Serve print-cert on the info API, with -address and preferring our v2 certificate

A program that verifies certificates against its own CAs, as
nebula-auth-request does, needs the certificate itself rather than the
parsed identity, and it asked the ssh debug server for it. The info API
now serves print-cert, so it can ask there instead.

- print-cert declares Identity: it reads a certificate from the hostmap or our own, and nothing operational
- -address names the vpn addr, with a port accepted and stripped and 4in6 unmapped, as identity takes it; the operand stays, and giving both is refused
- an address of our own answers with our own certificate, and a tunnel without one is not found, a 404 on the API
- with no address the certificate is the one whoami reports, the v2 when both versions are loaded, not the one handshakes start with
- GET /v1/print-cert?address=<addr>&raw=true answers {"pem": ...}; example config, CHANGELOG, surface test, goldens and an e2e check

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

e2e/info_api_test.go

@@ -64,11 +64,12 @@ func TestIdentityOverTheInfoAPI(t *testing.T) {
 	assertTunnel(t, myVpnIpNet[0].Addr(), theirVpnIpNet[0].Addr(), myControl, theirControl, r)
 
 	type identity struct {
-		Name     string         `json:"name"`
-		VpnAddrs []netip.Addr   `json:"vpnAddrs"`
-		Networks []netip.Prefix `json:"networks"`
-		Groups   []string       `json:"groups"`
-		Issuer   string         `json:"issuer"`
+		Name        string         `json:"name"`
+		VpnAddrs    []netip.Addr   `json:"vpnAddrs"`
+		Networks    []netip.Prefix `json:"networks"`
+		Groups      []string       `json:"groups"`
+		Issuer      string         `json:"issuer"`
+		Fingerprint string         `json:"fingerprint"`
 	}
 
 	// A connection's RemoteAddr, port and all, resolves to the peer.
@@ -102,6 +103,30 @@ func TestIdentityOverTheInfoAPI(t *testing.T) {
 	assert.Equal(t, http.StatusBadRequest, status)
 	assert.JSONEq(t, `{"error":"The provided vpn addr could not be parsed: "}`, body)
 
+	// The certificate itself, for a program that verifies it against its own CAs: the one
+	// nebula verified when the tunnel came up, as PEM, by the address a connection carries.
+	status, body = test.HTTPGet(t, path, "/v1/print-cert?address="+netip.AddrPortFrom(theirVpnIpNet[0].Addr(), 51234).String()+"&raw=true")
+	require.Equal(t, http.StatusOK, status, body)
+	var raw struct {
+		PEM string `json:"pem"`
+	}
+	require.NoError(t, json.Unmarshal([]byte(body), &raw))
+	theirs, _, err := cert.UnmarshalCertificateFromPEM([]byte(raw.PEM))
+	require.NoError(t, err)
+	assert.Equal(t, "them", theirs.Name())
+	fp, err := theirs.Fingerprint()
+	require.NoError(t, err)
+	assert.Equal(t, them.Fingerprint, fp, "the same certificate identity reports")
+
+	// Without raw it is the certificate's fields; without an address, our own.
+	status, body = test.HTTPGet(t, path, "/v1/print-cert")
+	require.Equal(t, http.StatusOK, status, body)
+	assert.Contains(t, body, `"name":"me"`)
+
+	status, body = test.HTTPGet(t, path, "/v1/print-cert?address=10.128.0.9")
+	assert.Equal(t, http.StatusNotFound, status)
+	assert.JSONEq(t, `{"error":"Could not find tunnel for vpn addr: 10.128.0.9"}`, body)
+
 	// Nothing else nebula serves is reachable here.
 	status, body = test.HTTPGet(t, path, "/v1/list-hostmap")
 	assert.Equal(t, http.StatusForbidden, status)

e2e/testdata/commands_output.golden

@@ -779,7 +779,7 @@ whoami - Prints the certificate identity of this node
 
 
 $ help -json
-[{"name":"change-remote","short":"Changes the remote address used in the tunnel for the provided vpn addr","flags":[{"name":"address","usage":"The new remote address, ip:port"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"close-tunnel","short":"Closes a tunnel for the provided vpn addr","flags":[{"name":"local-only","bool":true,"default":"false","usage":"Disables notifying the remote that the tunnel is shutting down"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"create-tunnel","short":"Creates a tunnel for the provided vpn address","help":"The lighthouses will be queried for real addresses but you can provide one as well.","flags":[{"name":"address","usage":"Optionally provide a real remote address, ip:port "},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"device-info","short":"Prints information about the network device.","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"help","short":"prints available commands or help \u003ccommand\u003e for specific usage info","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"identity","short":"Prints the certificate identity of the host owning the provided vpn addr","help":"Identity is what the certificate says: name, vpn addrs, networks, groups, fingerprint, issuer and validity. The address may carry a port, so a connection's remote address can be passed through as is. For this node's own identity use whoami.","flags":[{"name":"address","usage":"The vpn addr to look up, optionally with a port"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"list-hostmap","short":"List all known previously connected hosts","flags":[{"name":"by-index","bool":true,"default":"false","usage":"gets all hosts in the hostmap from the index table"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"list-lighthouse-addrmap","short":"List all lighthouse map entries","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"list-pending-hostmap","short":"List all handshaking hosts","flags":[{"name":"by-index","bool":true,"default":"false","usage":"gets all hosts in the hostmap from the index table"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"log-format","short":"Gets or sets the current log format","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"log-level","short":"Gets or sets the current log level","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"logout","short":"Ends the current session","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"print-cert","short":"Prints the current certificate being used or the certificate for the provided vpn addr","flags":[{"name":"raw","bool":true,"default":"false","usage":"prints the PEM encoded certificate; with -json, an object holding it"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"print-relays","short":"Prints json details about all relay info","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"print-tunnel","short":"Prints json details about a tunnel for the provided vpn addr","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"query-lighthouse","short":"Query the lighthouses for the provided vpn address","help":"This command Line truncated
+[{"name":"change-remote","short":"Changes the remote address used in the tunnel for the provided vpn addr","flags":[{"name":"address","usage":"The new remote address, ip:port"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"close-tunnel","short":"Closes a tunnel for the provided vpn addr","flags":[{"name":"local-only","bool":true,"default":"false","usage":"Disables notifying the remote that the tunnel is shutting down"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"create-tunnel","short":"Creates a tunnel for the provided vpn address","help":"The lighthouses will be queried for real addresses but you can provide one as well.","flags":[{"name":"address","usage":"Optionally provide a real remote address, ip:port "},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"device-info","short":"Prints information about the network device.","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"help","short":"prints available commands or help \u003ccommand\u003e for specific usage info","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"identity","short":"Prints the certificate identity of the host owning the provided vpn addr","help":"Identity is what the certificate says: name, vpn addrs, networks, groups, fingerprint, issuer and validity. The address may carry a port, so a connection's remote address can be passed through as is. For this node's own identity use whoami.","flags":[{"name":"address","usage":"The vpn addr to look up, optionally with a port"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"list-hostmap","short":"List all known previously connected hosts","flags":[{"name":"by-index","bool":true,"default":"false","usage":"gets all hosts in the hostmap from the index table"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"list-lighthouse-addrmap","short":"List all lighthouse map entries","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"list-pending-hostmap","short":"List all handshaking hosts","flags":[{"name":"by-index","bool":true,"default":"false","usage":"gets all hosts in the hostmap from the index table"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"log-format","short":"Gets or sets the current log format","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"log-level","short":"Gets or sets the current log level","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"logout","short":"Ends the current session","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"print-cert","short":"Prints the current certificate being used or the certificate for the provided vpn addr","help":"The vpn addr is an operand or -address, which may carry a port so a connection's remote address can be passed through as is. For a peer it is the certificate nebula verified when the tunnel came up; with no address it is this node's own, the v2 certificate when both versions are loaded. -raw prints the PEM.","flags":[{"name":"address","usage":"The vpn addr to look up, optionally with a port"},{"name":"raw","bool":true,"default":"false","usage":"prints the PEM encoded certificate; with -json, an object holding it"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]},{"name":"print-relays","short":"Prints json details about all relay info","flags":[{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, aLine truncated
 
 $ help -pretty
 [
@@ -1034,7 +1034,12 @@ $ help -pretty
     {
         "name": "print-cert",
         "short": "Prints the current certificate being used or the certificate for the provided vpn addr",
+        "help": "The vpn addr is an operand or -address, which may carry a port so a connection's remote address can be passed through as is. For a peer it is the certificate nebula verified when the tunnel came up; with no address it is this node's own, the v2 certificate when both versions are loaded. -raw prints the PEM.",
         "flags": [
+            {
+                "name": "address",
+                "usage": "The vpn addr to look up, optionally with a port"
+            },
             {
                 "name": "raw",
                 "bool": true,
@@ -1169,6 +1174,9 @@ $ help -pretty
 
 $ help print-cert
 print-cert - Prints the current certificate being used or the certificate for the provided vpn addr
+  The vpn addr is an operand or -address, which may carry a port so a connection's remote address can be passed through as is. For a peer it is the certificate nebula verified when the tunnel came up; with no address it is this node's own, the v2 certificate when both versions are loaded. -raw prints the PEM.
+  -address string
+    	The vpn addr to look up, optionally with a port
   -raw
     	prints the PEM encoded certificate; with -json, an object holding it
   -json
@@ -1177,13 +1185,18 @@ print-cert - Prints the current certificate being used or the certificate for th
     	pretty prints json, assumes -json
 
 $ help -json print-cert
-{"name":"print-cert","short":"Prints the current certificate being used or the certificate for the provided vpn addr","flags":[{"name":"raw","bool":true,"default":"false","usage":"prints the PEM encoded certificate; with -json, an object holding it"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]}
+{"name":"print-cert","short":"Prints the current certificate being used or the certificate for the provided vpn addr","help":"The vpn addr is an operand or -address, which may carry a port so a connection's remote address can be passed through as is. For a peer it is the certificate nebula verified when the tunnel came up; with no address it is this node's own, the v2 certificate when both versions are loaded. -raw prints the PEM.","flags":[{"name":"address","usage":"The vpn addr to look up, optionally with a port"},{"name":"raw","bool":true,"default":"false","usage":"prints the PEM encoded certificate; with -json, an object holding it"},{"name":"json","bool":true,"default":"false","usage":"outputs as json"},{"name":"pretty","bool":true,"default":"false","usage":"pretty prints json, assumes -json"}]}
 
 $ help -pretty print-cert
 {
     "name": "print-cert",
     "short": "Prints the current certificate being used or the certificate for the provided vpn addr",
+    "help": "The vpn addr is an operand or -address, which may carry a port so a connection's remote address can be passed through as is. For a peer it is the certificate nebula verified when the tunnel came up; with no address it is this node's own, the v2 certificate when both versions are loaded. -raw prints the PEM.",
     "flags": [
+        {
+            "name": "address",
+            "usage": "The vpn addr to look up, optionally with a port"
+        },
         {
             "name": "raw",
             "bool": true,