/usr/share/gocode/src/golang.org/x/crypto/cryptobyte/asn1.go is in golang-golang-x-crypto-dev 1:0.0~git20170629.0.5ef0053-2.
This file is owned by root:root, with mode 0o644.
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// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cryptobyte
import (
"encoding/asn1"
"fmt"
"math/big"
"reflect"
"time"
)
// This file contains ASN.1-related methods for String and Builder.
// Tag represents an ASN.1 tag number and class (together also referred to as
// identifier octets). Methods in this package only support the low-tag-number
// form, i.e. a single identifier octet with bits 7-8 encoding the class and
// bits 1-6 encoding the tag number.
type Tag uint8
// Contructed returns t with the context-specific class bit set.
func (t Tag) ContextSpecific() Tag { return t | 0x80 }
// Contructed returns t with the constructed class bit set.
func (t Tag) Constructed() Tag { return t | 0x20 }
// Builder
// AddASN1Int64 appends a DER-encoded ASN.1 INTEGER.
func (b *Builder) AddASN1Int64(v int64) {
b.addASN1Signed(asn1.TagInteger, v)
}
// AddASN1Enum appends a DER-encoded ASN.1 ENUMERATION.
func (b *Builder) AddASN1Enum(v int64) {
b.addASN1Signed(asn1.TagEnum, v)
}
func (b *Builder) addASN1Signed(tag Tag, v int64) {
b.AddASN1(tag, func(c *Builder) {
length := 1
for i := v; i >= 0x80 || i < -0x80; i >>= 8 {
length++
}
for ; length > 0; length-- {
i := v >> uint((length-1)*8) & 0xff
c.AddUint8(uint8(i))
}
})
}
// AddASN1Uint64 appends a DER-encoded ASN.1 INTEGER.
func (b *Builder) AddASN1Uint64(v uint64) {
b.AddASN1(asn1.TagInteger, func(c *Builder) {
length := 1
for i := v; i >= 0x80; i >>= 8 {
length++
}
for ; length > 0; length-- {
i := v >> uint((length-1)*8) & 0xff
c.AddUint8(uint8(i))
}
})
}
// AddASN1BigInt appends a DER-encoded ASN.1 INTEGER.
func (b *Builder) AddASN1BigInt(n *big.Int) {
if b.err != nil {
return
}
b.AddASN1(asn1.TagInteger, func(c *Builder) {
if n.Sign() < 0 {
// A negative number has to be converted to two's-complement form. So we
// invert and subtract 1. 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 bytes[0]&0x80 == 0 {
c.add(0xff)
}
c.add(bytes...)
} else if n.Sign() == 0 {
c.add(0)
} else {
bytes := n.Bytes()
if bytes[0]&0x80 != 0 {
c.add(0)
}
c.add(bytes...)
}
})
}
// AddASN1OctetString appends a DER-encoded ASN.1 OCTET STRING.
func (b *Builder) AddASN1OctetString(bytes []byte) {
b.AddASN1(asn1.TagOctetString, func(c *Builder) {
c.AddBytes(bytes)
})
}
const generalizedTimeFormatStr = "20060102150405Z0700"
// AddASN1GeneralizedTime appends a DER-encoded ASN.1 GENERALIZEDTIME.
func (b *Builder) AddASN1GeneralizedTime(t time.Time) {
if t.Year() < 0 || t.Year() > 9999 {
b.err = fmt.Errorf("cryptobyte: cannot represent %v as a GeneralizedTime", t)
return
}
b.AddASN1(asn1.TagGeneralizedTime, func(c *Builder) {
c.AddBytes([]byte(t.Format(generalizedTimeFormatStr)))
})
}
// AddASN1BitString appends a DER-encoded ASN.1 BIT STRING.
func (b *Builder) AddASN1BitString(s asn1.BitString) {
// TODO(martinkr): Implement.
b.MarshalASN1(s)
}
// MarshalASN1 calls asn1.Marshal on its input and appends the result if
// successful or records an error if one occurred.
func (b *Builder) MarshalASN1(v interface{}) {
// NOTE(martinkr): This is somewhat of a hack to allow propagation of
// asn1.Marshal errors into Builder.err. N.B. if you call MarshalASN1 with a
// value embedded into a struct, its tag information is lost.
if b.err != nil {
return
}
bytes, err := asn1.Marshal(v)
if err != nil {
b.err = err
return
}
b.AddBytes(bytes)
}
// AddASN1 appends an ASN.1 object. The object is prefixed with the given tag.
// Tags greater than 30 are not supported and result in an error (i.e.
// low-tag-number form only). The child builder passed to the
// BuilderContinuation can be used to build the content of the ASN.1 object.
func (b *Builder) AddASN1(tag Tag, f BuilderContinuation) {
if b.err != nil {
return
}
// Identifiers with the low five bits set indicate high-tag-number format
// (two or more octets), which we don't support.
if tag&0x1f == 0x1f {
b.err = fmt.Errorf("cryptobyte: high-tag number identifier octects not supported: 0x%x", tag)
return
}
b.AddUint8(uint8(tag))
b.addLengthPrefixed(1, true, f)
}
// String
var bigIntType = reflect.TypeOf((*big.Int)(nil)).Elem()
// ReadASN1Integer decodes an ASN.1 INTEGER into out and advances. If out does
// not point to an integer or to a big.Int, it panics. It returns true on
// success and false on error.
func (s *String) ReadASN1Integer(out interface{}) bool {
if reflect.TypeOf(out).Kind() != reflect.Ptr {
panic("out is not a pointer")
}
switch reflect.ValueOf(out).Elem().Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
var i int64
if !s.readASN1Int64(&i) || reflect.ValueOf(out).Elem().OverflowInt(i) {
return false
}
reflect.ValueOf(out).Elem().SetInt(i)
return true
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
var u uint64
if !s.readASN1Uint64(&u) || reflect.ValueOf(out).Elem().OverflowUint(u) {
return false
}
reflect.ValueOf(out).Elem().SetUint(u)
return true
case reflect.Struct:
if reflect.TypeOf(out).Elem() == bigIntType {
return s.readASN1BigInt(out.(*big.Int))
}
}
panic("out does not point to an integer type")
}
func checkASN1Integer(bytes []byte) bool {
if len(bytes) == 0 {
// An INTEGER is encoded with at least one octet.
return false
}
if len(bytes) == 1 {
return true
}
if bytes[0] == 0 && bytes[1]&0x80 == 0 || bytes[0] == 0xff && bytes[1]&0x80 == 0x80 {
// Value is not minimally encoded.
return false
}
return true
}
var bigOne = big.NewInt(1)
func (s *String) readASN1BigInt(out *big.Int) bool {
var bytes String
if !s.ReadASN1(&bytes, asn1.TagInteger) || !checkASN1Integer(bytes) {
return false
}
if bytes[0]&0x80 == 0x80 {
// Negative number.
neg := make([]byte, len(bytes))
for i, b := range bytes {
neg[i] = ^b
}
out.SetBytes(neg)
out.Add(out, bigOne)
out.Neg(out)
} else {
out.SetBytes(bytes)
}
return true
}
func (s *String) readASN1Int64(out *int64) bool {
var bytes String
if !s.ReadASN1(&bytes, asn1.TagInteger) || !checkASN1Integer(bytes) || !asn1Signed(out, bytes) {
return false
}
return true
}
func asn1Signed(out *int64, n []byte) bool {
length := len(n)
if length > 8 {
return false
}
for i := 0; i < length; i++ {
*out <<= 8
*out |= int64(n[i])
}
// Shift up and down in order to sign extend the result.
*out <<= 64 - uint8(length)*8
*out >>= 64 - uint8(length)*8
return true
}
func (s *String) readASN1Uint64(out *uint64) bool {
var bytes String
if !s.ReadASN1(&bytes, asn1.TagInteger) || !checkASN1Integer(bytes) || !asn1Unsigned(out, bytes) {
return false
}
return true
}
func asn1Unsigned(out *uint64, n []byte) bool {
length := len(n)
if length > 9 || length == 9 && n[0] != 0 {
// Too large for uint64.
return false
}
if n[0]&0x80 != 0 {
// Negative number.
return false
}
for i := 0; i < length; i++ {
*out <<= 8
*out |= uint64(n[i])
}
return true
}
// ReadASN1Enum decodes an ASN.1 ENUMERATION into out and advances. It returns
// true on success and false on error.
func (s *String) ReadASN1Enum(out *int) bool {
var bytes String
var i int64
if !s.ReadASN1(&bytes, asn1.TagEnum) || !checkASN1Integer(bytes) || !asn1Signed(&i, bytes) {
return false
}
if int64(int(i)) != i {
return false
}
*out = int(i)
return true
}
func (s *String) readBase128Int(out *int) bool {
ret := 0
for i := 0; len(*s) > 0; i++ {
if i == 4 {
return false
}
ret <<= 7
b := s.read(1)[0]
ret |= int(b & 0x7f)
if b&0x80 == 0 {
*out = ret
return true
}
}
return false // truncated
}
// ReadASN1ObjectIdentifier decodes an ASN.1 OBJECT IDENTIFIER into out and
// advances. It returns true on success and false on error.
func (s *String) ReadASN1ObjectIdentifier(out *asn1.ObjectIdentifier) bool {
var bytes String
if !s.ReadASN1(&bytes, asn1.TagOID) || len(bytes) == 0 {
return false
}
// 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.
components := 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.
var v int
if !bytes.readBase128Int(&v) {
return false
}
if v < 80 {
components[0] = v / 40
components[1] = v % 40
} else {
components[0] = 2
components[1] = v - 80
}
i := 2
for ; len(bytes) > 0; i++ {
if !bytes.readBase128Int(&v) {
return false
}
components[i] = v
}
*out = components[:i]
return true
}
// ReadASN1GeneralizedTime decodes an ASN.1 GENERALIZEDTIME into out and
// advances. It returns true on success and false on error.
func (s *String) ReadASN1GeneralizedTime(out *time.Time) bool {
var bytes String
if !s.ReadASN1(&bytes, asn1.TagGeneralizedTime) {
return false
}
t := string(bytes)
res, err := time.Parse(generalizedTimeFormatStr, t)
if err != nil {
return false
}
if serialized := res.Format(generalizedTimeFormatStr); serialized != t {
return false
}
*out = res
return true
}
// ReadASN1BitString decodes an ASN.1 BIT STRING into out and advances. It
// returns true on success and false on error.
func (s *String) ReadASN1BitString(out *asn1.BitString) bool {
var bytes String
if !s.ReadASN1(&bytes, asn1.TagBitString) || len(bytes) == 0 {
return false
}
paddingBits := uint8(bytes[0])
bytes = bytes[1:]
if paddingBits > 7 ||
len(bytes) == 0 && paddingBits != 0 ||
len(bytes) > 0 && bytes[len(bytes)-1]&(1<<paddingBits-1) != 0 {
return false
}
out.BitLength = len(bytes)*8 - int(paddingBits)
out.Bytes = bytes
return true
}
// ReadASN1Bytes reads the contents of a DER-encoded ASN.1 element (not including
// tag and length bytes) into out, and advances. The element must match the
// given tag. It returns true on success and false on error.
func (s *String) ReadASN1Bytes(out *[]byte, tag Tag) bool {
return s.ReadASN1((*String)(out), tag)
}
// ReadASN1 reads the contents of a DER-encoded ASN.1 element (not including
// tag and length bytes) into out, and advances. The element must match the
// given tag. It returns true on success and false on error.
//
// Tags greater than 30 are not supported (i.e. low-tag-number format only).
func (s *String) ReadASN1(out *String, tag Tag) bool {
var t Tag
if !s.ReadAnyASN1(out, &t) || t != tag {
return false
}
return true
}
// ReadASN1Element reads the contents of a DER-encoded ASN.1 element (including
// tag and length bytes) into out, and advances. The element must match the
// given tag. It returns true on success and false on error.
//
// Tags greater than 30 are not supported (i.e. low-tag-number format only).
func (s *String) ReadASN1Element(out *String, tag Tag) bool {
var t Tag
if !s.ReadAnyASN1Element(out, &t) || t != tag {
return false
}
return true
}
// ReadAnyASN1 reads the contents of a DER-encoded ASN.1 element (not including
// tag and length bytes) into out, sets outTag to its tag, and advances. It
// returns true on success and false on error.
//
// Tags greater than 30 are not supported (i.e. low-tag-number format only).
func (s *String) ReadAnyASN1(out *String, outTag *Tag) bool {
return s.readASN1(out, outTag, true /* skip header */)
}
// ReadAnyASN1Element reads the contents of a DER-encoded ASN.1 element
// (including tag and length bytes) into out, sets outTag to is tag, and
// advances. It returns true on success and false on error.
//
// Tags greater than 30 are not supported (i.e. low-tag-number format only).
func (s *String) ReadAnyASN1Element(out *String, outTag *Tag) bool {
return s.readASN1(out, outTag, false /* include header */)
}
// PeekASN1Tag returns true if the next ASN.1 value on the string starts with
// the given tag.
func (s String) PeekASN1Tag(tag Tag) bool {
if len(s) == 0 {
return false
}
return Tag(s[0]) == tag
}
// ReadOptionalASN1 attempts to read the contents of a DER-encoded ASN.Element
// (not including tag and length bytes) tagged with the given tag into out. It
// stores whether an element with the tag was found in outPresent, unless
// outPresent is nil. It returns true on success and false on error.
func (s *String) ReadOptionalASN1(out *String, outPresent *bool, tag Tag) bool {
present := s.PeekASN1Tag(tag)
if outPresent != nil {
*outPresent = present
}
if present && !s.ReadASN1(out, tag) {
return false
}
return true
}
// ReadOptionalASN1Integer attempts to read an optional ASN.1 INTEGER
// explicitly tagged with tag into out and advances. If no element with a
// matching tag is present, it writes defaultValue into out instead. If out
// does not point to an integer or to a big.Int, it panics. It returns true on
// success and false on error.
func (s *String) ReadOptionalASN1Integer(out interface{}, tag Tag, defaultValue interface{}) bool {
if reflect.TypeOf(out).Kind() != reflect.Ptr {
panic("out is not a pointer")
}
var present bool
var i String
if !s.ReadOptionalASN1(&i, &present, tag) {
return false
}
if !present {
switch reflect.ValueOf(out).Elem().Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
reflect.ValueOf(out).Elem().Set(reflect.ValueOf(defaultValue))
case reflect.Struct:
if reflect.TypeOf(out).Elem() != bigIntType {
panic("invalid integer type")
}
if reflect.TypeOf(defaultValue).Kind() != reflect.Ptr ||
reflect.TypeOf(defaultValue).Elem() != bigIntType {
panic("out points to big.Int, but defaultValue does not")
}
out.(*big.Int).Set(defaultValue.(*big.Int))
default:
panic("invalid integer type")
}
return true
}
if !i.ReadASN1Integer(out) || !i.Empty() {
return false
}
return true
}
// ReadOptionalASN1OctetString attempts to read an optional ASN.1 OCTET STRING
// explicitly tagged with tag into out and advances. If no element with a
// matching tag is present, it writes defaultValue into out instead. It returns
// true on success and false on error.
func (s *String) ReadOptionalASN1OctetString(out *[]byte, outPresent *bool, tag Tag) bool {
var present bool
var child String
if !s.ReadOptionalASN1(&child, &present, tag) {
return false
}
if outPresent != nil {
*outPresent = present
}
if present {
var oct String
if !child.ReadASN1(&oct, asn1.TagOctetString) || !child.Empty() {
return false
}
*out = oct
} else {
*out = nil
}
return true
}
func (s *String) readASN1(out *String, outTag *Tag, skipHeader bool) bool {
if len(*s) < 2 {
return false
}
tag, lenByte := (*s)[0], (*s)[1]
if tag&0x1f == 0x1f {
// ITU-T X.690 section 8.1.2
//
// An identifier octet with a tag part of 0x1f indicates a high-tag-number
// form identifier with two or more octets. We only support tags less than
// 31 (i.e. low-tag-number form, single octet identifier).
return false
}
if outTag != nil {
*outTag = Tag(tag)
}
// ITU-T X.690 section 8.1.3
//
// Bit 8 of the first length byte indicates whether the length is short- or
// long-form.
var length, headerLen uint32 // length includes headerLen
if lenByte&0x80 == 0 {
// Short-form length (section 8.1.3.4), encoded in bits 1-7.
length = uint32(lenByte) + 2
headerLen = 2
} else {
// Long-form length (section 8.1.3.5). Bits 1-7 encode the number of octets
// used to encode the length.
lenLen := lenByte & 0x7f
var len32 uint32
if lenLen == 0 || lenLen > 4 || len(*s) < int(2+lenLen) {
return false
}
lenBytes := String((*s)[2 : 2+lenLen])
if !lenBytes.readUnsigned(&len32, int(lenLen)) {
return false
}
// ITU-T X.690 section 10.1 (DER length forms) requires encoding the length
// with the minimum number of octets.
if len32 < 128 {
// Length should have used short-form encoding.
return false
}
if len32>>((lenLen-1)*8) == 0 {
// Leading octet is 0. Length should have been at least one byte shorter.
return false
}
headerLen = 2 + uint32(lenLen)
if headerLen+len32 < len32 {
// Overflow.
return false
}
length = headerLen + len32
}
if uint32(int(length)) != length || !s.ReadBytes((*[]byte)(out), int(length)) {
return false
}
if skipHeader && !out.Skip(int(headerLen)) {
panic("cryptobyte: internal error")
}
return true
}
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