forked from TrueCloudLab/certificates
ff1b46c95d
Instead of using the defaultPublicKeyValidator a new validator called publicKeyMinimumLengthValidator has been implemented that uses a configurable minimum length for public keys in CSRs. It's also an option to alter the defaultPublicKeyValidator to also take a parameter, but that would touch quite some lines of code. This might be a viable option after merging SCEP support.
489 lines
15 KiB
Go
489 lines
15 KiB
Go
package provisioner
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import (
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"crypto/ecdsa"
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"crypto/ed25519"
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"crypto/rsa"
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"crypto/x509"
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"crypto/x509/pkix"
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"encoding/asn1"
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"encoding/json"
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"fmt"
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"net"
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"net/url"
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"reflect"
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"time"
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"github.com/pkg/errors"
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"go.step.sm/crypto/x509util"
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)
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// DefaultCertValidity is the default validity for a certificate if none is specified.
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const DefaultCertValidity = 24 * time.Hour
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// SignOptions contains the options that can be passed to the Sign method. Backdate
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// is automatically filled and can only be configured in the CA.
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type SignOptions struct {
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NotAfter TimeDuration `json:"notAfter"`
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NotBefore TimeDuration `json:"notBefore"`
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TemplateData json.RawMessage `json:"templateData"`
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Backdate time.Duration `json:"-"`
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}
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// SignOption is the interface used to collect all extra options used in the
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// Sign method.
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type SignOption interface{}
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// CertificateValidator is an interface used to validate a given X.509 certificate.
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type CertificateValidator interface {
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Valid(cert *x509.Certificate, opts SignOptions) error
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}
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// CertificateRequestValidator is an interface used to validate a given X.509 certificate request.
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type CertificateRequestValidator interface {
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Valid(cr *x509.CertificateRequest) error
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}
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// CertificateModifier is an interface used to modify a given X.509 certificate.
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// Types implementing this interface will be validated with a
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// CertificateValidator.
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type CertificateModifier interface {
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Modify(cert *x509.Certificate, opts SignOptions) error
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}
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// CertificateEnforcer is an interface used to modify a given X.509 certificate.
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// Types implemented this interface will NOT be validated with a
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// CertificateValidator.
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type CertificateEnforcer interface {
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Enforce(cert *x509.Certificate) error
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}
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// CertificateModifierFunc allows to create simple certificate modifiers just
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// with a function.
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type CertificateModifierFunc func(cert *x509.Certificate, opts SignOptions) error
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// Modify implements CertificateModifier and just calls the defined function.
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func (fn CertificateModifierFunc) Modify(cert *x509.Certificate, opts SignOptions) error {
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return fn(cert, opts)
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}
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// CertificateEnforcerFunc allows to create simple certificate enforcer just
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// with a function.
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type CertificateEnforcerFunc func(cert *x509.Certificate) error
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// Enforce implements CertificateEnforcer and just calls the defined function.
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func (fn CertificateEnforcerFunc) Enforce(cert *x509.Certificate) error {
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return fn(cert)
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}
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// emailOnlyIdentity is a CertificateRequestValidator that checks that the only
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// SAN provided is the given email address.
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type emailOnlyIdentity string
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func (e emailOnlyIdentity) Valid(req *x509.CertificateRequest) error {
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switch {
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case len(req.DNSNames) > 0:
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return errors.New("certificate request cannot contain DNS names")
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case len(req.IPAddresses) > 0:
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return errors.New("certificate request cannot contain IP addresses")
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case len(req.URIs) > 0:
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return errors.New("certificate request cannot contain URIs")
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case len(req.EmailAddresses) == 0:
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return errors.New("certificate request does not contain any email address")
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case len(req.EmailAddresses) > 1:
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return errors.New("certificate request contains too many email addresses")
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case req.EmailAddresses[0] == "":
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return errors.New("certificate request cannot contain an empty email address")
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case req.EmailAddresses[0] != string(e):
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return errors.Errorf("certificate request does not contain the valid email address, got %s, want %s", req.EmailAddresses[0], e)
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default:
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return nil
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}
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}
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// defaultPublicKeyValidator validates the public key of a certificate request.
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type defaultPublicKeyValidator struct{}
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// Valid checks that certificate request common name matches the one configured.
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func (v defaultPublicKeyValidator) Valid(req *x509.CertificateRequest) error {
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switch k := req.PublicKey.(type) {
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case *rsa.PublicKey:
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if k.Size() < 256 {
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return errors.New("rsa key in CSR must be at least 2048 bits (256 bytes)")
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}
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case *ecdsa.PublicKey, ed25519.PublicKey:
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default:
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return errors.Errorf("unrecognized public key of type '%T' in CSR", k)
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}
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return nil
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}
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// publicKeyMinimumLengthValidator validates the length (in bits) of the public key
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// of a certificate request is at least a certain length
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type publicKeyMinimumLengthValidator struct {
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length int
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}
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// newPublicKeyMinimumLengthValidator creates a new publicKeyMinimumLengthValidator
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// with the given length as its minimum value
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// TODO: change the defaultPublicKeyValidator to have a configurable length instead?
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func newPublicKeyMinimumLengthValidator(length int) publicKeyMinimumLengthValidator {
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return publicKeyMinimumLengthValidator{
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length: length,
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}
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}
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// Valid checks that certificate request common name matches the one configured.
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func (v publicKeyMinimumLengthValidator) Valid(req *x509.CertificateRequest) error {
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switch k := req.PublicKey.(type) {
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case *rsa.PublicKey:
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minimumLengthInBytes := v.length / 8
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if k.Size() < minimumLengthInBytes {
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return fmt.Errorf("rsa key in CSR must be at least %d bits (%d bytes)", v.length, minimumLengthInBytes)
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}
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case *ecdsa.PublicKey, ed25519.PublicKey:
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default:
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return errors.Errorf("unrecognized public key of type '%T' in CSR", k)
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}
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return nil
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}
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// commonNameValidator validates the common name of a certificate request.
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type commonNameValidator string
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// Valid checks that certificate request common name matches the one configured.
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// An empty common name is considered valid.
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func (v commonNameValidator) Valid(req *x509.CertificateRequest) error {
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if req.Subject.CommonName == "" {
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return nil
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}
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if req.Subject.CommonName != string(v) {
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return errors.Errorf("certificate request does not contain the valid common name; requested common name = %s, token subject = %s", req.Subject.CommonName, v)
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}
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return nil
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}
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// commonNameSliceValidator validates thats the common name of a certificate
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// request is present in the slice. An empty common name is considered valid.
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type commonNameSliceValidator []string
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func (v commonNameSliceValidator) Valid(req *x509.CertificateRequest) error {
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if req.Subject.CommonName == "" {
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return nil
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}
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for _, cn := range v {
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if req.Subject.CommonName == cn {
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return nil
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}
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}
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return errors.Errorf("certificate request does not contain the valid common name, got %s, want %s", req.Subject.CommonName, v)
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}
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// dnsNamesValidator validates the DNS names SAN of a certificate request.
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type dnsNamesValidator []string
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// Valid checks that certificate request DNS Names match those configured in
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// the bootstrap (token) flow.
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func (v dnsNamesValidator) Valid(req *x509.CertificateRequest) error {
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if len(req.DNSNames) == 0 {
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return nil
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}
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want := make(map[string]bool)
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for _, s := range v {
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want[s] = true
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}
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got := make(map[string]bool)
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for _, s := range req.DNSNames {
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got[s] = true
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}
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if !reflect.DeepEqual(want, got) {
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return errors.Errorf("certificate request does not contain the valid DNS names - got %v, want %v", req.DNSNames, v)
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}
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return nil
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}
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// ipAddressesValidator validates the IP addresses SAN of a certificate request.
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type ipAddressesValidator []net.IP
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// Valid checks that certificate request IP Addresses match those configured in
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// the bootstrap (token) flow.
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func (v ipAddressesValidator) Valid(req *x509.CertificateRequest) error {
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if len(req.IPAddresses) == 0 {
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return nil
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}
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want := make(map[string]bool)
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for _, ip := range v {
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want[ip.String()] = true
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}
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got := make(map[string]bool)
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for _, ip := range req.IPAddresses {
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got[ip.String()] = true
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}
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if !reflect.DeepEqual(want, got) {
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return errors.Errorf("IP Addresses claim failed - got %v, want %v", req.IPAddresses, v)
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}
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return nil
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}
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// emailAddressesValidator validates the email address SANs of a certificate request.
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type emailAddressesValidator []string
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// Valid checks that certificate request IP Addresses match those configured in
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// the bootstrap (token) flow.
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func (v emailAddressesValidator) Valid(req *x509.CertificateRequest) error {
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if len(req.EmailAddresses) == 0 {
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return nil
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}
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want := make(map[string]bool)
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for _, s := range v {
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want[s] = true
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}
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got := make(map[string]bool)
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for _, s := range req.EmailAddresses {
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got[s] = true
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}
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if !reflect.DeepEqual(want, got) {
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return errors.Errorf("certificate request does not contain the valid Email Addresses - got %v, want %v", req.EmailAddresses, v)
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}
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return nil
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}
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// urisValidator validates the URI SANs of a certificate request.
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type urisValidator []*url.URL
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// Valid checks that certificate request IP Addresses match those configured in
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// the bootstrap (token) flow.
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func (v urisValidator) Valid(req *x509.CertificateRequest) error {
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if len(req.URIs) == 0 {
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return nil
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}
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want := make(map[string]bool)
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for _, u := range v {
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want[u.String()] = true
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}
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got := make(map[string]bool)
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for _, u := range req.URIs {
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got[u.String()] = true
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}
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if !reflect.DeepEqual(want, got) {
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return errors.Errorf("URIs claim failed - got %v, want %v", req.URIs, v)
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}
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return nil
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}
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// defaultsSANsValidator stores a set of SANs to eventually validate 1:1 against
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// the SANs in an x509 certificate request.
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type defaultSANsValidator []string
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// Valid verifies that the SANs stored in the validator match 1:1 with those
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// requested in the x509 certificate request.
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func (v defaultSANsValidator) Valid(req *x509.CertificateRequest) (err error) {
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dnsNames, ips, emails, uris := x509util.SplitSANs(v)
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if err = dnsNamesValidator(dnsNames).Valid(req); err != nil {
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return
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} else if err = emailAddressesValidator(emails).Valid(req); err != nil {
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return
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} else if err = ipAddressesValidator(ips).Valid(req); err != nil {
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return
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} else if err = urisValidator(uris).Valid(req); err != nil {
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return
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}
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return
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}
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// profileDefaultDuration is a modifier that sets the certificate
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// duration.
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type profileDefaultDuration time.Duration
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func (v profileDefaultDuration) Modify(cert *x509.Certificate, so SignOptions) error {
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var backdate time.Duration
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notBefore := so.NotBefore.Time()
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if notBefore.IsZero() {
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notBefore = now()
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backdate = -1 * so.Backdate
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}
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notAfter := so.NotAfter.RelativeTime(notBefore)
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if notAfter.IsZero() {
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if v != 0 {
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notAfter = notBefore.Add(time.Duration(v))
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} else {
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notAfter = notBefore.Add(DefaultCertValidity)
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}
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}
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cert.NotBefore = notBefore.Add(backdate)
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cert.NotAfter = notAfter
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return nil
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}
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// profileLimitDuration is an x509 profile option that modifies an x509 validity
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// period according to an imposed expiration time.
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type profileLimitDuration struct {
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def time.Duration
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notBefore, notAfter time.Time
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}
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// Option returns an x509util option that limits the validity period of a
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// certificate to one that is superficially imposed.
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func (v profileLimitDuration) Modify(cert *x509.Certificate, so SignOptions) error {
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var backdate time.Duration
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notBefore := so.NotBefore.Time()
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if notBefore.IsZero() {
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notBefore = now()
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backdate = -1 * so.Backdate
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}
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if notBefore.Before(v.notBefore) {
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return errors.Errorf("requested certificate notBefore (%s) is before "+
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"the active validity window of the provisioning credential (%s)",
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notBefore, v.notBefore)
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}
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notAfter := so.NotAfter.RelativeTime(notBefore)
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if notAfter.After(v.notAfter) {
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return errors.Errorf("requested certificate notAfter (%s) is after "+
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"the expiration of the provisioning credential (%s)",
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notAfter, v.notAfter)
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}
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if notAfter.IsZero() {
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t := notBefore.Add(v.def)
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if t.After(v.notAfter) {
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notAfter = v.notAfter
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} else {
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notAfter = t
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}
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}
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cert.NotBefore = notBefore.Add(backdate)
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cert.NotAfter = notAfter
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return nil
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}
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// validityValidator validates the certificate validity settings.
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type validityValidator struct {
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min time.Duration
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max time.Duration
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}
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// newValidityValidator return a new validity validator.
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func newValidityValidator(min, max time.Duration) *validityValidator {
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return &validityValidator{min: min, max: max}
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}
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// Valid validates the certificate validity settings (notBefore/notAfter) and
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// and total duration.
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func (v *validityValidator) Valid(cert *x509.Certificate, o SignOptions) error {
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var (
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na = cert.NotAfter.Truncate(time.Second)
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nb = cert.NotBefore.Truncate(time.Second)
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now = time.Now().Truncate(time.Second)
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)
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d := na.Sub(nb)
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if na.Before(now) {
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return errors.Errorf("notAfter cannot be in the past; na=%v", na)
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}
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if na.Before(nb) {
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return errors.Errorf("notAfter cannot be before notBefore; na=%v, nb=%v", na, nb)
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}
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if d < v.min {
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return errors.Errorf("requested duration of %v is less than the authorized minimum certificate duration of %v",
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d, v.min)
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}
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// NOTE: this check is not "technically correct". We're allowing the max
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// duration of a cert to be "max + backdate" and not all certificates will
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// be backdated (e.g. if a user passes the NotBefore value then we do not
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// apply a backdate). This is good enough.
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if d > v.max+o.Backdate {
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return errors.Errorf("requested duration of %v is more than the authorized maximum certificate duration of %v",
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d, v.max+o.Backdate)
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}
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return nil
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}
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var (
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stepOIDRoot = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 37476, 9000, 64}
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stepOIDProvisioner = append(asn1.ObjectIdentifier(nil), append(stepOIDRoot, 1)...)
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)
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type stepProvisionerASN1 struct {
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Type int
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Name []byte
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CredentialID []byte
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KeyValuePairs []string `asn1:"optional,omitempty"`
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}
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type forceCNOption struct {
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ForceCN bool
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}
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func newForceCNOption(forceCN bool) *forceCNOption {
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return &forceCNOption{forceCN}
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}
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func (o *forceCNOption) Modify(cert *x509.Certificate, _ SignOptions) error {
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if !o.ForceCN {
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// Forcing CN is disabled, do nothing to certificate
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return nil
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}
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if cert.Subject.CommonName == "" {
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if len(cert.DNSNames) > 0 {
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cert.Subject.CommonName = cert.DNSNames[0]
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} else {
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return errors.New("Cannot force CN, DNSNames is empty")
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}
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}
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return nil
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}
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type provisionerExtensionOption struct {
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Type int
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Name string
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CredentialID string
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KeyValuePairs []string
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}
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func newProvisionerExtensionOption(typ Type, name, credentialID string, keyValuePairs ...string) *provisionerExtensionOption {
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return &provisionerExtensionOption{
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Type: int(typ),
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Name: name,
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CredentialID: credentialID,
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KeyValuePairs: keyValuePairs,
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}
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}
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func (o *provisionerExtensionOption) Modify(cert *x509.Certificate, _ SignOptions) error {
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ext, err := createProvisionerExtension(o.Type, o.Name, o.CredentialID, o.KeyValuePairs...)
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if err != nil {
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return err
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}
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// Prepend the provisioner extension. In the auth.Sign code we will
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// force the resulting certificate to only have one extension, the
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// first stepOIDProvisioner that is found in the ExtraExtensions.
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// A client could pass a csr containing a malicious stepOIDProvisioner
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// ExtraExtension. If we were to append (rather than prepend) the correct
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// stepOIDProvisioner extension, then the resulting certificate would
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// contain the malicious extension, rather than the one applied by step-ca.
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cert.ExtraExtensions = append([]pkix.Extension{ext}, cert.ExtraExtensions...)
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return nil
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}
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func createProvisionerExtension(typ int, name, credentialID string, keyValuePairs ...string) (pkix.Extension, error) {
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b, err := asn1.Marshal(stepProvisionerASN1{
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Type: typ,
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Name: []byte(name),
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CredentialID: []byte(credentialID),
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KeyValuePairs: keyValuePairs,
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})
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if err != nil {
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return pkix.Extension{}, errors.Wrapf(err, "error marshaling provisioner extension")
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}
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return pkix.Extension{
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Id: stepOIDProvisioner,
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Critical: false,
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Value: b,
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}, nil
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}
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