metropolis: stub out log service

The server side and client-side implementations are not quite ready yet,
but we're commiting this early so that we can start implementing more
node-local management RPCs.

Change-Id: I81b615b0f77dc7750cc738d60ee4923c3182721b
Reviewed-on: https://review.monogon.dev/c/monogon/+/1429
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/cli/metroctl/BUILD.bazel b/metropolis/cli/metroctl/BUILD.bazel
index b2000fb..73a0a6e 100644
--- a/metropolis/cli/metroctl/BUILD.bazel
+++ b/metropolis/cli/metroctl/BUILD.bazel
@@ -7,6 +7,7 @@
         "cmd_k8scredplugin.go",
         "cmd_node.go",
         "cmd_node_approve.go",
+        "cmd_node_logs.go",
         "cmd_node_set.go",
         "cmd_takeownership.go",
         "main.go",
@@ -29,6 +30,7 @@
         "//metropolis/node",
         "//metropolis/node/core/identity",
         "//metropolis/node/core/rpc",
+        "//metropolis/pkg/logtree",
         "//metropolis/proto/api",
         "@com_github_adrg_xdg//:xdg",
         "@com_github_spf13_cobra//:cobra",
diff --git a/metropolis/cli/metroctl/cmd_node.go b/metropolis/cli/metroctl/cmd_node.go
index 97198d8..0f841ef 100644
--- a/metropolis/cli/metroctl/cmd_node.go
+++ b/metropolis/cli/metroctl/cmd_node.go
@@ -60,6 +60,7 @@
 func init() {
 	nodeCmd.AddCommand(nodeDescribeCmd)
 	nodeCmd.AddCommand(nodeListCmd)
+	nodeCmd.AddCommand(nodeLogsCmd)
 	rootCmd.AddCommand(nodeCmd)
 }
 
diff --git a/metropolis/cli/metroctl/cmd_node_logs.go b/metropolis/cli/metroctl/cmd_node_logs.go
new file mode 100644
index 0000000..21d5637
--- /dev/null
+++ b/metropolis/cli/metroctl/cmd_node_logs.go
@@ -0,0 +1,94 @@
+package main
+
+import (
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/spf13/cobra"
+
+	"source.monogon.dev/metropolis/cli/metroctl/core"
+	"source.monogon.dev/metropolis/pkg/logtree"
+	"source.monogon.dev/metropolis/proto/api"
+)
+
+var nodeLogsCmd = &cobra.Command{
+	Short: "Get/stream logs from node",
+	Use:   "logs [node-id]",
+	Args:  cobra.MinimumNArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		ctx := cmd.Context()
+
+		// First connect to the main management service and figure out the node's IP
+		// address.
+		cc := dialAuthenticated(ctx)
+		mgmt := api.NewManagementClient(cc)
+		nodes, err := core.GetNodes(ctx, mgmt, fmt.Sprintf("node.id == %q", args[0]))
+		if err != nil {
+			return fmt.Errorf("when getting node info: %w", err)
+		}
+
+		if len(nodes) == 0 {
+			return fmt.Errorf("no such node")
+		}
+		if len(nodes) > 1 {
+			return fmt.Errorf("expression matched more than one node")
+		}
+		n := nodes[0]
+		if n.Status == nil || n.Status.ExternalAddress == "" {
+			return fmt.Errorf("node has no external address")
+		}
+
+		// TODO(q3k): save CA certificate on takeover
+		info, err := mgmt.GetClusterInfo(ctx, &api.GetClusterInfoRequest{})
+		if err != nil {
+			return fmt.Errorf("couldn't get cluster info: %w", err)
+		}
+		cacert, err := x509.ParseCertificate(info.CaCertificate)
+		if err != nil {
+			return fmt.Errorf("remote CA certificate invalid: %w", err)
+		}
+
+		fmt.Printf("Getting logs from %s (%s)...\n", n.Id, n.Status.ExternalAddress)
+		// Dial the actual node at its management port.
+		cl := dialAuthenticatedNode(ctx, n.Id, n.Status.ExternalAddress, cacert)
+		nmgmt := api.NewNodeManagementClient(cl)
+
+		srv, err := nmgmt.Logs(ctx, &api.GetLogsRequest{
+			Dn:          "",
+			BacklogMode: api.GetLogsRequest_BACKLOG_ALL,
+			StreamMode:  api.GetLogsRequest_STREAM_DISABLE,
+			Filters: []*api.LogFilter{
+				{
+					Filter: &api.LogFilter_WithChildren_{
+						WithChildren: &api.LogFilter_WithChildren{},
+					},
+				},
+			},
+		})
+		if err != nil {
+			return fmt.Errorf("failed to get logs: %w", err)
+		}
+		for {
+			res, err := srv.Recv()
+			if errors.Is(err, io.EOF) {
+				fmt.Println("Done.")
+				break
+			}
+			if err != nil {
+				return fmt.Errorf("log stream failed: %w", err)
+			}
+			for _, entry := range res.BacklogEntries {
+				entry, err := logtree.LogEntryFromProto(entry)
+				if err != nil {
+					fmt.Printf("invalid entry: %v\n", err)
+					continue
+				}
+				fmt.Println(entry.String())
+			}
+		}
+
+		return nil
+	},
+}
diff --git a/metropolis/cli/metroctl/core/rpc.go b/metropolis/cli/metroctl/core/rpc.go
index 00f1f01..4aeda75 100644
--- a/metropolis/cli/metroctl/core/rpc.go
+++ b/metropolis/cli/metroctl/core/rpc.go
@@ -81,6 +81,33 @@
 	return c, nil
 }
 
+func DialNode(ctx context.Context, opkey ed25519.PrivateKey, ocert, ca *x509.Certificate, proxyAddr, nodeId, nodeAddr string) (*grpc.ClientConn, error) {
+	var dialOpts []grpc.DialOption
+
+	if opkey == nil {
+		return nil, fmt.Errorf("an owner's private key must be provided")
+	}
+	if proxyAddr != "" {
+		socksDialer, err := proxy.SOCKS5("tcp", proxyAddr, nil, proxy.Direct)
+		if err != nil {
+			return nil, fmt.Errorf("failed to build a SOCKS dialer: %v", err)
+		}
+		grpcd := func(_ context.Context, addr string) (net.Conn, error) {
+			return socksDialer.Dial("tcp", addr)
+		}
+		dialOpts = append(dialOpts, grpc.WithContextDialer(grpcd))
+	}
+	tlsc := tls.Certificate{
+		Certificate: [][]byte{ocert.Raw},
+		PrivateKey:  opkey,
+	}
+	creds := rpc.NewAuthenticatedCredentials(tlsc, rpc.WantRemoteCluster(ca), rpc.WantRemoteNode(nodeId))
+	dialOpts = append(dialOpts, grpc.WithTransportCredentials(creds))
+
+	endpoint := net.JoinHostPort(nodeAddr, node.NodeManagement.PortString())
+	return grpc.Dial(endpoint, dialOpts...)
+}
+
 // GetNodes retrieves node records, filtered by the supplied node filter
 // expression fexp.
 func GetNodes(ctx context.Context, mgmt api.ManagementClient, fexp string) ([]*api.Node, error) {
diff --git a/metropolis/cli/metroctl/rpc.go b/metropolis/cli/metroctl/rpc.go
index 8e8ee48..6d7beab 100644
--- a/metropolis/cli/metroctl/rpc.go
+++ b/metropolis/cli/metroctl/rpc.go
@@ -2,6 +2,7 @@
 
 import (
 	"context"
+	"crypto/x509"
 	"log"
 
 	"google.golang.org/grpc"
@@ -25,3 +26,17 @@
 	}
 	return cc
 }
+
+func dialAuthenticatedNode(ctx context.Context, id, address string, cacert *x509.Certificate) *grpc.ClientConn {
+	// Collect credentials, validate command parameters, and try dialing the
+	// cluster.
+	ocert, opkey, err := core.GetOwnerCredentials(flags.configPath)
+	if err == core.NoCredentialsError {
+		log.Fatalf("You have to take ownership of the cluster first: %v", err)
+	}
+	cc, err := core.DialNode(ctx, opkey, ocert, cacert, flags.proxyAddr, id, address)
+	if err != nil {
+		log.Fatalf("While dialing node: %v", err)
+	}
+	return cc
+}