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authhandler: Add support for PKCE

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This commit is contained in:
Andy Zhao
2022-06-06 12:42:11 -07:00
parent 0127caffc1
commit 0d1849c457
3 changed files with 104 additions and 6 deletions
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43
authhandler/authhandler.go
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@@ -13,6 +13,22 @@ 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 {
CodeChallenge string // The unpadded, base64-url-encoded string of the encrypted codeVerifier.
CodeChallengeMethod string // The encryption method (ex. S256).
CodeVerifier 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.
@@ -32,8 +48,16 @@ type AuthorizationHandler func(authCodeURL string) (code string, state string, e
// This token source will verify that the "state" is identical in the request
// and response before exchanging the auth code for OAuth token to prevent CSRF
// attacks.
//
// The pkce parameter supports PKCE flow.
// 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})
}
// Deprecated: Use TokenSourceWithPKCE instead.
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 +65,17 @@ 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 {
authCodeUrlOptions = []oauth2.AuthCodeOption{oauth2.SetAuthURLParam(codeChallengeKey, source.pkce.CodeChallenge),
oauth2.SetAuthURLParam(codeChallengeMethodKey, source.pkce.CodeChallengeMethod)}
}
url := source.config.AuthCodeURL(source.state, authCodeUrlOptions...)
code, state, err := source.authHandler(url)
if err != nil {
return nil, err
@@ -52,5 +83,11 @@ 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 {
exchangeOptions = []oauth2.AuthCodeOption{oauth2.SetAuthURLParam(codeVerifierKey, source.pkce.CodeVerifier)}
}
return source.config.Exchange(source.ctx, code, exchangeOptions...)
}