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-rw-r--r--src/encoding/asn1/asn1.go922
1 files changed, 922 insertions, 0 deletions
diff --git a/src/encoding/asn1/asn1.go b/src/encoding/asn1/asn1.go
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+++ b/src/encoding/asn1/asn1.go
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+// 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 implements parsing of DER-encoded ASN.1 data structures,
+// as defined in ITU-T Rec X.690.
+//
+// See also ``A Layman's Guide to a Subset of ASN.1, BER, and DER,''
+// http://luca.ntop.org/Teaching/Appunti/asn1.html.
+package asn1
+
+// ASN.1 is a syntax for specifying abstract objects and BER, DER, PER, XER etc
+// are different encoding formats for those objects. Here, we'll be dealing
+// with DER, the Distinguished Encoding Rules. DER is used in X.509 because
+// it's fast to parse and, unlike BER, has a unique encoding for every object.
+// When calculating hashes over objects, it's important that the resulting
+// bytes be the same at both ends and DER removes this margin of error.
+//
+// ASN.1 is very complex and this package doesn't attempt to implement
+// everything by any means.
+
+import (
+ "fmt"
+ "math/big"
+ "reflect"
+ "strconv"
+ "time"
+)
+
+// A StructuralError suggests that the ASN.1 data is valid, but the Go type
+// which is receiving it doesn't match.
+type StructuralError struct {
+ Msg string
+}
+
+func (e StructuralError) Error() string { return "asn1: structure error: " + e.Msg }
+
+// A SyntaxError suggests that the ASN.1 data is invalid.
+type SyntaxError struct {
+ Msg string
+}
+
+func (e SyntaxError) Error() string { return "asn1: syntax error: " + e.Msg }
+
+// We start by dealing with each of the primitive types in turn.
+
+// BOOLEAN
+
+func parseBool(bytes []byte) (ret bool, err error) {
+ if len(bytes) != 1 {
+ err = SyntaxError{"invalid boolean"}
+ return
+ }
+
+ // DER demands that "If the encoding represents the boolean value TRUE,
+ // its single contents octet shall have all eight bits set to one."
+ // Thus only 0 and 255 are valid encoded values.
+ switch bytes[0] {
+ case 0:
+ ret = false
+ case 0xff:
+ ret = true
+ default:
+ err = SyntaxError{"invalid boolean"}
+ }
+
+ return
+}
+
+// INTEGER
+
+// parseInt64 treats the given bytes as a big-endian, signed integer and
+// returns the result.
+func parseInt64(bytes []byte) (ret int64, err error) {
+ if len(bytes) > 8 {
+ // We'll overflow an int64 in this case.
+ err = StructuralError{"integer too large"}
+ return
+ }
+ for bytesRead := 0; bytesRead < len(bytes); bytesRead++ {
+ ret <<= 8
+ ret |= int64(bytes[bytesRead])
+ }
+
+ // Shift up and down in order to sign extend the result.
+ ret <<= 64 - uint8(len(bytes))*8
+ ret >>= 64 - uint8(len(bytes))*8
+ return
+}
+
+// parseInt treats the given bytes as a big-endian, signed integer and returns
+// the result.
+func parseInt32(bytes []byte) (int32, error) {
+ ret64, err := parseInt64(bytes)
+ if err != nil {
+ return 0, err
+ }
+ if ret64 != int64(int32(ret64)) {
+ return 0, StructuralError{"integer too large"}
+ }
+ return int32(ret64), nil
+}
+
+var bigOne = big.NewInt(1)
+
+// parseBigInt treats the given bytes as a big-endian, signed integer and returns
+// the result.
+func parseBigInt(bytes []byte) *big.Int {
+ ret := new(big.Int)
+ if len(bytes) > 0 && bytes[0]&0x80 == 0x80 {
+ // This is a negative number.
+ notBytes := make([]byte, len(bytes))
+ for i := range notBytes {
+ notBytes[i] = ^bytes[i]
+ }
+ ret.SetBytes(notBytes)
+ ret.Add(ret, bigOne)
+ ret.Neg(ret)
+ return ret
+ }
+ ret.SetBytes(bytes)
+ return ret
+}
+
+// BIT STRING
+
+// BitString is the structure to use when you want an ASN.1 BIT STRING type. A
+// bit string is padded up to the nearest byte in memory and the number of
+// valid bits is recorded. Padding bits will be zero.
+type BitString struct {
+ Bytes []byte // bits packed into bytes.
+ BitLength int // length in bits.
+}
+
+// At returns the bit at the given index. If the index is out of range it
+// returns false.
+func (b BitString) At(i int) int {
+ if i < 0 || i >= b.BitLength {
+ return 0
+ }
+ x := i / 8
+ y := 7 - uint(i%8)
+ return int(b.Bytes[x]>>y) & 1
+}
+
+// RightAlign returns a slice where the padding bits are at the beginning. The
+// slice may share memory with the BitString.
+func (b BitString) RightAlign() []byte {
+ shift := uint(8 - (b.BitLength % 8))
+ if shift == 8 || len(b.Bytes) == 0 {
+ return b.Bytes
+ }
+
+ a := make([]byte, len(b.Bytes))
+ a[0] = b.Bytes[0] >> shift
+ for i := 1; i < len(b.Bytes); i++ {
+ a[i] = b.Bytes[i-1] << (8 - shift)
+ a[i] |= b.Bytes[i] >> shift
+ }
+
+ return a
+}
+
+// parseBitString parses an ASN.1 bit string from the given byte slice and returns it.
+func parseBitString(bytes []byte) (ret BitString, err error) {
+ if len(bytes) == 0 {
+ err = SyntaxError{"zero length BIT STRING"}
+ return
+ }
+ paddingBits := int(bytes[0])
+ if paddingBits > 7 ||
+ len(bytes) == 1 && paddingBits > 0 ||
+ bytes[len(bytes)-1]&((1<<bytes[0])-1) != 0 {
+ err = SyntaxError{"invalid padding bits in BIT STRING"}
+ return
+ }
+ ret.BitLength = (len(bytes)-1)*8 - paddingBits
+ ret.Bytes = bytes[1:]
+ return
+}
+
+// OBJECT IDENTIFIER
+
+// An ObjectIdentifier represents an ASN.1 OBJECT IDENTIFIER.
+type ObjectIdentifier []int
+
+// Equal reports whether oi and other represent the same identifier.
+func (oi ObjectIdentifier) Equal(other ObjectIdentifier) bool {
+ if len(oi) != len(other) {
+ return false
+ }
+ for i := 0; i < len(oi); i++ {
+ if oi[i] != other[i] {
+ return false
+ }
+ }
+
+ return true
+}
+
+func (oi ObjectIdentifier) String() string {
+ var s string
+
+ for i, v := range oi {
+ if i > 0 {
+ s += "."
+ }
+ s += strconv.Itoa(v)
+ }
+
+ return s
+}
+
+// parseObjectIdentifier parses an OBJECT IDENTIFIER from the given bytes and
+// returns it. An object identifier is a sequence of variable length integers
+// that are assigned in a hierarchy.
+func parseObjectIdentifier(bytes []byte) (s []int, err error) {
+ if len(bytes) == 0 {
+ err = SyntaxError{"zero length OBJECT IDENTIFIER"}
+ return
+ }
+
+ // In the worst case, we get two elements from the first byte (which is
+ // encoded differently) and then every varint is a single byte long.
+ s = make([]int, len(bytes)+1)
+
+ // The first varint is 40*value1 + value2:
+ // According to this packing, value1 can take the values 0, 1 and 2 only.
+ // When value1 = 0 or value1 = 1, then value2 is <= 39. When value1 = 2,
+ // then there are no restrictions on value2.
+ v, offset, err := parseBase128Int(bytes, 0)
+ if err != nil {
+ return
+ }
+ if v < 80 {
+ s[0] = v / 40
+ s[1] = v % 40
+ } else {
+ s[0] = 2
+ s[1] = v - 80
+ }
+
+ i := 2
+ for ; offset < len(bytes); i++ {
+ v, offset, err = parseBase128Int(bytes, offset)
+ if err != nil {
+ return
+ }
+ s[i] = v
+ }
+ s = s[0:i]
+ return
+}
+
+// ENUMERATED
+
+// An Enumerated is represented as a plain int.
+type Enumerated int
+
+// FLAG
+
+// A Flag accepts any data and is set to true if present.
+type Flag bool
+
+// parseBase128Int parses a base-128 encoded int from the given offset in the
+// given byte slice. It returns the value and the new offset.
+func parseBase128Int(bytes []byte, initOffset int) (ret, offset int, err error) {
+ offset = initOffset
+ for shifted := 0; offset < len(bytes); shifted++ {
+ if shifted > 4 {
+ err = StructuralError{"base 128 integer too large"}
+ return
+ }
+ ret <<= 7
+ b := bytes[offset]
+ ret |= int(b & 0x7f)
+ offset++
+ if b&0x80 == 0 {
+ return
+ }
+ }
+ err = SyntaxError{"truncated base 128 integer"}
+ return
+}
+
+// UTCTime
+
+func parseUTCTime(bytes []byte) (ret time.Time, err error) {
+ s := string(bytes)
+ ret, err = time.Parse("0601021504Z0700", s)
+ if err != nil {
+ ret, err = time.Parse("060102150405Z0700", s)
+ }
+ if err == nil && ret.Year() >= 2050 {
+ // UTCTime only encodes times prior to 2050. See https://tools.ietf.org/html/rfc5280#section-4.1.2.5.1
+ ret = ret.AddDate(-100, 0, 0)
+ }
+
+ return
+}
+
+// parseGeneralizedTime parses the GeneralizedTime from the given byte slice
+// and returns the resulting time.
+func parseGeneralizedTime(bytes []byte) (ret time.Time, err error) {
+ return time.Parse("20060102150405Z0700", string(bytes))
+}
+
+// PrintableString
+
+// parsePrintableString parses a ASN.1 PrintableString from the given byte
+// array and returns it.
+func parsePrintableString(bytes []byte) (ret string, err error) {
+ for _, b := range bytes {
+ if !isPrintable(b) {
+ err = SyntaxError{"PrintableString contains invalid character"}
+ return
+ }
+ }
+ ret = string(bytes)
+ return
+}
+
+// isPrintable returns true iff the given b is in the ASN.1 PrintableString set.
+func isPrintable(b byte) bool {
+ return 'a' <= b && b <= 'z' ||
+ 'A' <= b && b <= 'Z' ||
+ '0' <= b && b <= '9' ||
+ '\'' <= b && b <= ')' ||
+ '+' <= b && b <= '/' ||
+ b == ' ' ||
+ b == ':' ||
+ b == '=' ||
+ b == '?' ||
+ // This is technically not allowed in a PrintableString.
+ // However, x509 certificates with wildcard strings don't
+ // always use the correct string type so we permit it.
+ b == '*'
+}
+
+// IA5String
+
+// parseIA5String parses a ASN.1 IA5String (ASCII string) from the given
+// byte slice and returns it.
+func parseIA5String(bytes []byte) (ret string, err error) {
+ for _, b := range bytes {
+ if b >= 0x80 {
+ err = SyntaxError{"IA5String contains invalid character"}
+ return
+ }
+ }
+ ret = string(bytes)
+ return
+}
+
+// T61String
+
+// parseT61String parses a ASN.1 T61String (8-bit clean string) from the given
+// byte slice and returns it.
+func parseT61String(bytes []byte) (ret string, err error) {
+ return string(bytes), nil
+}
+
+// UTF8String
+
+// parseUTF8String parses a ASN.1 UTF8String (raw UTF-8) from the given byte
+// array and returns it.
+func parseUTF8String(bytes []byte) (ret string, err error) {
+ return string(bytes), nil
+}
+
+// A RawValue represents an undecoded ASN.1 object.
+type RawValue struct {
+ Class, Tag int
+ IsCompound bool
+ Bytes []byte
+ FullBytes []byte // includes the tag and length
+}
+
+// RawContent is used to signal that the undecoded, DER data needs to be
+// preserved for a struct. To use it, the first field of the struct must have
+// this type. It's an error for any of the other fields to have this type.
+type RawContent []byte
+
+// Tagging
+
+// parseTagAndLength parses an ASN.1 tag and length pair from the given offset
+// into a byte slice. It returns the parsed data and the new offset. SET and
+// SET OF (tag 17) are mapped to SEQUENCE and SEQUENCE OF (tag 16) since we
+// don't distinguish between ordered and unordered objects in this code.
+func parseTagAndLength(bytes []byte, initOffset int) (ret tagAndLength, offset int, err error) {
+ offset = initOffset
+ b := bytes[offset]
+ offset++
+ ret.class = int(b >> 6)
+ ret.isCompound = b&0x20 == 0x20
+ ret.tag = int(b & 0x1f)
+
+ // If the bottom five bits are set, then the tag number is actually base 128
+ // encoded afterwards
+ if ret.tag == 0x1f {
+ ret.tag, offset, err = parseBase128Int(bytes, offset)
+ if err != nil {
+ return
+ }
+ }
+ if offset >= len(bytes) {
+ err = SyntaxError{"truncated tag or length"}
+ return
+ }
+ b = bytes[offset]
+ offset++
+ if b&0x80 == 0 {
+ // The length is encoded in the bottom 7 bits.
+ ret.length = int(b & 0x7f)
+ } else {
+ // Bottom 7 bits give the number of length bytes to follow.
+ numBytes := int(b & 0x7f)
+ if numBytes == 0 {
+ err = SyntaxError{"indefinite length found (not DER)"}
+ return
+ }
+ ret.length = 0
+ for i := 0; i < numBytes; i++ {
+ if offset >= len(bytes) {
+ err = SyntaxError{"truncated tag or length"}
+ return
+ }
+ b = bytes[offset]
+ offset++
+ if ret.length >= 1<<23 {
+ // We can't shift ret.length up without
+ // overflowing.
+ err = StructuralError{"length too large"}
+ return
+ }
+ ret.length <<= 8
+ ret.length |= int(b)
+ if ret.length == 0 {
+ // DER requires that lengths be minimal.
+ err = StructuralError{"superfluous leading zeros in length"}
+ return
+ }
+ }
+ }
+
+ return
+}
+
+// parseSequenceOf is used for SEQUENCE OF and SET OF values. It tries to parse
+// a number of ASN.1 values from the given byte slice and returns them as a
+// slice of Go values of the given type.
+func parseSequenceOf(bytes []byte, sliceType reflect.Type, elemType reflect.Type) (ret reflect.Value, err error) {
+ expectedTag, compoundType, ok := getUniversalType(elemType)
+ if !ok {
+ err = StructuralError{"unknown Go type for slice"}
+ return
+ }
+
+ // First we iterate over the input and count the number of elements,
+ // checking that the types are correct in each case.
+ numElements := 0
+ for offset := 0; offset < len(bytes); {
+ var t tagAndLength
+ t, offset, err = parseTagAndLength(bytes, offset)
+ if err != nil {
+ return
+ }
+ switch t.tag {
+ case tagIA5String, tagGeneralString, tagT61String, tagUTF8String:
+ // We pretend that various other string types are
+ // PRINTABLE STRINGs so that a sequence of them can be
+ // parsed into a []string.
+ t.tag = tagPrintableString
+ case tagGeneralizedTime, tagUTCTime:
+ // Likewise, both time types are treated the same.
+ t.tag = tagUTCTime
+ }
+
+ if t.class != classUniversal || t.isCompound != compoundType || t.tag != expectedTag {
+ err = StructuralError{"sequence tag mismatch"}
+ return
+ }
+ if invalidLength(offset, t.length, len(bytes)) {
+ err = SyntaxError{"truncated sequence"}
+ return
+ }
+ offset += t.length
+ numElements++
+ }
+ ret = reflect.MakeSlice(sliceType, numElements, numElements)
+ params := fieldParameters{}
+ offset := 0
+ for i := 0; i < numElements; i++ {
+ offset, err = parseField(ret.Index(i), bytes, offset, params)
+ if err != nil {
+ return
+ }
+ }
+ return
+}
+
+var (
+ bitStringType = reflect.TypeOf(BitString{})
+ objectIdentifierType = reflect.TypeOf(ObjectIdentifier{})
+ enumeratedType = reflect.TypeOf(Enumerated(0))
+ flagType = reflect.TypeOf(Flag(false))
+ timeType = reflect.TypeOf(time.Time{})
+ rawValueType = reflect.TypeOf(RawValue{})
+ rawContentsType = reflect.TypeOf(RawContent(nil))
+ bigIntType = reflect.TypeOf(new(big.Int))
+)
+
+// invalidLength returns true iff offset + length > sliceLength, or if the
+// addition would overflow.
+func invalidLength(offset, length, sliceLength int) bool {
+ return offset+length < offset || offset+length > sliceLength
+}
+
+// parseField is the main parsing function. Given a byte slice and an offset
+// into the array, it will try to parse a suitable ASN.1 value out and store it
+// in the given Value.
+func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParameters) (offset int, err error) {
+ offset = initOffset
+ fieldType := v.Type()
+
+ // If we have run out of data, it may be that there are optional elements at the end.
+ if offset == len(bytes) {
+ if !setDefaultValue(v, params) {
+ err = SyntaxError{"sequence truncated"}
+ }
+ return
+ }
+
+ // Deal with raw values.
+ if fieldType == rawValueType {
+ var t tagAndLength
+ t, offset, err = parseTagAndLength(bytes, offset)
+ if err != nil {
+ return
+ }
+ if invalidLength(offset, t.length, len(bytes)) {
+ err = SyntaxError{"data truncated"}
+ return
+ }
+ result := RawValue{t.class, t.tag, t.isCompound, bytes[offset : offset+t.length], bytes[initOffset : offset+t.length]}
+ offset += t.length
+ v.Set(reflect.ValueOf(result))
+ return
+ }
+
+ // Deal with the ANY type.
+ if ifaceType := fieldType; ifaceType.Kind() == reflect.Interface && ifaceType.NumMethod() == 0 {
+ var t tagAndLength
+ t, offset, err = parseTagAndLength(bytes, offset)
+ if err != nil {
+ return
+ }
+ if invalidLength(offset, t.length, len(bytes)) {
+ err = SyntaxError{"data truncated"}
+ return
+ }
+ var result interface{}
+ if !t.isCompound && t.class == classUniversal {
+ innerBytes := bytes[offset : offset+t.length]
+ switch t.tag {
+ case tagPrintableString:
+ result, err = parsePrintableString(innerBytes)
+ case tagIA5String:
+ result, err = parseIA5String(innerBytes)
+ case tagT61String:
+ result, err = parseT61String(innerBytes)
+ case tagUTF8String:
+ result, err = parseUTF8String(innerBytes)
+ case tagInteger:
+ result, err = parseInt64(innerBytes)
+ case tagBitString:
+ result, err = parseBitString(innerBytes)
+ case tagOID:
+ result, err = parseObjectIdentifier(innerBytes)
+ case tagUTCTime:
+ result, err = parseUTCTime(innerBytes)
+ case tagOctetString:
+ result = innerBytes
+ default:
+ // If we don't know how to handle the type, we just leave Value as nil.
+ }
+ }
+ offset += t.length
+ if err != nil {
+ return
+ }
+ if result != nil {
+ v.Set(reflect.ValueOf(result))
+ }
+ return
+ }
+ universalTag, compoundType, ok1 := getUniversalType(fieldType)
+ if !ok1 {
+ err = StructuralError{fmt.Sprintf("unknown Go type: %v", fieldType)}
+ return
+ }
+
+ t, offset, err := parseTagAndLength(bytes, offset)
+ if err != nil {
+ return
+ }
+ if params.explicit {
+ expectedClass := classContextSpecific
+ if params.application {
+ expectedClass = classApplication
+ }
+ if t.class == expectedClass && t.tag == *params.tag && (t.length == 0 || t.isCompound) {
+ if t.length > 0 {
+ t, offset, err = parseTagAndLength(bytes, offset)
+ if err != nil {
+ return
+ }
+ } else {
+ if fieldType != flagType {
+ err = StructuralError{"zero length explicit tag was not an asn1.Flag"}
+ return
+ }
+ v.SetBool(true)
+ return
+ }
+ } else {
+ // The tags didn't match, it might be an optional element.
+ ok := setDefaultValue(v, params)
+ if ok {
+ offset = initOffset
+ } else {
+ err = StructuralError{"explicitly tagged member didn't match"}
+ }
+ return
+ }
+ }
+
+ // Special case for strings: all the ASN.1 string types map to the Go
+ // type string. getUniversalType returns the tag for PrintableString
+ // when it sees a string, so if we see a different string type on the
+ // wire, we change the universal type to match.
+ if universalTag == tagPrintableString {
+ if t.class == classUniversal {
+ switch t.tag {
+ case tagIA5String, tagGeneralString, tagT61String, tagUTF8String:
+ universalTag = t.tag
+ }
+ } else if params.stringType != 0 {
+ universalTag = params.stringType
+ }
+ }
+
+ // Special case for time: UTCTime and GeneralizedTime both map to the
+ // Go type time.Time.
+ if universalTag == tagUTCTime && t.tag == tagGeneralizedTime && t.class == classUniversal {
+ universalTag = tagGeneralizedTime
+ }
+
+ if params.set {
+ universalTag = tagSet
+ }
+
+ expectedClass := classUniversal
+ expectedTag := universalTag
+
+ if !params.explicit && params.tag != nil {
+ expectedClass = classContextSpecific
+ expectedTag = *params.tag
+ }
+
+ if !params.explicit && params.application && params.tag != nil {
+ expectedClass = classApplication
+ expectedTag = *params.tag
+ }
+
+ // We have unwrapped any explicit tagging at this point.
+ if t.class != expectedClass || t.tag != expectedTag || t.isCompound != compoundType {
+ // Tags don't match. Again, it could be an optional element.
+ ok := setDefaultValue(v, params)
+ if ok {
+ offset = initOffset
+ } else {
+ err = StructuralError{fmt.Sprintf("tags don't match (%d vs %+v) %+v %s @%d", expectedTag, t, params, fieldType.Name(), offset)}
+ }
+ return
+ }
+ if invalidLength(offset, t.length, len(bytes)) {
+ err = SyntaxError{"data truncated"}
+ return
+ }
+ innerBytes := bytes[offset : offset+t.length]
+ offset += t.length
+
+ // We deal with the structures defined in this package first.
+ switch fieldType {
+ case objectIdentifierType:
+ newSlice, err1 := parseObjectIdentifier(innerBytes)
+ v.Set(reflect.MakeSlice(v.Type(), len(newSlice), len(newSlice)))
+ if err1 == nil {
+ reflect.Copy(v, reflect.ValueOf(newSlice))
+ }
+ err = err1
+ return
+ case bitStringType:
+ bs, err1 := parseBitString(innerBytes)
+ if err1 == nil {
+ v.Set(reflect.ValueOf(bs))
+ }
+ err = err1
+ return
+ case timeType:
+ var time time.Time
+ var err1 error
+ if universalTag == tagUTCTime {
+ time, err1 = parseUTCTime(innerBytes)
+ } else {
+ time, err1 = parseGeneralizedTime(innerBytes)
+ }
+ if err1 == nil {
+ v.Set(reflect.ValueOf(time))
+ }
+ err = err1
+ return
+ case enumeratedType:
+ parsedInt, err1 := parseInt32(innerBytes)
+ if err1 == nil {
+ v.SetInt(int64(parsedInt))
+ }
+ err = err1
+ return
+ case flagType:
+ v.SetBool(true)
+ return
+ case bigIntType:
+ parsedInt := parseBigInt(innerBytes)
+ v.Set(reflect.ValueOf(parsedInt))
+ return
+ }
+ switch val := v; val.Kind() {
+ case reflect.Bool:
+ parsedBool, err1 := parseBool(innerBytes)
+ if err1 == nil {
+ val.SetBool(parsedBool)
+ }
+ err = err1
+ return
+ case reflect.Int, reflect.Int32, reflect.Int64:
+ if val.Type().Size() == 4 {
+ parsedInt, err1 := parseInt32(innerBytes)
+ if err1 == nil {
+ val.SetInt(int64(parsedInt))
+ }
+ err = err1
+ } else {
+ parsedInt, err1 := parseInt64(innerBytes)
+ if err1 == nil {
+ val.SetInt(parsedInt)
+ }
+ err = err1
+ }
+ return
+ // TODO(dfc) Add support for the remaining integer types
+ case reflect.Struct:
+ structType := fieldType
+
+ if structType.NumField() > 0 &&
+ structType.Field(0).Type == rawContentsType {
+ bytes := bytes[initOffset:offset]
+ val.Field(0).Set(reflect.ValueOf(RawContent(bytes)))
+ }
+
+ innerOffset := 0
+ for i := 0; i < structType.NumField(); i++ {
+ field := structType.Field(i)
+ if i == 0 && field.Type == rawContentsType {
+ continue
+ }
+ innerOffset, err = parseField(val.Field(i), innerBytes, innerOffset, parseFieldParameters(field.Tag.Get("asn1")))
+ if err != nil {
+ return
+ }
+ }
+ // We allow extra bytes at the end of the SEQUENCE because
+ // adding elements to the end has been used in X.509 as the
+ // version numbers have increased.
+ return
+ case reflect.Slice:
+ sliceType := fieldType
+ if sliceType.Elem().Kind() == reflect.Uint8 {
+ val.Set(reflect.MakeSlice(sliceType, len(innerBytes), len(innerBytes)))
+ reflect.Copy(val, reflect.ValueOf(innerBytes))
+ return
+ }
+ newSlice, err1 := parseSequenceOf(innerBytes, sliceType, sliceType.Elem())
+ if err1 == nil {
+ val.Set(newSlice)
+ }
+ err = err1
+ return
+ case reflect.String:
+ var v string
+ switch universalTag {
+ case tagPrintableString:
+ v, err = parsePrintableString(innerBytes)
+ case tagIA5String:
+ v, err = parseIA5String(innerBytes)
+ case tagT61String:
+ v, err = parseT61String(innerBytes)
+ case tagUTF8String:
+ v, err = parseUTF8String(innerBytes)
+ case tagGeneralString:
+ // GeneralString is specified in ISO-2022/ECMA-35,
+ // A brief review suggests that it includes structures
+ // that allow the encoding to change midstring and
+ // such. We give up and pass it as an 8-bit string.
+ v, err = parseT61String(innerBytes)
+ default:
+ err = SyntaxError{fmt.Sprintf("internal error: unknown string type %d", universalTag)}
+ }
+ if err == nil {
+ val.SetString(v)
+ }
+ return
+ }
+ err = StructuralError{"unsupported: " + v.Type().String()}
+ return
+}
+
+// canHaveDefaultValue reports whether k is a Kind that we will set a default
+// value for. (A signed integer, essentially.)
+func canHaveDefaultValue(k reflect.Kind) bool {
+ switch k {
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ return true
+ }
+
+ return false
+}
+
+// setDefaultValue is used to install a default value, from a tag string, into
+// a Value. It is successful if the field was optional, even if a default value
+// wasn't provided or it failed to install it into the Value.
+func setDefaultValue(v reflect.Value, params fieldParameters) (ok bool) {
+ if !params.optional {
+ return
+ }
+ ok = true
+ if params.defaultValue == nil {
+ return
+ }
+ if canHaveDefaultValue(v.Kind()) {
+ v.SetInt(*params.defaultValue)
+ }
+ return
+}
+
+// Unmarshal parses the DER-encoded ASN.1 data structure b
+// and uses the reflect package to fill in an arbitrary value pointed at by val.
+// Because Unmarshal uses the reflect package, the structs
+// being written to must use upper case field names.
+//
+// An ASN.1 INTEGER can be written to an int, int32, int64,
+// or *big.Int (from the math/big package).
+// If the encoded value does not fit in the Go type,
+// Unmarshal returns a parse error.
+//
+// An ASN.1 BIT STRING can be written to a BitString.
+//
+// An ASN.1 OCTET STRING can be written to a []byte.
+//
+// An ASN.1 OBJECT IDENTIFIER can be written to an
+// ObjectIdentifier.
+//
+// An ASN.1 ENUMERATED can be written to an Enumerated.
+//
+// An ASN.1 UTCTIME or GENERALIZEDTIME can be written to a time.Time.
+//
+// An ASN.1 PrintableString or IA5String can be written to a string.
+//
+// Any of the above ASN.1 values can be written to an interface{}.
+// The value stored in the interface has the corresponding Go type.
+// For integers, that type is int64.
+//
+// An ASN.1 SEQUENCE OF x or SET OF x can be written
+// to a slice if an x can be written to the slice's element type.
+//
+// An ASN.1 SEQUENCE or SET can be written to a struct
+// if each of the elements in the sequence can be
+// written to the corresponding element in the struct.
+//
+// The following tags on struct fields have special meaning to Unmarshal:
+//
+// application specifies that a APPLICATION tag is used
+// default:x sets the default value for optional integer fields
+// explicit specifies that an additional, explicit tag wraps the implicit one
+// optional marks the field as ASN.1 OPTIONAL
+// set causes a SET, rather than a SEQUENCE type to be expected
+// tag:x specifies the ASN.1 tag number; implies ASN.1 CONTEXT SPECIFIC
+//
+// If the type of the first field of a structure is RawContent then the raw
+// ASN1 contents of the struct will be stored in it.
+//
+// If the type name of a slice element ends with "SET" then it's treated as if
+// the "set" tag was set on it. This can be used with nested slices where a
+// struct tag cannot be given.
+//
+// Other ASN.1 types are not supported; if it encounters them,
+// Unmarshal returns a parse error.
+func Unmarshal(b []byte, val interface{}) (rest []byte, err error) {
+ return UnmarshalWithParams(b, val, "")
+}
+
+// UnmarshalWithParams allows field parameters to be specified for the
+// top-level element. The form of the params is the same as the field tags.
+func UnmarshalWithParams(b []byte, val interface{}, params string) (rest []byte, err error) {
+ v := reflect.ValueOf(val).Elem()
+ offset, err := parseField(v, b, 0, parseFieldParameters(params))
+ if err != nil {
+ return nil, err
+ }
+ return b[offset:], nil
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-03 05:47:44 +0000