sign.go

package ca

import (
	"crypto/x509"
	"strings"

	"github.com/pkg/errors"
	"github.com/smallstep/certificates/api"
	"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 signCertificateCommand() cli.Command {
	return cli.Command{
		Name:   "sign",
		Action: command.ActionFunc(signCertificateAction),
		Usage:  "generate a new certificate signing a certificate request",
		UsageText: `**step ca sign** <csr-file> <crt-file>
[**--token**=<token>] [**--issuer**=<name>] [**--ca-url**=<uri>] [**--root**=<file>]
[**--not-before**=<time|duration>] [**--not-after**=<time|duration>]
[**--acme**=<uri>] [**--standalone**] [**--webroot**=<path>]
[**--contact**=<email>] [**--http-listen**=<address>] [**--console**]`,
		Description: `**step ca sign** command signs the given csr and generates a new certificate.

## POSITIONAL ARGUMENTS

<csr-file>
:  File with the certificate signing request (PEM format)

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

## EXAMPLES

Sign a new certificate for the given CSR:
'''
$ TOKEN=$(step ca token internal.example.com)
$ step ca sign --token $TOKEN internal.csr internal.crt
'''

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

Sign a new certificate using the offline mode, requires the configuration
files, certificates, and keys created with **step ca init**:
'''
$ step ca sign --offline internal internal.csr internal.crt
'''

**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**.

Sign a CSR using the step CA ACME server and a standalone server
to serve the challenges locally (standalone mode is the default):
'''
$ step ca sign foo.csr foo.crt --provisioner my-acme-provisioner
'''

Sign a CSR using the step CA ACME server and an existing server
along with webroot mode to serve the challenges locally:
'''
$ step ca sign foo.csr foo.crt \
  --provisioner my-acme-provisioner --webroot "./acme-www" \
'''

Sign a CSR using the ACME protocol served by another online CA (not 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 sign foo.csr foo.crt \
--acme https://acme-staging-v02.api.letsencrypt.org/directory
'''`,
		Flags: []cli.Flag{
			flags.CaConfig,
			flags.CaURL,
			flags.Force,
			flags.NotBefore,
			flags.NotAfter,
			flags.Offline,
			flags.Provisioner,
			flags.Root,
			flags.Token,
			consoleFlag,
			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",
			},
		},
	}
}

func signCertificateAction(ctx *cli.Context) error {
	if err := errs.NumberOfArguments(ctx, 2); err != nil {
		return err
	}

	args := ctx.Args()
	csrFile := args.Get(0)
	crtFile := args.Get(1)
	tok := ctx.String("token")
	offline := ctx.Bool("offline")

	csrInt, err := pemutil.Read(csrFile)
	if err != nil {
		return err
	}
	csr, ok := csrInt.(*x509.CertificateRequest)
	if !ok {
		return errors.Errorf("error parsing %s: file is not a certificate request", csrFile)
	}
	if err = csr.CheckSignature(); err != nil {
		return errors.Wrapf(err, "csr has invalid signature")
	}

	// 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.ACMESignCSRFlow(ctx, csr, crtFile, "")
		}
		sans := mergeSans(ctx, csr)
		if tok, err = flow.GenerateToken(ctx, csr.Subject.CommonName, sans); err != nil {
			switch k := err.(type) {
			// Use the ACME flow with the step certificate authority.
			case *cautils.ErrACMEToken:
				return cautils.ACMESignCSRFlow(ctx, csr, crtFile, k.Name)
			default:
				return err
			}
		}
	}

	// Validate common name
	jwt, err := token.ParseInsecure(tok)
	if err != nil {
		return errors.Wrap(err, "error parsing flag '--token'")
	}
	switch jwt.Payload.Type() {
	case token.AWS, token.GCP, token.Azure:
		// Common name will be validated on the server side, it depends on
		// server configuration.
	default:
		if strings.ToLower(jwt.Payload.Subject) != strings.ToLower(csr.Subject.CommonName) {
			return errors.Errorf("token subject '%s' and CSR CommonName '%s' do not match", jwt.Payload.Subject, csr.Subject.CommonName)
		}
	}

	// Sign
	if err := flow.Sign(ctx, tok, api.NewCertificateRequest(csr), crtFile); err != nil {
		return err
	}

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

func mergeSans(ctx *cli.Context, csr *x509.CertificateRequest) []string {
	uniq := make([]string, 0)
	m := make(map[string]bool)
	for _, s := range ctx.StringSlice("san") {
		if _, ok := m[s]; !ok {
			uniq = append(uniq, s)
			m[s] = true
		}
	}
	for _, s := range csr.DNSNames {
		if _, ok := m[s]; !ok {
			uniq = append(uniq, s)
			m[s] = true
		}
	}
	for _, ip := range csr.IPAddresses {
		s := ip.String()
		if _, ok := m[s]; !ok {
			uniq = append(uniq, s)
			m[s] = true
		}
	}
	for _, s := range csr.EmailAddresses {
		if _, ok := m[s]; !ok {
			uniq = append(uniq, s)
			m[s] = true
		}
	}
	return uniq
}