   660  }