protected override async Task <OAuthTokenResponse> ExchangeCodeAsync([NotNull] OAuthCodeExchangeContext context)
{
// See https://opendocs.alipay.com/apis/api_9/alipay.system.oauth.token for details.
var tokenRequestParameters = new SortedDictionary <string, string?>()
{
["app_id"] = Options.ClientId,
["charset"] = "utf-8",
["code"] = context.Code,
["format"] = "JSON",
["grant_type"] = "authorization_code",
["method"] = "alipay.system.oauth.token",
["sign_type"] = "RSA2",
["timestamp"] = Clock.UtcNow.ToString("yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture),
["version"] = "1.0",
};
tokenRequestParameters.Add("sign", GetRSA2Signature(tokenRequestParameters));
// PKCE https://tools.ietf.org/html/rfc7636#section-4.5, see BuildChallengeUrl
if (context.Properties.Items.TryGetValue(OAuthConstants.CodeVerifierKey, out var codeVerifier))
{
tokenRequestParameters.Add(OAuthConstants.CodeVerifierKey, codeVerifier);
context.Properties.Items.Remove(OAuthConstants.CodeVerifierKey);
}
var address = QueryHelpers.AddQueryString(Options.TokenEndpoint, tokenRequestParameters);
using var response = await Backchannel.GetAsync(address, HttpCompletionOption.ResponseHeadersRead, Context.RequestAborted);
if (!response.IsSuccessStatusCode)
{
await Log.AccessTokenError(Logger, response, Context.RequestAborted);
return(OAuthTokenResponse.Failed(new Exception("An error occurred while retrieving an access token.")));
}
using var stream = await response.Content.ReadAsStreamAsync(Context.RequestAborted);
using var document = JsonDocument.Parse(stream);
var mainElement = document.RootElement.GetProperty("alipay_system_oauth_token_response");
if (!ValidateReturnCode(mainElement, out var code))
{
return(OAuthTokenResponse.Failed(new Exception($"An error (Code:{code}) occurred while retrieving an access token.")));
}
var payload = JsonDocument.Parse(mainElement.GetRawText());
return(OAuthTokenResponse.Success(payload));
}
