Use HTTP 303 instead of 307 for oidc redirects (#1133)

* Use SeeOther for redirects, not TemporaryRedirect

Co-authored-by: contact <contact@ophir.dev>

* Fix OIDC login redirect to use HTTP 303

Co-authored-by: contact <contact@ophir.dev>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

CHANGELOG.md

@@ -1,6 +1,7 @@
 # CHANGELOG.md
 
 ## 0.40.0 (unreleased)
+ - OIDC login redirects now use HTTP 303 responses so POST submissions are converted to safe GET requests before reaching the identity provider, fixing incorrect reuse of the original POST (HTTP 307) that could break standard auth flows.
  - SQLPage now respects [HTTP accept headers](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Accept) for JSON. You can now easily process the contents of any existing sql page programmatically with:
     - `curl -H "Accept: application/json" http://example.com/page.sql`: returns a json array
     - `curl -H "Accept: application/x-ndjson" http://example.com/page.sql`: returns one json object per line.

src/webserver/oidc.rs

@@ -488,14 +488,14 @@ async fn build_auth_provider_redirect_response(
 ) -> HttpResponse {
     let AuthUrl { url, params } = build_auth_url(oidc_state).await;
     let tmp_login_flow_state_cookie = create_tmp_login_flow_state_cookie(&params, initial_url);
-    HttpResponse::TemporaryRedirect()
+    HttpResponse::SeeOther()
         .append_header((header::LOCATION, url.to_string()))
         .cookie(tmp_login_flow_state_cookie)
         .body("Redirecting...")
 }
 
 fn build_redirect_response(target_url: String) -> HttpResponse {
-    HttpResponse::TemporaryRedirect()
+    HttpResponse::SeeOther()
         .append_header(("Location", target_url))
         .body("Redirecting...")
 }
@@ -835,3 +835,22 @@ fn validate_redirect_url(url: String) -> String {
     log::warn!("Refusing to redirect to {url}");
     '/'.to_string()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use actix_web::http::StatusCode;
+
+    #[test]
+    fn login_redirects_use_see_other() {
+        let response = build_redirect_response("/foo".to_string());
+        assert_eq!(response.status(), StatusCode::SEE_OTHER);
+        let location = response
+            .headers()
+            .get(header::LOCATION)
+            .expect("missing location header")
+            .to_str()
+            .expect("invalid location header");
+        assert_eq!(location, "/foo");
+    }
+}