605 lines
16 KiB
Go
605 lines
16 KiB
Go
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// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package cryptobyte
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import (
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"encoding/asn1"
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"fmt"
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"math/big"
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"reflect"
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"time"
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)
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// This file contains ASN.1-related methods for String and Builder.
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// Tag represents an ASN.1 tag number and class (together also referred to as
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// identifier octets). Methods in this package only support the low-tag-number
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// form, i.e. a single identifier octet with bits 7-8 encoding the class and
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// bits 1-6 encoding the tag number.
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type Tag uint8
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// Contructed returns t with the context-specific class bit set.
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func (t Tag) ContextSpecific() Tag { return t | 0x80 }
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// Contructed returns t with the constructed class bit set.
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func (t Tag) Constructed() Tag { return t | 0x20 }
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// Builder
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// AddASN1Int64 appends a DER-encoded ASN.1 INTEGER.
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func (b *Builder) AddASN1Int64(v int64) {
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b.addASN1Signed(asn1.TagInteger, v)
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}
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// AddASN1Enum appends a DER-encoded ASN.1 ENUMERATION.
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func (b *Builder) AddASN1Enum(v int64) {
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b.addASN1Signed(asn1.TagEnum, v)
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}
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func (b *Builder) addASN1Signed(tag Tag, v int64) {
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b.AddASN1(tag, func(c *Builder) {
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length := 1
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for i := v; i >= 0x80 || i < -0x80; i >>= 8 {
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length++
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}
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for ; length > 0; length-- {
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i := v >> uint((length-1)*8) & 0xff
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c.AddUint8(uint8(i))
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}
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})
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}
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// AddASN1Uint64 appends a DER-encoded ASN.1 INTEGER.
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func (b *Builder) AddASN1Uint64(v uint64) {
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b.AddASN1(asn1.TagInteger, func(c *Builder) {
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length := 1
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for i := v; i >= 0x80; i >>= 8 {
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length++
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}
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for ; length > 0; length-- {
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i := v >> uint((length-1)*8) & 0xff
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c.AddUint8(uint8(i))
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}
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})
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}
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// AddASN1BigInt appends a DER-encoded ASN.1 INTEGER.
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func (b *Builder) AddASN1BigInt(n *big.Int) {
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if b.err != nil {
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return
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}
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b.AddASN1(asn1.TagInteger, func(c *Builder) {
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if n.Sign() < 0 {
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// A negative number has to be converted to two's-complement form. So we
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// invert and subtract 1. If the most-significant-bit isn't set then
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// we'll need to pad the beginning with 0xff in order to keep the number
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// negative.
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nMinus1 := new(big.Int).Neg(n)
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nMinus1.Sub(nMinus1, bigOne)
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bytes := nMinus1.Bytes()
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for i := range bytes {
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bytes[i] ^= 0xff
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}
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if bytes[0]&0x80 == 0 {
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c.add(0xff)
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}
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c.add(bytes...)
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} else if n.Sign() == 0 {
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c.add(0)
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} else {
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bytes := n.Bytes()
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if bytes[0]&0x80 != 0 {
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c.add(0)
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}
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c.add(bytes...)
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}
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})
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}
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// AddASN1OctetString appends a DER-encoded ASN.1 OCTET STRING.
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func (b *Builder) AddASN1OctetString(bytes []byte) {
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b.AddASN1(asn1.TagOctetString, func(c *Builder) {
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c.AddBytes(bytes)
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})
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}
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const generalizedTimeFormatStr = "20060102150405Z0700"
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// AddASN1GeneralizedTime appends a DER-encoded ASN.1 GENERALIZEDTIME.
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func (b *Builder) AddASN1GeneralizedTime(t time.Time) {
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if t.Year() < 0 || t.Year() > 9999 {
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b.err = fmt.Errorf("cryptobyte: cannot represent %v as a GeneralizedTime", t)
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return
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}
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b.AddASN1(asn1.TagGeneralizedTime, func(c *Builder) {
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c.AddBytes([]byte(t.Format(generalizedTimeFormatStr)))
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})
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}
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// AddASN1BitString appends a DER-encoded ASN.1 BIT STRING.
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func (b *Builder) AddASN1BitString(s asn1.BitString) {
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// TODO(martinkr): Implement.
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b.MarshalASN1(s)
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}
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// MarshalASN1 calls asn1.Marshal on its input and appends the result if
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// successful or records an error if one occurred.
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func (b *Builder) MarshalASN1(v interface{}) {
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// NOTE(martinkr): This is somewhat of a hack to allow propagation of
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// asn1.Marshal errors into Builder.err. N.B. if you call MarshalASN1 with a
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// value embedded into a struct, its tag information is lost.
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if b.err != nil {
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return
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}
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bytes, err := asn1.Marshal(v)
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if err != nil {
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b.err = err
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return
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}
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b.AddBytes(bytes)
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}
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// AddASN1 appends an ASN.1 object. The object is prefixed with the given tag.
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// Tags greater than 30 are not supported and result in an error (i.e.
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// low-tag-number form only). The child builder passed to the
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// BuilderContinuation can be used to build the content of the ASN.1 object.
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func (b *Builder) AddASN1(tag Tag, f BuilderContinuation) {
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if b.err != nil {
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return
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}
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// Identifiers with the low five bits set indicate high-tag-number format
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// (two or more octets), which we don't support.
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if tag&0x1f == 0x1f {
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b.err = fmt.Errorf("cryptobyte: high-tag number identifier octects not supported: 0x%x", tag)
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return
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}
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b.AddUint8(uint8(tag))
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b.addLengthPrefixed(1, true, f)
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}
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// String
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var bigIntType = reflect.TypeOf((*big.Int)(nil)).Elem()
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// ReadASN1Integer decodes an ASN.1 INTEGER into out and advances. If out does
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// not point to an integer or to a big.Int, it panics. It returns true on
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// success and false on error.
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func (s *String) ReadASN1Integer(out interface{}) bool {
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if reflect.TypeOf(out).Kind() != reflect.Ptr {
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panic("out is not a pointer")
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}
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switch reflect.ValueOf(out).Elem().Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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var i int64
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if !s.readASN1Int64(&i) || reflect.ValueOf(out).Elem().OverflowInt(i) {
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return false
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}
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reflect.ValueOf(out).Elem().SetInt(i)
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return true
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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var u uint64
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if !s.readASN1Uint64(&u) || reflect.ValueOf(out).Elem().OverflowUint(u) {
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return false
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}
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reflect.ValueOf(out).Elem().SetUint(u)
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return true
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case reflect.Struct:
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if reflect.TypeOf(out).Elem() == bigIntType {
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return s.readASN1BigInt(out.(*big.Int))
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}
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}
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panic("out does not point to an integer type")
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}
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func checkASN1Integer(bytes []byte) bool {
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if len(bytes) == 0 {
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// An INTEGER is encoded with at least one octet.
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return false
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}
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if len(bytes) == 1 {
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return true
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}
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if bytes[0] == 0 && bytes[1]&0x80 == 0 || bytes[0] == 0xff && bytes[1]&0x80 == 0x80 {
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// Value is not minimally encoded.
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return false
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}
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return true
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}
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var bigOne = big.NewInt(1)
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func (s *String) readASN1BigInt(out *big.Int) bool {
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var bytes String
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if !s.ReadASN1(&bytes, asn1.TagInteger) || !checkASN1Integer(bytes) {
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return false
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}
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if bytes[0]&0x80 == 0x80 {
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// Negative number.
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neg := make([]byte, len(bytes))
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for i, b := range bytes {
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neg[i] = ^b
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}
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out.SetBytes(neg)
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out.Add(out, bigOne)
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out.Neg(out)
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} else {
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out.SetBytes(bytes)
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}
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return true
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}
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func (s *String) readASN1Int64(out *int64) bool {
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var bytes String
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if !s.ReadASN1(&bytes, asn1.TagInteger) || !checkASN1Integer(bytes) || !asn1Signed(out, bytes) {
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return false
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}
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return true
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}
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func asn1Signed(out *int64, n []byte) bool {
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length := len(n)
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if length > 8 {
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return false
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}
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for i := 0; i < length; i++ {
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*out <<= 8
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*out |= int64(n[i])
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}
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// Shift up and down in order to sign extend the result.
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*out <<= 64 - uint8(length)*8
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*out >>= 64 - uint8(length)*8
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return true
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}
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func (s *String) readASN1Uint64(out *uint64) bool {
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var bytes String
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if !s.ReadASN1(&bytes, asn1.TagInteger) || !checkASN1Integer(bytes) || !asn1Unsigned(out, bytes) {
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return false
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}
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return true
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}
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func asn1Unsigned(out *uint64, n []byte) bool {
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length := len(n)
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if length > 9 || length == 9 && n[0] != 0 {
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// Too large for uint64.
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return false
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}
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if n[0]&0x80 != 0 {
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// Negative number.
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return false
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}
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for i := 0; i < length; i++ {
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*out <<= 8
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*out |= uint64(n[i])
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}
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return true
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}
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// ReadASN1Enum decodes an ASN.1 ENUMERATION into out and advances. It returns
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// true on success and false on error.
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func (s *String) ReadASN1Enum(out *int) bool {
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var bytes String
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var i int64
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if !s.ReadASN1(&bytes, asn1.TagEnum) || !checkASN1Integer(bytes) || !asn1Signed(&i, bytes) {
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return false
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}
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if int64(int(i)) != i {
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return false
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}
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*out = int(i)
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return true
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}
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func (s *String) readBase128Int(out *int) bool {
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ret := 0
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for i := 0; len(*s) > 0; i++ {
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if i == 4 {
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return false
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}
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ret <<= 7
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b := s.read(1)[0]
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ret |= int(b & 0x7f)
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if b&0x80 == 0 {
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*out = ret
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return true
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}
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}
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return false // truncated
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}
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// ReadASN1ObjectIdentifier decodes an ASN.1 OBJECT IDENTIFIER into out and
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// advances. It returns true on success and false on error.
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func (s *String) ReadASN1ObjectIdentifier(out *asn1.ObjectIdentifier) bool {
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var bytes String
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if !s.ReadASN1(&bytes, asn1.TagOID) || len(bytes) == 0 {
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return false
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}
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// In the worst case, we get two elements from the first byte (which is
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// encoded differently) and then every varint is a single byte long.
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components := make([]int, len(bytes)+1)
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// The first varint is 40*value1 + value2:
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// According to this packing, value1 can take the values 0, 1 and 2 only.
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// When value1 = 0 or value1 = 1, then value2 is <= 39. When value1 = 2,
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// then there are no restrictions on value2.
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var v int
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if !bytes.readBase128Int(&v) {
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return false
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}
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if v < 80 {
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components[0] = v / 40
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components[1] = v % 40
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} else {
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components[0] = 2
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components[1] = v - 80
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}
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i := 2
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for ; len(bytes) > 0; i++ {
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if !bytes.readBase128Int(&v) {
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return false
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}
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components[i] = v
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}
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*out = components[:i]
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return true
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}
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// ReadASN1GeneralizedTime decodes an ASN.1 GENERALIZEDTIME into out and
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// advances. It returns true on success and false on error.
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func (s *String) ReadASN1GeneralizedTime(out *time.Time) bool {
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var bytes String
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if !s.ReadASN1(&bytes, asn1.TagGeneralizedTime) {
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return false
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}
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t := string(bytes)
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res, err := time.Parse(generalizedTimeFormatStr, t)
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if err != nil {
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return false
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}
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if serialized := res.Format(generalizedTimeFormatStr); serialized != t {
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return false
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}
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*out = res
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return true
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}
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|
|
|
||
|
|
// 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
|
||
|
|
}
|