feat: block file transfers for security (#13501)

cli/agent.go

@@ -27,6 +27,7 @@ import (
 	"cdr.dev/slog/sloggers/slogstackdriver"
 	"github.com/coder/coder/v2/agent"
 	"github.com/coder/coder/v2/agent/agentproc"
+	"github.com/coder/coder/v2/agent/agentssh"
 	"github.com/coder/coder/v2/agent/reaper"
 	"github.com/coder/coder/v2/buildinfo"
 	"github.com/coder/coder/v2/codersdk"
@@ -48,6 +49,7 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 		slogHumanPath       string
 		slogJSONPath        string
 		slogStackdriverPath string
+		blockFileTransfer   bool
 	)
 	cmd := &serpent.Command{
 		Use:   "agent",
@@ -314,6 +316,8 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 				// Intentionally set this to nil. It's mainly used
 				// for testing.
 				ModifiedProcesses: nil,
+
+				BlockFileTransfer: blockFileTransfer,
 			})
 
 			promHandler := agent.PrometheusMetricsHandler(prometheusRegistry, logger)
@@ -417,6 +421,13 @@ func (r *RootCmd) workspaceAgent() *serpent.Command {
 			Default:     "",
 			Value:       serpent.StringOf(&slogStackdriverPath),
 		},
+		{
+			Flag:        "block-file-transfer",
+			Default:     "false",
+			Env:         "CODER_AGENT_BLOCK_FILE_TRANSFER",
+			Description: fmt.Sprintf("Block file transfer using known applications: %s.", strings.Join(agentssh.BlockedFileTransferCommands, ",")),
+			Value:       serpent.BoolOf(&blockFileTransfer),
+		},
 	}
 
 	return cmd

cli/testdata/coder_agent_--help.golden

@@ -18,6 +18,9 @@ OPTIONS:
       --auth string, $CODER_AGENT_AUTH (default: token)
           Specify the authentication type to use for the agent.
 
+      --block-file-transfer bool, $CODER_AGENT_BLOCK_FILE_TRANSFER (default: false)
+          Block file transfer using known applications: nc,rsync,scp,sftp.
+
       --debug-address string, $CODER_AGENT_DEBUG_ADDRESS (default: 127.0.0.1:2113)
           The bind address to serve a debug HTTP server.