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68 lines
2.3 KiB
Go
68 lines
2.3 KiB
Go
// Copyright 2023 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 oauth2
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import (
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"crypto/rand"
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"crypto/sha256"
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"encoding/base64"
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"net/url"
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)
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const (
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codeChallengeKey = "code_challenge"
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codeChallengeMethodKey = "code_challenge_method"
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codeVerifierKey = "code_verifier"
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)
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// GenerateVerifier generates a PKCE code verifier with 32 octets of randomness.
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// This follows recommendations in RFC 7636.
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//
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// A fresh verifier should be generated for each authorization.
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// S256ChallengeOption(verifier) should then be passed to Config.AuthCodeURL
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// (or Config.DeviceAccess) and VerifierOption(verifier) to Config.Exchange
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// (or Config.DeviceAccessToken).
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func GenerateVerifier() string {
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// "RECOMMENDED that the output of a suitable random number generator be
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// used to create a 32-octet sequence. The octet sequence is then
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// base64url-encoded to produce a 43-octet URL-safe string to use as the
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// code verifier."
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// https://datatracker.ietf.org/doc/html/rfc7636#section-4.1
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data := make([]byte, 32)
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if _, err := rand.Read(data); err != nil {
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panic(err)
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}
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return base64.RawURLEncoding.EncodeToString(data)
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}
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// VerifierOption returns a PKCE code verifier AuthCodeOption. It should be
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// passed to Config.Exchange or Config.DeviceAccessToken only.
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func VerifierOption(verifier string) AuthCodeOption {
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return setParam{k: codeVerifierKey, v: verifier}
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}
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// S256ChallengeFromVerifier returns a PKCE code challenge derived from verifier with method S256.
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//
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// Prefer to use S256ChallengeOption where possible.
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func S256ChallengeFromVerifier(verifier string) string {
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sha := sha256.Sum256([]byte(verifier))
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return base64.RawURLEncoding.EncodeToString(sha[:])
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}
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// S256ChallengeOption derives a PKCE code challenge derived from verifier with
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// method S256. It should be passed to Config.AuthCodeURL or Config.DeviceAccess
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// only.
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func S256ChallengeOption(verifier string) AuthCodeOption {
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return challengeOption{
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challenge_method: "S256",
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challenge: S256ChallengeFromVerifier(verifier),
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}
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}
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type challengeOption struct{ challenge_method, challenge string }
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func (p challengeOption) setValue(m url.Values) {
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m.Set(codeChallengeMethodKey, p.challenge_method)
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m.Set(codeChallengeKey, p.challenge)
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}
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