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csr.go
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csr.go
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// Package csr implements certificate requests for CFSSL.
package csr
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"errors"
"net"
"strings"
cferr "github.com/cloudflare/cfssl/errors"
"github.com/cloudflare/cfssl/log"
)
const (
curveP256 = 256
curveP384 = 384
curveP521 = 521
)
// A Name contains the SubjectInfo fields.
type Name struct {
C string // Country
ST string // State
L string // Locality
O string // OrganisationName
OU string // OrganisationalUnitName
}
// A KeyRequest contains the algorithm and key size for a new private
// key.
type KeyRequest struct {
Algo string `json:"algo"`
Size int `json:"size"`
}
// The DefaultKeyRequest is used when no key request data is provided
// in the request. This should be a safe default.
var DefaultKeyRequest = KeyRequest{
Algo: "ecdsa",
Size: curveP256,
}
// Generate generates a key as specified in the request. Currently,
// only ECDSA and RSA are supported.
func (kr *KeyRequest) Generate() (interface{}, error) {
log.Debugf("generate key from request: algo=%s, size=%d", kr.Algo, kr.Size)
switch kr.Algo {
case "rsa":
if kr.Size < 2048 {
return nil, errors.New("RSA key is too weak")
}
return rsa.GenerateKey(rand.Reader, kr.Size)
case "ecdsa":
var curve elliptic.Curve
switch kr.Size {
case curveP256:
curve = elliptic.P256()
case curveP384:
curve = elliptic.P384()
case curveP521:
curve = elliptic.P521()
default:
return nil, errors.New("invalid curve")
}
return ecdsa.GenerateKey(curve, rand.Reader)
default:
return nil, errors.New("invalid algorithm")
}
}
// SigAlgo returns an appropriate X.509 signature algorithm given the
// key request's type and size.
func (kr *KeyRequest) SigAlgo() x509.SignatureAlgorithm {
switch kr.Algo {
case "rsa":
switch {
case kr.Size >= 4096:
return x509.SHA512WithRSA
case kr.Size >= 3072:
return x509.SHA384WithRSA
case kr.Size >= 2048:
return x509.SHA256WithRSA
default:
return x509.SHA1WithRSA
}
case "ecdsa":
switch {
case kr.Size == curveP521:
return x509.ECDSAWithSHA512
case kr.Size == curveP384:
return x509.ECDSAWithSHA384
case kr.Size == curveP256:
return x509.ECDSAWithSHA256
default:
return x509.ECDSAWithSHA1
}
default:
return x509.UnknownSignatureAlgorithm
}
}
// CAConfig is a section used in the requests initialising a new CA.
type CAConfig struct {
PathLength int `json:"pathlen"`
Expiry string `json:"expiry"`
}
// A CertificateRequest encapsulates the API interface to the
// certificate request functionality.
type CertificateRequest struct {
CN string
Names []Name `json:"names"`
Hosts []string `json:"hosts"`
KeyRequest *KeyRequest `json:"key,omitempty"`
CA *CAConfig `json:"ca,omitempty"`
}
// 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 request.
func (cr *CertificateRequest) Name() pkix.Name {
var name pkix.Name
name.CommonName = cr.CN
for _, n := range cr.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)
}
return name
}
// ParseRequest takes a certificate request and generates a key and
// CSR from it. It does no validation -- caveat emptor. It will,
// however, fail if the key request is not valid (i.e., an unsupported
// curve or RSA key size). The lack of validation was specifically
// chosen to allow the end user to define a policy and validate the
// request appropriately before calling this function.
func ParseRequest(req *CertificateRequest) (csr, key []byte, err error) {
log.Info("received CSR")
if req.KeyRequest == nil {
req.KeyRequest = &KeyRequest{
Algo: DefaultKeyRequest.Algo,
Size: DefaultKeyRequest.Size,
}
}
log.Infof("generating key: %s-%d", req.KeyRequest.Algo, req.KeyRequest.Size)
priv, err := req.KeyRequest.Generate()
if err != nil {
err = cferr.Wrap(cferr.PrivateKeyError, cferr.GenerationFailed, err)
return
}
switch priv := priv.(type) {
case *rsa.PrivateKey:
key = x509.MarshalPKCS1PrivateKey(priv)
block := pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: key,
}
key = pem.EncodeToMemory(&block)
case *ecdsa.PrivateKey:
key, err = x509.MarshalECPrivateKey(priv)
if err != nil {
err = cferr.Wrap(cferr.PrivateKeyError, cferr.Unknown, err)
return
}
block := pem.Block{
Type: "EC PRIVATE KEY",
Bytes: key,
}
key = pem.EncodeToMemory(&block)
default:
panic("Generate should have failed to produce a valid key.")
}
var tpl = x509.CertificateRequest{
Subject: req.Name(),
SignatureAlgorithm: req.KeyRequest.SigAlgo(),
}
for i := range req.Hosts {
if ip := net.ParseIP(req.Hosts[i]); ip != nil {
tpl.IPAddresses = append(tpl.IPAddresses, ip)
} else {
tpl.DNSNames = append(tpl.DNSNames, req.Hosts[i])
}
}
csr, err = x509.CreateCertificateRequest(rand.Reader, &tpl, priv)
if err != nil {
log.Errorf("failed to generate a CSR: %v", err)
err = cferr.Wrap(cferr.CSRError, cferr.BadRequest, err)
return
}
block := pem.Block{
Type: "CERTIFICATE REQUEST",
Bytes: csr,
}
log.Info("encoded CSR")
csr = pem.EncodeToMemory(&block)
return
}
// A Generator is responsible for validating certificate requests.
type Generator struct {
Validator func(*CertificateRequest) error
}
// ProcessRequest validates and processes the incoming request. It is
// a wrapper around a validator and the ParseRequest function.
func (g *Generator) ProcessRequest(req *CertificateRequest) (csr, key []byte, err error) {
log.Info("generate received request")
err = g.Validator(req)
if err != nil {
log.Warningf("invalid request: %v", err)
return
}
csr, key, err = ParseRequest(req)
if err != nil {
return nil, nil, err
}
return
}
// IsNameEmpty returns true if the name has no identifying information in it.
func IsNameEmpty(n Name) bool {
empty := func(s string) bool { return strings.TrimSpace(s) == "" }
if empty(n.C) && empty(n.ST) && empty(n.L) && empty(n.O) && empty(n.OU) {
return true
}
return false
}