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Diffstat (limited to 'src/encoding/asn1/asn1.go')
| -rw-r--r-- | src/encoding/asn1/asn1.go | 1122 |
1 files changed, 1122 insertions, 0 deletions
diff --git a/src/encoding/asn1/asn1.go b/src/encoding/asn1/asn1.go new file mode 100644 index 0000000..f9b9cb4 --- /dev/null +++ b/src/encoding/asn1/asn1.go @@ -0,0 +1,1122 @@ +// 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 ( + "errors" + "fmt" + "math" + "math/big" + "reflect" + "strconv" + "time" + "unicode/utf16" + "unicode/utf8" +) + +// 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 + +// checkInteger returns nil if the given bytes are a valid DER-encoded +// INTEGER and an error otherwise. +func checkInteger(bytes []byte) error { + if len(bytes) == 0 { + return StructuralError{"empty integer"} + } + if len(bytes) == 1 { + return nil + } + if (bytes[0] == 0 && bytes[1]&0x80 == 0) || (bytes[0] == 0xff && bytes[1]&0x80 == 0x80) { + return StructuralError{"integer not minimally-encoded"} + } + return nil +} + +// parseInt64 treats the given bytes as a big-endian, signed integer and +// returns the result. +func parseInt64(bytes []byte) (ret int64, err error) { + err = checkInteger(bytes) + if err != nil { + return + } + 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) { + if err := checkInteger(bytes); err != nil { + return 0, err + } + 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, error) { + if err := checkInteger(bytes); err != nil { + return nil, err + } + 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, nil + } + ret.SetBytes(bytes) + return ret, nil +} + +// 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 +} + +// NULL + +// NullRawValue is a RawValue with its Tag set to the ASN.1 NULL type tag (5). +var NullRawValue = RawValue{Tag: TagNull} + +// NullBytes contains bytes representing the DER-encoded ASN.1 NULL type. +var NullBytes = []byte{TagNull, 0} + +// 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 ObjectIdentifier, 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 + var ret64 int64 + for shifted := 0; offset < len(bytes); shifted++ { + // 5 * 7 bits per byte == 35 bits of data + // Thus the representation is either non-minimal or too large for an int32 + if shifted == 5 { + err = StructuralError{"base 128 integer too large"} + return + } + ret64 <<= 7 + b := bytes[offset] + // integers should be minimally encoded, so the leading octet should + // never be 0x80 + if shifted == 0 && b == 0x80 { + err = SyntaxError{"integer is not minimally encoded"} + return + } + ret64 |= int64(b & 0x7f) + offset++ + if b&0x80 == 0 { + ret = int(ret64) + // Ensure that the returned value fits in an int on all platforms + if ret64 > math.MaxInt32 { + err = StructuralError{"base 128 integer too large"} + } + return + } + } + err = SyntaxError{"truncated base 128 integer"} + return +} + +// UTCTime + +func parseUTCTime(bytes []byte) (ret time.Time, err error) { + s := string(bytes) + + formatStr := "0601021504Z0700" + ret, err = time.Parse(formatStr, s) + if err != nil { + formatStr = "060102150405Z0700" + ret, err = time.Parse(formatStr, s) + } + if err != nil { + return + } + + if serialized := ret.Format(formatStr); serialized != s { + err = fmt.Errorf("asn1: time did not serialize back to the original value and may be invalid: given %q, but serialized as %q", s, serialized) + return + } + + if 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) { + const formatStr = "20060102150405Z0700" + s := string(bytes) + + if ret, err = time.Parse(formatStr, s); err != nil { + return + } + + if serialized := ret.Format(formatStr); serialized != s { + err = fmt.Errorf("asn1: time did not serialize back to the original value and may be invalid: given %q, but serialized as %q", s, serialized) + } + + return +} + +// NumericString + +// parseNumericString parses an ASN.1 NumericString from the given byte array +// and returns it. +func parseNumericString(bytes []byte) (ret string, err error) { + for _, b := range bytes { + if !isNumeric(b) { + return "", SyntaxError{"NumericString contains invalid character"} + } + } + return string(bytes), nil +} + +// isNumeric reports whether the given b is in the ASN.1 NumericString set. +func isNumeric(b byte) bool { + return '0' <= b && b <= '9' || + b == ' ' +} + +// PrintableString + +// parsePrintableString parses an 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, allowAsterisk, allowAmpersand) { + err = SyntaxError{"PrintableString contains invalid character"} + return + } + } + ret = string(bytes) + return +} + +type asteriskFlag bool +type ampersandFlag bool + +const ( + allowAsterisk asteriskFlag = true + rejectAsterisk asteriskFlag = false + + allowAmpersand ampersandFlag = true + rejectAmpersand ampersandFlag = false +) + +// isPrintable reports whether the given b is in the ASN.1 PrintableString set. +// If asterisk is allowAsterisk then '*' is also allowed, reflecting existing +// practice. If ampersand is allowAmpersand then '&' is allowed as well. +func isPrintable(b byte, asterisk asteriskFlag, ampersand ampersandFlag) 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. + (bool(asterisk) && b == '*') || + // This is not technically allowed either. However, not + // only is it relatively common, but there are also a + // handful of CA certificates that contain it. At least + // one of which will not expire until 2027. + (bool(ampersand) && b == '&') +} + +// IA5String + +// parseIA5String parses an 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 >= utf8.RuneSelf { + err = SyntaxError{"IA5String contains invalid character"} + return + } + } + ret = string(bytes) + return +} + +// T61String + +// parseT61String parses an 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 an ASN.1 UTF8String (raw UTF-8) from the given byte +// array and returns it. +func parseUTF8String(bytes []byte) (ret string, err error) { + if !utf8.Valid(bytes) { + return "", errors.New("asn1: invalid UTF-8 string") + } + return string(bytes), nil +} + +// BMPString + +// parseBMPString parses an ASN.1 BMPString (Basic Multilingual Plane of +// ISO/IEC/ITU 10646-1) from the given byte slice and returns it. +func parseBMPString(bmpString []byte) (string, error) { + if len(bmpString)%2 != 0 { + return "", errors.New("pkcs12: odd-length BMP string") + } + + // Strip terminator if present. + if l := len(bmpString); l >= 2 && bmpString[l-1] == 0 && bmpString[l-2] == 0 { + bmpString = bmpString[:l-2] + } + + s := make([]uint16, 0, len(bmpString)/2) + for len(bmpString) > 0 { + s = append(s, uint16(bmpString[0])<<8+uint16(bmpString[1])) + bmpString = bmpString[2:] + } + + return string(utf16.Decode(s)), 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 + // parseTagAndLength should not be called without at least a single + // byte to read. Thus this check is for robustness: + if offset >= len(bytes) { + err = errors.New("asn1: internal error in parseTagAndLength") + return + } + 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 + } + // Tags should be encoded in minimal form. + if ret.tag < 0x1f { + err = SyntaxError{"non-minimal tag"} + 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 + } + } + // Short lengths must be encoded in short form. + if ret.length < 0x80 { + err = StructuralError{"non-minimal 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) { + matchAny, 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, TagNumericString, TagBMPString: + // 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 !matchAny && (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 reports whether 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 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 TagNumericString: + result, err = parseNumericString(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 TagGeneralizedTime: + result, err = parseGeneralizedTime(innerBytes) + case TagOctetString: + result = innerBytes + case TagBMPString: + result, err = parseBMPString(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 + } + + t, offset, err := parseTagAndLength(bytes, offset) + if err != nil { + return + } + if params.explicit { + expectedClass := ClassContextSpecific + if params.application { + expectedClass = ClassApplication + } + if offset == len(bytes) { + err = StructuralError{"explicit tag has no child"} + return + } + if t.class == expectedClass && t.tag == *params.tag && (t.length == 0 || t.isCompound) { + if fieldType == rawValueType { + // The inner element should not be parsed for RawValues. + } else 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 + } + } + + matchAny, universalTag, compoundType, ok1 := getUniversalType(fieldType) + if !ok1 { + err = StructuralError{fmt.Sprintf("unknown Go type: %v", fieldType)} + 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, TagNumericString, TagBMPString: + 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 + } + + matchAnyClassAndTag := matchAny + expectedClass := ClassUniversal + expectedTag := universalTag + + if !params.explicit && params.tag != nil { + expectedClass = ClassContextSpecific + expectedTag = *params.tag + matchAnyClassAndTag = false + } + + if !params.explicit && params.application && params.tag != nil { + expectedClass = ClassApplication + expectedTag = *params.tag + matchAnyClassAndTag = false + } + + if !params.explicit && params.private && params.tag != nil { + expectedClass = ClassPrivate + expectedTag = *params.tag + matchAnyClassAndTag = false + } + + // We have unwrapped any explicit tagging at this point. + if !matchAnyClassAndTag && (t.class != expectedClass || t.tag != expectedTag) || + (!matchAny && 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 v := v.Addr().Interface().(type) { + case *RawValue: + *v = RawValue{t.class, t.tag, t.isCompound, innerBytes, bytes[initOffset:offset]} + return + case *ObjectIdentifier: + *v, err = parseObjectIdentifier(innerBytes) + return + case *BitString: + *v, err = parseBitString(innerBytes) + return + case *time.Time: + if universalTag == TagUTCTime { + *v, err = parseUTCTime(innerBytes) + return + } + *v, err = parseGeneralizedTime(innerBytes) + return + case *Enumerated: + parsedInt, err1 := parseInt32(innerBytes) + if err1 == nil { + *v = Enumerated(parsedInt) + } + err = err1 + return + case *Flag: + *v = true + return + case **big.Int: + parsedInt, err1 := parseBigInt(innerBytes) + if err1 == nil { + *v = parsedInt + } + err = err1 + 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 + + for i := 0; i < structType.NumField(); i++ { + if structType.Field(i).PkgPath != "" { + err = StructuralError{"struct contains unexported fields"} + return + } + } + + 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 TagNumericString: + v, err = parseNumericString(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) + case TagBMPString: + v, err = parseBMPString(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. If val +// is nil or not a pointer, Unmarshal returns an error. +// +// After parsing b, any bytes that were leftover and not used to fill +// val will be returned in rest. When parsing a SEQUENCE into a struct, +// any trailing elements of the SEQUENCE that do not have matching +// fields in val will not be included in rest, as these are considered +// valid elements of the SEQUENCE and not trailing data. +// +// 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, IA5String, or NumericString 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 an APPLICATION tag is used +// private specifies that a PRIVATE tag is used +// default:x sets the default value for optional integer fields (only used if optional is also present) +// 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 +// +// When decoding an ASN.1 value with an IMPLICIT tag into a string field, +// Unmarshal will default to a PrintableString, which doesn't support +// characters such as '@' and '&'. To force other encodings, use the following +// tags: +// +// ia5 causes strings to be unmarshaled as ASN.1 IA5String values +// numeric causes strings to be unmarshaled as ASN.1 NumericString values +// utf8 causes strings to be unmarshaled as ASN.1 UTF8String values +// +// 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 name of a slice type ends with "SET" then it's treated as if +// the "set" tag was set on it. This results in interpreting the type as a +// SET OF x rather than a SEQUENCE OF x. 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, "") +} + +// An invalidUnmarshalError describes an invalid argument passed to Unmarshal. +// (The argument to Unmarshal must be a non-nil pointer.) +type invalidUnmarshalError struct { + Type reflect.Type +} + +func (e *invalidUnmarshalError) Error() string { + if e.Type == nil { + return "asn1: Unmarshal recipient value is nil" + } + + if e.Type.Kind() != reflect.Ptr { + return "asn1: Unmarshal recipient value is non-pointer " + e.Type.String() + } + return "asn1: Unmarshal recipient value is nil " + e.Type.String() +} + +// 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) + if v.Kind() != reflect.Ptr || v.IsNil() { + return nil, &invalidUnmarshalError{reflect.TypeOf(val)} + } + offset, err := parseField(v.Elem(), b, 0, parseFieldParameters(params)) + if err != nil { + return nil, err + } + return b[offset:], nil +} |