drivers/exec+java: reduce default set of linux capabilities

CHANGELOG.md

@@ -13,6 +13,7 @@ FEATURES:
 
 __BACKWARDS INCOMPATIBILITIES:__
  * csi: The `attachment_mode` and `access_mode` field are required for `volume` blocks in job specifications. Registering a volume requires at least one `capability` block with the `attachment_mode` and `access_mode` fields set. [[GH-10330](https://github.com/hashicorp/nomad/issues/10330)]
+ * drivers/exec+java: Reduce set of linux capabilities enabled by default [[GH-10600](https://github.com/hashicorp/nomad/pull/10600)]
  * licensing: Enterprise licenses are no longer stored in raft or synced between servers. Loading the Enterprise license from disk or environment is required. The `nomad license put` command has been removed. [[GH-10458](https://github.com/hashicorp/nomad/issues/10458)]
 
 SECURITY:

drivers/docker/config.go

@@ -10,6 +10,7 @@ import (
 
 	docker "github.com/fsouza/go-dockerclient"
 	"github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/nomad/drivers/shared/capabilities"
 	"github.com/hashicorp/nomad/helper/pluginutils/hclutils"
 	"github.com/hashicorp/nomad/helper/pluginutils/loader"
 	"github.com/hashicorp/nomad/plugins/base"
@@ -41,36 +42,6 @@ const (
 	dockerAuthHelperPrefix = "docker-credential-"
 )
 
-// nomadDefaultCaps is the subset of dockerDefaultCaps that Nomad enables by
-// default and is used to compute the set of capabilities to add/drop given
-// docker driver configuration.
-func nomadDefaultCaps() []string {
-	return []string{
-		"AUDIT_WRITE",
-		"CHOWN",
-		"DAC_OVERRIDE",
-		"FOWNER",
-		"FSETID",
-		"KILL",
-		"MKNOD",
-		"NET_BIND_SERVICE",
-		"SETFCAP",
-		"SETGID",
-		"SETPCAP",
-		"SETUID",
-		"SYS_CHROOT",
-	}
-}
-
-// dockerDefaultCaps is a list of Linux capabilities enabled by docker by default
-// and is used to compute the set of capabilities to add/drop given docker driver
-// configuration, as well as Nomad built-in limitations.
-//
-// https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities
-func dockerDefaultCaps() []string {
-	return append(nomadDefaultCaps(), "NET_RAW")
-}
-
 func PluginLoader(opts map[string]string) (map[string]interface{}, error) {
 	conf := map[string]interface{}{}
 	if v, ok := opts["docker.endpoint"]; ok {
@@ -287,7 +258,7 @@ var (
 		"allow_privileged": hclspec.NewAttr("allow_privileged", "bool", false),
 		"allow_caps": hclspec.NewDefault(
 			hclspec.NewAttr("allow_caps", "list(string)", false),
-			hclspec.NewLiteral(`["CHOWN","DAC_OVERRIDE","FSETID","FOWNER","MKNOD","SETGID","SETUID","SETFCAP","SETPCAP","NET_BIND_SERVICE","SYS_CHROOT","KILL","AUDIT_WRITE"]`),
+			hclspec.NewLiteral(capabilities.HCLSpecLiteral),
 		),
 		"nvidia_runtime": hclspec.NewDefault(
 			hclspec.NewAttr("nvidia_runtime", "string", false),
@@ -427,9 +398,9 @@ var (
 		"work_dir":        hclspec.NewAttr("work_dir", "string", false),
 	})
 
-	// capabilities is returned by the Capabilities RPC and indicates what
-	// optional features this driver supports
-	capabilities = &drivers.Capabilities{
+	// driverCapabilities represents the RPC response for what features are
+	// implemented by the docker task driver
+	driverCapabilities = &drivers.Capabilities{
 		SendSignals: true,
 		Exec:        true,
 		FSIsolation: drivers.FSIsolationImage,
@@ -788,8 +759,10 @@ func (d *Driver) TaskConfigSchema() (*hclspec.Spec, error) {
 	return taskConfigSpec, nil
 }
 
+// Capabilities is returned by the Capabilities RPC and indicates what optional
+// features this driver supports.
 func (d *Driver) Capabilities() (*drivers.Capabilities, error) {
-	return capabilities, nil
+	return driverCapabilities, nil
 }
 
 var _ drivers.InternalCapabilitiesDriver = (*Driver)(nil)

drivers/docker/driver.go

@@ -10,7 +10,6 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
-	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -23,10 +22,9 @@ import (
 	plugin "github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/nomad/client/taskenv"
 	"github.com/hashicorp/nomad/drivers/docker/docklog"
+	"github.com/hashicorp/nomad/drivers/shared/capabilities"
 	"github.com/hashicorp/nomad/drivers/shared/eventer"
-	"github.com/hashicorp/nomad/drivers/shared/executor"
 	"github.com/hashicorp/nomad/drivers/shared/resolvconf"
-	"github.com/hashicorp/nomad/helper"
 	nstructs "github.com/hashicorp/nomad/nomad/structs"
 	"github.com/hashicorp/nomad/plugins/base"
 	"github.com/hashicorp/nomad/plugins/drivers"
@@ -913,8 +911,9 @@ func (d *Driver) createContainerConfig(task *drivers.TaskConfig, driverConfig *T
 	hostConfig.Privileged = driverConfig.Privileged
 
 	// set add/drop capabilities
-	hostConfig.CapAdd, hostConfig.CapDrop, err = d.getCaps(driverConfig)
-	if err != nil {
+	if hostConfig.CapAdd, hostConfig.CapDrop, err = capabilities.Delta(
+		capabilities.DockerDefaults(), d.config.AllowCaps, driverConfig.CapAdd, driverConfig.CapDrop,
+	); err != nil {
 		return c, err
 	}
 
@@ -1184,119 +1183,6 @@ func (d *Driver) createContainerConfig(task *drivers.TaskConfig, driverConfig *T
 	}, nil
 }
 
-// getCaps computes the capabilities to supply to the --add-cap and --drop-cap
-// options to the docker driver, which override the default capabilities enabled
-// by docker itself.
-func (d *Driver) getCaps(taskConfig *TaskConfig) ([]string, []string, error) {
-
-	// capabilities allowable by client docker plugin configuration
-	allowCaps := expandAllowCaps(d.config.AllowCaps)
-
-	// capabilities the task docker config is asking for based on the default
-	// capabilities allowable by nomad
-	desiredCaps, err := tweakCapabilities(nomadDefaultCaps(), taskConfig.CapAdd, taskConfig.CapDrop)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	// capabilities the task is requesting that are NOT allowed by the docker plugin
-	if missing := missingCaps(allowCaps, desiredCaps); len(missing) > 0 {
-		return nil, nil, fmt.Errorf("Docker driver does not have the following caps allow-listed on this Nomad agent: %s", missing)
-	}
-
-	// capabilities that should be dropped relative to the docker default capabilities
-	dropCaps := capDrops(taskConfig.CapDrop, allowCaps)
-
-	return taskConfig.CapAdd, dropCaps, nil
-}
-
-// capDrops will compute the total dropped capabilities set
-//
-// {task cap_drop} U ({docker defaults} \ {driver allow caps})
-func capDrops(dropCaps []string, allowCaps []string) []string {
-	dropSet := make(map[string]struct{})
-
-	for _, c := range normalizeCaps(dropCaps) {
-		dropSet[c] = struct{}{}
-	}
-
-	// if dropCaps includes ALL, no need to iterate every capability
-	if _, exists := dropSet["ALL"]; exists {
-		return []string{"ALL"}
-	}
-
-	dockerDefaults := helper.SliceStringToSet(normalizeCaps(dockerDefaultCaps()))
-	allowedCaps := helper.SliceStringToSet(normalizeCaps(allowCaps))
-
-	// find the docker default caps not in allowed caps
-	for dCap := range dockerDefaults {
-		if _, exists := allowedCaps[dCap]; !exists {
-			dropSet[dCap] = struct{}{}
-		}
-	}
-
-	drops := make([]string, 0, len(dropSet))
-	for c := range dropSet {
-		drops = append(drops, c)
-	}
-	sort.Strings(drops)
-	return drops
-}
-
-// expandAllowCaps returns the normalized set of allowable capabilities set
-// for the docker plugin configuration.
-func expandAllowCaps(allowCaps []string) []string {
-	if len(allowCaps) == 0 {
-		return nil
-	}
-
-	set := make(map[string]struct{}, len(allowCaps))
-
-	for _, rawCap := range allowCaps {
-		capability := strings.ToUpper(rawCap)
-		if capability == "ALL" {
-			for _, defCap := range normalizeCaps(executor.SupportedCaps(true)) {
-				set[defCap] = struct{}{}
-			}
-		} else {
-			set[capability] = struct{}{}
-		}
-	}
-
-	result := make([]string, 0, len(set))
-	for capability := range set {
-		result = append(result, capability)
-	}
-	sort.Strings(result)
-	return result
-}
-
-// missingCaps returns the set of elements in desired that are not present in
-// allowed. The elements in desired are first upper-cased before comparison.
-// The elements in allowed are assumed to be upper-cased.
-func missingCaps(allowed, desired []string) []string {
-	_, missing := helper.SliceStringIsSubset(allowed, normalizeCaps(desired))
-	sort.Strings(missing)
-	return missing
-}
-
-// normalizeCaps returns a copy of caps with duplicate elements removed and all
-// elements upper-cased.
-func normalizeCaps(caps []string) []string {
-	set := make(map[string]struct{}, len(caps))
-	for _, c := range caps {
-		normal := strings.TrimPrefix(strings.ToUpper(c), "CAP_")
-		set[strings.ToUpper(normal)] = struct{}{}
-	}
-
-	result := make([]string, 0, len(set))
-	for c := range set {
-		result = append(result, c)
-	}
-	sort.Strings(result)
-	return result
-}
-
 func (d *Driver) toDockerMount(m *DockerMount, task *drivers.TaskConfig) (*docker.HostMount, error) {
 	hm, err := m.toDockerHostMount()
 	if err != nil {

drivers/docker/driver_default.go

@@ -3,30 +3,9 @@
 package docker
 
 import (
-	"github.com/docker/docker/oci/caps"
 	docker "github.com/fsouza/go-dockerclient"
 )
 
 func getPortBinding(ip string, port string) docker.PortBinding {
 	return docker.PortBinding{HostIP: ip, HostPort: port}
 }
-
-func tweakCapabilities(basics, adds, drops []string) ([]string, error) {
-	// Moby mixes 2 different capabilities formats: prefixed with "CAP_"
-	// and not. We do the conversion here to have a consistent,
-	// non-prefixed format on the Nomad side.
-	for i, cap := range basics {
-		basics[i] = "CAP_" + cap
-	}
-
-	effectiveCaps, err := caps.TweakCapabilities(basics, adds, drops, nil, false)
-	if err != nil {
-		return effectiveCaps, err
-	}
-
-	for i, cap := range effectiveCaps {
-		effectiveCaps[i] = cap[len("CAP_"):]
-	}
-
-	return effectiveCaps, nil
-}