certificate.go

package ca

import (
	"strings"

	"github.com/pkg/errors"
	"github.com/smallstep/cli/command"
	"github.com/smallstep/cli/crypto/pemutil"
	"github.com/smallstep/cli/errs"
	"github.com/smallstep/cli/flags"
	"github.com/smallstep/cli/token"
	"github.com/smallstep/cli/ui"
	"github.com/smallstep/cli/utils/cautils"
	"github.com/urfave/cli"
)

func certificateCommand() cli.Command {
	return cli.Command{
		Name:   "certificate",
		Action: command.ActionFunc(certificateAction),
		Usage:  "generate a new private key and certificate signed by the root certificate",
		UsageText: `**step ca certificate** <subject> <crt-file> <key-file>
[**--token**=<token>]  [**--issuer**=<name>] [**--ca-url**=<uri>] [**--root**=<file>]
[**--not-before**=<time|duration>] [**--not-after**=<time|duration>]
[**--san**=<SAN>] [**--acme**=<path>] [**--standalone**] [**--webroot**=<path>]
[**--contact**=<email>] [**--http-listen**=<address>] [**--bundle**]
[**--kty**=<type>] [**--curve**=<curve>] [**--size**=<size>] [**--console**]`,
		Description: `**step ca certificate** command generates a new certificate pair

## POSITIONAL ARGUMENTS

<subject>
:  The Common Name, DNS Name, or IP address that will be set as the
Subject Common Name for the certificate. If no Subject Alternative Names (SANs)
are configured (via the --san flag) then the <subject> will be set as the only SAN.

<crt-file>
:  File to write the certificate (PEM format)

<key-file>
:  File to write the private key (PEM format)

## EXAMPLES

Request a new certificate for a given domain. There are no additional SANs
configured, therefore (by default) the <subject> will be used as the only
SAN extension: DNS Name internal.example.com:
'''
$ TOKEN=$(step ca token internal.example.com)
$ step ca certificate --token $TOKEN internal.example.com internal.crt internal.key
'''

Request a new certificate with multiple Subject Alternative Names. The Subject
Common Name of the certificate will be 'foobar'. However, because additional SANs are
configured using the --san flag and 'foobar' is not one of these, 'foobar' will
not be in the SAN extensions of the certificate. The certificate will have 2
IP Address extensions (1.1.1.1, 10.2.3.4) and 1 DNS Name extension (hello.example.com):
'''
$ step ca certificate --san 1.1.1.1 --san hello.example.com --san 10.2.3.4 foobar internal.crt internal.key
'''

Request a new certificate with a 1h validity:
'''
$ TOKEN=$(step ca token internal.example.com)
$ step ca certificate --token $TOKEN --not-after=1h internal.example.com internal.crt internal.key
'''

Request a new certificate using the offline mode, requires the configuration
files, certificates, and keys created with **step ca init**:
'''
$ step ca certificate --offline internal.example.com internal.crt internal.key
'''

Request a new certificate using an OIDC provisioner:
'''
$ step ca certificate --token $(step oauth --oidc --bare) joe@example.com joe.crt joe.key
'''

Request a new certificate using an OIDC provisioner while remaining in the console:
'''
$ step ca certificate joe@example.com joe.crt joe.key --issuer Google --console
'''

Request a new certificate with an RSA public key (default is ECDSA256):
'''
$ step ca certificate foo.internal foo.crt foo.key --kty RSA --size 4096
'''

**step CA ACME** - In order to use the step CA ACME protocol you must add a
ACME provisioner to the step CA config. See **step ca provisioner add -h**.

Request a new certificate using the step CA ACME server and a standalone server
to serve the challenges locally (standalone mode is the default):
'''
$ step ca certificate foobar foo.crt foo.key --provisioner my-acme-provisioner --san foo.internal --san bar.internal
'''

Request a new certificate using the step CA ACME server and an existing server
along with webroot mode to serve the challenges locally:
'''
$ step ca certificate foobar foo.crt foo.key --provisioner my-acme-provisioner --webroot "./acme-www" \
--san foo.internal --san bar.internal
'''

Request a new certificate using the ACME protocol not served via the step CA
(e.g. letsencrypt). NOTE: Let's Encrypt requires that the Subject Common Name
of a requested certificate be validated as an Identifier in the ACME order along
with any other SANS. Therefore, the Common Name must be a valid DNS Name. The
step CA does not impose this requirement.
'''
$ step ca certificate foo.internal foo.crt foo.key \
--acme https://acme-staging-v02.api.letsencrypt.org/directory --san bar.internal
'''`,
		Flags: []cli.Flag{
			consoleFlag,
			flags.CaConfig,
			flags.CaURL,
			flags.Curve,
			flags.Force,
			flags.KTY,
			flags.NotAfter,
			flags.NotBefore,
			flags.Provisioner,
			flags.Root,
			flags.Size,
			flags.Token,
			flags.Offline,
			cli.StringSliceFlag{
				Name: "san",
				Usage: `Add DNS Name, IP Address, or Email Address Subjective Alternative Names (SANs)
that the token is authorized to request. A certificate signing request using
this token must match the complete set of subjective alternative names in the
token 1:1. Use the '--san' flag multiple times to configure multiple SANs. The
'--san' flag and the '--token' flag are mutually exlusive.`,
			},
			cli.StringFlag{
				Name: "acme",
				Usage: `ACME directory URL to be used for requesting certificates via the ACME protocol.
Use this flag to define an ACME server other than the Step CA. If this flag is
absent and an ACME provisioner has been selected then the '--ca-url' flag must be defined.`,
			},
			cli.BoolFlag{
				Name: "standalone",
				Usage: `Get a certificate using the ACME protocol and standalone mode for validation.
Standalone is a mode in which the step process will run a server that will
will respond to ACME challenge validation requests. Standalone is the default
mode for serving challenge validation requests.`,
			},
			cli.StringFlag{
				Name: "webroot",
				Usage: `Get a certificate using the ACME protocol and webroot mode for validation.
Webroot is a mode in which the step process will write a challenge file to a location
being served by an existing fileserver in order to respond to ACME challenge
validation requests.`,
			},
			cli.StringSliceFlag{
				Name: "contact",
				Usage: `Email addresses for contact as part of the ACME protocol. These contacts
may be used to warn of certificate expration or other certificate lifetime events.
Use the '--contact' flag multiple times to configure multiple contacts.`,
			},
			cli.StringFlag{
				Name: "http-listen",
				Usage: `Use a non-standard http address, behind a reverse proxy or load balancer, for
serving ACME challenges. The default address is :80, which requires super user
(sudo) privileges. This flag must be used in conjunction with the '--standalone'
flag.`,
				Value: ":80",
			},
			/*
							TODO: Not implemented yet.
							cli.StringFlag{
								Name: "https-listen",
								Usage: `Use a non-standard https address, behind a reverse proxy or load balancer, for
				serving ACME challenges. The default address is :443, which requires super user
				(sudo) privileges. This flag must be used in conjunction with the '--standalone'
				flag.`,
								Value: ":443",
							},
			*/
		},
	}
}

func certificateAction(ctx *cli.Context) error {
	if err := errs.NumberOfArguments(ctx, 3); err != nil {
		return err
	}

	args := ctx.Args()
	subject := args.Get(0)
	crtFile, keyFile := args.Get(1), args.Get(2)

	tok := ctx.String("token")
	offline := ctx.Bool("offline")
	sans := ctx.StringSlice("san")

	// offline and token are incompatible because the token is generated before
	// the start of the offline CA.
	if offline && len(tok) != 0 {
		return errs.IncompatibleFlagWithFlag(ctx, "offline", "token")
	}

	// certificate flow unifies online and offline flows on a single api
	flow, err := cautils.NewCertificateFlow(ctx)
	if err != nil {
		return err
	}

	if len(tok) == 0 {
		// Use the ACME protocol with a different certificate authority.
		if ctx.IsSet("acme") {
			return cautils.ACMECreateCertFlow(ctx, "")
		}
		if tok, err = flow.GenerateToken(ctx, subject, sans); err != nil {
			switch k := err.(type) {
			// Use the ACME flow with the step certificate authority.
			case *cautils.ErrACMEToken:
				return cautils.ACMECreateCertFlow(ctx, k.Name)
			default:
				return err
			}
		}
	}

	req, pk, err := flow.CreateSignRequest(ctx, tok, subject, sans)
	if err != nil {
		return err
	}

	jwt, err := token.ParseInsecure(tok)
	if err != nil {
		return err
	}

	switch jwt.Payload.Type() {
	case token.JWK: // Validate that subject matches the CSR common name.
		if ctx.String("token") != "" && len(sans) > 0 {
			return errs.MutuallyExclusiveFlags(ctx, "token", "san")
		}
		if strings.ToLower(subject) != strings.ToLower(req.CsrPEM.Subject.CommonName) {
			return errors.Errorf("token subject '%s' and argument '%s' do not match", req.CsrPEM.Subject.CommonName, subject)
		}
	case token.OIDC: // Validate that the subject matches an email SAN
		if len(req.CsrPEM.EmailAddresses) == 0 {
			return errors.New("unexpected token: payload does not contain an email claim")
		}
		if email := req.CsrPEM.EmailAddresses[0]; email != subject {
			return errors.Errorf("token email '%s' and argument '%s' do not match", email, subject)
		}
	case token.AWS, token.GCP, token.Azure:
		// Common name will be validated on the server side, it depends on
		// server configuration.
	default:
		return errors.New("token is not supported")
	}

	if err = flow.Sign(ctx, tok, req.CsrPEM, crtFile); err != nil {
		return err
	}

	_, err = pemutil.Serialize(pk, pemutil.ToFile(keyFile, 0600))
	if err != nil {
		return err
	}

	ui.PrintSelected("Certificate", crtFile)
	ui.PrintSelected("Private Key", keyFile)
	return nil
}