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fix(backend): detect Sentinel in JSON Errors field, evict session on block

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Microsoft's WAF returns HTTP 200 with {"Errors":[{"Value":"Sentinel marked
this request as rejected."}]}. The existing Sentinel check only ran for
non-200 responses, so the session was never evicted — every subsequent
request reused the poisoned session and hit Sentinel again.

Add the same eviction + rateLimitError logic inside the errMap["Value"]
branch so the session is evicted regardless of the WAF's HTTP status code.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Shekhar Vaidya 2026-06-22 11:08:41 +05:30
parent 68466da7da
commit 0525015ca9
1 changed files with 9 additions and 2 deletions
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11
backend/main.go
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@ -793,9 +793,9 @@ func fetchDownloadLinksFromMS(productID, skuID string) ([]byte, error) {
if exists && time.Since(cached.CreatedAt) < SESSION_TTL {
sessionID = cached.SessionID
jar = cached.Jar
log.Printf("MS fetch /proxy: reusing session %s for product_id=%s\n", sessionID[:8], productID)
log.Printf("MS fetch /proxy: reusing session %s for product_id=%s sku_id=%s\n", sessionID[:8], productID, skuID)
} else {
log.Printf("MS fetch /proxy: new session for product_id=%s\n", productID)
log.Printf("MS fetch /proxy: new session for product_id=%s sku_id=%s\n", productID, skuID)
sessionID, jar, _ = setupSession()
// Warm the session with a SKU info call so cookies from setup carry through
@ -887,6 +887,13 @@ func fetchDownloadLinksFromMS(productID, skuID string) ([]byte, error) {
return nil, &rateLimitError{msg}
}
if val, exists := errMap["Value"].(string); exists {
if strings.Contains(val, "Sentinel") {
cacheMutex.Lock()
delete(sessionCache, productID)
cacheMutex.Unlock()
log.Printf("MS fetch /proxy: Sentinel block for product_id=%s — session evicted\n", productID)
return nil, &rateLimitError{"Sentinel marked this request as rejected."}
}
return nil, fmt.Errorf("%s", val)
}
}