fix(auth): robustly enforce readonly scopes by injecting prompt=consent

.changeset/fix-issue-168-readonly-scope.md

@@ -0,0 +1,5 @@
+---
+'gws': patch
+---
+
+fix(auth): robustly enforce readonly scopes by injecting prompt=consent

src/auth_commands.rs

@@ -178,6 +178,7 @@ pub async fn run_login(args: &[String]) -> Result<(), GwsError> {
 /// Optionally includes `login_hint` in the URL for account pre-selection.
 struct CliFlowDelegate {
     login_hint: Option<String>,
+    force_consent: bool,
 }
 
 impl yup_oauth2::authenticator_delegate::InstalledFlowDelegate for CliFlowDelegate {
@@ -189,7 +190,7 @@ impl yup_oauth2::authenticator_delegate::InstalledFlowDelegate for CliFlowDelega
     {
         Box::pin(async move {
             // Inject login_hint into the OAuth URL if we have one
-            let display_url = if let Some(ref hint) = self.login_hint {
+            let mut display_url = if let Some(ref hint) = self.login_hint {
                 let encoded: String = percent_encoding::percent_encode(
                     hint.as_bytes(),
                     percent_encoding::NON_ALPHANUMERIC,
@@ -203,6 +204,29 @@ impl yup_oauth2::authenticator_delegate::InstalledFlowDelegate for CliFlowDelega
             } else {
                 url.to_string()
             };
+
+            // Inject prompt=consent if requested (for readonly enforcement)
+            if self.force_consent {
+                if let Some(pos) = display_url.find("prompt=") {
+                    let end_pos = display_url[pos..]
+                        .find('&')
+                        .map(|i| pos + i)
+                        .unwrap_or(display_url.len());
+                    let current_prompt = &display_url[pos + 7..end_pos];
+                    if !current_prompt.split("%20").any(|p| p == "consent") {
+                        let new_prompt = if current_prompt.is_empty() {
+                            "consent".to_string()
+                        } else {
+                            format!("{}%20consent", current_prompt)
+                        };
+                        display_url.replace_range(pos + 7..end_pos, &new_prompt);
+                    }
+                } else if display_url.contains('?') {
+                    display_url.push_str("&prompt=consent");
+                } else {
+                    display_url.push_str("?prompt=consent");
+                }
+            }
             eprintln!("Open this URL in your browser to authenticate:\n");
             eprintln!("  {display_url}\n");
             Ok(String::new())
@@ -296,6 +320,8 @@ async fn handle_login(args: &[String]) -> Result<(), GwsError> {
             .map_err(|e| GwsError::Validation(format!("Failed to create config directory: {e}")))?;
     }
 
+    let is_readonly = args.iter().any(|a| a == "--readonly");
+
     let auth = yup_oauth2::InstalledFlowAuthenticator::builder(
         secret,
         yup_oauth2::InstalledFlowReturnMethod::HTTPRedirect,
@@ -304,7 +330,10 @@ async fn handle_login(args: &[String]) -> Result<(), GwsError> {
         temp_path.clone(),
     )))
     .force_account_selection(true) // Adds prompt=consent so Google always returns a refresh_token
-    .flow_delegate(Box::new(CliFlowDelegate { login_hint: None }))
+    .flow_delegate(Box::new(CliFlowDelegate {
+        login_hint: None,
+        force_consent: is_readonly,
+    }))
     .build()
     .await
     .map_err(|e| GwsError::Auth(format!("Failed to build authenticator: {e}")))?;