Allow 'runsc do' to run without root

'--rootless' flag lets a non-root user execute 'runsc do'.
The drawback is that the sandbox and gofer processes will
run as root inside a user namespace that is mapped to the
caller's user, intead of nobody. And network is defaulted
to '--network=host' inside the root network namespace. On
the bright side, it's very convenient for testing:

runsc --rootless do ls
runsc --rootless do curl www.google.com

PiperOrigin-RevId: 252840970

1 files changed, 34 insertions, 29 deletions

diff --git a/runsc/main.go b/runsc/main.go
index a214f6ba0..cfe3a78d0 100644
--- a/runsc/main.go
+++ b/runsc/main.go
@@ -61,16 +61,19 @@ var (
 	straceLogSize  = flag.Uint("strace-log-size", 1024, "default size (in bytes) to log data argument blobs")
 
 	// Flags that control sandbox runtime behavior.
-	platform                                   = flag.String("platform", "ptrace", "specifies which platform to use: ptrace (default), kvm")
-	network                                    = flag.String("network", "sandbox", "specifies which network to use: sandbox (default), host, none. Using network inside the sandbox is more secure because it's isolated from the host network.")
-	gso                                        = flag.Bool("gso", true, "enable generic segmenation offload")
-	fileAccess                                 = flag.String("file-access", "exclusive", "specifies which filesystem to use for the root mount: exclusive (default), shared. Volume mounts are always shared.")
-	overlay                                    = flag.Bool("overlay", false, "wrap filesystem mounts with writable overlay. All modifications are stored in memory inside the sandbox.")
-	watchdogAction                             = flag.String("watchdog-action", "log", "sets what action the watchdog takes when triggered: log (default), panic.")
-	panicSignal                                = flag.Int("panic-signal", -1, "register signal handling that panics. Usually set to SIGUSR2(12) to troubleshoot hangs. -1 disables it.")
-	profile                                    = flag.Bool("profile", false, "prepares the sandbox to use Golang profiler. Note that enabling profiler loosens the seccomp protection added to the sandbox (DO NOT USE IN PRODUCTION).")
-	netRaw                                     = flag.Bool("net-raw", false, "enable raw sockets. When false, raw sockets are disabled by removing CAP_NET_RAW from containers (`runsc exec` will still be able to utilize raw sockets). Raw sockets allow malicious containers to craft packets and potentially attack the network.")
-	numNetworkChannels                         = flag.Int("num-network-channels", 1, "number of underlying channels(FDs) to use for network link endpoints.")
+	platform           = flag.String("platform", "ptrace", "specifies which platform to use: ptrace (default), kvm")
+	network            = flag.String("network", "sandbox", "specifies which network to use: sandbox (default), host, none. Using network inside the sandbox is more secure because it's isolated from the host network.")
+	gso                = flag.Bool("gso", true, "enable generic segmenation offload")
+	fileAccess         = flag.String("file-access", "exclusive", "specifies which filesystem to use for the root mount: exclusive (default), shared. Volume mounts are always shared.")
+	overlay            = flag.Bool("overlay", false, "wrap filesystem mounts with writable overlay. All modifications are stored in memory inside the sandbox.")
+	watchdogAction     = flag.String("watchdog-action", "log", "sets what action the watchdog takes when triggered: log (default), panic.")
+	panicSignal        = flag.Int("panic-signal", -1, "register signal handling that panics. Usually set to SIGUSR2(12) to troubleshoot hangs. -1 disables it.")
+	profile            = flag.Bool("profile", false, "prepares the sandbox to use Golang profiler. Note that enabling profiler loosens the seccomp protection added to the sandbox (DO NOT USE IN PRODUCTION).")
+	netRaw             = flag.Bool("net-raw", false, "enable raw sockets. When false, raw sockets are disabled by removing CAP_NET_RAW from containers (`runsc exec` will still be able to utilize raw sockets). Raw sockets allow malicious containers to craft packets and potentially attack the network.")
+	numNetworkChannels = flag.Int("num-network-channels", 1, "number of underlying channels(FDs) to use for network link endpoints.")
+	rootless           = flag.Bool("rootless", false, "it allows the sandbox to be started with a user that is not root. Sandbox and Gofer processes may run with same privileges as current user.")
+
+	// Test flags, not to be used outside tests, ever.
 	testOnlyAllowRunAsCurrentUserWithoutChroot = flag.Bool("TESTONLY-unsafe-nonroot", false, "TEST ONLY; do not ever use! This skips many security measures that isolate the host from the sandbox.")
 )
 
@@ -166,26 +169,28 @@ func main() {
 
 	// Create a new Config from the flags.
 	conf := &boot.Config{
-		RootDir:        *rootDir,
-		Debug:          *debug,
-		LogFilename:    *logFilename,
-		LogFormat:      *logFormat,
-		DebugLog:       *debugLog,
-		DebugLogFormat: *debugLogFormat,
-		FileAccess:     fsAccess,
-		Overlay:        *overlay,
-		Network:        netType,
-		GSO:            *gso,
-		LogPackets:     *logPackets,
-		Platform:       platformType,
-		Strace:         *strace,
-		StraceLogSize:  *straceLogSize,
-		WatchdogAction: wa,
-		PanicSignal:    *panicSignal,
-		ProfileEnable:  *profile,
-		EnableRaw:      *netRaw,
+		RootDir:            *rootDir,
+		Debug:              *debug,
+		LogFilename:        *logFilename,
+		LogFormat:          *logFormat,
+		DebugLog:           *debugLog,
+		DebugLogFormat:     *debugLogFormat,
+		FileAccess:         fsAccess,
+		Overlay:            *overlay,
+		Network:            netType,
+		GSO:                *gso,
+		LogPackets:         *logPackets,
+		Platform:           platformType,
+		Strace:             *strace,
+		StraceLogSize:      *straceLogSize,
+		WatchdogAction:     wa,
+		PanicSignal:        *panicSignal,
+		ProfileEnable:      *profile,
+		EnableRaw:          *netRaw,
+		NumNetworkChannels: *numNetworkChannels,
+		Rootless:           *rootless,
+
 		TestOnlyAllowRunAsCurrentUserWithoutChroot: *testOnlyAllowRunAsCurrentUserWithoutChroot,
-		NumNetworkChannels:                         *numNetworkChannels,
 	}
 	if len(*straceSyscalls) != 0 {
 		conf.StraceSyscalls = strings.Split(*straceSyscalls, ",")