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// Package signer implements certificate signature functionality for CFSSL.
package signer
import (
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rsa"
"crypto/sha1"
"crypto/x509"
"crypto/x509/pkix"
"encoding/asn1"
"errors"
"math/big"
"net/http"
"strings"
"time"
"github.com/cloudflare/cfssl/certdb"
"github.com/cloudflare/cfssl/config"
"github.com/cloudflare/cfssl/csr"
cferr "github.com/cloudflare/cfssl/errors"
"github.com/cloudflare/cfssl/info"
)
// Subject contains the information that should be used to override the
// subject information when signing a certificate.
type Subject struct {
CN string
Names []csr.Name `json:"names"`
SerialNumber string
}
// Extension represents a raw extension to be included in the certificate. The
// "value" field must be hex encoded.
type Extension struct {
ID config.OID `json:"id"`
Critical bool `json:"critical"`
Value string `json:"value"`
}
// SignRequest stores a signature request, which contains the hostname,
// the CSR, optional subject information, and the signature profile.
//
// Extensions provided in the signRequest are copied into the certificate, as
// long as they are in the ExtensionWhitelist for the signer's policy.
// Extensions requested in the CSR are ignored, except for those processed by
// ParseCertificateRequest (mainly subjectAltName).
type SignRequest struct {
Hosts []string `json:"hosts"`
Request string `json:"certificate_request"`
Subject *Subject `json:"subject,omitempty"`
Profile string `json:"profile"`
CRLOverride string `json:"crl_override"`
Label string `json:"label"`
Serial *big.Int `json:"serial,omitempty"`
Extensions []Extension `json:"extensions,omitempty"`
// If provided, NotBefore will be used without modification (except
// for canonicalization) as the value of the notBefore field of the
// certificate. In particular no backdating adjustment will be made
// when NotBefore is provided.
NotBefore time.Time
// If provided, NotAfter will be used without modification (except
// for canonicalization) as the value of the notAfter field of the
// certificate.
NotAfter time.Time
// If ReturnPrecert is true a certificate with the CT poison extension
// will be returned from the Signer instead of attempting to retrieve
// SCTs and populate the tbsCert with them itself. This precert can then
// be passed to SignFromPrecert with the SCTs in order to create a
// valid certificate.
ReturnPrecert bool
}
// appendIf appends to a if s is not an empty string.
func appendIf(s string, a *[]string) {
if s != "" {
*a = append(*a, s)
}
}
// Name returns the PKIX name for the subject.
func (s *Subject) Name() pkix.Name {
var name pkix.Name
name.CommonName = s.CN
for _, n := range s.Names {
appendIf(n.C, &name.Country)
appendIf(n.ST, &name.Province)
appendIf(n.L, &name.Locality)
appendIf(n.O, &name.Organization)
appendIf(n.OU, &name.OrganizationalUnit)
}
name.SerialNumber = s.SerialNumber
return name
}
// SplitHosts takes a comma-spearated list of hosts and returns a slice
// with the hosts split
func SplitHosts(hostList string) []string {
if hostList == "" {
return nil
}
return strings.Split(hostList, ",")
}
// A Signer contains a CA's certificate and private key for signing
// certificates, a Signing policy to refer to and a SignatureAlgorithm.
type Signer interface {
Info(info.Req) (*info.Resp, error)
Policy() *config.Signing
SetDBAccessor(certdb.Accessor)
GetDBAccessor() certdb.Accessor
SetPolicy(*config.Signing)
SigAlgo() x509.SignatureAlgorithm
Sign(req SignRequest) (cert []byte, err error)
SetReqModifier(func(*http.Request, []byte))
}
// Profile gets the specific profile from the signer
func Profile(s Signer, profile string) (*config.SigningProfile, error) {
var p *config.SigningProfile
policy := s.Policy()
if policy != nil && policy.Profiles != nil && profile != "" {
p = policy.Profiles[profile]
}
if p == nil && policy != nil {
p = policy.Default
}
if p == nil {
return nil, cferr.Wrap(cferr.APIClientError, cferr.ClientHTTPError, errors.New("profile must not be nil"))
}
return p, nil
}
// DefaultSigAlgo returns an appropriate X.509 signature algorithm given
// the CA's private key.
func DefaultSigAlgo(priv crypto.Signer) x509.SignatureAlgorithm {
pub := priv.Public()
switch pub := pub.(type) {
case *rsa.PublicKey:
keySize := pub.N.BitLen()
switch {
case keySize >= 4096:
return x509.SHA512WithRSA
case keySize >= 3072:
return x509.SHA384WithRSA
case keySize >= 2048:
return x509.SHA256WithRSA
default:
return x509.SHA1WithRSA
}
case *ecdsa.PublicKey:
switch pub.Curve {
case elliptic.P256():
return x509.ECDSAWithSHA256
case elliptic.P384():
return x509.ECDSAWithSHA384
case elliptic.P521():
return x509.ECDSAWithSHA512
default:
return x509.ECDSAWithSHA1
}
default:
return x509.UnknownSignatureAlgorithm
}
}
// ParseCertificateRequest takes an incoming certificate request and
// builds a certificate template from it.
func ParseCertificateRequest(s Signer, csrBytes []byte) (template *x509.Certificate, err error) {
csrv, err := x509.ParseCertificateRequest(csrBytes)
if err != nil {
err = cferr.Wrap(cferr.CSRError, cferr.ParseFailed, err)
return
}
err = csrv.CheckSignature()
if err != nil {
err = cferr.Wrap(cferr.CSRError, cferr.KeyMismatch, err)
return
}
template = &x509.Certificate{
Subject: csrv.Subject,
PublicKeyAlgorithm: csrv.PublicKeyAlgorithm,
PublicKey: csrv.PublicKey,
SignatureAlgorithm: s.SigAlgo(),
DNSNames: csrv.DNSNames,
IPAddresses: csrv.IPAddresses,
EmailAddresses: csrv.EmailAddresses,
}
for _, val := range csrv.Extensions {
// Check the CSR for the X.509 BasicConstraints (RFC 5280, 4.2.1.9)
// extension and append to template if necessary
if val.Id.Equal(asn1.ObjectIdentifier{2, 5, 29, 19}) {
var constraints csr.BasicConstraints
var rest []byte
if rest, err = asn1.Unmarshal(val.Value, &constraints); err != nil {
return nil, cferr.Wrap(cferr.CSRError, cferr.ParseFailed, err)
} else if len(rest) != 0 {
return nil, cferr.Wrap(cferr.CSRError, cferr.ParseFailed, errors.New("x509: trailing data after X.509 BasicConstraints"))
}
template.BasicConstraintsValid = true
template.IsCA = constraints.IsCA
template.MaxPathLen = constraints.MaxPathLen
template.MaxPathLenZero = template.MaxPathLen == 0
}
}
return
}
type subjectPublicKeyInfo struct {
Algorithm pkix.AlgorithmIdentifier
SubjectPublicKey asn1.BitString
}
// ComputeSKI derives an SKI from the certificate's public key in a
// standard manner. This is done by computing the SHA-1 digest of the
// SubjectPublicKeyInfo component of the certificate.
func ComputeSKI(template *x509.Certificate) ([]byte, error) {
pub := template.PublicKey
encodedPub, err := x509.MarshalPKIXPublicKey(pub)
if err != nil {
return nil, err
}
var subPKI subjectPublicKeyInfo
_, err = asn1.Unmarshal(encodedPub, &subPKI)
if err != nil {
return nil, err
}
pubHash := sha1.Sum(subPKI.SubjectPublicKey.Bytes)
return pubHash[:], nil
}
// FillTemplate is a utility function that tries to load as much of
// the certificate template as possible from the profiles and current
// template. It fills in the key uses, expiration, revocation URLs
// and SKI.
func FillTemplate(template *x509.Certificate, defaultProfile, profile *config.SigningProfile, notBefore time.Time, notAfter time.Time) error {
ski, err := ComputeSKI(template)
if err != nil {
return err
}
var (
eku []x509.ExtKeyUsage
ku x509.KeyUsage
backdate time.Duration
expiry time.Duration
crlURL, ocspURL string
issuerURL = profile.IssuerURL
)
// The third value returned from Usages is a list of unknown key usages.
// This should be used when validating the profile at load, and isn't used
// here.
ku, eku, _ = profile.Usages()
if profile.IssuerURL == nil {
issuerURL = defaultProfile.IssuerURL
}
if ku == 0 && len(eku) == 0 {
return cferr.New(cferr.PolicyError, cferr.NoKeyUsages)
}
if expiry = profile.Expiry; expiry == 0 {
expiry = defaultProfile.Expiry
}
if crlURL = profile.CRL; crlURL == "" {
crlURL = defaultProfile.CRL
}
if ocspURL = profile.OCSP; ocspURL == "" {
ocspURL = defaultProfile.OCSP
}
if notBefore.IsZero() {
if !profile.NotBefore.IsZero() {
notBefore = profile.NotBefore
} else {
if backdate = profile.Backdate; backdate == 0 {
backdate = -5 * time.Minute
} else {
backdate = -1 * profile.Backdate
}
notBefore = time.Now().Round(time.Minute).Add(backdate)
}
}
notBefore = notBefore.UTC()
if notAfter.IsZero() {
if !profile.NotAfter.IsZero() {
notAfter = profile.NotAfter
} else {
notAfter = notBefore.Add(expiry)
}
}
notAfter = notAfter.UTC()
template.NotBefore = notBefore
template.NotAfter = notAfter
template.KeyUsage = ku
template.ExtKeyUsage = eku
template.BasicConstraintsValid = true
template.IsCA = profile.CAConstraint.IsCA
if template.IsCA {
template.MaxPathLen = profile.CAConstraint.MaxPathLen
if template.MaxPathLen == 0 {
template.MaxPathLenZero = profile.CAConstraint.MaxPathLenZero
}
template.DNSNames = nil
template.EmailAddresses = nil
}
template.SubjectKeyId = ski
if ocspURL != "" {
template.OCSPServer = []string{ocspURL}
}
if crlURL != "" {
template.CRLDistributionPoints = []string{crlURL}
}
if len(issuerURL) != 0 {
template.IssuingCertificateURL = issuerURL
}
if len(profile.Policies) != 0 {
err = addPolicies(template, profile.Policies)
if err != nil {
return cferr.Wrap(cferr.PolicyError, cferr.InvalidPolicy, err)
}
}
if profile.OCSPNoCheck {
ocspNoCheckExtension := pkix.Extension{
Id: asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 48, 1, 5},
Critical: false,
Value: []byte{0x05, 0x00},
}
template.ExtraExtensions = append(template.ExtraExtensions, ocspNoCheckExtension)
}
return nil
}
type policyInformation struct {
PolicyIdentifier asn1.ObjectIdentifier
Qualifiers []interface{} `asn1:"tag:optional,omitempty"`
}
type cpsPolicyQualifier struct {
PolicyQualifierID asn1.ObjectIdentifier
Qualifier string `asn1:"tag:optional,ia5"`
}
type userNotice struct {
ExplicitText string `asn1:"tag:optional,utf8"`
}
type userNoticePolicyQualifier struct {
PolicyQualifierID asn1.ObjectIdentifier
Qualifier userNotice
}
var (
// Per https://tools.ietf.org/html/rfc3280.html#page-106, this represents:
// iso(1) identified-organization(3) dod(6) internet(1) security(5)
// mechanisms(5) pkix(7) id-qt(2) id-qt-cps(1)
iDQTCertificationPracticeStatement = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 2, 1}
// iso(1) identified-organization(3) dod(6) internet(1) security(5)
// mechanisms(5) pkix(7) id-qt(2) id-qt-unotice(2)
iDQTUserNotice = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 2, 2}
// CTPoisonOID is the object ID of the critical poison extension for precertificates
// https://tools.ietf.org/html/rfc6962#page-9
CTPoisonOID = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 11129, 2, 4, 3}
// SCTListOID is the object ID for the Signed Certificate Timestamp certificate extension
// https://tools.ietf.org/html/rfc6962#page-14
SCTListOID = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 11129, 2, 4, 2}
)
// addPolicies adds Certificate Policies and optional Policy Qualifiers to a
// certificate, based on the input config. Go's x509 library allows setting
// Certificate Policies easily, but does not support nested Policy Qualifiers
// under those policies. So we need to construct the ASN.1 structure ourselves.
func addPolicies(template *x509.Certificate, policies []config.CertificatePolicy) error {
asn1PolicyList := []policyInformation{}
for _, policy := range policies {
pi := policyInformation{
// The PolicyIdentifier is an OID assigned to a given issuer.
PolicyIdentifier: asn1.ObjectIdentifier(policy.ID),
}
for _, qualifier := range policy.Qualifiers {
switch qualifier.Type {
case "id-qt-unotice":
pi.Qualifiers = append(pi.Qualifiers,
userNoticePolicyQualifier{
PolicyQualifierID: iDQTUserNotice,
Qualifier: userNotice{
ExplicitText: qualifier.Value,
},
})
case "id-qt-cps":
pi.Qualifiers = append(pi.Qualifiers,
cpsPolicyQualifier{
PolicyQualifierID: iDQTCertificationPracticeStatement,
Qualifier: qualifier.Value,
})
default:
return errors.New("Invalid qualifier type in Policies " + qualifier.Type)
}
}
asn1PolicyList = append(asn1PolicyList, pi)
}
asn1Bytes, err := asn1.Marshal(asn1PolicyList)
if err != nil {
return err
}
template.ExtraExtensions = append(template.ExtraExtensions, pkix.Extension{
Id: asn1.ObjectIdentifier{2, 5, 29, 32},
Critical: false,
Value: asn1Bytes,
})
return nil
}