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22507adf54
This makes connectivity between ancient and new tailscale nodes slightly worse in some cases, but only in cases where the ancient version would likely have failed to get connectivity anyway. Signed-off-by: David Anderson <danderson@tailscale.com>
125 lines
3.2 KiB
Go
125 lines
3.2 KiB
Go
// Copyright (c) 2020 Tailscale Inc & 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 key defines some types related to curve25519 keys.
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package key
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import (
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crand "crypto/rand"
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"encoding/base64"
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"errors"
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"fmt"
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"io"
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"go4.org/mem"
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"golang.org/x/crypto/curve25519"
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)
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// Private represents a curve25519 private key.
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type Private [32]byte
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// Private reports whether p is the zero value.
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func (p Private) IsZero() bool { return p == Private{} }
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// NewPrivate returns a new private key.
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func NewPrivate() Private {
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var p Private
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if _, err := io.ReadFull(crand.Reader, p[:]); err != nil {
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panic(err)
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}
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p[0] &= 248
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p[31] = (p[31] & 127) | 64
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return p
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}
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// B32 returns k as the *[32]byte type that's used by the
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// golang.org/x/crypto packages. This allocates; it might
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// not be appropriate for performance-sensitive paths.
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func (k Private) B32() *[32]byte { return (*[32]byte)(&k) }
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// Public represents a curve25519 public key.
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type Public [32]byte
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// Public reports whether p is the zero value.
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func (p Public) IsZero() bool { return p == Public{} }
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// ShortString returns the Tailscale conventional debug representation
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// of a public key: the first five base64 digits of the key, in square
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// brackets.
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func (p Public) ShortString() string {
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return "[" + base64.StdEncoding.EncodeToString(p[:])[:5] + "]"
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}
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func (p Public) MarshalText() ([]byte, error) {
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buf := make([]byte, base64.StdEncoding.EncodedLen(len(p)))
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base64.StdEncoding.Encode(buf, p[:])
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return buf, nil
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}
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func (p *Public) UnmarshalText(txt []byte) error {
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if *p != (Public{}) {
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return errors.New("refusing to unmarshal into non-zero key.Public")
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}
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n, err := base64.StdEncoding.Decode(p[:], txt)
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if err != nil {
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return err
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}
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if n != 32 {
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return fmt.Errorf("short decode of %d; want 32", n)
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}
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return nil
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}
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// B32 returns k as the *[32]byte type that's used by the
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// golang.org/x/crypto packages. This allocates; it might
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// not be appropriate for performance-sensitive paths.
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func (k Public) B32() *[32]byte { return (*[32]byte)(&k) }
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func (k Private) Public() Public {
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var pub [32]byte
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curve25519.ScalarBaseMult(&pub, (*[32]byte)(&k))
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return Public(pub)
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}
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func (k Private) SharedSecret(pub Public) (ss [32]byte) {
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apk := (*[32]byte)(&pub)
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ask := (*[32]byte)(&k)
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//lint:ignore SA1019 Code copied from wireguard-go, we aim for
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//minimal changes from it.
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curve25519.ScalarMult(&ss, ask, apk)
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return ss
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}
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// NewPublicFromHexMem parses a public key in its hex form, given in m.
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// The provided m must be exactly 64 bytes in length.
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func NewPublicFromHexMem(m mem.RO) (Public, error) {
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if m.Len() != 64 {
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return Public{}, errors.New("invalid length")
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}
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var p Public
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for i := range p {
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a, ok1 := fromHexChar(m.At(i*2 + 0))
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b, ok2 := fromHexChar(m.At(i*2 + 1))
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if !ok1 || !ok2 {
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return Public{}, errors.New("invalid hex character")
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}
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p[i] = (a << 4) | b
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}
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return p, nil
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}
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// fromHexChar converts a hex character into its value and a success flag.
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func fromHexChar(c byte) (byte, bool) {
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switch {
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case '0' <= c && c <= '9':
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return c - '0', true
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case 'a' <= c && c <= 'f':
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return c - 'a' + 10, true
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case 'A' <= c && c <= 'F':
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return c - 'A' + 10, true
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}
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return 0, false
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}
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