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pki.go
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pki.go
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// Package pki provides PKI all the PKI functions necessary to run micro over an untrusted network
// including a CA
package pki
import (
"bytes"
"crypto/ed25519"
"crypto/rand"
"crypto/x509"
"encoding/pem"
"github.com/pkg/errors"
)
// GenerateKey returns an ed25519 key
func GenerateKey() (ed25519.PublicKey, ed25519.PrivateKey, error) {
return ed25519.GenerateKey(rand.Reader)
}
// CA generates a self signed CA and returns cert, key in PEM format
func CA(opts ...CertOption) ([]byte, []byte, error) {
opts = append(opts, IsCA())
options := CertOptions{}
for _, o := range opts {
o(&options)
}
template := &x509.Certificate{
SignatureAlgorithm: x509.PureEd25519,
Subject: options.Subject,
DNSNames: options.DNSNames,
IPAddresses: options.IPAddresses,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
NotBefore: options.NotBefore,
NotAfter: options.NotAfter,
SerialNumber: options.SerialNumber,
BasicConstraintsValid: true,
}
if options.IsCA {
template.IsCA = true
template.KeyUsage |= x509.KeyUsageCertSign
}
x509Cert, err := x509.CreateCertificate(rand.Reader, template, template, options.Pub, options.Priv)
if err != nil {
return nil, nil, err
}
cert, key := &bytes.Buffer{}, &bytes.Buffer{}
if err := pem.Encode(cert, &pem.Block{Type: "CERTIFICATE", Bytes: x509Cert}); err != nil {
return nil, nil, err
}
x509Key, err := x509.MarshalPKCS8PrivateKey(options.Priv)
if err != nil {
return nil, nil, err
}
if err := pem.Encode(key, &pem.Block{Type: "PRIVATE KEY", Bytes: x509Key}); err != nil {
return nil, nil, err
}
return cert.Bytes(), key.Bytes(), nil
}
// CSR generates a certificate request in PEM format
func CSR(opts ...CertOption) ([]byte, error) {
options := CertOptions{}
for _, o := range opts {
o(&options)
}
csrTemplate := &x509.CertificateRequest{
Subject: options.Subject,
SignatureAlgorithm: x509.PureEd25519,
DNSNames: options.DNSNames,
IPAddresses: options.IPAddresses,
}
out := &bytes.Buffer{}
csr, err := x509.CreateCertificateRequest(rand.Reader, csrTemplate, options.Priv)
if err != nil {
return nil, err
}
if err := pem.Encode(out, &pem.Block{Type: "CERTIFICATE REQUEST", Bytes: csr}); err != nil {
return nil, err
}
return out.Bytes(), nil
}
// Sign decodes a CSR and signs it with the CA
func Sign(CACrt, CAKey, CSR []byte, opts ...CertOption) ([]byte, error) {
options := CertOptions{}
for _, o := range opts {
o(&options)
}
asn1CACrt, err := decodePEM(CACrt)
if err != nil {
return nil, errors.Wrap(err, "failed to decode CA Crt PEM")
}
if len(asn1CACrt) != 1 {
return nil, errors.Errorf("expected 1 CA Crt, got %d", len(asn1CACrt))
}
caCrt, err := x509.ParseCertificate(asn1CACrt[0].Bytes)
if err != nil {
return nil, errors.Wrap(err, "ca is not a valid certificate")
}
asn1CAKey, err := decodePEM(CAKey)
if err != nil {
return nil, errors.Wrap(err, "failed to decode CA Key PEM")
}
if len(asn1CAKey) != 1 {
return nil, errors.Errorf("expected 1 CA Key, got %d", len(asn1CACrt))
}
caKey, err := x509.ParsePKCS8PrivateKey(asn1CAKey[0].Bytes)
if err != nil {
return nil, errors.Wrap(err, "ca key is not a valid private key")
}
asn1CSR, err := decodePEM(CSR)
if err != nil {
return nil, errors.Wrap(err, "failed to decode CSR PEM")
}
if len(asn1CSR) != 1 {
return nil, errors.Errorf("expected 1 CSR, got %d", len(asn1CSR))
}
csr, err := x509.ParseCertificateRequest(asn1CSR[0].Bytes)
if err != nil {
return nil, errors.Wrap(err, "csr is invalid")
}
template := &x509.Certificate{
SignatureAlgorithm: x509.PureEd25519,
Subject: csr.Subject,
DNSNames: csr.DNSNames,
IPAddresses: csr.IPAddresses,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
NotBefore: options.NotBefore,
NotAfter: options.NotAfter,
SerialNumber: options.SerialNumber,
BasicConstraintsValid: true,
}
x509Cert, err := x509.CreateCertificate(rand.Reader, template, caCrt, caCrt.PublicKey, caKey)
if err != nil {
return nil, errors.Wrap(err, "Couldn't sign certificate")
}
out := &bytes.Buffer{}
if err := pem.Encode(out, &pem.Block{Type: "CERTIFICATE", Bytes: x509Cert}); err != nil {
return nil, errors.Wrap(err, "couldn't encode cert")
}
return out.Bytes(), nil
}
func decodePEM(PEM []byte) ([]*pem.Block, error) {
var blocks []*pem.Block
var asn1 *pem.Block
var rest []byte
for {
asn1, rest = pem.Decode(PEM)
if asn1 == nil {
return nil, errors.New("PEM is not valid")
}
blocks = append(blocks, asn1)
if len(rest) == 0 {
break
}
}
return blocks, nil
}