Add file_perms parameter to job's vault stanza

At the moment, `/secrets/vault_token` is written using the nomad
process' umask, which - by default - is `0022`, which results in
writing the vault_token world-readable (`0644` / `rw-r--r--`).

This patch aims to address this by allowing to change the
permissions used from the default `666` (before umask).

The name `file_perms` was chosen to distinguish this from the
parameter `perms` in the `template` stanza (as templates always
operate on files, while Vault tokens are about permissions as
well, which would've been confusing otherwise).

Example of use:

    vault {
        policies = ["nomad-tls-policy"]
        change_mode = "noop"
        file_perms = "600"
    }

I tried to extend unit tests to include basic checks for the
feature, not sure if this is sufficient, though.

Resolves #11900

api/tasks.go

@@ -856,6 +856,7 @@ type Vault struct {
 	Env          *bool    `hcl:"env,optional"`
 	ChangeMode   *string  `mapstructure:"change_mode" hcl:"change_mode,optional"`
 	ChangeSignal *string  `mapstructure:"change_signal" hcl:"change_signal,optional"`
+	FilePerms    *string  `mapstructure:"file_perms" hcl:"file_perms,optional"`
 }
 
 func (v *Vault) Canonicalize() {
@@ -871,6 +872,9 @@ func (v *Vault) Canonicalize() {
 	if v.ChangeSignal == nil {
 		v.ChangeSignal = stringToPtr("SIGHUP")
 	}
+	if v.FilePerms == nil {
+		v.FilePerms = stringToPtr("0666")
+	}
 }
 
 // NewTask creates and initializes a new Task.

client/allocrunner/taskrunner/vault_hook.go

@@ -4,8 +4,10 @@ import (
 	"context"
 	"fmt"
 	"io/ioutil"
+	"io/fs"
 	"os"
 	"path/filepath"
+	"strconv"
 	"sync"
 	"time"
 
@@ -81,6 +83,9 @@ type vaultHook struct {
 	// tokenPath is the path in which to read and write the token
 	tokenPath string
 
+	// tokenFilePerms are the file permissions applied to tokenPath
+	tokenPerms fs.FileMode
+
 	// alloc is the allocation
 	alloc *structs.Allocation
 
@@ -103,6 +108,7 @@ func newVaultHook(config *vaultHookConfig) *vaultHook {
 		lifecycle:    config.lifecycle,
 		updater:      config.updater,
 		alloc:        config.alloc,
+		tokenPerms:   0666,
 		taskName:     config.task,
 		firstRun:     true,
 		ctx:          ctx,
@@ -126,6 +132,15 @@ func (h *vaultHook) Prestart(ctx context.Context, req *interfaces.TaskPrestartRe
 		return nil
 	}
 
+	// Set vaultTokenPath file permissions
+	if h.vaultStanza.FilePerms != "" {
+		v, err := strconv.ParseUint(h.vaultStanza.FilePerms, 8, 12)
+		if err != nil {
+			return fmt.Errorf("Failed to parse %q as octal: %v", h.vaultStanza.FilePerms, err)
+		}
+		h.tokenPerms = fs.FileMode(v)
+	}
+
 	// Try to recover a token if it was previously written in the secrets
 	// directory
 	recoveredToken := ""
@@ -343,7 +358,7 @@ func (h *vaultHook) deriveVaultToken() (token string, exit bool) {
 
 // writeToken writes the given token to disk
 func (h *vaultHook) writeToken(token string) error {
-	if err := ioutil.WriteFile(h.tokenPath, []byte(token), 0666); err != nil {
+	if err := ioutil.WriteFile(h.tokenPath, []byte(token), h.tokenPerms); err != nil {
 		return fmt.Errorf("failed to write vault token: %v", err)
 	}
 

command/agent/job_endpoint.go

@@ -1140,6 +1140,7 @@ func ApiTaskToStructsTask(job *structs.Job, group *structs.TaskGroup,
 			Env:          *apiTask.Vault.Env,
 			ChangeMode:   *apiTask.Vault.ChangeMode,
 			ChangeSignal: *apiTask.Vault.ChangeSignal,
+			FilePerms:    *apiTask.Vault.FilePerms,
 		}
 	}
 

jobspec/parse.go

@@ -510,6 +510,7 @@ func parseVault(result *api.Vault, list *ast.ObjectList) error {
 		"env",
 		"change_mode",
 		"change_signal",
+		"file_perms",
 	}
 	if err := checkHCLKeys(listVal, valid); err != nil {
 		return multierror.Prefix(err, "vault ->")

jobspec/parse_test.go

@@ -402,6 +402,7 @@ func TestParse(t *testing.T) {
 									Env:          boolToPtr(false),
 									ChangeMode:   stringToPtr(vaultChangeModeSignal),
 									ChangeSignal: stringToPtr("SIGUSR1"),
+									FilePerms:    stringToPtr("0666"),
 								},
 							},
 						},

jobspec/test-fixtures/basic.hcl

@@ -349,6 +349,7 @@ job "binstore-storagelocker" {
         env           = false
         change_mode   = "signal"
         change_signal = "SIGUSR1"
+        file_perms    = "644"
       }
     }
 

nomad/structs/diff_test.go

@@ -6624,6 +6624,7 @@ func TestTaskDiff(t *testing.T) {
 					Env:          true,
 					ChangeMode:   "signal",
 					ChangeSignal: "SIGUSR1",
+					FilePerms:    "0644",
 				},
 			},
 			Expected: &TaskDiff{
@@ -6651,6 +6652,12 @@ func TestTaskDiff(t *testing.T) {
 								Old:  "",
 								New:  "true",
 							},
+							{
+								Type: DiffTypeAdded,
+								Name: "FilePerms",
+								Old:  "",
+								New:  "0644",
+							},
 						},
 						Objects: []*ObjectDiff{
 							{
@@ -6684,6 +6691,7 @@ func TestTaskDiff(t *testing.T) {
 					Env:          true,
 					ChangeMode:   "signal",
 					ChangeSignal: "SIGUSR1",
+					FilePerms:    "0644",
 				},
 			},
 			New: &Task{},
@@ -6712,6 +6720,12 @@ func TestTaskDiff(t *testing.T) {
 								Old:  "true",
 								New:  "",
 							},
+							{
+								Type: DiffTypeDeleted,
+								Name: "FilePerms",
+								Old:  "0644",
+								New:  "",
+							},
 						},
 						Objects: []*ObjectDiff{
 							{
@@ -6746,6 +6760,7 @@ func TestTaskDiff(t *testing.T) {
 					Env:          true,
 					ChangeMode:   "signal",
 					ChangeSignal: "SIGUSR1",
+					FilePerms:    "0666",
 				},
 			},
 			New: &Task{
@@ -6755,6 +6770,7 @@ func TestTaskDiff(t *testing.T) {
 					Env:          false,
 					ChangeMode:   "restart",
 					ChangeSignal: "foo",
+					FilePerms:    "0644",
 				},
 			},
 			Expected: &TaskDiff{
@@ -6782,6 +6798,12 @@ func TestTaskDiff(t *testing.T) {
 								Old:  "true",
 								New:  "false",
 							},
+							{
+								Type: DiffTypeEdited,
+								Name: "FilePerms",
+								Old:  "0666",
+								New:  "0644",
+							},
 							{
 								Type: DiffTypeEdited,
 								Name: "Namespace",
@@ -6823,6 +6845,7 @@ func TestTaskDiff(t *testing.T) {
 					Env:          true,
 					ChangeMode:   "signal",
 					ChangeSignal: "SIGUSR1",
+					FilePerms:    "",
 				},
 			},
 			New: &Task{
@@ -6832,6 +6855,7 @@ func TestTaskDiff(t *testing.T) {
 					Env:          true,
 					ChangeMode:   "signal",
 					ChangeSignal: "SIGUSR1",
+					FilePerms:    "",
 				},
 			},
 			Expected: &TaskDiff{
@@ -6859,6 +6883,12 @@ func TestTaskDiff(t *testing.T) {
 								Old:  "true",
 								New:  "true",
 							},
+							{
+								Type: DiffTypeNone,
+								Name: "FilePerms",
+								Old:  "",
+								New:  "",
+							},
 							{
 								Type: DiffTypeNone,
 								Name: "Namespace",

nomad/structs/structs.go

@@ -8851,12 +8851,16 @@ type Vault struct {
 	// ChangeSignal is the signal sent to the task when a new token is
 	// retrieved. This is only valid when using the signal change mode.
 	ChangeSignal string
+
+	// FilePerms is the file permissions vault_token should be written out with.
+	FilePerms string
 }
 
 func DefaultVaultBlock() *Vault {
 	return &Vault{
 		Env:        true,
 		ChangeMode: VaultChangeModeRestart,
+		FilePerms:  "0666",
 	}
 }
 
@@ -8904,6 +8908,13 @@ func (v *Vault) Validate() error {
 		_ = multierror.Append(&mErr, fmt.Errorf("Unknown change mode %q", v.ChangeMode))
 	}
 
+	// Verify vault_token file permissions
+	if v.FilePerms != "" {
+		if _, err := strconv.ParseUint(v.FilePerms, 8, 12); err != nil {
+			_ = multierror.Append(&mErr, fmt.Errorf("Failed to parse %q as octal: %v", v.FilePerms, err))
+		}
+	}
+
 	return mErr.ErrorOrNil()
 }
 

website/content/docs/job-specification/vault.mdx

@@ -34,17 +34,20 @@ job "docs" {
 
         change_mode   = "signal"
         change_signal = "SIGUSR1"
+        file_perms = "600"
       }
     }
   }
 }
 ```
 
 The Nomad client will make the Vault token available to the task by writing it
-to the secret directory at `secrets/vault_token` and by injecting a `VAULT_TOKEN`
-environment variable. If the Nomad cluster is [configured](/docs/configuration/vault#namespace)
-to use [Vault Namespaces](https://www.vaultproject.io/docs/enterprise/namespaces),
-a `VAULT_NAMESPACE` environment variable will be injected whenever `VAULT_TOKEN` is set.
+to the secret directory at `secrets/vault_token` with access permissions as
+specified in `file_perms` and by injecting a `VAULT_TOKEN` environment variable. If the
+Nomad cluster is [configured](/docs/configuration/vault#namespace) to use
+[Vault Namespaces](https://www.vaultproject.io/docs/enterprise/namespaces),
+a `VAULT_NAMESPACE` environment variable will be injected whenever `VAULT_TOKEN`
+is set.
 
 If Nomad is unable to renew the Vault token (perhaps due to a Vault outage or
 network error), the client will attempt to retrieve a new Vault token. If successful, the
@@ -78,6 +81,12 @@ with Vault as well.
   the task requires. The Nomad client will retrieve a Vault token that is
   limited to those policies.
 
+- `file_perms` `(string: "666")` - Specifies file permissions when creating
+  `secrets/vault_token`, the file containing the Vault token retrieved by
+  Nomad. File permissions are given in Unix octal notation _before applying
+  the Nomad process' umask_. Given the common _umask_ of `0022`, default
+  `file_perms` result in effective file permissions of `644` (`rw-r--r--`).
+
 ## `vault` Examples
 
 The following examples only show the `vault` stanzas. Remember that the