12cbafe54dadd extra checks for the default oauth discovery client: * disallow redirects which downgrade to http * disallow redirects to localhost or private ip * disallow the initial call to a private ip * proxy configuration opts out of dial time checking
49 lines
1.4 KiB
Go
49 lines
1.4 KiB
Go
// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
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// Use of this source code is governed by the license
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// that can be found in the LICENSE file.
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package util
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import (
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"net"
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"net/netip"
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"strings"
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)
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func IsLoopback(addr string) bool {
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host, _, err := net.SplitHostPort(addr)
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if err != nil {
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// If SplitHostPort fails, it might be just a host without a port.
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host = strings.Trim(addr, "[]")
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}
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if host == "localhost" {
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return true
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}
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ip, err := netip.ParseAddr(host)
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if err != nil {
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return false
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}
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return ip.IsLoopback()
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}
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// cgnat is the RFC 6598 carrier-grade NAT range (100.64.0.0/10). netip's
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// IsPrivate does not report it, but it is shared ISP space that is not publicly
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// routable and could point at another tenant behind the same NAT.
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var cgnat = netip.MustParsePrefix("100.64.0.0/10")
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// IsPrivateOrReserved reports whether ip belongs to a range that must not be
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// reachable through a server-controlled URL, as a defense against SSRF: private
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// (RFC 1918 / RFC 4193 ULA), link-local (including the 169.254.169.254 cloud
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// metadata endpoint), carrier-grade NAT, multicast, and the unspecified address.
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func IsPrivateOrReserved(ip netip.Addr) bool {
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ip = ip.Unmap()
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if !ip.IsValid() {
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return true
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}
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if ip.IsPrivate() ||
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ip.IsLinkLocalUnicast() ||
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ip.IsMulticast() ||
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ip.IsUnspecified() {
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return true
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}
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return cgnat.Contains(ip)
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}
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