57 lines
1.7 KiB
Go
57 lines
1.7 KiB
Go
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// Copyright 2020 the Pinniped contributors. All Rights Reserved.
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// SPDX-License-Identifier: Apache-2.0
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package state
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import (
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"crypto/rand"
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"crypto/subtle"
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"encoding/hex"
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"fmt"
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"io"
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)
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// Generate generates a new random state parameter of an appropriate size.
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func Generate() (State, error) { return generate(rand.Reader) }
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func generate(rand io.Reader) (State, error) {
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// From https://tools.ietf.org/html/rfc6749#section-10.12:
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// The binding value used for CSRF
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// protection MUST contain a non-guessable value (as described in
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// Section 10.10), and the user-agent's authenticated state (e.g.,
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// session cookie, HTML5 local storage) MUST be kept in a location
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// accessible only to the client and the user-agent (i.e., protected by
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// same-origin policy).
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var buf [16]byte
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if _, err := io.ReadFull(rand, buf[:]); err != nil {
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return "", fmt.Errorf("could not generate random state: %w", err)
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}
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return State(hex.EncodeToString(buf[:])), nil
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}
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// State implements some utilities for working with OAuth2 state parameters.
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type State string
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// String returns the string encoding of this state value.
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func (s *State) String() string {
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return string(*s)
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}
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// Validate the returned state (from a callback parameter).
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func (s *State) Validate(returnedState string) error {
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if subtle.ConstantTimeCompare([]byte(returnedState), []byte(*s)) != 1 {
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return InvalidStateError{Expected: *s, Got: State(returnedState)}
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}
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return nil
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}
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// InvalidStateError is returned by Validate when the returned state is invalid.
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type InvalidStateError struct {
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Expected State
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Got State
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}
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func (e InvalidStateError) Error() string {
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return fmt.Sprintf("invalid state (expected %q, got %q)", e.Expected.String(), e.Got.String())
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}
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