[iOS/iPhone] AppAuth prevents redirect uri deeplink from azure b2c

[weissmanuel]

I'am working with azure b2c and configured an redirect uri deep link. If I successfully signed in in the web view I don't get the response due of the following code snipped in OIDAuthorizationService.m. As soon as I comment out the if condition it works as expected.

Using this pod wrapped by the flutter plugin https://pub.dev/packages/flutter_appauth

- (BOOL)resumeExternalUserAgentFlowWithURL:(NSURL *)URL {
  // rejects URLs that don't match redirect (these may be completely unrelated to the authorization)
  if (![self shouldHandleURL:URL]) {
    return NO;
  }

[rotoudjimaye]

Your suggestion to comment that code helped me track down the issue.

The deep link copied from the Azure Portal does not include a "path" component. Say you copied msauth.com.package.name://auth. When you run it, the redirect URL returned from the sign in flow looks like msauth.com.package.name://auth/?code=XXXX&state=YYYY. The matchesRedirectionURL function attempts to compare (down to the path component) the actual redirect URL msauth.com.package.name://auth/ with the original one msauth.com.package.name://auth but they don't match.

The fix seems simple: append a forward slash to redirect URL copied from Azure before passing it to authorizeAndExchangeCode of the flutter plugin.

[guidedways]

Ideally shouldHandleURL: should be a method that the client calls before calling resumeExternalUserAgentFlowWithURL. This is how most other external URL handling services behave and this way the client gets an opportunity to accept a particular URL it knows is fine to be handled.

[petea]

Duplicate of #446