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// Copyright 2022 The Sigstore Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package internal includes functions to support OAuth/OIDC
package internal
import (
"encoding/json"
"fmt"
"io"
"mime"
"net/http"
"net/url"
"strconv"
"time"
"golang.org/x/oauth2"
)
// var for testing
var currentTime = time.Now
// tokenRespJSON is the struct representing the JSON form of a RFC6749 access token success response.
// See: https://datatracker.ietf.org/doc/html/rfc6749#section-5.1
type tokenRespJSON struct {
AccessToken string `json:"access_token"`
TokenType string `json:"token_type"`
RefreshToken string `json:"refresh_token"`
ExpiresIn int `json:"expires_in"`
Scope string `json:"scope"`
}
func parseFormURLEncodedAccessTokenSuccess(body []byte) (token *oauth2.Token, err error) {
vals, err := url.ParseQuery(string(body))
if err != nil {
return nil, err
}
token = &oauth2.Token{
AccessToken: vals.Get("access_token"),
TokenType: vals.Get("token_type"),
RefreshToken: vals.Get("refresh_token"),
}
ei := vals.Get("expires_in")
if ei != "" {
expires, err := strconv.Atoi(ei)
if err != nil {
return nil, fmt.Errorf(`failed to parse "expires_in": %w`, err)
}
if expires != 0 {
token.Expiry = currentTime().Add(time.Duration(expires) * time.Second)
}
}
return token.WithExtra(vals), nil
}
func parseJSONAccessTokenSuccess(body []byte) (token *oauth2.Token, err error) {
var tj tokenRespJSON
if err = json.Unmarshal(body, &tj); err != nil {
return nil, err
}
token = &oauth2.Token{
AccessToken: tj.AccessToken,
TokenType: tj.TokenType,
RefreshToken: tj.RefreshToken,
}
if tj.ExpiresIn != 0 {
token.Expiry = currentTime().Add(time.Duration(tj.ExpiresIn) * time.Second)
}
raw := map[string]interface{}{}
if err = json.Unmarshal(body, &raw); err != nil {
return nil, err
}
return token.WithExtra(raw), nil
}
func parseAccessTokenSuccess(body []byte, contentType string) (token *oauth2.Token, err error) {
if contentType == "application/x-www-form-urlencoded" {
return parseFormURLEncodedAccessTokenSuccess(body)
}
return parseJSONAccessTokenSuccess(body)
}
// ErrorTokenResponse represents an RFC6749 access token error response.
// See: https://datatracker.ietf.org/doc/html/rfc6749#section-5.2
type ErrorTokenResponse struct {
Code string `json:"error"`
Description string `json:"error_description,omitempty"`
URI string `json:"error_uri,omitempty"`
}
// Error implements `error`
func (e *ErrorTokenResponse) Error() string {
str, _ := json.Marshal(e)
return string(str)
}
func parseFormURLEncodedAccessTokenError(body []byte) (*ErrorTokenResponse, error) {
vals, parseErr := url.ParseQuery(string(body))
if parseErr != nil {
return nil, parseErr
}
return &ErrorTokenResponse{
Code: vals.Get("error"),
Description: vals.Get("error_description"),
URI: vals.Get("error_uri"),
}, nil
}
func parseJSONAccessTokenError(body []byte) (respErr *ErrorTokenResponse, parseErr error) {
var ej ErrorTokenResponse
if parseErr = json.Unmarshal(body, &ej); parseErr != nil {
return nil, parseErr
}
return &ej, nil
}
func parseAccessTokenError(body []byte, contentType string) (respErr *ErrorTokenResponse, parseErr error) {
if contentType == "application/x-www-form-urlencoded" {
return parseFormURLEncodedAccessTokenError(body)
}
return parseJSONAccessTokenError(body)
}
// ParseAccessTokenResponse parses an RFC6749 access token response and returns either an `*oauth2.Token` on success, an `*ErrorTokenResponse` on failure, or any other error if the response cannot be parsed.
// See: https://datatracker.ietf.org/doc/html/rfc6749#section-5
func ParseAccessTokenResponse(tokenResp *http.Response) (token *oauth2.Token, err error) {
body, err := io.ReadAll(io.LimitReader(tokenResp.Body, 1<<20))
if err != nil {
return nil, err
}
contentType, _, _ := mime.ParseMediaType(tokenResp.Header.Get("Content-Type"))
if tokenResp.StatusCode != http.StatusOK {
respErr, parseErr := parseAccessTokenError(body, contentType)
if parseErr != nil {
return nil, parseErr
}
return nil, respErr
}
token, err = parseAccessTokenSuccess(body, contentType)
if err != nil {
return nil, err
}
if token.AccessToken == "" {
return nil, fmt.Errorf(`response did not contain "access_token". Content-Type: %q, Body: %s`, contentType, string(body))
}
return token, nil
}
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