Initial sanitized code sync

pkg/stripe/checksum.go

@@ -0,0 +1,47 @@
+package stripe
+
+import (
+	"encoding/base64"
+	"net/url"
+)
+
+// mcL applies XOR(5) to each byte, then base64 encodes, then URL encodes.
+// Mirrors the MC_L function in stripe.js.
+func mcL(data string) string {
+	xored := make([]byte, len(data))
+	for i := 0; i < len(data); i++ {
+		xored[i] = data[i] ^ 5
+	}
+	b64 := base64.StdEncoding.EncodeToString(xored)
+	return url.QueryEscape(b64)
+}
+
+// lc applies a Caesar cipher on printable ASCII (32-126) with the given shift.
+// Mirrors the LC function in stripe.js.
+func lc(s string, shift int) string {
+	result := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		c := int(s[i])
+		if c >= 32 && c <= 126 {
+			result[i] = byte(((c - 32 + shift) % 95) + 32)
+		} else {
+			result[i] = s[i]
+		}
+	}
+	return string(result)
+}
+
+// JsChecksum computes the js_checksum field for Stripe confirm requests.
+// ppageID is the checkout session ID (cs_xxx).
+// Uses dynamically fetched SV from Stripe.js.
+func JsChecksum(ppageID string) string {
+	sc := FetchStripeConstants()
+	return mcL(ppageID + ":" + sc.SV)
+}
+
+// RvTimestamp computes the rv_timestamp field for Stripe confirm requests.
+// Uses dynamically fetched RV and RVTS from Stripe.js.
+func RvTimestamp() string {
+	sc := FetchStripeConstants()
+	return lc(sc.RV+":"+sc.RVTS, 5)
+}