shekhar/windows-iso-downloader
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fix: support P1 (Unix timestamp) expiry param in contribute endpoint

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Consumer ISO CDN URLs use P1 (Unix timestamp) instead of se (RFC3339).
extractRawExpiry now tries se first then falls back to P1, so CLI
contributions of consumer ISOs are no longer rejected.

Also refactors parseLinkExpiry to call extractRawExpiry (DRY) and
fixes stale log message referencing 'se param'.
This commit is contained in:
Shekhar Vaidya 2026-06-21 19:40:18 +05:30
commit 1ca871a839
1 changed files with 25 additions and 37 deletions
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62
backend/main.go
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@ -207,40 +207,19 @@ func jitter(base, maxJ time.Duration) time.Duration {
return base + offset
}
// parseLinkExpiry reads the `se` (signed expiry) query param from the first
// parseLinkExpiry reads the expiration parameter (se or P1) from the first
// download URL in a Microsoft GetProductDownloadLinksBySku response and returns
// a cache expiry time of (se - now) - 30min, with ±5min jitter.
// a cache expiry time of (expiration - now) - 30min, with ±5min jitter.
// Falls back to 22h on any parse failure.
func parseLinkExpiry(rawJSON []byte) time.Time {
fallback := func() time.Time {
return time.Now().Add(jitter(22*time.Hour, 5*time.Minute))
}
var data map[string]interface{}
if err := json.Unmarshal(rawJSON, &data); err != nil {
expStr := extractRawExpiry(rawJSON)
if expStr == "" {
return fallback()
}
opts, ok := data["ProductDownloadOptions"].([]interface{})
if !ok || len(opts) == 0 {
return fallback()
}
first, ok := opts[0].(map[string]interface{})
if !ok {
return fallback()
}
uri, ok := first["Uri"].(string)
if !ok {
return fallback()
}
u, err := url.Parse(uri)
if err != nil {
return fallback()
}
se := u.Query().Get("se")
if se == "" {
return fallback()
}
t, err := time.Parse(time.RFC3339, se)
t, err := time.Parse(time.RFC3339, expStr)
if err != nil {
return fallback()
}
@ -251,9 +230,10 @@ func parseLinkExpiry(rawJSON []byte) time.Time {
return time.Now().Add(jitter(ttl, 5*time.Minute))
}
// extractRawExpiry returns the raw `se` signed-expiry query param from the
// first URL in a GetProductDownloadLinksBySku response (RFC3339 string).
// Returns "" if absent, unparseable, or not present in the JSON.
// extractRawExpiry returns the raw expiration timestamp from the first URL
// in a GetProductDownloadLinksBySku response (RFC3339 string).
// It supports `se` (RFC3339) and `P1` (Unix timestamp) query parameters.
// Returns "" if absent or unparseable.
func extractRawExpiry(rawJSON []byte) string {
var data map[string]interface{}
if err := json.Unmarshal(rawJSON, &data); err != nil {
@ -275,14 +255,22 @@ func extractRawExpiry(rawJSON []byte) string {
if err != nil {
return ""
}
se := u.Query().Get("se")
if se == "" {
return ""
// 1. Try "se" query parameter (used on Server/Eval ISOs)
if se := u.Query().Get("se"); se != "" {
if _, err := time.Parse(time.RFC3339, se); err == nil {
return se
}
}
if _, err := time.Parse(time.RFC3339, se); err != nil {
return ""
// 2. Try "P1" query parameter (Unix timestamp, used on Consumer ISOs)
if p1 := u.Query().Get("P1"); p1 != "" {
if p1Int, err := strconv.ParseInt(p1, 10, 64); err == nil {
return time.Unix(p1Int, 0).Format(time.RFC3339)
}
}
return se
return ""
}
// rateLimitError marks a Microsoft rate-limit response so callers can choose
@ -1275,11 +1263,11 @@ func handleContribute(w http.ResponseWriter, r *http.Request) {
}
// Validation 3: expiry must be > 1 hour out.
// Use extractRawExpiry (direct se timestamp) — NOT parseLinkExpiry, which has
// Use extractRawExpiry (direct expiry timestamp) — NOT parseLinkExpiry, which has
// a 1h safety floor that would accept already-expired URLs.
seStr := extractRawExpiry(raw)
if seStr == "" {
log.Printf("contribute: product_id=%s sku_id=%s -> rejected (no valid se param)\n", productID, skuID)
log.Printf("contribute: product_id=%s sku_id=%s -> rejected (no valid expiry param)\n", productID, skuID)
respondJSONError(w, http.StatusUnprocessableEntity, "no valid signed expiry found in download URL")
return
}