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authhandler: Add support for PKCE

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- Added new TokenSourceWithPKCE function to authhandler package.
- Updated Token method to support PKCE flow, sending code challenge and challenge method on the auth-code request, and sending code verifier on the exchange request.
- Updated google/default.go to support PKCE param.

Change-Id: Iab895bc01407c4742706061753f5329a772068ec
GitHub-Last-Rev: c1fddd28bcc4c7bd265573111808427711d7ba37
GitHub-Pull-Request: golang/oauth2#568
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/410515
Run-TryBot: Cody Oss <codyoss@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Shin Fan <shinfan@google.com>
Reviewed-by: Cody Oss <codyoss@google.com>
This commit is contained in:
Andy Zhao
2022-06-09 18:27:12 +00:00
committed by Cody Oss
parent d0670ef3b1
commit fd043fe589
3 changed files with 105 additions and 6 deletions
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44
authhandler/authhandler.go
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@@ -13,11 +13,36 @@ import (
"golang.org/x/oauth2"
)
const (
// Parameter keys for AuthCodeURL method to support PKCE.
codeChallengeKey = "code_challenge"
codeChallengeMethodKey = "code_challenge_method"
// Parameter key for Exchange method to support PKCE.
codeVerifierKey = "code_verifier"
)
// PKCEParams holds parameters to support PKCE.
type PKCEParams struct {
Challenge string // The unpadded, base64-url-encoded string of the encrypted code verifier.
ChallengeMethod string // The encryption method (ex. S256).
Verifier string // The original, non-encrypted secret.
}
// AuthorizationHandler is a 3-legged-OAuth helper that prompts
// the user for OAuth consent at the specified auth code URL
// and returns an auth code and state upon approval.
type AuthorizationHandler func(authCodeURL string) (code string, state string, err error)
// TokenSourceWithPKCE is an enhanced version of TokenSource with PKCE support.
//
// The pkce parameter supports PKCE flow, which uses code challenge and code verifier
// to prevent CSRF attacks. A unique code challenge and code verifier should be generated
// by the caller at runtime. See https://www.oauth.com/oauth2-servers/pkce/ for more info.
func TokenSourceWithPKCE(ctx context.Context, config *oauth2.Config, state string, authHandler AuthorizationHandler, pkce *PKCEParams) oauth2.TokenSource {
return oauth2.ReuseTokenSource(nil, authHandlerSource{config: config, ctx: ctx, authHandler: authHandler, state: state, pkce: pkce})
}
// TokenSource returns an oauth2.TokenSource that fetches access tokens
// using 3-legged-OAuth flow.
//
@@ -33,7 +58,7 @@ type AuthorizationHandler func(authCodeURL string) (code string, state string, e
// and response before exchanging the auth code for OAuth token to prevent CSRF
// attacks.
func TokenSource(ctx context.Context, config *oauth2.Config, state string, authHandler AuthorizationHandler) oauth2.TokenSource {
return oauth2.ReuseTokenSource(nil, authHandlerSource{config: config, ctx: ctx, authHandler: authHandler, state: state})
return TokenSourceWithPKCE(ctx, config, state, authHandler, nil)
}
type authHandlerSource struct {
@@ -41,10 +66,17 @@ type authHandlerSource struct {
config *oauth2.Config
authHandler AuthorizationHandler
state string
pkce *PKCEParams
}
func (source authHandlerSource) Token() (*oauth2.Token, error) {
url := source.config.AuthCodeURL(source.state)
// Step 1: Obtain auth code.
var authCodeUrlOptions []oauth2.AuthCodeOption
if source.pkce != nil && source.pkce.Challenge != "" && source.pkce.ChallengeMethod != "" {
authCodeUrlOptions = []oauth2.AuthCodeOption{oauth2.SetAuthURLParam(codeChallengeKey, source.pkce.Challenge),
oauth2.SetAuthURLParam(codeChallengeMethodKey, source.pkce.ChallengeMethod)}
}
url := source.config.AuthCodeURL(source.state, authCodeUrlOptions...)
code, state, err := source.authHandler(url)
if err != nil {
return nil, err
@@ -52,5 +84,11 @@ func (source authHandlerSource) Token() (*oauth2.Token, error) {
if state != source.state {
return nil, errors.New("state mismatch in 3-legged-OAuth flow")
}
return source.config.Exchange(source.ctx, code)
// Step 2: Exchange auth code for access token.
var exchangeOptions []oauth2.AuthCodeOption
if source.pkce != nil && source.pkce.Verifier != "" {
exchangeOptions = []oauth2.AuthCodeOption{oauth2.SetAuthURLParam(codeVerifierKey, source.pkce.Verifier)}
}
return source.config.Exchange(source.ctx, code, exchangeOptions...)
}