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e72c528a5f
Add mesh key support to derpprobe for probing derpers with verify set to true. Move MeshKey checking to central point for code reuse. Fix a bad error fmt msg. Fixes tailscale/corp#27294 Fixes tailscale/corp#25756 Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>
91 lines
2.6 KiB
Go
91 lines
2.6 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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"crypto/subtle"
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"encoding/hex"
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"encoding/json"
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"errors"
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"fmt"
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"strings"
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"go4.org/mem"
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"tailscale.com/types/structs"
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)
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var ErrInvalidMeshKey = errors.New("invalid mesh key")
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// DERPMesh is a mesh key, used for inter-DERP-node communication and for
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// privileged DERP clients.
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type DERPMesh struct {
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_ structs.Incomparable // == isn't constant-time
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k [32]byte // 64-digit hexadecimal numbers fit in 32 bytes
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}
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// MarshalJSON implements the [encoding/json.Marshaler] interface.
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func (k DERPMesh) MarshalJSON() ([]byte, error) {
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return json.Marshal(k.String())
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}
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// UnmarshalJSON implements the [encoding/json.Unmarshaler] interface.
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func (k *DERPMesh) UnmarshalJSON(data []byte) error {
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var s string
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json.Unmarshal(data, &s)
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if hex.DecodedLen(len(s)) != len(k.k) {
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return fmt.Errorf("types/key/derp: cannot unmarshal, incorrect size mesh key len: %d, must be %d, %w", hex.DecodedLen(len(s)), len(k.k), ErrInvalidMeshKey)
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}
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_, err := hex.Decode(k.k[:], []byte(s))
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if err != nil {
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return fmt.Errorf("types/key/derp: cannot unmarshal, invalid mesh key: %w", err)
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}
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return nil
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}
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// DERPMeshFromRaw32 parses a 32-byte raw value as a DERP mesh key.
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func DERPMeshFromRaw32(raw mem.RO) DERPMesh {
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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 DERPMesh
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raw.Copy(ret.k[:])
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return ret
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}
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// ParseDERPMesh parses a DERP mesh key from a string.
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// This function trims whitespace around the string.
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// If the key is not a 64-digit hexadecimal number, ErrInvalidMeshKey is returned.
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func ParseDERPMesh(key string) (DERPMesh, error) {
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key = strings.TrimSpace(key)
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if len(key) != 64 {
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return DERPMesh{}, fmt.Errorf("%w: must be 64-digit hexadecimal number", ErrInvalidMeshKey)
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}
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decoded, err := hex.DecodeString(key)
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if err != nil {
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return DERPMesh{}, fmt.Errorf("%w: %v", ErrInvalidMeshKey, err)
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}
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return DERPMeshFromRaw32(mem.B(decoded)), nil
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}
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// IsZero reports whether k is the zero value.
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func (k DERPMesh) IsZero() bool {
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return k.Equal(DERPMesh{})
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}
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// Equal reports whether k and other are the same key.
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func (k DERPMesh) Equal(other DERPMesh) bool {
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// Compare mesh keys in constant time to prevent timing attacks.
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// Since mesh keys are a fixed length, we don’t need to be concerned
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// about timing attacks on client mesh keys that are the wrong length.
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// See https://github.com/tailscale/corp/issues/28720
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return subtle.ConstantTimeCompare(k.k[:], other.k[:]) == 1
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}
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// String returns k as a hex-encoded 64-digit number.
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func (k DERPMesh) String() string {
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return hex.EncodeToString(k.k[:])
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}
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