refactor: add isDomainNameAndNotPeerID

This ensures we exclude valid PeerIDs from code paths that require
DNSLink names.

Ref.
ipfs/kubo#8071 (review)


This commit was moved from ipfs/kubo@28d4d9b

Author: lidel

gateway/core/corehttp/hostname.go

@@ -349,15 +349,27 @@ func knownSubdomainDetails(hostname string, knownGateways gatewayHosts) (gw *con
 	return nil, "", "", "", false
 }
 
+// isDomainNameAndNotPeerID returns bool if string looks like a valid DNS name AND is not a PeerID
+func isDomainNameAndNotPeerID(hostname string) bool {
+	if len(hostname) == 0 {
+		return false
+	}
+	if _, err := peer.Decode(hostname); err == nil {
+		return false
+	}
+	_, ok := dns.IsDomainName(hostname)
+	return ok
+}
+
 // isDNSLinkName returns bool if a valid DNS TXT record exist for provided host
 func isDNSLinkName(ctx context.Context, ipfs iface.CoreAPI, host string) bool {
-	fqdn := stripPort(host)
+	dnslinkName := stripPort(host)
 
-	if _, ok := dns.IsDomainName(fqdn); !ok && len(fqdn) == 0 {
+	if !isDomainNameAndNotPeerID(dnslinkName) {
 		return false
 	}
 
-	name := "/ipns/" + fqdn
+	name := "/ipns/" + dnslinkName
 	// check if DNSLink exists
 	depth := options.Name.ResolveOption(nsopts.Depth(1))
 	_, err := ipfs.Name().Resolve(ctx, name, depth)
@@ -476,7 +488,7 @@ func toSubdomainURL(hostname, path string, r *http.Request, ipfs iface.CoreAPI)
 	}
 
 	// Normalize problematic PeerIDs (eg. ed25519+identity) to CID representation
-	if _, ok := dns.IsDomainName(rootID); !ok && isPeerIDNamespace(ns) {
+	if isPeerIDNamespace(ns) && !isDomainNameAndNotPeerID(rootID) {
 		peerID, err := peer.Decode(rootID)
 		// Note: PeerID CIDv1 with protobuf multicodec will fail, but we fix it
 		// in the next block

gateway/core/corehttp/hostname_test.go

@@ -55,7 +55,7 @@ func TestToSubdomainURL(t *testing.T) {
 		{httpRequest, "localhost", "/ipns/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", "http://k2k4r8n0flx3ra0y5dr8fmyvwbzy3eiztmtq6th694k5a3rznayp3e4o.ipns.localhost/", nil},
 		{httpRequest, "localhost", "/ipns/bafybeickencdqw37dpz3ha36ewrh4undfjt2do52chtcky4rxkj447qhdm", "http://k2k4r8l9ja7hkzynavdqup76ou46tnvuaqegbd04a4o1mpbsey0meucb.ipns.localhost/", nil},
 		// PeerID: ed25519+identity multihash → CIDv1Base36
-		{httpRequest, "localhost", "/ipns/12D3KooWFB51PRY9BxcXSH6khFXw1BZeszeLDy7C8GciskqCTZn5", "http://12D3KooWFB51PRY9BxcXSH6khFXw1BZeszeLDy7C8GciskqCTZn5.ipns.localhost/", nil},
+		{httpRequest, "localhost", "/ipns/12D3KooWFB51PRY9BxcXSH6khFXw1BZeszeLDy7C8GciskqCTZn5", "http://k51qzi5uqu5di608geewp3nqkg0bpujoasmka7ftkyxgcm3fh1aroup0gsdrna.ipns.localhost/", nil},
 		{httpRequest, "sub.localhost", "/ipfs/QmbCMUZw6JFeZ7Wp9jkzbye3Fzp2GGcPgC3nmeUjfVF87n", "http://bafybeif7a7gdklt6hodwdrmwmxnhksctcuav6lfxlcyfz4khzl3qfmvcgu.ipfs.sub.localhost/", nil},
 		// HTTPS requires DNSLink name to fit in a single DNS label – see "Option C" from https://github.com/ipfs/in-web-browsers/issues/169
 		{httpRequest, "dweb.link", "/ipns/dnslink.long-name.example.com", "http://dnslink.long-name.example.com.ipns.dweb.link/", nil},
@@ -144,6 +144,25 @@ func TestHasPrefix(t *testing.T) {
 	}
 }
 
+func TestIsDomainNameAndNotPeerID(t *testing.T) {
+	for _, test := range []struct {
+		hostname string
+		out      bool
+	}{
+		{"", false},
+		{"example.com", true},
+		{"non-icann.something", true},
+		{"..", false},
+		{"12D3KooWFB51PRY9BxcXSH6khFXw1BZeszeLDy7C8GciskqCTZn5", false},           // valid peerid
+		{"k51qzi5uqu5di608geewp3nqkg0bpujoasmka7ftkyxgcm3fh1aroup0gsdrna", false}, // valid peerid
+	} {
+		out := isDomainNameAndNotPeerID(test.hostname)
+		if out != test.out {
+			t.Errorf("(%s) returned '%t', expected '%t'", test.hostname, out, test.out)
+		}
+	}
+}
+
 func TestPortStripping(t *testing.T) {
 	for _, test := range []struct {
 		in  string