feat(clbot): Create Gerrit watcher and basic clbot binary. r/950

gerrit.Watcher is a class which watches the Gerrit stream-events SSH
connection and produces events.

There's a basic CLBot binary as well, to demonstrate driving it to
produce messages on the logging output. It doesn't really do anything
else.

Change-Id: I274fe0a77c8329f79456425405e2fbdc3ca2edf0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/245
Reviewed-by: tazjin <mail@tazj.in>

1 files changed, 190 insertions, 0 deletions

diff --git a/fun/clbot/gerrit/watcher_test.go b/fun/clbot/gerrit/watcher_test.go
new file mode 100644
index 000000000000..ae69b2fc4c18
--- /dev/null
+++ b/fun/clbot/gerrit/watcher_test.go
@@ -0,0 +1,190 @@
+package gerrit
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/subtle"
+	"fmt"
+	"net"
+	"testing"
+	"time"
+
+	"code.tvl.fyi/fun/clbot/gerrit/gerritevents"
+	log "github.com/golang/glog"
+	"github.com/google/go-cmp/cmp"
+	"golang.org/x/crypto/ssh"
+)
+
+var (
+	sshServerSigner, sshServerPublicKey = mustNewKey()
+	sshClientSigner, sshClientPublicKey = mustNewKey()
+)
+
+func mustNewKey() (ssh.Signer, ssh.PublicKey) {
+	key, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	if err != nil {
+		panic(err)
+	}
+	signer, err := ssh.NewSignerFromKey(key)
+	if err != nil {
+		panic(err)
+	}
+	publicKey, err := ssh.NewPublicKey(key.Public())
+	if err != nil {
+		panic(err)
+	}
+	return signer, publicKey
+}
+
+func newSSHServer(lines string) (addr string, cleanup func(), err error) {
+	config := &ssh.ServerConfig{
+		PublicKeyCallback: func(c ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error) {
+			pkBytes := pubKey.Marshal()
+			wantPKBytes := sshClientPublicKey.Marshal()
+			if subtle.ConstantTimeCompare(pkBytes, wantPKBytes) == 0 {
+				return nil, fmt.Errorf("unauthorized")
+			}
+			return &ssh.Permissions{}, nil
+		},
+	}
+	config.AddHostKey(sshServerSigner)
+
+	ln, err := net.Listen("tcp", ":0")
+	if err != nil {
+		log.Fatalf("Listen on tcp/:0: %v", err)
+	}
+	handle := func(conn net.Conn) {
+		defer conn.Close()
+
+		sc, newchch, newreqch, err := ssh.NewServerConn(conn, config)
+		if err != nil {
+			log.Fatalf("NewServerConn: %v", err)
+		}
+		go ssh.DiscardRequests(newreqch)
+		for newCh := range newchch {
+			if newCh.ChannelType() != "session" {
+				newCh.Reject(ssh.UnknownChannelType, "unknown channel type")
+				continue
+			}
+
+			channel, reqs, err := newCh.Accept()
+			if err != nil {
+				log.Fatalf("Could not accept channel: %v", err)
+			}
+			go func(in <-chan *ssh.Request) {
+				for req := range in {
+					req.Reply(req.Type == "exec", nil)
+				}
+			}(reqs)
+			channel.Write([]byte(lines))
+			sc.SendRequest("goaway", false, nil)
+		}
+	}
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			go handle(conn)
+		}
+	}()
+
+	cleanup = func() {
+		ln.Close()
+	}
+	return ln.Addr().String(), cleanup, err
+}
+
+func ts(s string) gerritevents.Time {
+	t, err := time.Parse("2006-01-02 15:04:05 -0700 MST", s)
+	if err != nil {
+		panic(err)
+	}
+	return gerritevents.Time{t}
+}
+
+func optStr(s string) *string { return &s }
+
+func TestWatcher(t *testing.T) {
+	tcs := []struct {
+		name  string
+		lines string
+		want  []gerritevents.Event
+	}{{
+		name: "no events",
+	}, {
+		name: "single test event",
+		lines: `{"author":{"name":"tazjin","email":"mail@tazj.in","username":"tazjin"},"approvals":[{"type":"Code-Review","description":"Code-Review","value":"2","oldValue":"0"}],"comment":"Patch Set 3: Code-Review+2","patchSet":{"number":3,"revision":"6fe272d3f82c6efdfe1167fab98bf918efc03fe5","parents":["d984b6018cf68c7e8b7169b475d90134fbcee767"],"ref":"refs/changes/44/244/3","uploader":{"name":"tazjin","email":"mail@tazj.in","username":"tazjin"},"createdOn":1592081910,"author":{"name":"tazjin","email":"mail@tazj.in","username":"tazjin"},"kind":"REWORK","sizeInsertions":83,"sizeDeletions":-156},"change":{"project":"depot","branch":"master","id":"I546c701145fa204b7ba7518a8a56a783588629e0","number":244,"subject":"refactor(ops/nixos): Move my NixOS configurations to //users/tazjin","owner":{"name":"tazjin","email":"mail@tazj.in","username":"tazjin"},"url":"https://cl.tvl.fyi/c/depot/+/244","commitMessage":"refactor(ops/nixos): Move my NixOS configurations to //users/tazjin\n\nNixOS modules move one level up because it\u0027s unlikely that //ops/nixos\nwill contain actual systems at this point (they\u0027re user-specific).\n\nThis is the first users folder, so it is also added to the root\nreadTree invocation for the repository.\n\nChange-Id: I546c701145fa204b7ba7518a8a56a783588629e0\n","createdOn":1592081577,"status":"NEW"},"project":"depot","refName":"refs/heads/master","changeKey":{"id":"I546c701145fa204b7ba7518a8a56a783588629e0"},"type":"comment-added","eventCreatedOn":1592081929}
+`,
+		want: []gerritevents.Event{
+			&gerritevents.CommentAdded{
+				Type: "comment-added",
+				Change: gerritevents.Change{
+					Project:       "depot",
+					Branch:        "master",
+					ID:            "I546c701145fa204b7ba7518a8a56a783588629e0",
+					Number:        244,
+					Subject:       "refactor(ops/nixos): Move my NixOS configurations to //users/tazjin",
+					Owner:         gerritevents.Account{Name: "tazjin", Email: "mail@tazj.in", Username: "tazjin"},
+					URL:           "https://cl.tvl.fyi/c/depot/+/244",
+					CommitMessage: "refactor(ops/nixos): Move my NixOS configurations to //users/tazjin\n\nNixOS modules move one level up because it's unlikely that //ops/nixos\nwill contain actual systems at this point (they're user-specific).\n\nThis is the first users folder, so it is also added to the root\nreadTree invocation for the repository.\n\nChange-Id: I546c701145fa204b7ba7518a8a56a783588629e0\n",
+					CreatedOn:     ts("2020-06-13 21:52:57 +0100 BST"),
+					Status:        "NEW",
+				},
+				PatchSet: gerritevents.PatchSet{
+					Number:         3,
+					Revision:       "6fe272d3f82c6efdfe1167fab98bf918efc03fe5",
+					Parents:        []string{"d984b6018cf68c7e8b7169b475d90134fbcee767"},
+					Ref:            "refs/changes/44/244/3",
+					Uploader:       gerritevents.Account{Name: "tazjin", Email: "mail@tazj.in", Username: "tazjin"},
+					Author:         gerritevents.Account{Name: "tazjin", Email: "mail@tazj.in", Username: "tazjin"},
+					CreatedOn:      ts("2020-06-13 21:58:30 +0100 BST"),
+					Kind:           "REWORK",
+					SizeInsertions: 83,
+					SizeDeletions:  -156,
+				},
+				Author:         gerritevents.Account{Name: "tazjin", Email: "mail@tazj.in", Username: "tazjin"},
+				Approvals:      []gerritevents.Approval{{Type: "Code-Review", Description: "Code-Review", Value: "2", OldValue: optStr("0")}},
+				Comment:        "Patch Set 3: Code-Review+2",
+				EventCreatedOn: ts("2020-06-13 21:58:49 +0100 BST"),
+			},
+		},
+	}}
+	for _, tc := range tcs {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+
+			serverAddr, cleanup, err := newSSHServer(tc.lines)
+			if err != nil {
+				t.Fatalf("newSSHServer: %v", err)
+			}
+			t.Cleanup(cleanup)
+
+			config := &ssh.ClientConfig{
+				User:            "bert",
+				Auth:            []ssh.AuthMethod{ssh.PublicKeys(sshClientSigner)},
+				HostKeyCallback: ssh.FixedHostKey(sshServerPublicKey),
+				Timeout:         10 * time.Millisecond,
+			}
+			w, err := New(ctx, "tcp", serverAddr, config)
+			if err != nil {
+				t.Fatalf("New: %v", err)
+			}
+
+			var gotEvents []gerritevents.Event
+			for ev := range w.Events() {
+				gotEvents = append(gotEvents, ev)
+			}
+			if diff := cmp.Diff(gotEvents, tc.want); diff != "" {
+				t.Errorf("got events != want events: diff:\n%v", diff)
+			}
+		})
+	}
+}