step-ca-cli/command/certificate/create.go

package certificate

import (
	"crypto"
	"crypto/x509"
	"encoding/pem"
	"time"

	"github.com/pkg/errors"
	"github.com/urfave/cli"

	"github.com/smallstep/cli-utils/command"
	"github.com/smallstep/cli-utils/errs"
	"github.com/smallstep/cli-utils/fileutil"
	"github.com/smallstep/cli-utils/ui"
	"go.step.sm/crypto/keyutil"
	"go.step.sm/crypto/pemutil"
	"go.step.sm/crypto/x509util"

	"github.com/smallstep/cli/flags"
	"github.com/smallstep/cli/internal/cryptoutil"
	"github.com/smallstep/cli/utils"
)

const (
	// Supported profiles
	profileLeaf           = "leaf"
	profileSelfSigned     = "self-signed"
	profileIntermediateCA = "intermediate-ca"
	profileRootCA         = "root-ca"
	profileCSR            = "csr" // Used only on sign

	// Default durations
	defaultLeafValidity         = 24 * time.Hour
	defaultSelfSignedValidity   = 24 * time.Hour
	defaultIntermediateValidity = time.Hour * 24 * 365 * 10
	defaultRootValidity         = time.Hour * 24 * 365 * 10
	defaultTemplatevalidity     = 24 * time.Hour
)

func createCommand() cli.Command {
	return cli.Command{
		Name:   "create",
		Action: command.ActionFunc(createAction),
		Usage:  "create a certificate or certificate signing request",
		UsageText: `**step certificate create** <subject> <crt-file> <key-file>
[**--kty**=<type>] [**--curve**=<curve>] [**--size**=<size>]
[**--csr**] [**--profile**=<profile>] [**--template**=<file>]
[**--set**=<key=value>] [**--set-file**=<file>]
[**--not-before**=<duration>] [**--not-after**=<duration>] [**--san**=<SAN>]
[**--ca**=<issuer-cert>] [**--ca-kms**=<uri>]
[**--ca-key**=<issuer-key>] [**--ca-password-file**=<file>]
[**--kms**=<uri>] [**--key**=<file>] [**--password-file**=<file>]
[**--bundle**] [**--skip-csr-signature**]
[**--no-password**] [**--subtle**] [**--insecure**]`,
		Description: `**step certificate create** generates a certificate or a
certificate signing request (CSR) that can be signed later using 'step
certificate sign' (or some other tool) to produce a certificate.

By default this command creates x.509 certificates or CSRs for use with TLS. If
you need something else, you can customize the output using templates. See **TEMPLATES** below.

## POSITIONAL ARGUMENTS

<subject>
: The subject of the certificate. Typically this is a hostname for services or an email address for people.

<crt-file>
: File to write CRT or CSR to (PEM format)

<key-file>
: File to write private key to (PEM format). This argument is optional if **--key** is passed.

## EXIT CODES

This command returns 0 on success and \>0 if any error occurs.

## TEMPLATES

With templates, you can customize the generated certificate or CSR.
Templates are JSON files representing a [certificate](https://pkg.go.dev/go.step.sm/crypto/x509util?tab=doc#Certificate) [1]
or a [certificate request](https://pkg.go.dev/go.step.sm/crypto/x509util?tab=doc#CertificateRequest) [2].
They use Golang's [<text/template>](https://golang.org/pkg/text/template/) package [3] and
[<Sprig>](https://masterminds.github.io/sprig/) functions [4].

Here's the default template used for generating a leaf certificate:
'''
{
	"subject": {{ toJson .Subject }},
	"sans": {{ toJson .SANs }},
{{- if typeIs "*_rsa.PublicKey" .Insecure.CR.PublicKey }}
	"keyUsage": ["keyEncipherment", "digitalSignature"],
{{- else }}
	"keyUsage": ["digitalSignature"],
{{- end }}
	"extKeyUsage": ["serverAuth", "clientAuth"]
}
'''

And this is the default template for a CSR:
'''
{
	"subject": {{ toJson .Subject }},
	"sans": {{ toJson .SANs }}
}
'''

In a custom template, you can change the **subject**, **dnsNames**,
**emailAddresses**, **ipAddresses**, and **uris**, and you can add custom
x.509 **extensions** or set the **signatureAlgorithm**.

For certificate templates, the common extensions **keyUsage**, **extKeyUsage**, and
**basicConstraints** are also represented as JSON fields.

Two variables are available in templates: **.Subject** contains the <subject> argument,
and **.SANs** contains the SANs provided with the **--san** flag.

Both .Subject and .SANs are objects, and they must be converted to JSON to be used in
the template, you can do this using Sprig's **toJson** function. On the .Subject
object you can access the common name string using the template variable
**.Subject.CommonName**. In **EXAMPLES** below, you can see how these
variables are used in a certificate request.

For more information on the template properties and functions see:
'''raw
[1] https://pkg.go.dev/go.step.sm/crypto/x509util?tab=doc#Certificate
[2] https://pkg.go.dev/go.step.sm/crypto/x509util?tab=doc#CertificateRequest
[3] https://golang.org/pkg/text/template/
[4] https://masterminds.github.io/sprig/
'''

## EXAMPLES

Create a CSR and key:

'''
$ step certificate create foo foo.csr foo.key --csr
'''

Create a CSR using an existing private key:

'''
$ step certificate create --csr --key key.priv foo foo.csr
'''

Create a CSR using an existing encrypted private key:

'''
$ step certificate create --csr --key key.priv --password-file key.pass foo foo.csr
'''

Create a CSR and key with custom Subject Alternative Names:

'''
$ step certificate create foo foo.csr foo.key --csr \
  --san inter.smallstep.com --san 1.1.1.1 --san ca.smallstep.com
'''

Create a CSR and key - do not encrypt the key when writing to disk:

'''
$ step certificate create foo foo.csr foo.key --csr --no-password --insecure
'''

Create a root certificate and key:

'''
$ step certificate create root-ca root-ca.crt root-ca.key --profile root-ca
'''

Create an intermediate certificate and key:

'''
$ step certificate create intermediate-ca intermediate-ca.crt intermediate-ca.key \
  --profile intermediate-ca --ca ./root-ca.crt --ca-key ./root-ca.key
'''

Create a leaf certificate and key:

'''
$ step certificate create foo foo.crt foo.key --profile leaf \
  --ca ./intermediate-ca.crt --ca-key ./intermediate-ca.key
'''

Create a leaf certificate and encrypt the private key:

'''
$ step certificate create foo foo.crt foo.key --profile leaf \
   --password-file ./leaf.pass \
   --ca ./intermediate-ca.crt --ca-key ./intermediate-ca.key
'''

Create a leaf certificate and decrypt the CA private key:

'''
$ step certificate create foo foo.crt foo.key --profile leaf \
   --ca ./intermediate-ca.crt --ca-key ./intermediate-ca.key --ca-password-file ./intermediate.pass
'''

Create a leaf certificate and key with custom Subject Alternative Names:

'''
$ step certificate create foo foo.crt foo.key --profile leaf \
  --ca ./intermediate-ca.crt --ca-key ./intermediate-ca.key \
  --san inter.smallstep.com --san 1.1.1.1 --san ca.smallstep.com
'''

Create a leaf certificate and key with custom validity:

'''
$ step certificate create foo foo.crt foo.key --profile leaf \
  --ca ./intermediate-ca.crt --ca-key ./intermediate-ca.key \
  --not-before 24h --not-after 2160h
'''

Create a self-signed leaf certificate and key:

'''
$ step certificate create self-signed-leaf.local leaf.crt leaf.key --profile self-signed --subtle
'''

Create a root certificate and key with underlying OKP Ed25519:

'''
$ step certificate create root-ca root-ca.crt root-ca.key --profile root-ca \
  --kty OKP --curve Ed25519
'''

Create an intermediate certificate and key with underlying EC P-256 key pair:

'''
$ step certificate create intermediate-ca intermediate-ca.crt intermediate-ca.key \
  --profile intermediate-ca --ca ./root-ca.crt --ca-key ./root-ca.key --kty EC --curve P-256
'''

Create a leaf certificate and key with underlying RSA 2048 key pair:

'''
$ step certificate create foo foo.crt foo.key --profile leaf \
  --ca ./intermediate-ca.crt --ca-key ./intermediate-ca.key --kty RSA --size 2048
'''

Create a CSR and key with underlying OKP Ed25519:

'''
$ step certificate create foo foo.csr foo.key --csr --kty OKP --curve Ed25519
'''

Create a root certificate using a custom template. The root certificate will
have a path length constraint that allows at least 2 intermediates:
'''
$ cat root.tpl
{
	"subject": {
		"commonName": "Acme Corporation Root CA"
	},
	"issuer": {
		"commonName": "Acme Corporation Root CA"
	},
	"keyUsage": ["certSign", "crlSign"],
	"basicConstraints": {
		"isCA": true,
		"maxPathLen": 2
	}
}
$ step certificate create --template root.tpl \
  "Acme Corporation Root CA" root_ca.crt root_ca_key
'''

Create an intermediate certificate using the previous root. By extending the
maxPathLen we are enabling this intermediate sign leaf and intermediate
certificates. We will also make the subject configurable using the **--set** and
**--set-file** flags.
'''
$ cat intermediate.tpl
{
	"subject": {
		"country": {{ toJson .Insecure.User.country }},
		"organization": {{ toJson .Insecure.User.organization }},
		"organizationalUnit": {{ toJson .Insecure.User.organizationUnit }},
		"commonName": {{toJson .Subject.CommonName }}
	},
	"keyUsage": ["certSign", "crlSign"],
	"basicConstraints": {
		"isCA": true,
		"maxPathLen": 1
	}
}
$ cat organization.json
{
	"country": "US",
	"organization": "Acme Corporation",
	"organizationUnit": "HQ"
}
$ step certificate create --template intermediate.tpl \
  --ca root_ca.crt --ca-key root_ca_key \
  --set-file organization.json --set organizationUnit=Engineering \
  "Acme Corporation Intermediate CA" intermediate_ca.crt intermediate_ca_key
'''

Sign a new intermediate using the previous intermediate, now with path
length 0 using the **--profile** flag:
'''
$ step certificate create --profile intermediate-ca \
  --ca intermediate_ca.crt --ca-key intermediate_ca_key \
  "Coyote Corporation" coyote_ca.crt coyote_ca_key
'''

Create a leaf certificate, that is the default profile and bundle it with
the two intermediate certificates and validate it:
'''
$ step certificate create --ca coyote_ca.crt --ca-key coyote_ca_key \
  "coyote@acme.corp" leaf.crt coyote.key
$ cat leaf.crt coyote_ca.crt intermediate_ca.crt > coyote.crt
$ step certificate verify --roots root_ca.crt coyote.crt
'''

Create a certificate request using a template:
'''
$ cat csr.tpl
{
    "subject": {
        "country": "US",
        "organization": "Coyote Corporation",
        "commonName": "{{ .Subject.CommonName }}"
    },
	"sans": {{ toJson .SANs }}
}
$ step certificate create --csr --template csr.tpl --san coyote@acme.corp \
  "Wile E. Coyote" coyote.csr coyote.key
'''

Create a CSR using <step-kms-plugin>:
'''
$ step certificate create --csr --key 'yubikey:slot-id=9a?pin=value=123456' coyote@acme.corp coyote.csr
'''

Create a root certificate using <step-kms-plugin>:
'''
$ step certificate create --profile root-ca --key 'yubikey:slot-id=9a?pin=value=123456' 'KMS Root' root_ca.crt
'''

Create a root certificate using <step-kms-plugin> and the <--kms> flag:
'''
$ step kms create \
  --kms 'pkcs11:module-path=/usr/local/lib/softhsm/libsofthsm2.so;token=smallstep?pin-value=password' \
  'pkcs11:id=4000;object=root-key'
$ step certificate create \
  --profile root-ca \
  --kms 'pkcs11:module-path=/usr/local/lib/softhsm/libsofthsm2.so;token=smallstep?pin-value=password' \
  --key 'pkcs11:id=4000' \
  'KMS Root' root_ca.crt
'''

Create an intermediate certificate using <step-kms-plugin>:
'''
$ step kms create \
  --kms 'pkcs11:module-path=/usr/local/lib/softhsm/libsofthsm2.so;token=smallstep?pin-value=password' \
  'pkcs11:id=4001;object=intermediate-key'
$ step certificate create \
  --profile intermediate-ca \
  --ca-kms 'pkcs11:module-path=/usr/local/lib/softhsm/libsofthsm2.so;token=smallstep?pin-value=password'
  --ca root_ca.crt --ca-key 'pkcs11:id=4000' \
  --kms 'pkcs11:module-path=/usr/local/lib/softhsm/libsofthsm2.so;token=smallstep?pin-value=password' \
  --key 'pkcs11:id=4001' \
  'My KMS Intermediate' intermediate_ca.crt
'''

Create an intermediate certificate for an RSA decryption key in Google Cloud KMS, signed by a root stored on disk, using <step-kms-plugin>:
'''
$ step certificate create \
  --profile intermediate-ca \
  --ca root_ca.crt --ca-key root_ca_key \
  --kms cloudkms: \
  --key 'projects/myProjectID/locations/global/keyRings/myKeyRing/cryptoKeys/myKey/cryptoKeyVersions/1' \
  --skip-csr-signature \
  'My RSA Intermediate' intermediate_rsa_ca.crt
'''

Create an intermediate certificate for an RSA signing key in Google Cloud KMS, signed by a root stored in an HSM, using <step-kms-plugin>:
'''
$ step certificate create \
  --profile intermediate-ca \
  --ca-kms 'pkcs11:module-path=/usr/local/lib/softhsm/libsofthsm2.so;token=smallstep?pin-value=password' \
  --ca root_ca.crt --ca-key 'pkcs11:id=4000' \
  --kms cloudkms: \
  --key 'projects/myProjectID/locations/global/keyRings/myKeyRing/cryptoKeys/myKey/cryptoKeyVersions/1' \
  'My RSA Intermediate' intermediate_rsa_ca.crt
'''
`,
		Flags: []cli.Flag{
			flags.KTY,
			flags.Size,
			flags.Curve,
			cli.BoolFlag{
				Name:  "csr",
				Usage: `Generate a certificate signing request (CSR) instead of a certificate.`,
			},
			cli.StringFlag{
				Name:  "profile",
				Value: profileLeaf,
				Usage: `The certificate profile sets various certificate details such as
  certificate use and expiration. The default profile is 'leaf' which is suitable
  for a client or server using TLS.

: <profile> is a case-sensitive string and must be one of:

    **leaf**
	:  Generate a leaf x.509 certificate suitable for use with TLS.

    **intermediate-ca**
    :  Generate a certificate that can be used to sign additional leaf certificates.

    **root-ca**
    :  Generate a new self-signed root certificate suitable for use as a root CA.

    **self-signed**
    :  Generate a new self-signed leaf certificate suitable for use with TLS.
	This profile requires the **--subtle** flag because the use of self-signed leaf
	certificates is discouraged unless absolutely necessary.`,
			},
			flags.Template,
			flags.TemplateSet,
			flags.TemplateSetFile,
			cli.StringFlag{
				Name: "not-before",
				Usage: `The <time|duration> set in the NotBefore property of the certificate. If a
<time> is used it is expected to be in RFC 3339 format. If a <duration> is
used, it is a sequence of decimal numbers, each with optional fraction and a
unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns",
"us" (or "µs"), "ms", "s", "m", "h".`,
			},
			cli.StringFlag{
				Name: "not-after",
				Usage: `The <time|duration> set in the NotAfter property of the certificate. If a
<time> is used it is expected to be in RFC 3339 format. If a <duration> is
used, it is a sequence of decimal numbers, each with optional fraction and a
unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns",
"us" (or "µs"), "ms", "s", "m", "h".`,
			},
			cli.StringSliceFlag{
				Name: "san",
				Usage: `Add DNS or IP Address Subjective Alternative Names (SANs). Use the '--san'
flag multiple times to configure multiple SANs.`,
			},
			cli.StringFlag{
				Name:  "ca",
				Usage: `The certificate authority used to issue the new certificate (PEM file).`,
			},
			cli.StringFlag{
				Name:  "ca-kms",
				Usage: "The <uri> to configure the KMS used for signing the certificate",
			},
			cli.StringFlag{
				Name:  "ca-key",
				Usage: `The certificate authority private key used to sign the new certificate (PEM file).`,
			},
			cli.StringFlag{
				Name: "ca-password-file",
				Usage: `The path to the <file> containing the password to
decrypt the CA private key.`,
			},
			flags.KMSUri,
			cli.StringFlag{
				Name:  "key",
				Usage: "The <file> of the private key to use instead of creating a new one (PEM file).",
			},
			cli.StringFlag{
				Name: "password-file",
				Usage: `The path to the <file> containing the password to
encrypt the new private key or decrypt the user submitted private key.`,
			},
			cli.BoolFlag{
				Name: "no-password",
				Usage: `Do not ask for a password to encrypt the private key.
Sensitive key material will be written to disk unencrypted. This is not
recommended. Requires **--insecure** flag.`,
			},
			cli.BoolFlag{
				Name: "bundle",
				Usage: `Bundle the new leaf certificate with the signing certificate. This flag requires
the **--ca** flag.`,
			},
			cli.BoolFlag{
				Name:  "skip-csr-signature",
				Usage: "Skip creating and signing a CSR.",
			},
			flags.Force,
			flags.Subtle,
			flags.InsecureHidden,
		},
	}
}

func createAction(ctx *cli.Context) error {
	minArg := 2
	if key := ctx.String("key"); key == "" {
		minArg = 3
	}
	if err := errs.MinMaxNumberOfArguments(ctx, minArg, 3); err != nil {
		return err
	}

	insecureMode := ctx.Bool("insecure")
	noPass := ctx.Bool("no-password")
	if noPass && !insecureMode {
		return errs.RequiredWithFlag(ctx, "no-password", "insecure")
	}

	subject := ctx.Args().Get(0)
	crtFile := ctx.Args().Get(1)
	keyFile := ctx.Args().Get(2)
	if crtFile == keyFile {
		return errs.EqualArguments(ctx, "<crt-file>", "<key-file>")
	}

	notBefore, ok := flags.ParseTimeOrDuration(ctx.String("not-before"))
	if !ok {
		return errs.InvalidFlagValue(ctx, "not-before", ctx.String("not-before"), "")
	}
	notAfter, ok := flags.ParseTimeOrDuration(ctx.String("not-after"))
	if !ok {
		return errs.InvalidFlagValue(ctx, "not-after", ctx.String("not-after"), "")
	}
	if !notAfter.IsZero() && !notBefore.IsZero() && notBefore.After(notAfter) {
		return errs.IncompatibleFlagValues(ctx, "not-before", ctx.String("not-before"), "not-after", ctx.String("not-after"))
	}

	var (
		sans             = ctx.StringSlice("san")
		profile          = ctx.String("profile")
		templateFile     = ctx.String("template")
		bundle           = ctx.Bool("bundle")
		subtle           = ctx.Bool("subtle")
		skipCSRSignature = ctx.Bool("skip-csr-signature")
	)

	if ctx.IsSet("profile") && templateFile != "" {
		return errs.IncompatibleFlagWithFlag(ctx, "profile", "template")
	}

	if ctx.Bool("csr") && skipCSRSignature {
		return errs.IncompatibleFlagWithFlag(ctx, "csr", "skip-csr-signature")
	}

	// Read template if passed
	var template string
	if templateFile != "" {
		b, err := utils.ReadFile(templateFile)
		if err != nil {
			return err
		}
		template = string(b)
	}

	// Parse --set and --set-file
	userData, err := flags.GetTemplateData(ctx)
	if err != nil {
		return err
	}

	// Read or generate key pair.
	// When the flag --key has a public key, priv will be nil.
	pub, priv, err := parseOrCreateKey(ctx)
	if err != nil {
		return err
	}

	// Create certificate request
	if ctx.Bool("csr") {
		if priv == nil {
			return errors.New("invalid value for flag --key: a private key is required")
		}
		if bundle {
			return errs.IncompatibleFlagWithFlag(ctx, "bundle", "csr")
		}
		if profile != "" && profile != profileLeaf {
			return errs.IncompatibleFlagWithFlag(ctx, "profile", "csr")
		}
		if ctx.IsSet("ca") {
			return errs.IncompatibleFlagWithFlag(ctx, "ca", "csr")
		}
		if ctx.IsSet("ca-key") {
			return errs.IncompatibleFlagWithFlag(ctx, "ca-key", "csr")
		}
		if ctx.IsSet("ca-password-file") {
			return errs.IncompatibleFlagWithFlag(ctx, "ca-password-file", "csr")
		}
		if ctx.IsSet("not-before") {
			return errs.IncompatibleFlagWithFlag(ctx, "not-before", "csr")
		}
		if ctx.IsSet("not-after") {
			return errs.IncompatibleFlagWithFlag(ctx, "not-after", "csr")
		}

		// Use subject as default san
		if len(sans) == 0 {
			sans = append(sans, subject)
		}

		// Use default template if empty
		if template == "" {
			template = x509util.DefaultCertificateRequestTemplate
		}

		// Create certificate request
		data := x509util.CreateTemplateData(subject, sans)
		data.SetUserData(userData)
		csr, err := x509util.NewCertificateRequest(priv, x509util.WithTemplate(template, data))
		if err != nil {
			return err
		}
		cr, err := csr.GetCertificateRequest()
		if err != nil {
			return err
		}

		block, err := pemutil.Serialize(cr)
		if err != nil {
			return err
		}

		// Save key and certificate request
		if keyFile != "" {
			if err := savePrivateKey(ctx, keyFile, priv, noPass); err != nil {
				return err
			}
		}

		if err = fileutil.WriteFile(crtFile, pem.EncodeToMemory(block), 0o600); err != nil {
			return errs.FileError(err, crtFile)
		}

		ui.Printf("Your certificate signing request has been saved in %s.\n", crtFile)
		if keyFile != "" {
			ui.Printf("Your private key has been saved in %s.\n", keyFile)
		}

		return nil
	}

	// Bundle is only valid for leaf certificates
	if bundle && profile != profileLeaf {
		return errs.IncompatibleFlagValue(ctx, "bundle", "profile", profile)
	}

	// Subtle is required on self-signed certificates
	if !subtle && profile == profileSelfSigned {
		return errs.RequiredWithFlagValue(ctx, "profile", "self-signed", "subtle")
	}

	// When a public key is given with the flag --key, priv is nil and
	// --skip-csr-signature is required.
	if priv == nil && !skipCSRSignature {
		return errors.New("flag '--skip-csr-signature' is required with a public key")
	}

	// Parse --ca and --ca-key flags and check when those flags are required.
	parent, signer, err := parseSigner(ctx, priv)
	if err != nil {
		return err
	}

	// Use subject as default SAN when using a template or for leaf and self-signed certificates.
	if len(sans) == 0 && (template != "" || profile == profileLeaf || profile == profileSelfSigned) {
		sans = append(sans, subject)
	}

	var defaultValidity time.Duration
	if template == "" {
		switch profile {
		case profileLeaf:
			template = x509util.DefaultLeafTemplate
			defaultValidity = defaultLeafValidity
		case profileIntermediateCA:
			template = x509util.DefaultIntermediateTemplate
			defaultValidity = defaultIntermediateValidity
		case profileRootCA:
			template = x509util.DefaultRootTemplate
			defaultValidity = defaultRootValidity
		case profileSelfSigned:
			template = x509util.DefaultLeafTemplate
			defaultValidity = defaultSelfSignedValidity
		default:
			return errs.InvalidFlagValue(ctx, "profile", profile, "leaf, intermediate-ca, root-ca, self-signed")
		}
	} else {
		defaultValidity = defaultTemplatevalidity
	}

	// Create X.509 certificate
	templateData := x509util.CreateTemplateData(subject, sans)
	templateData.SetUserData(userData)

	certTemplate := &x509.Certificate{}
	if skipCSRSignature {
		certTemplate.PublicKey = pub
		certificate, err := x509util.NewCertificateFromX509(certTemplate, x509util.WithTemplate(template, templateData))
		if err != nil {
			return err
		}
		certTemplate = certificate.GetCertificate()
	} else {
		// Create X.509 certificate used as base for the certificate
		cr, err := x509util.CreateCertificateRequest(subject, sans, priv)
		if err != nil {
			return err
		}
		certificate, err := x509util.NewCertificate(cr, x509util.WithTemplate(template, templateData))
		if err != nil {
			return err
		}
		certTemplate = certificate.GetCertificate()
	}

	if parent == nil {
		parent = certTemplate
	}

	// Set certificate validity
	certTemplate.NotBefore = notBefore
	certTemplate.NotAfter = notAfter

	if certTemplate.NotBefore.IsZero() {
		certTemplate.NotBefore = time.Now()
	}
	if certTemplate.NotAfter.IsZero() {
		certTemplate.NotAfter = certTemplate.NotBefore.Add(defaultValidity)
	}
	// Check that the certificate is not already expired
	if certTemplate.NotBefore.After(certTemplate.NotAfter) {
		return errors.Errorf("invalid value '%s' for flag '--not-after': certificate is already expired", ctx.String("not-after"))
	}

	cert, err := x509util.CreateCertificate(certTemplate, parent, pub, signer)
	if err != nil {
		return err
	}

	// Serialize certificate
	block, err := pemutil.Serialize(cert)
	if err != nil {
		return err
	}

	pubBytes := pem.EncodeToMemory(block)
	if bundle {
		if block, err = pemutil.Serialize(parent); err != nil {
			return err
		}
		pubBytes = append(pubBytes, pem.EncodeToMemory(block)...)
	}

	// Save key and certificate request
	if keyFile != "" && priv != nil && !cryptoutil.IsKMSSigner(priv) {
		if err := savePrivateKey(ctx, keyFile, priv, noPass); err != nil {
			return err
		}
	}

	if err = fileutil.WriteFile(crtFile, pubBytes, 0o600); err != nil {
		return errs.FileError(err, crtFile)
	}

	ui.Printf("Your certificate has been saved in %s.\n", crtFile)
	if keyFile != "" {
		ui.Printf("Your private key has been saved in %s.\n", keyFile)
	}

	return nil
}

func parseOrCreateKey(ctx *cli.Context) (crypto.PublicKey, crypto.Signer, error) {
	var (
		kms     = ctx.String("kms")
		keyFile = ctx.String("key")
	)

	// Validate key parameters and generate key pair
	if keyFile == "" {
		insecureMode := ctx.Bool("insecure")
		kty, crv, size, err := utils.GetKeyDetailsFromCLI(ctx, insecureMode, "kty", "curve", "size")
		if err != nil {
			return nil, nil, err
		}
		if insecureMode { // put keyutil in insecure mode, allowing RSA keys shorter than 2048 bits
			undoInsecure := keyutil.Insecure()
			defer undoInsecure()
		}
		pub, priv, err := keyutil.GenerateKeyPair(kty, crv, size)
		if err != nil {
			return nil, nil, err
		}
		signer, ok := priv.(crypto.Signer)
		if !ok {
			return nil, nil, errors.Errorf("private key of type %T is not a crypto.Signer", priv)
		}
		return pub, signer, nil
	}

	// Validate incompatible flags and read a key file
	switch {
	case ctx.IsSet("kty"):
		return nil, nil, errs.IncompatibleFlag(ctx, "key", "kty")
	case ctx.IsSet("crv"):
		return nil, nil, errs.IncompatibleFlag(ctx, "key", "crv")
	case ctx.IsSet("size"):
		return nil, nil, errs.IncompatibleFlag(ctx, "key", "size")
	}

	opts := []pemutil.Options{}
	passFile := ctx.String("password-file")
	if passFile != "" {
		opts = append(opts, pemutil.WithPasswordFile(passFile))
	}

	var pub crypto.PublicKey
	var signer crypto.Signer

	signer, err := cryptoutil.CreateSigner(kms, keyFile, opts...)
	if err != nil {
		// TODO: check sentinel error; if it's not a signer, it could be a public key instead
		pub, err = cryptoutil.PublicKey(kms, keyFile, opts...)
		if err != nil {
			return nil, nil, err
		}
	} else {
		pub = signer.Public()
		// Make sure we can sign X509 certificates with it.
		if !cryptoutil.IsX509Signer(signer) {
			return nil, nil, errs.InvalidFlagValueMsg(ctx, "key", keyFile, "the given key cannot sign X509 certificates")
		}
	}

	return pub, signer, nil
}

// parseSigner returns the parent certificate and key for leaf and intermediate
// certificates. When a template is used, it will return the key only if the
// flags --ca and --ca-key are passed.
func parseSigner(ctx *cli.Context, defaultSigner crypto.Signer) (*x509.Certificate, crypto.Signer, error) {
	var (
		caCert   = ctx.String("ca")
		caKey    = ctx.String("ca-key")
		caKMS    = ctx.String("ca-kms")
		profile  = ctx.String("profile")
		template = ctx.String("template")
	)

	// Check required flags when profile is used.
	if template == "" {
		switch profile {
		case profileLeaf, profileIntermediateCA:
			if caCert == "" {
				return nil, nil, errs.RequiredWithFlagValue(ctx, "profile", profile, "ca")
			}
			if caKey == "" {
				return nil, nil, errs.RequiredWithFlagValue(ctx, "profile", profile, "ca-key")
			}
		case profileRootCA, profileSelfSigned:
			if caCert != "" {
				return nil, nil, errs.IncompatibleFlagValue(ctx, "ca", "profile", profile)
			}
			if caKey != "" {
				return nil, nil, errs.IncompatibleFlagValue(ctx, "ca-key", "profile", profile)
			}
		default:
			return nil, nil, errs.InvalidFlagValue(ctx, "profile", profile, "leaf, intermediate-ca, root-ca, self-signed")
		}
	}

	// Root, self-signed, or template with no parent.
	if caCert == "" && caKey == "" {
		return nil, defaultSigner, nil
	}

	// Leaf, intermediate or template with
	switch {
	case caCert != "" && caKey == "":
		return nil, nil, errs.RequiredWithFlag(ctx, "ca", "ca-key")
	case caCert == "" && caKey != "":
		return nil, nil, errs.RequiredWithFlag(ctx, "ca-key", "ca")
	}

	// Parse --ca as a certificate.
	cert, err := pemutil.ReadCertificate(caCert)
	if err != nil {
		return nil, nil, err
	}

	// Parse --ca-key as a crypto.Signer.
	passFile := ctx.String("ca-password-file")
	opts := []pemutil.Options{}
	if passFile != "" {
		opts = append(opts, pemutil.WithPasswordFile(passFile))
	}

	signer, err := cryptoutil.CreateSigner(caKMS, caKey, opts...)
	if err != nil {
		return nil, nil, err
	}

	// Make sure we can sign X509 certificates with it.
	if !cryptoutil.IsX509Signer(signer) {
		return nil, nil, errs.InvalidFlagValueMsg(ctx, "ca-key", caKey, "the given key cannot sign X509 certificates")
	}

	return cert, signer, nil
}

// savePrivateKey saves the given key, asking the password if necessary.
func savePrivateKey(ctx *cli.Context, filename string, priv interface{}, insecure bool) error {
	var err error
	if insecure {
		_, err = pemutil.Serialize(priv, pemutil.ToFile(filename, 0o600))
		return err
	}

	var pass []byte
	if passFile := ctx.String("password-file"); passFile != "" {
		pass, err = utils.ReadPasswordFromFile(passFile)
		if err != nil {
			return errors.Wrap(err, "error reading encrypting password from file")
		}
	} else {
		pass, err = ui.PromptPassword("Please enter the password to encrypt the private key",
			ui.WithValidateNotEmpty())
		if err != nil {
			return errors.Wrap(err, "error reading password")
		}
	}
	_, err = pemutil.Serialize(priv, pemutil.WithPassword(pass), pemutil.ToFile(filename, 0o600))
	return err
}