fix: allow startup scripts larger than 32k (#12060)

Fixes #12057 and adds a regression test.

coderd/workspaceagentsrpc_test.go

@@ -0,0 +1,50 @@
+package coderd_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	agentproto "github.com/coder/coder/v2/agent/proto"
+	"github.com/coder/coder/v2/coderd/coderdtest"
+	"github.com/coder/coder/v2/coderd/database"
+	"github.com/coder/coder/v2/coderd/database/dbfake"
+	"github.com/coder/coder/v2/codersdk/agentsdk"
+	"github.com/coder/coder/v2/provisionersdk/proto"
+	"github.com/coder/coder/v2/testutil"
+)
+
+func TestAgentAPI_LargeManifest(t *testing.T) {
+	t.Parallel()
+	ctx := testutil.Context(t, testutil.WaitLong)
+	client, store := coderdtest.NewWithDatabase(t, nil)
+	adminUser := coderdtest.CreateFirstUser(t, client)
+	n := 512000
+	longScript := make([]byte, n)
+	for i := range longScript {
+		longScript[i] = 'q'
+	}
+	r := dbfake.WorkspaceBuild(t, store, database.Workspace{
+		OrganizationID: adminUser.OrganizationID,
+		OwnerID:        adminUser.UserID,
+	}).WithAgent(func(agents []*proto.Agent) []*proto.Agent {
+		agents[0].Scripts = []*proto.Script{
+			{
+				Script: string(longScript),
+			},
+		}
+		return agents
+	}).Do()
+	ac := agentsdk.New(client.URL)
+	ac.SetSessionToken(r.AgentToken)
+	conn, err := ac.ConnectRPC(ctx)
+	defer func() {
+		_ = conn.Close()
+	}()
+	require.NoError(t, err)
+	agentAPI := agentproto.NewDRPCAgentClient(conn)
+	manifest, err := agentAPI.GetManifest(ctx, &agentproto.GetManifestRequest{})
+	require.NoError(t, err)
+	require.Len(t, manifest.Scripts, 1)
+	require.Len(t, manifest.Scripts[0].Script, n)
+}

codersdk/agentsdk/agentsdk.go

@@ -629,6 +629,9 @@ func (c *wsNetConn) Close() error {
 // during read or write will cancel the context, but not close the
 // conn. Close should be called to release context resources.
 func websocketNetConn(ctx context.Context, conn *websocket.Conn, msgType websocket.MessageType) (context.Context, net.Conn) {
+	// Set the read limit to 4 MiB -- about the limit for protobufs.  This needs to be larger than
+	// the default because some of our protocols can include large messages like startup scripts.
+	conn.SetReadLimit(1 << 22)
 	ctx, cancel := context.WithCancel(ctx)
 	nc := websocket.NetConn(ctx, conn, msgType)
 	return ctx, &wsNetConn{