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Generate a swarm joining secret if none is specified

Browse source 
The current behavior of `docker swarm init` is to set up a swarm that
has no secret for joining, and does not require manual acceptance for
workers. Since workers may sometimes receive sensitive data such as pull
credentials, it makes sense to harden the defaults.

This change makes `docker swarm init` generate a random secret if none
is provided, and print it to the terminal. This secret will be needed to
join workers or managers to the swarm. In addition to improving access
control to the cluster, this setup removes an avenue for
denial-of-service attacks, since the secret is necessary to even create
an entry in the node list.

`docker swarm init --secret ""` will set up a swarm without a secret,
matching the old behavior. `docker swarm update --secret ""` removes the
automatically generated secret after `docker swarm init`.

Closes #23785

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
(cherry picked from commit 7342e42fce)
Signed-off-by: Tibor Vass <tibor@docker.com>
This commit is contained in:
Aaron Lehmann 2016-07-05 15:39:26 -07:00 committed by Tibor Vass
parent 23be238414
commit a00d12a8dd
8 changed files with 84 additions and 13 deletions
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34
api/client/swarm/init.go
View file

@ -12,6 +12,13 @@ import (
"github.com/spf13/pflag"
)
const (
generatedSecretEntropyBytes = 16
generatedSecretBase = 36
// floor(log(2^128-1, 36)) + 1
maxGeneratedSecretLength = 25
)
type initOptions struct {
swarmOptions
listenAddr NodeAddrOption
@ -46,6 +53,12 @@ func runInit(dockerCli *client.DockerCli, flags *pflag.FlagSet, opts initOptions
client := dockerCli.Client()
ctx := context.Background()
// If no secret was specified, we create a random one
if !flags.Changed("secret") {
opts.secret = generateRandomSecret()
fmt.Fprintf(dockerCli.Out(), "No --secret provided. Generated random secret:\n\t%s\n\n", opts.secret)
}
req := swarm.InitRequest{
ListenAddr: opts.listenAddr.String(),
ForceNewCluster: opts.forceNewCluster,
@ -57,7 +70,26 @@ func runInit(dockerCli *client.DockerCli, flags *pflag.FlagSet, opts initOptions
return err
}
fmt.Fprintf(dockerCli.Out(), "Swarm initialized: current node (%s) is now a manager.\n", nodeID)
fmt.Fprintf(dockerCli.Out(), "Swarm initialized: current node (%s) is now a manager.\n\n", nodeID)
// Fetch CAHash and Address from the API
info, err := client.Info(ctx)
if err != nil {
return err
}
node, _, err := client.NodeInspectWithRaw(ctx, nodeID)
if err != nil {
return err
}
if node.ManagerStatus != nil && info.Swarm.CACertHash != "" {
var secretArgs string
if opts.secret != "" {
secretArgs = "--secret " + opts.secret
}
fmt.Fprintf(dockerCli.Out(), "To add a worker to this swarm, run the following command:\n\tdocker swarm join %s \\\n\t--ca-hash %s \\\n\t%s\n", secretArgs, info.Swarm.CACertHash, node.ManagerStatus.Addr)
}
return nil
}

2
api/client/swarm/opts.go
View file

@ -237,7 +237,7 @@ func parseExternalCA(caSpec string) (*swarm.ExternalCA, error) {
func addSwarmFlags(flags *pflag.FlagSet, opts *swarmOptions) {
flags.Var(&opts.autoAccept, flagAutoAccept, "Auto acceptance policy (worker, manager or none)")
flags.StringVar(&opts.secret, flagSecret, "", "Set secret value needed to accept nodes into cluster")
flags.StringVar(&opts.secret, flagSecret, "", "Set secret value needed to join a cluster")
flags.Int64Var(&opts.taskHistoryLimit, flagTaskHistoryLimit, 10, "Task history retention limit")
flags.DurationVar(&opts.dispatcherHeartbeat, flagDispatcherHeartbeat, time.Duration(5*time.Second), "Dispatcher heartbeat period")
flags.DurationVar(&opts.nodeCertExpiry, flagCertExpiry, time.Duration(90*24*time.Hour), "Validity period for node certificates")

19
api/client/swarm/secret.go Normal file
View file

@ -0,0 +1,19 @@
package swarm
import (
cryptorand "crypto/rand"
"fmt"
"math/big"
)
func generateRandomSecret() string {
var secretBytes [generatedSecretEntropyBytes]byte
if _, err := cryptorand.Read(secretBytes[:]); err != nil {
panic(fmt.Errorf("failed to read random bytes: %v", err))
}
var nn big.Int
nn.SetBytes(secretBytes[:])
return fmt.Sprintf("%0[1]*s", maxGeneratedSecretLength, nn.Text(generatedSecretBase))
}

13
docs/reference/commandline/swarm_init.md
View file

@ -30,12 +30,24 @@ in the newly created one node Swarm cluster.
```bash
$ docker swarm init --listen-addr 192.168.99.121:2377
No --secret provided. Generated random secret:
4ao565v9jsuogtq5t8s379ulb
Swarm initialized: current node (1ujecd0j9n3ro9i6628smdmth) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --secret 4ao565v9jsuogtq5t8s379ulb \
--ca-hash sha256:07ce22bd1a7619f2adc0d63bd110479a170e7c4e69df05b67a1aa2705c88ef09 \
192.168.99.121:2377
$ docker node ls
ID HOSTNAME MEMBERSHIP STATUS AVAILABILITY MANAGER STATUS LEADER
1ujecd0j9n3ro9i6628smdmth * manager1 Accepted Ready Active Reachable Yes
```
If a secret for joining new nodes is not provided with `--secret`, `docker swarm init` will
generate a random one and print it to the terminal (as seen in the example above). To initialize
a swarm with no secret, use `--secret ""`.
### `--auto-accept value`
This flag controls node acceptance into the cluster. By default, `worker` nodes are
@ -48,7 +60,6 @@ For example, the following initializes a cluster with auto-acceptance of workers
```bash
$ docker swarm init --listen-addr 192.168.99.121:2377 --auto-accept worker
Swarm initialized: current node (1m8cdsylxbf3lk8qriqt07hx1) is now a manager.
```
### `--external-ca value`

4
docs/reference/commandline/swarm_join.md
View file

@ -28,7 +28,7 @@ targeted by this command becomes a `manager`. If it is not specified, it becomes
### Join a node to swarm as a manager
```bash
$ docker swarm join --manager --listen-addr 192.168.99.122:2377 192.168.99.121:2377
$ docker swarm join --secret 4ao565v9jsuogtq5t8s379ulb --manager --listen-addr 192.168.99.122:2377 192.168.99.121:2377
This node joined a Swarm as a manager.
$ docker node ls
ID HOSTNAME MEMBERSHIP STATUS AVAILABILITY MANAGER STATUS LEADER
@ -39,7 +39,7 @@ dvfxp4zseq4s0rih1selh0d20 manager1 Accepted Ready Active Reachab
### Join a node to swarm as a worker
```bash
$ docker swarm join --listen-addr 192.168.99.123:2377 192.168.99.121:2377
$ docker swarm join --secret 4ao565v9jsuogtq5t8s379ulb --listen-addr 192.168.99.123:2377 192.168.99.121:2377
This node joined a Swarm as a worker.
$ docker node ls
ID HOSTNAME MEMBERSHIP STATUS AVAILABILITY MANAGER STATUS LEADER

16
docs/swarm/swarm-tutorial/add-nodes.md
View file

@ -23,16 +23,17 @@ This tutorial uses the name `worker1`.
the existing swarm:
```
docker swarm join <MANAGER-IP>:<PORT>
docker swarm join --secret <SECRET> <MANAGER-IP>:<PORT>
```
Replace `<MANAGER-IP>` with the address of the manager node and `<PORT>`
with the port where the manager listens.
Replace `<SECRET>` with the secret that was printed by `docker swarm init` in the
previous step. Replace `<MANAGER-IP>` with the address of the manager node
and `<PORT>` with the port where the manager listens.
In the tutorial, the following command joins `worker1` to the swarm on `manager1`:
```
$ docker swarm join 192.168.99.100:2377
$ docker swarm join --secret 4ao565v9jsuogtq5t8s379ulb 192.168.99.100:2377
This node joined a Swarm as a worker.
```
@ -40,11 +41,12 @@ the existing swarm:
3. Open a terminal and ssh into the machine where you want to run a second
worker node. This tutorial uses the name `worker2`.
4. Run `docker swarm join <MANAGER-IP>:<PORT>` to create a worker node joined to
4. Run `docker swarm join --secret <SECRET> <MANAGER-IP>:<PORT>` to create a worker node joined to
the existing Swarm.
Replace `<MANAGER-IP>` with the address of the manager node and `<PORT>`
with the port where the manager listens.
Replace `<SECRET>` with the secret that was printed by `docker swarm init` in the
previous step. Replace `<MANAGER-IP>` with the address of the manager node
and `<PORT>` with the port where the manager listens.
5. Open a terminal and ssh into the machine where the manager node runs and run
the `docker node ls` command to see the worker nodes:

7
docs/swarm/swarm-tutorial/create-swarm.md
View file

@ -30,8 +30,15 @@ node. For example, the tutorial uses a machine named `manager1`.
```
$ docker swarm init --listen-addr 192.168.99.100:2377
No --secret provided. Generated random secret:
4ao565v9jsuogtq5t8s379ulb
Swarm initialized: current node (dxn1zf6l61qsb1josjja83ngz) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --secret 4ao565v9jsuogtq5t8s379ulb \
--ca-hash sha256:07ce22bd1a7619f2adc0d63bd110479a170e7c4e69df05b67a1aa2705c88ef09 \
192.168.99.100:2377
```
The `--listen-addr` flag configures the manager node to listen on port

2
integration-cli/docker_cli_swarm_test.go
View file

@ -106,7 +106,7 @@ func (s *DockerSwarmSuite) TestSwarmInit(c *check.C) {
c.Assert(d.Leave(true), checker.IsNil)
out, err = d.Cmd("swarm", "init", "--auto-accept", "none")
out, err = d.Cmd("swarm", "init", "--auto-accept", "none", "--secret", "")
c.Assert(err, checker.IsNil, check.Commentf("out: %v", out))
spec = getSpec()