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8b47322acc
This commit implements probing of UDP path lifetime on the tail end of an active direct connection. Probing configuration has two parts - Cliffs, which are various timeout cliffs of interest, and CycleCanStartEvery, which limits how often a probing cycle can start, per-endpoint. Initially a statically defined default configuration will be used. The default configuration has cliffs of 10s, 30s, and 60s, with a CycleCanStartEvery of 24h. Probing results are communicated via clientmetric counters. Probing is off by default, and can be enabled via control knob. Probing is purely informational and does not yet drive any magicsock behaviors. Updates #540 Signed-off-by: Jordan Whited <jordan@tailscale.com>
193 lines
5.1 KiB
Go
193 lines
5.1 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package key
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import (
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"bytes"
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"crypto/subtle"
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"fmt"
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"go4.org/mem"
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"golang.org/x/crypto/curve25519"
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"golang.org/x/crypto/nacl/box"
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"tailscale.com/types/structs"
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)
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const (
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// discoPublicHexPrefix is the prefix used to identify a
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// hex-encoded disco public key.
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//
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// This prefix is used in the control protocol, so cannot be
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// changed.
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discoPublicHexPrefix = "discokey:"
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// DiscoPublicRawLen is the length in bytes of a DiscoPublic, when
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// serialized with AppendTo, Raw32 or WriteRawWithoutAllocating.
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DiscoPublicRawLen = 32
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)
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// DiscoPrivate is a disco key, used for peer-to-peer path discovery.
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type DiscoPrivate struct {
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_ structs.Incomparable // because == isn't constant-time
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k [32]byte
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}
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// NewDisco creates and returns a new disco private key.
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func NewDisco() DiscoPrivate {
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var ret DiscoPrivate
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rand(ret.k[:])
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// Key used for nacl seal/open, so needs to be clamped.
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clamp25519Private(ret.k[:])
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return ret
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}
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// IsZero reports whether k is the zero value.
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func (k DiscoPrivate) IsZero() bool {
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return k.Equal(DiscoPrivate{})
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}
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// Equal reports whether k and other are the same key.
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func (k DiscoPrivate) Equal(other DiscoPrivate) bool {
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return subtle.ConstantTimeCompare(k.k[:], other.k[:]) == 1
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}
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// Public returns the DiscoPublic for k.
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// Panics if DiscoPrivate is zero.
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func (k DiscoPrivate) Public() DiscoPublic {
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if k.IsZero() {
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panic("can't take the public key of a zero DiscoPrivate")
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}
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var ret DiscoPublic
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curve25519.ScalarBaseMult(&ret.k, &k.k)
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return ret
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}
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// Shared returns the DiscoShared for communication between k and p.
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func (k DiscoPrivate) Shared(p DiscoPublic) DiscoShared {
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if k.IsZero() || p.IsZero() {
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panic("can't compute shared secret with zero keys")
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}
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var ret DiscoShared
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box.Precompute(&ret.k, &p.k, &k.k)
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return ret
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}
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// DiscoPublic is the public portion of a DiscoPrivate.
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type DiscoPublic struct {
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k [32]byte
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}
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// DiscoPublicFromRaw32 parses a 32-byte raw value as a DiscoPublic.
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//
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// This should be used only when deserializing a DiscoPublic from a
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// binary protocol.
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func DiscoPublicFromRaw32(raw mem.RO) DiscoPublic {
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if raw.Len() != 32 {
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panic("input has wrong size")
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}
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var ret DiscoPublic
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raw.Copy(ret.k[:])
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return ret
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}
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// IsZero reports whether k is the zero value.
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func (k DiscoPublic) IsZero() bool {
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return k == DiscoPublic{}
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}
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// Raw32 returns k encoded as 32 raw bytes.
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//
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// Deprecated: only needed for a temporary compat shim in tailcfg, do
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// not add more uses.
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func (k DiscoPublic) Raw32() [32]byte {
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return k.k
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}
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// ShortString returns the Tailscale conventional debug representation
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// of a disco key.
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func (k DiscoPublic) ShortString() string {
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if k.IsZero() {
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return ""
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}
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return fmt.Sprintf("d:%x", k.k[:8])
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}
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// AppendTo appends k, serialized as a 32-byte binary value, to
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// buf. Returns the new slice.
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func (k DiscoPublic) AppendTo(buf []byte) []byte {
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return append(buf, k.k[:]...)
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}
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// String returns the output of MarshalText as a string.
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func (k DiscoPublic) String() string {
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bs, err := k.MarshalText()
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if err != nil {
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panic(err)
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}
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return string(bs)
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}
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// Compare returns an integer comparing DiscoPublic k and l lexicographically.
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// The result will be 0 if k == l, -1 if k < l, and +1 if k > l. This is useful
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// for situations requiring only one node in a pair to perform some operation,
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// e.g. probing UDP path lifetime.
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func (k DiscoPublic) Compare(l DiscoPublic) int {
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return bytes.Compare(k.k[:], l.k[:])
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}
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// AppendText implements encoding.TextAppender.
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func (k DiscoPublic) AppendText(b []byte) ([]byte, error) {
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return appendHexKey(b, discoPublicHexPrefix, k.k[:]), nil
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}
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// MarshalText implements encoding.TextMarshaler.
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func (k DiscoPublic) MarshalText() ([]byte, error) {
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return k.AppendText(nil)
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}
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// MarshalText implements encoding.TextUnmarshaler.
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func (k *DiscoPublic) UnmarshalText(b []byte) error {
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return parseHex(k.k[:], mem.B(b), mem.S(discoPublicHexPrefix))
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}
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type DiscoShared struct {
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_ structs.Incomparable // because == isn't constant-time
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k [32]byte
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}
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// Equal reports whether k and other are the same key.
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func (k DiscoShared) Equal(other DiscoShared) bool {
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return subtle.ConstantTimeCompare(k.k[:], other.k[:]) == 1
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}
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func (k DiscoShared) IsZero() bool {
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return k.Equal(DiscoShared{})
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}
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// Seal wraps cleartext into a NaCl box (see
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// golang.org/x/crypto/nacl), using k as the shared secret and a
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// random nonce.
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func (k DiscoShared) Seal(cleartext []byte) (ciphertext []byte) {
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if k.IsZero() {
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panic("can't seal with zero key")
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}
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var nonce [24]byte
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rand(nonce[:])
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return box.SealAfterPrecomputation(nonce[:], cleartext, &nonce, &k.k)
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}
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// Open opens the NaCl box ciphertext, which must be a value created
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// by Seal, and returns the inner cleartext if ciphertext is a valid
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// box using shared secret k.
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func (k DiscoShared) Open(ciphertext []byte) (cleartext []byte, ok bool) {
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if k.IsZero() {
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panic("can't open with zero key")
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}
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if len(ciphertext) < 24 {
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return nil, false
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}
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nonce := (*[24]byte)(ciphertext)
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return box.OpenAfterPrecomputation(nil, ciphertext[24:], nonce, &k.k)
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}
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