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237276efcd* fix(artwork): block private and loopback addresses in remote image fetches fromURL fetched any URL with a plain HTTP client, and two untrusted inputs reach it. A playlist can set #EXTALBUMARTURL to an http(s) URL, which the artwork worker later fetches when EnableM3UExternalAlbumArt is on, so any user who can import a playlist controls the target. Metadata agents, including WASM plugins without the http permission, return image URLs that the core fetches too. Either path could make the server request loopback, LAN or link-local addresses and store the response as artwork that is served back. Add httpclient.NewExternal, which dials through a net.Dialer Control hook that rejects private, loopback, link-local and unspecified addresses. The check runs at dial time on the resolved IP, so DNS names, redirects and DNS rebinding are covered. fromURL now uses one shared client built with it and treats a refused address as a definitive miss, so the item settles absent instead of retrying and tripping the agent's circuit breaker. httpclient.New is unchanged for the other callers. The IP classification moves from plugins to the new utils/netguard package, shared by the plugin host client and the new constructor. The artwork test suite swaps in a client that allows loopback so existing specs can keep using httptest servers; the fromURL specs use the production client to assert the refusal. * fix(httpclient): keep dialing a configured proxy in the guarded client The guard runs on the resolved address, and with HTTP_PROXY set that address is the proxy, not the image host. A proxy on a private address would have had every remote artwork fetch refused, and a refusal settles the item as absent, so covers would silently disappear for those setups. Dial the configured proxy endpoint directly and keep the guard for every other dial. A proxy relays the request itself, so it is the operator's egress policy, the same one every other httpclient.New caller already goes through. * fix(httpclient): exempt only the hop that actually goes through the proxy The exemption matched any dial to a configured proxy's address, but net/http never proxies loopback targets, so a URL aimed at a loopback proxy was dialed directly and skipped the guard. That let an image URL reach that one address. Tag each request with the proxy it resolves to and exempt a dial only when it is that hop. Redirects re-enter the RoundTripper, so every hop is tagged on its own.
38 lines
1.2 KiB
Go
38 lines
1.2 KiB
Go
// Package netguard keeps outbound connections driven by untrusted input away from internal addresses.
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package netguard
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import (
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"errors"
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"fmt"
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"net"
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"net/netip"
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"syscall"
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)
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var ErrPrivateAddress = errors.New("dial to private/loopback address blocked")
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// IsPrivateIP reports whether ip is loopback, private, link-local or unspecified.
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func IsPrivateIP(ip net.IP) bool {
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return ip.IsLoopback() || ip.IsUnspecified() || ip.IsPrivate() || ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast()
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}
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// DialControl returns a net.Dialer Control hook that rejects private addresses not covered by allowed.
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// It sees the resolved IP, so DNS names, redirects and rebinding cannot get around it.
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func DialControl(allowed ...netip.Prefix) func(network, address string, c syscall.RawConn) error {
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return func(_, address string, _ syscall.RawConn) error {
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ap, err := netip.ParseAddrPort(address)
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if err != nil {
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return fmt.Errorf("%w: unparseable address %q: %w", ErrPrivateAddress, address, err)
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}
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addr := ap.Addr().Unmap()
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if !IsPrivateIP(addr.AsSlice()) {
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return nil
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}
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for _, p := range allowed {
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if p.Contains(addr) {
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return nil
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}
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}
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return fmt.Errorf("%w: %s", ErrPrivateAddress, address)
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}
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}
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