Fix composer#10366: Improve messaging when GitHub tokens need SSO aut…

…horization

src/Composer/Util/AuthHelper.php

@@ -92,6 +92,22 @@ public function promptAuthIfNeeded($url, $origin, $statusCode, $reason = null, $
             $message = "\n";
 
             $rateLimited = $gitHubUtil->isRateLimited($headers);
+            $requiresSso = $gitHubUtil->requiresSso($headers);
+
+            if ($requiresSso) {
+                $ssoUrl = $gitHubUtil->getSsoUrl($headers);
+                $message = sprintf(
+                        'GitHub API token requires SSO authorization. Authorize this token at ' . $ssoUrl,
+                        $ssoUrl
+                    ) . "\n";
+                $this->io->writeError($message);
+                if (!$this->io->isInteractive()) {
+                    throw new TransportException('Could not authenticate against ' . $origin, 403);
+                }
+                $this->io->ask('After authorizing your token, confirm that you would like to retry the request');
+                return ['retry' => TRUE, 'storeAuth' => $storeAuth];
+            }
+
             if ($rateLimited) {
                 $rateLimit = $gitHubUtil->getRateLimit($headers);
                 if ($this->io->hasAuthentication($origin)) {

src/Composer/Util/GitHub.php

@@ -171,6 +171,27 @@ public function getRateLimit(array $headers)
         return $rateLimit;
     }
 
+    /**
+     * Extract SSO URL from response.
+     *
+     * @param string[] $headers Headers from Composer\Downloader\TransportException.
+     *
+     * @return string|null
+     */
+    public function getSsoUrl(array $headers)
+    {
+        foreach ($headers as $header) {
+            $header = trim($header);
+            if (false === strpos($header, 'x-github-sso: required')) {
+                continue;
+            }
+            list(, $url) = explode('=', $header, 2);
+            return $url;
+        }
+
+        return null;
+    }
+
     /**
      * Finds whether a request failed due to rate limiting
      *
@@ -188,4 +209,24 @@ public function isRateLimited(array $headers)
 
         return false;
     }
+
+    /**
+     * Finds whether a request failed due to lacking SSO authorization
+     *
+     * @see https://docs.github.com/en/rest/overview/other-authentication-methods#authenticating-for-saml-sso
+     *
+     * @param string[] $headers Headers from Composer\Downloader\TransportException.
+     *
+     * @return bool
+     */
+    public function requiresSso(array $headers)
+    {
+        foreach ($headers as $header) {
+            if (Preg::isMatch('{^X-GitHub-SSO: required}i', trim($header))) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }