certificates/authority/provisioner/controller.go
Herman Slatman 479eda7339
Improve error message when client renews with expired certificate
When a client provides an expired certificate and `AllowAfterExpiry`
is not enabled, the client would get a rather generic error with
instructions to view the CA logs. Viewing the CA logs can be done
when running `step-ca`, but they can't be accessed easily in the
hosted solution.

This commit returns a slightly more informational message to the
client in this specific situation.
2022-05-19 01:25:30 +02:00

210 lines
7 KiB
Go

package provisioner
import (
"context"
"crypto/x509"
"net/http"
"regexp"
"strings"
"time"
"github.com/pkg/errors"
"github.com/smallstep/certificates/errs"
"golang.org/x/crypto/ssh"
)
// Controller wraps a provisioner with other attributes useful in callback
// functions.
type Controller struct {
Interface
Audiences *Audiences
Claimer *Claimer
IdentityFunc GetIdentityFunc
AuthorizeRenewFunc AuthorizeRenewFunc
AuthorizeSSHRenewFunc AuthorizeSSHRenewFunc
policy *policyEngine
}
// NewController initializes a new provisioner controller.
func NewController(p Interface, claims *Claims, config Config, options *Options) (*Controller, error) {
claimer, err := NewClaimer(claims, config.Claims)
if err != nil {
return nil, err
}
policy, err := newPolicyEngine(options)
if err != nil {
return nil, err
}
return &Controller{
Interface: p,
Audiences: &config.Audiences,
Claimer: claimer,
IdentityFunc: config.GetIdentityFunc,
AuthorizeRenewFunc: config.AuthorizeRenewFunc,
AuthorizeSSHRenewFunc: config.AuthorizeSSHRenewFunc,
policy: policy,
}, nil
}
// GetIdentity returns the identity for a given email.
func (c *Controller) GetIdentity(ctx context.Context, email string) (*Identity, error) {
if c.IdentityFunc != nil {
return c.IdentityFunc(ctx, c.Interface, email)
}
return DefaultIdentityFunc(ctx, c.Interface, email)
}
// AuthorizeRenew returns nil if the given cert can be renewed, returns an error
// otherwise.
func (c *Controller) AuthorizeRenew(ctx context.Context, cert *x509.Certificate) error {
if c.AuthorizeRenewFunc != nil {
return c.AuthorizeRenewFunc(ctx, c, cert)
}
return DefaultAuthorizeRenew(ctx, c, cert)
}
// AuthorizeSSHRenew returns nil if the given cert can be renewed, returns an
// error otherwise.
func (c *Controller) AuthorizeSSHRenew(ctx context.Context, cert *ssh.Certificate) error {
if c.AuthorizeSSHRenewFunc != nil {
return c.AuthorizeSSHRenewFunc(ctx, c, cert)
}
return DefaultAuthorizeSSHRenew(ctx, c, cert)
}
// Identity is the type representing an externally supplied identity that is used
// by provisioners to populate certificate fields.
type Identity struct {
Usernames []string `json:"usernames"`
Permissions `json:"permissions"`
}
// GetIdentityFunc is a function that returns an identity.
type GetIdentityFunc func(ctx context.Context, p Interface, email string) (*Identity, error)
// AuthorizeRenewFunc is a function that returns nil if the renewal of a
// certificate is enabled.
type AuthorizeRenewFunc func(ctx context.Context, p *Controller, cert *x509.Certificate) error
// AuthorizeSSHRenewFunc is a function that returns nil if the renewal of the
// given SSH certificate is enabled.
type AuthorizeSSHRenewFunc func(ctx context.Context, p *Controller, cert *ssh.Certificate) error
// DefaultIdentityFunc return a default identity depending on the provisioner
// type. For OIDC email is always present and the usernames might
// contain empty strings.
func DefaultIdentityFunc(ctx context.Context, p Interface, email string) (*Identity, error) {
switch k := p.(type) {
case *OIDC:
// OIDC principals would be:
// ~~1. Preferred usernames.~~ Note: Under discussion, currently disabled
// 2. Sanitized local.
// 3. Raw local (if different).
// 4. Email address.
name := SanitizeSSHUserPrincipal(email)
if !sshUserRegex.MatchString(name) {
return nil, errors.Errorf("invalid principal '%s' from email '%s'", name, email)
}
usernames := []string{name}
if i := strings.LastIndex(email, "@"); i >= 0 {
usernames = append(usernames, email[:i])
}
usernames = append(usernames, email)
return &Identity{
Usernames: SanitizeStringSlices(usernames),
}, nil
default:
return nil, errors.Errorf("provisioner type '%T' not supported by identity function", k)
}
}
// DefaultAuthorizeRenew is the default implementation of AuthorizeRenew. It
// will return an error if the provisioner has the renewal disabled, if the
// certificate is not yet valid or if the certificate is expired and renew after
// expiry is disabled.
func DefaultAuthorizeRenew(ctx context.Context, p *Controller, cert *x509.Certificate) error {
if p.Claimer.IsDisableRenewal() {
return errs.Unauthorized("renew is disabled for provisioner '%s'", p.GetName())
}
now := time.Now().Truncate(time.Second)
if now.Before(cert.NotBefore) {
return errs.Unauthorized("certificate is not yet valid" + " " + now.UTC().Format(time.RFC3339Nano) + " vs " + cert.NotBefore.Format(time.RFC3339Nano))
}
if now.After(cert.NotAfter) && !p.Claimer.AllowRenewalAfterExpiry() {
// return a custom 401 Unauthorized error with a clearer message for the client
// TODO(hs): these errors likely need to be refactored as a whole; HTTP status codes shouldn't be in this layer.
return errs.New(http.StatusUnauthorized, "The request lacked necessary authorization to be completed: certificate expired on %s", cert.NotAfter)
}
return nil
}
// DefaultAuthorizeSSHRenew is the default implementation of AuthorizeSSHRenew. It
// will return an error if the provisioner has the renewal disabled, if the
// certificate is not yet valid or if the certificate is expired and renew after
// expiry is disabled.
func DefaultAuthorizeSSHRenew(ctx context.Context, p *Controller, cert *ssh.Certificate) error {
if p.Claimer.IsDisableRenewal() {
return errs.Unauthorized("renew is disabled for provisioner '%s'", p.GetName())
}
unixNow := time.Now().Unix()
if after := int64(cert.ValidAfter); after < 0 || unixNow < int64(cert.ValidAfter) {
return errs.Unauthorized("certificate is not yet valid")
}
if before := int64(cert.ValidBefore); cert.ValidBefore != uint64(ssh.CertTimeInfinity) && (unixNow >= before || before < 0) && !p.Claimer.AllowRenewalAfterExpiry() {
return errs.Unauthorized("certificate has expired")
}
return nil
}
var sshUserRegex = regexp.MustCompile("^[a-z][-a-z0-9_]*$")
// SanitizeStringSlices removes duplicated an empty strings.
func SanitizeStringSlices(original []string) []string {
output := []string{}
seen := make(map[string]struct{})
for _, entry := range original {
if entry == "" {
continue
}
if _, value := seen[entry]; !value {
seen[entry] = struct{}{}
output = append(output, entry)
}
}
return output
}
// SanitizeSSHUserPrincipal grabs an email or a string with the format
// local@domain and returns a sanitized version of the local, valid to be used
// as a user name. If the email starts with a letter between a and z, the
// resulting string will match the regular expression `^[a-z][-a-z0-9_]*$`.
func SanitizeSSHUserPrincipal(email string) string {
if i := strings.LastIndex(email, "@"); i >= 0 {
email = email[:i]
}
return strings.Map(func(r rune) rune {
switch {
case r >= 'a' && r <= 'z':
return r
case r >= '0' && r <= '9':
return r
case r == '-':
return '-'
case r == '.': // drop dots
return -1
default:
return '_'
}
}, strings.ToLower(email))
}
func (c *Controller) getPolicy() *policyEngine {
if c == nil {
return nil
}
return c.policy
}