Merge pull request #40 from smallstep/minica

MiniCA

README.md

@@ -60,4 +60,8 @@ utilities to parse and generate JWT, JWK and JWKSets.
 ### x25519
 
 Package `x25519` adds support for X25519 keys and the
-[XEdDSA](https://signal.org/docs/specifications/xeddsa/) signature scheme.
+[XEdDSA](https://signal.org/docs/specifications/xeddsa/) signature scheme.
+
+### minica
+
+Package `minica` implements a simple certificate authority.

minica/minica.go

@@ -0,0 +1,178 @@
+package minica
+
+import (
+	"crypto"
+	"crypto/x509"
+	"fmt"
+	"time"
+
+	"go.step.sm/crypto/sshutil"
+	"go.step.sm/crypto/x509util"
+	"golang.org/x/crypto/ssh"
+)
+
+// CA is the implementation of a simple X.509 and SSH CA.
+type CA struct {
+	Root          *x509.Certificate
+	Intermediate  *x509.Certificate
+	Signer        crypto.Signer
+	SSHHostSigner ssh.Signer
+	SSHUserSigner ssh.Signer
+}
+
+// New creates a new MiniCA, the custom options allows to overwrite templates,
+// signer types and certificate names.
+func New(opts ...Option) (*CA, error) {
+	now := time.Now()
+	o := newOptions().apply(opts)
+
+	// Create root
+	rootSubject := o.Name + " Root CA"
+	rootSigner, err := o.GetSigner()
+	if err != nil {
+		return nil, err
+	}
+	rootCR, err := x509util.CreateCertificateRequest(rootSubject, []string{}, rootSigner)
+	if err != nil {
+		return nil, err
+	}
+	cert, err := x509util.NewCertificate(rootCR, x509util.WithTemplate(o.RootTemplate, x509util.CreateTemplateData(rootSubject, []string{})))
+	if err != nil {
+		return nil, err
+	}
+	template := cert.GetCertificate()
+	template.NotBefore = now
+	template.NotAfter = now.Add(24 * time.Hour)
+	root, err := x509util.CreateCertificate(template, template, rootSigner.Public(), rootSigner)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create intermediate
+	intSubject := o.Name + " Intermediate CA"
+	intSigner, err := o.GetSigner()
+	if err != nil {
+		return nil, err
+	}
+	intCR, err := x509util.CreateCertificateRequest(intSubject, []string{}, intSigner)
+	if err != nil {
+		return nil, err
+	}
+	cert, err = x509util.NewCertificate(intCR, x509util.WithTemplate(o.IntermediateTemplate, x509util.CreateTemplateData(intSubject, []string{})))
+	if err != nil {
+		return nil, err
+	}
+	template = cert.GetCertificate()
+	template.NotBefore = now
+	template.NotAfter = now.Add(24 * time.Hour)
+	intermediate, err := x509util.CreateCertificate(template, root, intSigner.Public(), rootSigner)
+	if err != nil {
+		return nil, err
+	}
+
+	// Ssh host signer
+	signer, err := o.GetSigner()
+	if err != nil {
+		return nil, err
+	}
+	sshHostSigner, err := ssh.NewSignerFromSigner(signer)
+	if err != nil {
+		return nil, err
+	}
+
+	// Ssh user signer
+	signer, err = o.GetSigner()
+	if err != nil {
+		return nil, err
+	}
+	sshUserSigner, err := ssh.NewSignerFromSigner(signer)
+	if err != nil {
+		return nil, err
+	}
+
+	return &CA{
+		Root:          root,
+		Intermediate:  intermediate,
+		Signer:        intSigner,
+		SSHHostSigner: sshHostSigner,
+		SSHUserSigner: sshUserSigner,
+	}, nil
+}
+
+// Sign signs an X.509 certificate template using the intermediate certificate.
+// Sign will automatically populate the following fields if they are not
+// specified:
+//
+//   - NotBefore will be set to the current time.
+//   - NotAfter will be set to 24 hours after NotBefore.
+//   - SerialNumber will be automatically generated.
+//   - SubjectKeyId will be automatically generated.
+func (c *CA) Sign(template *x509.Certificate) (*x509.Certificate, error) {
+	mut := *template
+	if mut.NotBefore.IsZero() {
+		mut.NotBefore = time.Now()
+	}
+	if mut.NotAfter.IsZero() {
+		mut.NotAfter = mut.NotBefore.Add(24 * time.Hour)
+	}
+	return x509util.CreateCertificate(&mut, c.Intermediate, mut.PublicKey, c.Signer)
+}
+
+// SignCSR signs an X.509 certificate signing request. The custom options allows
+// to change the template used to convert the CSR to a certificate.
+func (c *CA) SignCSR(csr *x509.CertificateRequest, opts ...SignOption) (*x509.Certificate, error) {
+	sans := append([]string{}, csr.DNSNames...)
+	sans = append(sans, csr.EmailAddresses...)
+	for _, ip := range csr.IPAddresses {
+		sans = append(sans, ip.String())
+	}
+	for _, u := range csr.URIs {
+		sans = append(sans, u.String())
+	}
+
+	o := newSignOptions().apply(opts)
+	crt, err := x509util.NewCertificate(csr, x509util.WithTemplate(o.Template, x509util.CreateTemplateData(csr.Subject.CommonName, sans)))
+	if err != nil {
+		return nil, err
+	}
+
+	cert := crt.GetCertificate()
+	if o.Modify != nil {
+		if err := o.Modify(cert); err != nil {
+			return nil, err
+		}
+	}
+
+	return c.Sign(cert)
+}
+
+// SignSSH signs an SSH host or user certificate. SignSSH will automatically
+// populate the following fields if they are not specified:
+//
+//   - ValidAfter will be set to the current time unless ValidBefore is set to ssh.CertTimeInfinity.
+//   - ValidBefore will be set to 24 hours after ValidAfter.
+//   - Nonce will be automatically generated.
+//   - Serial will be automatically generated.
+//
+// If the SSH signer is an RSA key, it will use rsa-sha2-256 instead of the
+// default ssh-rsa (SHA-1), this method is currently deprecated and
+// rsa-sha2-256/512 are supported since OpenSSH 7.2 (2016).
+func (c *CA) SignSSH(template *ssh.Certificate) (*ssh.Certificate, error) {
+	mut := *template
+	if mut.ValidAfter == 0 && mut.ValidBefore != ssh.CertTimeInfinity {
+		mut.ValidAfter = uint64(time.Now().Unix())
+	}
+	if mut.ValidBefore == 0 {
+		mut.ValidBefore = mut.ValidAfter + 24*60*60
+	}
+
+	switch mut.CertType {
+	case ssh.HostCert:
+		return sshutil.CreateCertificate(&mut, c.SSHHostSigner)
+	case ssh.UserCert:
+		return sshutil.CreateCertificate(&mut, c.SSHUserSigner)
+	default:
+		return nil, fmt.Errorf("unknown certificate type")
+	}
+
+}