Made setting of proxied headers deterministic based on configuration

alone

Previously some headers that are normally set by the proxy (and may be
replied upstream for authorization decisiions) were not being set
depending on values in the users sesssion.

This change ensure that if a given header is sometimes set, it will
always be either set or removed.

It might be worth considerating always deleting these headers if we
didn't add them.

CHANGELOG.md

@@ -39,6 +39,7 @@
 - [#234](https://github.com/pusher/oauth2_proxy/pull/234) Added option `-ssl-upstream-insecure-skip-validation` to skip validation of upstream SSL certificates (@jansinger)
 - [#224](https://github.com/pusher/oauth2_proxy/pull/224) Check Google group membership using hasMember to support nested groups and external users (@jpalpant)
 - [#231](https://github.com/pusher/oauth2_proxy/pull/231) Add optional group membership and email domain checks to the GitLab provider (@Overv)
+- [#226](https://github.com/pusher/oauth2_proxy/pull/226) Made setting of proxied headers deterministic based on configuration alone (@aeijdenberg)
 - [#178](https://github.com/pusher/oauth2_proxy/pull/178) Add Silence Ping Logging and Exclude Logging Paths flags (@kskewes)
 - [#209](https://github.com/pusher/oauth2_proxy/pull/209) Improve docker build caching of layers (@dekimsey)
 - [#186](https://github.com/pusher/oauth2_proxy/pull/186) Make config consistent (@JoelSpeed)

oauthproxy.go

@@ -820,32 +820,60 @@ func (p *OAuthProxy) addHeadersForProxying(rw http.ResponseWriter, req *http.Req
 		req.Header["X-Forwarded-User"] = []string{session.User}
 		if session.Email != "" {
 			req.Header["X-Forwarded-Email"] = []string{session.Email}
+		} else {
+			req.Header.Del("X-Forwarded-Email")
 		}
 	}
+
 	if p.PassUserHeaders {
 		req.Header["X-Forwarded-User"] = []string{session.User}
 		if session.Email != "" {
 			req.Header["X-Forwarded-Email"] = []string{session.Email}
+		} else {
+			req.Header.Del("X-Forwarded-Email")
 		}
 	}
+
 	if p.SetXAuthRequest {
 		rw.Header().Set("X-Auth-Request-User", session.User)
 		if session.Email != "" {
 			rw.Header().Set("X-Auth-Request-Email", session.Email)
+		} else {
+			rw.Header().Del("X-Auth-Request-Email")
 		}
-		if p.PassAccessToken && session.AccessToken != "" {
+
+		if p.PassAccessToken {
+			if session.AccessToken != "" {
 				rw.Header().Set("X-Auth-Request-Access-Token", session.AccessToken)
+			} else {
+				rw.Header().Del("X-Auth-Request-Access-Token")
 			}
 		}
-	if p.PassAccessToken && session.AccessToken != "" {
+	}
+
+	if p.PassAccessToken {
+		if session.AccessToken != "" {
 			req.Header["X-Forwarded-Access-Token"] = []string{session.AccessToken}
+		} else {
+			req.Header.Del("X-Forwarded-Access-Token")
 		}
-	if p.PassAuthorization && session.IDToken != "" {
+	}
+
+	if p.PassAuthorization {
+		if session.IDToken != "" {
 			req.Header["Authorization"] = []string{fmt.Sprintf("Bearer %s", session.IDToken)}
+		} else {
+			req.Header.Del("Authorization")
 		}
-	if p.SetAuthorization && session.IDToken != "" {
+	}
+	if p.SetAuthorization {
+		if session.IDToken != "" {
 			rw.Header().Set("Authorization", fmt.Sprintf("Bearer %s", session.IDToken))
+		} else {
+			rw.Header().Del("Authorization")
 		}
+	}
+
 	if session.Email == "" {
 		rw.Header().Set("GAP-Auth", session.User)
 	} else {