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backend/internal/misc/header_utils.go

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+// Package misc provides miscellaneous utility functions for the CLI Proxy API server.
+// It includes helper functions for HTTP header manipulation and other common operations
+// that don't fit into more specific packages.
+package misc
+
+import (
+	"net/http"
+	"strings"
+)
+
+// ScrubProxyAndFingerprintHeaders removes all headers that could reveal
+// proxy infrastructure, client identity, or browser fingerprints from an
+// outgoing request. This ensures requests to upstream services look like they
+// originate directly from a native client rather than a third-party client
+// behind a reverse proxy.
+func ScrubProxyAndFingerprintHeaders(req *http.Request) {
+	if req == nil {
+		return
+	}
+
+	// --- Proxy tracing headers ---
+	req.Header.Del("X-Forwarded-For")
+	req.Header.Del("X-Forwarded-Host")
+	req.Header.Del("X-Forwarded-Proto")
+	req.Header.Del("X-Forwarded-Port")
+	req.Header.Del("X-Real-IP")
+	req.Header.Del("Forwarded")
+	req.Header.Del("Via")
+
+	// --- Client identity headers ---
+	req.Header.Del("X-Title")
+	req.Header.Del("X-Stainless-Lang")
+	req.Header.Del("X-Stainless-Package-Version")
+	req.Header.Del("X-Stainless-Os")
+	req.Header.Del("X-Stainless-Arch")
+	req.Header.Del("X-Stainless-Runtime")
+	req.Header.Del("X-Stainless-Runtime-Version")
+	req.Header.Del("Http-Referer")
+	req.Header.Del("Referer")
+
+	// --- Browser / Chromium fingerprint headers ---
+	// These are sent by Electron-based clients (e.g. CherryStudio) using the
+	// Fetch API, but NOT by Node.js https module (which Antigravity uses).
+	req.Header.Del("Sec-Ch-Ua")
+	req.Header.Del("Sec-Ch-Ua-Mobile")
+	req.Header.Del("Sec-Ch-Ua-Platform")
+	req.Header.Del("Sec-Fetch-Mode")
+	req.Header.Del("Sec-Fetch-Site")
+	req.Header.Del("Sec-Fetch-Dest")
+	req.Header.Del("Priority")
+
+	// --- Encoding negotiation ---
+	// Antigravity (Node.js) sends "gzip, deflate, br" by default;
+	// Electron-based clients may add "zstd" which is a fingerprint mismatch.
+	req.Header.Del("Accept-Encoding")
+}
+
+// EnsureHeader ensures that a header exists in the target header map by checking
+// multiple sources in order of priority: source headers, existing target headers,
+// and finally the default value. It only sets the header if it's not already present
+// and the value is not empty after trimming whitespace.
+//
+// Parameters:
+//   - target: The target header map to modify
+//   - source: The source header map to check first (can be nil)
+//   - key: The header key to ensure
+//   - defaultValue: The default value to use if no other source provides a value
+func EnsureHeader(target http.Header, source http.Header, key, defaultValue string) {
+	if target == nil {
+		return
+	}
+	if source != nil {
+		if val := strings.TrimSpace(source.Get(key)); val != "" {
+			target.Set(key, val)
+			return
+		}
+	}
+	if strings.TrimSpace(target.Get(key)) != "" {
+		return
+	}
+	if val := strings.TrimSpace(defaultValue); val != "" {
+		target.Set(key, val)
+	}
+}