2019-08-01 00:46:28 +00:00
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package provisioner
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import (
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"crypto"
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"crypto/rand"
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"fmt"
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"reflect"
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"time"
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"golang.org/x/crypto/ssh"
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)
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func validateSSHCertificate(cert *ssh.Certificate, opts *SSHOptions) error {
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switch {
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case cert == nil:
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return fmt.Errorf("certificate is nil")
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case cert.Signature == nil:
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return fmt.Errorf("certificate signature is nil")
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case cert.SignatureKey == nil:
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return fmt.Errorf("certificate signature is nil")
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case !reflect.DeepEqual(cert.ValidPrincipals, opts.Principals):
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return fmt.Errorf("certificate principals are not equal, want %v, got %v", opts.Principals, cert.ValidPrincipals)
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case cert.CertType != ssh.UserCert && cert.CertType != ssh.HostCert:
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return fmt.Errorf("certificate type %v is not valid", cert.CertType)
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case opts.CertType == "user" && cert.CertType != ssh.UserCert:
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return fmt.Errorf("certificate type is not valid, want %v, got %v", ssh.UserCert, cert.CertType)
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case opts.CertType == "host" && cert.CertType != ssh.HostCert:
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return fmt.Errorf("certificate type is not valid, want %v, got %v", ssh.HostCert, cert.CertType)
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case cert.ValidAfter != uint64(opts.ValidAfter.Unix()):
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return fmt.Errorf("certificate valid after is not valid, want %v, got %v", opts.ValidAfter.Unix(), time.Unix(int64(cert.ValidAfter), 0))
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case cert.ValidBefore != uint64(opts.ValidBefore.Unix()):
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return fmt.Errorf("certificate valid after is not valid, want %v, got %v", opts.ValidAfter.Unix(), time.Unix(int64(cert.ValidAfter), 0))
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case opts.CertType == "user" && len(cert.Extensions) != 5:
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return fmt.Errorf("certificate extensions number is invalid, want 5, got %d", len(cert.Extensions))
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case opts.CertType == "host" && len(cert.Extensions) != 0:
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return fmt.Errorf("certificate extensions number is invalid, want 0, got %d", len(cert.Extensions))
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default:
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return nil
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}
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}
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func signSSHCertificate(key crypto.PublicKey, opts SSHOptions, signOpts []SignOption, signKey crypto.Signer) (*ssh.Certificate, error) {
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pub, err := ssh.NewPublicKey(key)
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if err != nil {
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return nil, err
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}
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2020-01-24 06:04:34 +00:00
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var mods []SSHCertModifier
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var validators []SSHCertValidator
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2019-08-01 00:46:28 +00:00
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for _, op := range signOpts {
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switch o := op.(type) {
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// modify the ssh.Certificate
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2020-01-24 06:04:34 +00:00
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case SSHCertModifier:
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2019-08-01 00:46:28 +00:00
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mods = append(mods, o)
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// modify the ssh.Certificate given the SSHOptions
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2020-01-24 06:04:34 +00:00
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case SSHCertOptionModifier:
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2019-08-01 00:46:28 +00:00
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mods = append(mods, o.Option(opts))
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// validate the ssh.Certificate
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2020-01-24 06:04:34 +00:00
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case SSHCertValidator:
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2019-08-01 00:46:28 +00:00
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validators = append(validators, o)
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// validate the given SSHOptions
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2020-01-24 06:04:34 +00:00
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case SSHCertOptionsValidator:
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2019-08-01 00:46:28 +00:00
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if err := o.Valid(opts); err != nil {
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return nil, err
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}
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default:
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return nil, fmt.Errorf("signSSH: invalid extra option type %T", o)
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}
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}
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// Build base certificate with the key and some random values
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cert := &ssh.Certificate{
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Nonce: []byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 0},
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Key: pub,
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Serial: 1234567890,
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}
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// Use opts to modify the certificate
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if err := opts.Modify(cert); err != nil {
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return nil, err
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}
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// Use provisioner modifiers
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for _, m := range mods {
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if err := m.Modify(cert); err != nil {
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return nil, err
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}
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}
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// Get signer from authority keys
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var signer ssh.Signer
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switch cert.CertType {
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case ssh.UserCert:
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signer, err = ssh.NewSignerFromSigner(signKey)
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case ssh.HostCert:
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signer, err = ssh.NewSignerFromSigner(signKey)
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default:
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return nil, fmt.Errorf("unexpected ssh certificate type: %d", cert.CertType)
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}
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2019-08-05 23:14:25 +00:00
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if err != nil {
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return nil, err
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}
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2019-08-01 00:46:28 +00:00
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cert.SignatureKey = signer.PublicKey()
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// Get bytes for signing trailing the signature length.
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data := cert.Marshal()
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data = data[:len(data)-4]
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// Sign the certificate
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sig, err := signer.Sign(rand.Reader, data)
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if err != nil {
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return nil, err
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}
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cert.Signature = sig
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// User provisioners validators
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for _, v := range validators {
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if err := v.Valid(cert); err != nil {
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return nil, err
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}
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}
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return cert, nil
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}
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