certificates/authority/provisioner/x5c.go

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package provisioner
import (
"context"
"crypto/x509"
"encoding/pem"
"net/http"
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"time"
"github.com/pkg/errors"
"github.com/smallstep/certificates/errs"
"go.step.sm/crypto/jose"
"go.step.sm/crypto/sshutil"
"go.step.sm/crypto/x509util"
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)
// x5cPayload extends jwt.Claims with step attributes.
type x5cPayload struct {
jose.Claims
SANs []string `json:"sans,omitempty"`
Step *stepPayload `json:"step,omitempty"`
chains [][]*x509.Certificate
}
// X5C is the default provisioner, an entity that can sign tokens necessary for
// signature requests.
type X5C struct {
*base
Type string `json:"type"`
Name string `json:"name"`
Roots []byte `json:"roots"`
Claims *Claims `json:"claims,omitempty"`
Options *Options `json:"options,omitempty"`
claimer *Claimer
audiences Audiences
rootPool *x509.CertPool
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}
// GetID returns the provisioner unique identifier. The name and credential id
// should uniquely identify any X5C provisioner.
func (p *X5C) GetID() string {
return "x5c/" + p.Name
}
// GetTokenID returns the identifier of the token.
func (p *X5C) GetTokenID(ott string) (string, error) {
// Validate payload
token, err := jose.ParseSigned(ott)
if err != nil {
return "", errors.Wrap(err, "error parsing token")
}
// Get claims w/out verification. We need to look up the provisioner
// key in order to verify the claims and we need the issuer from the claims
// before we can look up the provisioner.
var claims jose.Claims
if err = token.UnsafeClaimsWithoutVerification(&claims); err != nil {
return "", errors.Wrap(err, "error verifying claims")
}
return claims.ID, nil
}
// GetName returns the name of the provisioner.
func (p *X5C) GetName() string {
return p.Name
}
// GetType returns the type of provisioner.
func (p *X5C) GetType() Type {
return TypeX5C
}
// GetEncryptedKey returns the base provisioner encrypted key if it's defined.
func (p *X5C) GetEncryptedKey() (string, string, bool) {
return "", "", false
}
// Init initializes and validates the fields of a X5C type.
func (p *X5C) Init(config Config) error {
switch {
case p.Type == "":
return errors.New("provisioner type cannot be empty")
case p.Name == "":
return errors.New("provisioner name cannot be empty")
case len(p.Roots) == 0:
return errors.New("provisioner root(s) cannot be empty")
}
p.rootPool = x509.NewCertPool()
var (
block *pem.Block
rest = p.Roots
)
for rest != nil {
block, rest = pem.Decode(rest)
if block == nil {
break
}
cert, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return errors.Wrap(err, "error parsing x509 certificate from PEM block")
}
p.rootPool.AddCert(cert)
}
// Verify that at least one root was found.
if len(p.rootPool.Subjects()) == 0 {
return errors.Errorf("no x509 certificates found in roots attribute for provisioner %s", p.GetName())
}
// Update claims with global ones
var err error
if p.claimer, err = NewClaimer(p.Claims, config.Claims); err != nil {
return err
}
p.audiences = config.Audiences.WithFragment(p.GetID())
return nil
}
// authorizeToken performs common jwt authorization actions and returns the
// claims for case specific downstream parsing.
// e.g. a Sign request will auth/validate different fields than a Revoke request.
func (p *X5C) authorizeToken(token string, audiences []string) (*x5cPayload, error) {
jwt, err := jose.ParseSigned(token)
if err != nil {
return nil, errs.Wrap(http.StatusUnauthorized, err, "x5c.authorizeToken; error parsing x5c token")
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}
verifiedChains, err := jwt.Headers[0].Certificates(x509.VerifyOptions{
Roots: p.rootPool,
})
if err != nil {
return nil, errs.Wrap(http.StatusUnauthorized, err,
"x5c.authorizeToken; error verifying x5c certificate chain in token")
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}
leaf := verifiedChains[0][0]
if leaf.KeyUsage&x509.KeyUsageDigitalSignature == 0 {
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return nil, errs.Unauthorized("x5c.authorizeToken; certificate used to sign x5c token cannot be used for digital signature")
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}
// Using the leaf certificates key to validate the claims accomplishes two
// things:
// 1. Asserts that the private key used to sign the token corresponds
// to the public certificate in the `x5c` header of the token.
// 2. Asserts that the claims are valid - have not been tampered with.
var claims x5cPayload
if err = jwt.Claims(leaf.PublicKey, &claims); err != nil {
return nil, errs.Wrap(http.StatusUnauthorized, err, "x5c.authorizeToken; error parsing x5c claims")
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}
// According to "rfc7519 JSON Web Token" acceptable skew should be no
// more than a few minutes.
if err = claims.ValidateWithLeeway(jose.Expected{
Issuer: p.Name,
Time: time.Now().UTC(),
}, time.Minute); err != nil {
return nil, errs.Wrapf(http.StatusUnauthorized, err, "x5c.authorizeToken; invalid x5c claims")
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}
// validate audiences with the defaults
if !matchesAudience(claims.Audience, audiences) {
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return nil, errs.Unauthorized("x5c.authorizeToken; x5c token has invalid audience "+
"claim (aud); expected %s, but got %s", audiences, claims.Audience)
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}
if claims.Subject == "" {
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return nil, errs.Unauthorized("x5c.authorizeToken; x5c token subject cannot be empty")
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}
// Save the verified chains on the x5c payload object.
claims.chains = verifiedChains
return &claims, nil
}
// AuthorizeRevoke returns an error if the provisioner does not have rights to
// revoke the certificate with serial number in the `sub` property.
func (p *X5C) AuthorizeRevoke(ctx context.Context, token string) error {
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_, err := p.authorizeToken(token, p.audiences.Revoke)
return errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeRevoke")
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}
// AuthorizeSign validates the given token.
func (p *X5C) AuthorizeSign(ctx context.Context, token string) ([]SignOption, error) {
claims, err := p.authorizeToken(token, p.audiences.Sign)
if err != nil {
return nil, errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeSign")
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}
// NOTE: This is for backwards compatibility with older versions of cli
// and certificates. Older versions added the token subject as the only SAN
// in a CSR by default.
if len(claims.SANs) == 0 {
claims.SANs = []string{claims.Subject}
}
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// Certificate templates
data := x509util.CreateTemplateData(claims.Subject, claims.SANs)
if v, err := unsafeParseSigned(token); err == nil {
data.SetToken(v)
}
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templateOptions, err := TemplateOptions(p.Options, data)
if err != nil {
return nil, errs.Wrap(http.StatusInternalServerError, err, "jwk.AuthorizeSign")
}
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return []SignOption{
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templateOptions,
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// modifiers / withOptions
newProvisionerExtensionOption(TypeX5C, p.Name, ""),
profileLimitDuration{p.claimer.DefaultTLSCertDuration(),
claims.chains[0][0].NotBefore, claims.chains[0][0].NotAfter},
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// validators
commonNameValidator(claims.Subject),
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defaultSANsValidator(claims.SANs),
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defaultPublicKeyValidator{},
newValidityValidator(p.claimer.MinTLSCertDuration(), p.claimer.MaxTLSCertDuration()),
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}, nil
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}
// AuthorizeRenew returns an error if the renewal is disabled.
func (p *X5C) AuthorizeRenew(ctx context.Context, cert *x509.Certificate) error {
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if p.claimer.IsDisableRenewal() {
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return errs.Unauthorized("x5c.AuthorizeRenew; renew is disabled for x5c provisioner %s", p.GetID())
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}
return nil
}
// AuthorizeSSHSign returns the list of SignOption for a SignSSH request.
func (p *X5C) AuthorizeSSHSign(ctx context.Context, token string) ([]SignOption, error) {
if !p.claimer.IsSSHCAEnabled() {
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return nil, errs.Unauthorized("x5c.AuthorizeSSHSign; sshCA is disabled for x5c provisioner %s", p.GetID())
}
claims, err := p.authorizeToken(token, p.audiences.SSHSign)
if err != nil {
return nil, errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeSSHSign")
}
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if claims.Step == nil || claims.Step.SSH == nil {
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return nil, errs.Unauthorized("x5c.AuthorizeSSHSign; x5c token must be an SSH provisioning token")
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}
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opts := claims.Step.SSH
signOptions := []SignOption{
// validates user's SSHOptions with the ones in the token
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sshCertOptionsValidator(*opts),
// validate users's KeyID is the token subject.
sshCertOptionsValidator(SignSSHOptions{KeyID: claims.Subject}),
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}
// Default template attributes.
certType := sshutil.UserCert
keyID := claims.Subject
principals := []string{claims.Subject}
// Use options in the token.
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if opts.CertType != "" {
if certType, err = sshutil.CertTypeFromString(opts.CertType); err != nil {
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return nil, errs.Wrap(http.StatusBadRequest, err, "x5c.AuthorizeSSHSign")
}
}
if opts.KeyID != "" {
keyID = opts.KeyID
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}
if len(opts.Principals) > 0 {
principals = opts.Principals
}
// Certificate templates.
data := sshutil.CreateTemplateData(certType, keyID, principals)
if v, err := unsafeParseSigned(token); err == nil {
data.SetToken(v)
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}
templateOptions, err := TemplateSSHOptions(p.Options, data)
if err != nil {
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return nil, errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeSSHSign")
}
signOptions = append(signOptions, templateOptions)
// Add modifiers from custom claims
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t := now()
if !opts.ValidAfter.IsZero() {
signOptions = append(signOptions, sshCertValidAfterModifier(opts.ValidAfter.RelativeTime(t).Unix()))
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}
if !opts.ValidBefore.IsZero() {
signOptions = append(signOptions, sshCertValidBeforeModifier(opts.ValidBefore.RelativeTime(t).Unix()))
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}
return append(signOptions,
// Checks the validity bounds, and set the validity if has not been set.
&sshLimitDuration{p.claimer, claims.chains[0][0].NotAfter},
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// Validate public key.
&sshDefaultPublicKeyValidator{},
// Validate the validity period.
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&sshCertValidityValidator{p.claimer},
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// Require all the fields in the SSH certificate
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&sshCertDefaultValidator{},
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), nil
}