Only allow host-relative LDConfig paths

This change only allows host-relative LDConfig paths.

An allow-ldconfig-from-container feature flag is added to allow for this
the default behaviour to be changed.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

internal/config/cli.go

@@ -17,6 +17,7 @@
 package config
 
 import (
+	"fmt"
 	"os"
 	"strings"
 )
@@ -34,29 +35,62 @@ type ContainerCLIConfig struct {
 	NoPivot   bool   `toml:"no-pivot,omitempty"`
 	NoCgroups bool   `toml:"no-cgroups"`
 	User      string `toml:"user"`
-	Ldconfig  string `toml:"ldconfig"`
+	// Ldconfig represents the path to the ldconfig binary to be used to update
+	// the ldcache in a container as it is being created.
+	// If this path starts with a '@' the path is relative to the host and if
+	// not it is treated as a container path.
+	//
+	// Note that the use of container paths are disabled by default and if this
+	// is required, the features.allow-ldconfig-from-container feature gate must
+	// be enabled explicitly.
+	Ldconfig ldconfigPath `toml:"ldconfig"`
 }
 
 // NormalizeLDConfigPath returns the resolved path of the configured LDConfig binary.
 // This is only done for host LDConfigs and is required to handle systems where
 // /sbin/ldconfig is a wrapper around /sbin/ldconfig.real.
 func (c *ContainerCLIConfig) NormalizeLDConfigPath() string {
-	return NormalizeLDConfigPath(c.Ldconfig)
+	return string(c.Ldconfig.normalize())
+}
+
+// An ldconfigPath is used to represent the path to ldconfig.
+type ldconfigPath string
+
+func (p ldconfigPath) assertValid(allowContainerRelativePath bool) error {
+	if p.isHostRelative() {
+		return nil
+	}
+	if allowContainerRelativePath {
+		return nil
+	}
+	return fmt.Errorf("nvidia-container-cli.ldconfig value %q is not host-relative (does not start with a '@')", p)
+}
+
+func (p ldconfigPath) isHostRelative() bool {
+	return strings.HasPrefix(string(p), "@")
+}
+
+// normalize returns the resolved path of the configured LDConfig binary.
+// This is only done for host LDConfigs and is required to handle systems where
+// /sbin/ldconfig is a wrapper around /sbin/ldconfig.real.
+func (p ldconfigPath) normalize() ldconfigPath {
+	if !p.isHostRelative() {
+		return p
+	}
+
+	path := string(p)
+	trimmedPath := strings.TrimSuffix(strings.TrimPrefix(path, "@"), ".real")
+	// If the .real path exists, we return that.
+	if _, err := os.Stat(trimmedPath + ".real"); err == nil {
+		return ldconfigPath("@" + trimmedPath + ".real")
+	}
+	// If the .real path does not exists (or cannot be read) we return the non-.real path.
+	return ldconfigPath("@" + trimmedPath)
 }
 
 // NormalizeLDConfigPath returns the resolved path of the configured LDConfig binary.
 // This is only done for host LDConfigs and is required to handle systems where
 // /sbin/ldconfig is a wrapper around /sbin/ldconfig.real.
 func NormalizeLDConfigPath(path string) string {
-	if !strings.HasPrefix(path, "@") {
-		return path
-	}
-
-	trimmedPath := strings.TrimSuffix(strings.TrimPrefix(path, "@"), ".real")
-	// If the .real path exists, we return that.
-	if _, err := os.Stat(trimmedPath + ".real"); err == nil {
-		return "@" + trimmedPath + ".real"
-	}
-	// If the .real path does not exists (or cannot be read) we return the non-.real path.
-	return "@" + trimmedPath
+	return string(ldconfigPath(path).normalize())
 }

internal/config/cli_test.go

@@ -33,7 +33,7 @@ func TestNormalizeLDConfigPath(t *testing.T) {
 
 	testCases := []struct {
 		description string
-		ldconfig    string
+		ldconfig    ldconfigPath
 		expected    string
 	}{
 		{
@@ -51,12 +51,12 @@ func TestNormalizeLDConfigPath(t *testing.T) {
 		},
 		{
 			description: "host .real file exists is returned",
-			ldconfig:    "@" + filepath.Join(testDir, "exists.real"),
+			ldconfig:    ldconfigPath("@" + filepath.Join(testDir, "exists.real")),
 			expected:    "@" + filepath.Join(testDir, "exists.real"),
 		},
 		{
 			description: "host resolves .real file",
-			ldconfig:    "@" + filepath.Join(testDir, "exists"),
+			ldconfig:    ldconfigPath("@" + filepath.Join(testDir, "exists")),
 			expected:    "@" + filepath.Join(testDir, "exists.real"),
 		},
 		{

internal/config/config.go

@@ -18,6 +18,7 @@ package config
 
 import (
 	"bufio"
+	"errors"
 	"os"
 	"path/filepath"
 	"strings"
@@ -51,6 +52,8 @@ var (
 	NVIDIAContainerToolkitExecutable = "nvidia-container-toolkit"
 )
 
+var errInvalidConfig = errors.New("invalid config value")
+
 // Config represents the contents of the config.toml file for the NVIDIA Container Toolkit
 // Note: This is currently duplicated by the HookConfig in cmd/nvidia-container-toolkit/hook_config.go
 type Config struct {
@@ -127,8 +130,20 @@ func GetDefault() (*Config, error) {
 	return &d, nil
 }
 
-func getLdConfigPath() string {
-	return NormalizeLDConfigPath("@/sbin/ldconfig")
+// assertValid checks for a valid config.
+func (c *Config) assertValid() error {
+	err := c.NVIDIAContainerCLIConfig.Ldconfig.assertValid(c.Features.AllowLDConfigFromContainer.IsEnabled())
+	if err != nil {
+		return errors.Join(err, errInvalidConfig)
+	}
+	return nil
+}
+
+// getLdConfigPath allows us to override this function for testing.
+var getLdConfigPath = getLdConfigPathStub
+
+func getLdConfigPathStub() ldconfigPath {
+	return ldconfigPath("@/sbin/ldconfig").normalize()
 }
 
 func getUserGroup() string {

internal/config/config_test.go

@@ -47,20 +47,18 @@ func TestGetConfig(t *testing.T) {
 		description    string
 		contents       []string
 		expectedError  error
-		inspectLdconfig bool
 		distIdsLike    []string
 		expectedConfig *Config
 	}{
 		{
 			description: "empty config is default",
-			inspectLdconfig: true,
 			expectedConfig: &Config{
 				AcceptEnvvarUnprivileged:    true,
 				SupportedDriverCapabilities: "compat32,compute,display,graphics,ngx,utility,video",
 				NVIDIAContainerCLIConfig: ContainerCLIConfig{
 					Root:      "",
 					LoadKmods: true,
-					Ldconfig:  "WAS_CHECKED",
+					Ldconfig:  "@/test/ld/config/path",
 				},
 				NVIDIAContainerRuntimeConfig: RuntimeConfig{
 					DebugFilePath: "/dev/null",
@@ -93,7 +91,7 @@ func TestGetConfig(t *testing.T) {
 				"supported-driver-capabilities = \"compute,utility\"",
 				"nvidia-container-cli.root = \"/bar/baz\"",
 				"nvidia-container-cli.load-kmods = false",
-				"nvidia-container-cli.ldconfig = \"/foo/bar/ldconfig\"",
+				"nvidia-container-cli.ldconfig = \"@/foo/bar/ldconfig\"",
 				"nvidia-container-cli.user = \"foo:bar\"",
 				"nvidia-container-runtime.debug = \"/foo/bar\"",
 				"nvidia-container-runtime.discover-mode = \"not-legacy\"",
@@ -113,7 +111,7 @@ func TestGetConfig(t *testing.T) {
 				NVIDIAContainerCLIConfig: ContainerCLIConfig{
 					Root:      "/bar/baz",
 					LoadKmods: false,
-					Ldconfig:  "/foo/bar/ldconfig",
+					Ldconfig:  "@/foo/bar/ldconfig",
 					User:      "foo:bar",
 				},
 				NVIDIAContainerRuntimeConfig: RuntimeConfig{
@@ -146,6 +144,53 @@ func TestGetConfig(t *testing.T) {
 				},
 			},
 		},
+		{
+			description: "feature allows ldconfig to be overridden",
+			contents: []string{
+				"[nvidia-container-cli]",
+				"ldconfig = \"/foo/bar/ldconfig\"",
+				"[features]",
+				"allow-ldconfig-from-container = true",
+			},
+			expectedConfig: &Config{
+				AcceptEnvvarUnprivileged:    true,
+				SupportedDriverCapabilities: "compat32,compute,display,graphics,ngx,utility,video",
+				NVIDIAContainerCLIConfig: ContainerCLIConfig{
+					Ldconfig:  "/foo/bar/ldconfig",
+					LoadKmods: true,
+				},
+				NVIDIAContainerRuntimeConfig: RuntimeConfig{
+					DebugFilePath: "/dev/null",
+					LogLevel:      "info",
+					Runtimes:      []string{"docker-runc", "runc", "crun"},
+					Mode:          "auto",
+					Modes: modesConfig{
+						CSV: csvModeConfig{
+							MountSpecPath: "/etc/nvidia-container-runtime/host-files-for-container.d",
+						},
+						CDI: cdiModeConfig{
+							DefaultKind: "nvidia.com/gpu",
+							AnnotationPrefixes: []string{
+								"cdi.k8s.io/",
+							},
+							SpecDirs: []string{
+								"/etc/cdi",
+								"/var/run/cdi",
+							},
+						},
+					},
+				},
+				NVIDIAContainerRuntimeHookConfig: RuntimeHookConfig{
+					Path: "nvidia-container-runtime-hook",
+				},
+				NVIDIACTKConfig: CTKConfig{
+					Path: "nvidia-ctk",
+				},
+				Features: features{
+					AllowLDConfigFromContainer: ptr(feature(true)),
+				},
+			},
+		},
 		{
 			description: "config options set in section",
 			contents: []string{
@@ -154,7 +199,7 @@ func TestGetConfig(t *testing.T) {
 				"[nvidia-container-cli]",
 				"root = \"/bar/baz\"",
 				"load-kmods = false",
-				"ldconfig = \"/foo/bar/ldconfig\"",
+				"ldconfig = \"@/foo/bar/ldconfig\"",
 				"user = \"foo:bar\"",
 				"[nvidia-container-runtime]",
 				"debug = \"/foo/bar\"",
@@ -179,7 +224,7 @@ func TestGetConfig(t *testing.T) {
 				NVIDIAContainerCLIConfig: ContainerCLIConfig{
 					Root:      "/bar/baz",
 					LoadKmods: false,
-					Ldconfig:  "/foo/bar/ldconfig",
+					Ldconfig:  "@/foo/bar/ldconfig",
 					User:      "foo:bar",
 				},
 				NVIDIAContainerRuntimeConfig: RuntimeConfig{
@@ -215,14 +260,13 @@ func TestGetConfig(t *testing.T) {
 		{
 			description: "suse config",
 			distIdsLike: []string{"suse", "opensuse"},
-			inspectLdconfig: true,
 			expectedConfig: &Config{
 				AcceptEnvvarUnprivileged:    true,
 				SupportedDriverCapabilities: "compat32,compute,display,graphics,ngx,utility,video",
 				NVIDIAContainerCLIConfig: ContainerCLIConfig{
 					Root:      "",
 					LoadKmods: true,
-					Ldconfig:  "WAS_CHECKED",
+					Ldconfig:  "@/test/ld/config/path",
 					User:      "root:video",
 				},
 				NVIDIAContainerRuntimeConfig: RuntimeConfig{
@@ -252,7 +296,6 @@ func TestGetConfig(t *testing.T) {
 		{
 			description: "suse config overrides user",
 			distIdsLike: []string{"suse", "opensuse"},
-			inspectLdconfig: true,
 			contents: []string{
 				"nvidia-container-cli.user = \"foo:bar\"",
 			},
@@ -262,7 +305,7 @@ func TestGetConfig(t *testing.T) {
 				NVIDIAContainerCLIConfig: ContainerCLIConfig{
 					Root:      "",
 					LoadKmods: true,
-					Ldconfig:  "WAS_CHECKED",
+					Ldconfig:  "@/test/ld/config/path",
 					User:      "foo:bar",
 				},
 				NVIDIAContainerRuntimeConfig: RuntimeConfig{
@@ -293,6 +336,7 @@ func TestGetConfig(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.description, func(t *testing.T) {
+			defer setGetLdConfigPathForTest()()
 			defer setGetDistIDLikeForTest(tc.distIdsLike)()
 			reader := strings.NewReader(strings.Join(tc.contents, "\n"))
 
@@ -305,17 +349,59 @@ func TestGetConfig(t *testing.T) {
 			cfg, err := tomlCfg.Config()
 			require.NoError(t, err)
 
-			// We first handle the ldconfig path since this is currently system-dependent.
-			if tc.inspectLdconfig {
-				ldconfig := cfg.NVIDIAContainerCLIConfig.Ldconfig
-				require.True(t, strings.HasPrefix(ldconfig, "@/sbin/ldconfig"))
-				remaining := strings.TrimPrefix(ldconfig, "@/sbin/ldconfig")
-				require.True(t, remaining == ".real" || remaining == "")
+			require.EqualValues(t, tc.expectedConfig, cfg)
+		})
+	}
+}
 
-				cfg.NVIDIAContainerCLIConfig.Ldconfig = "WAS_CHECKED"
+func TestAssertValid(t *testing.T) {
+	defer setGetLdConfigPathForTest()()
+
+	testCases := []struct {
+		description   string
+		config        *Config
+		expectedError error
+	}{
+		{
+			description: "default is valid",
+			config: func() *Config {
+				config, _ := GetDefault()
+				return config
+			}(),
+		},
+		{
+			description: "alternative host ldconfig path is valid",
+			config: &Config{
+				NVIDIAContainerCLIConfig: ContainerCLIConfig{
+					Ldconfig: "@/some/host/path",
+				},
+			},
+		},
+		{
+			description: "non-host path is invalid",
+			config: &Config{
+				NVIDIAContainerCLIConfig: ContainerCLIConfig{
+					Ldconfig: "/non/host/path",
+				},
+			},
+			expectedError: errInvalidConfig,
+		},
+		{
+			description: "feature flag allows non-host path",
+			config: &Config{
+				NVIDIAContainerCLIConfig: ContainerCLIConfig{
+					Ldconfig: "/non/host/path",
+				},
+				Features: features{
+					AllowLDConfigFromContainer: ptr(feature(true)),
+				},
+			},
+		},
 	}
 
-			require.EqualValues(t, tc.expectedConfig, cfg)
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			require.ErrorIs(t, tc.config.assertValid(), tc.expectedError)
 		})
 	}
 }
@@ -335,3 +421,18 @@ func setGetDistIDLikeForTest(ids []string) func() {
 		getDistIDLike = original
 	}
 }
+
+// prt returns a reference to whatever type is passed into it
+func ptr[T any](x T) *T {
+	return &x
+}
+
+func setGetLdConfigPathForTest() func() {
+	previous := getLdConfigPath
+	getLdConfigPath = func() ldconfigPath {
+		return "@/test/ld/config/path"
+	}
+	return func() {
+		getLdConfigPath = previous
+	}
+}

internal/config/features.go

@@ -21,14 +21,15 @@ type features struct {
 	// DisableImexChannelCreation ensures that the implicit creation of
 	// requested IMEX channels is skipped when invoking the nvidia-container-cli.
 	DisableImexChannelCreation *feature `toml:"disable-imex-channel-creation,omitempty"`
+	// AllowLDConfigFromContainer allows non-host ldconfig paths to be used.
+	// If this feature flag is not set to 'true' only host-rooted config paths
+	// (i.e. paths starting with an '@' are considered valid)
+	AllowLDConfigFromContainer *feature `toml:"allow-ldconfig-from-container,omitempty"`
 }
 
-//nolint:unused
 type feature bool
 
 // IsEnabled checks whether a feature is explicitly enabled.
-//
-//nolint:unused
 func (f *feature) IsEnabled() bool {
 	if f != nil {
 		return bool(*f)

internal/config/toml.go

@@ -108,6 +108,19 @@ func loadConfigTomlFrom(reader io.Reader) (*Toml, error) {
 
 // Config returns the typed config associated with the toml tree.
 func (t *Toml) Config() (*Config, error) {
+	cfg, err := t.configNoOverrides()
+	if err != nil {
+		return nil, err
+	}
+	if err := cfg.assertValid(); err != nil {
+		return nil, err
+	}
+	return cfg, nil
+}
+
+// configNoOverrides returns the typed config associated with the toml tree.
+// This config does not include feature-specific overrides.
+func (t *Toml) configNoOverrides() (*Config, error) {
 	cfg, err := GetDefault()
 	if err != nil {
 		return nil, err

internal/config/toml_test.go

@@ -198,9 +198,12 @@ func TestTomlContents(t *testing.T) {
 }
 
 func TestConfigFromToml(t *testing.T) {
+	defer setGetLdConfigPathForTest()()
+
 	testCases := []struct {
 		description    string
 		contents       map[string]interface{}
+		expectedError  error
 		expectedConfig *Config
 	}{
 		{
@@ -226,13 +229,39 @@ func TestConfigFromToml(t *testing.T) {
 				return c
 			}(),
 		},
+		{
+			description: "invalid ldconfig value raises error",
+			contents: map[string]interface{}{
+				"nvidia-container-cli": map[string]interface{}{
+					"ldconfig": "/some/ldconfig/path",
+				},
+			},
+			expectedError: errInvalidConfig,
+		},
+		{
+			description: "feature allows ldconfig override",
+			contents: map[string]interface{}{
+				"nvidia-container-cli": map[string]interface{}{
+					"ldconfig": "/some/ldconfig/path",
+				},
+				"features": map[string]interface{}{
+					"allow-ldconfig-from-container": true,
+				},
+			},
+			expectedConfig: func() *Config {
+				c, _ := GetDefault()
+				c.NVIDIAContainerCLIConfig.Ldconfig = "/some/ldconfig/path"
+				c.Features.AllowLDConfigFromContainer = ptr(feature(true))
+				return c
+			}(),
+		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.description, func(t *testing.T) {
 			tomlCfg := fromMap(tc.contents)
 			config, err := tomlCfg.Config()
-			require.NoError(t, err)
+			require.ErrorIs(t, err, tc.expectedError)
 			require.EqualValues(t, tc.expectedConfig, config)
 		})
 	}

tools/container/toolkit/toolkit_test.go

@@ -161,7 +161,7 @@ kind: example.com/class
 			// Ensure that the config file has the required contents.
 			// TODO: Add checks for additional config options.
 			require.Equal(t, "/host/driver/root", cfg.NVIDIAContainerCLIConfig.Root)
-			require.Equal(t, "@/host/driver/root/sbin/ldconfig", cfg.NVIDIAContainerCLIConfig.Ldconfig)
+			require.Equal(t, "@/host/driver/root/sbin/ldconfig", string(cfg.NVIDIAContainerCLIConfig.Ldconfig))
 			require.EqualValues(t, filepath.Join(toolkitRoot, "nvidia-container-cli"), cfg.NVIDIAContainerCLIConfig.Path)
 			require.EqualValues(t, filepath.Join(toolkitRoot, "nvidia-ctk"), cfg.NVIDIACTKConfig.Path)