Provision SSHPublicKey while use custom SSH Private key (#101)

* Provision SSHPublicKey while use custom SSH Private key

* Add tests

communicator/sshkey/pubkey.go

@@ -0,0 +1,16 @@
+package sshkey
+
+import (
+	"fmt"
+
+	"golang.org/x/crypto/ssh"
+)
+
+func PublicKeyFromPrivate(privateKeyBytes []byte) ([]byte, error) {
+	key, err := ssh.ParsePrivateKey(privateKeyBytes)
+	if err != nil {
+		return nil, fmt.Errorf("Error on parsing SSH private key: %s", err)
+	}
+
+	return ssh.MarshalAuthorizedKey(key.PublicKey()), nil
+}

communicator/sshkey/pubkey_test.go

@@ -0,0 +1,93 @@
+package sshkey
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+const (
+	privDSA = `-----BEGIN DSA PRIVATE KEY-----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+-----END DSA PRIVATE KEY-----
+`
+	priv_RSA = `-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----
+`
+	priv_ECDSA = `-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIHpwAwKnukGd3q39ImG5cdpZV1rVRVKn85jhXgX9ASc5oAoGCCqGSM49
+AwEHoUQDQgAEI+QrxZsRkHFbkHCIo1hh8WrikT1bAaHZpTEfVi1w7bQtXErA/2hv
+lvVZHAGSJinAHEnO5ZDM0nP5wjUf3OrAqw==
+-----END EC PRIVATE KEY-----
+`
+	priv_ED25519 = `-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+QyNTUxOQAAACCttg8eP6zngqQlQB5YvPepOLADodc6mqIwXTxAdr4ZMAAAAJj+rLIa/qyy
+GgAAAAtzc2gtZWQyNTUxOQAAACCttg8eP6zngqQlQB5YvPepOLADodc6mqIwXTxAdr4ZMA
+AAAECOJsldUUkAGQ1DXzX0eM9/mTEzYZMFmxsiVquCXCCBRq22Dx4/rOeCpCVAHli896k4
+sAOh1zqaojBdPEB2vhkwAAAAD3hnZW5AaTEwNzUxNjk2NgECAwQFBg==
+-----END OPENSSH PRIVATE KEY-----
+`
+	pub_DSA     = "ssh-dss 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\n"
+	pub_RSA     = "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQCviEbCEYL3HbR/CfERnnN/5PVyH2FVPlQO1fH0QNmaBXQor2lK/wKR1jHhpjCyyJqzf81UdiXPQP+dC4TNQtQXyXKAbPwCbOw1AveON429nH72dz3BHYF9vyxBzYCGPUwtferViPe15/3m68W0sNKlldt+OXASVKNK0objAm0xgQ==\n"
+	pub_ECDSA   = "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBCPkK8WbEZBxW5BwiKNYYfFq4pE9WwGh2aUxH1YtcO20LVxKwP9ob5b1WRwBkiYpwBxJzuWQzNJz+cI1H9zqwKs=\n"
+	pub_ED25519 = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIK22Dx4/rOeCpCVAHli896k4sAOh1zqaojBdPEB2vhkw\n"
+)
+
+func TestPublicKeyFromPrivate(t *testing.T) {
+	tests := []struct {
+		t       Algorithm
+		privKey []byte
+		pubKey  []byte
+	}{
+		{DSA,
+			[]byte(privDSA),
+			[]byte(pub_DSA),
+		},
+		{RSA,
+			[]byte(priv_RSA),
+			[]byte(pub_RSA),
+		},
+		{ECDSA,
+			[]byte(priv_ECDSA),
+			[]byte(pub_ECDSA),
+		},
+		{ED25519,
+			[]byte(priv_ED25519),
+			[]byte(pub_ED25519),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.t.String(), func(t *testing.T) {
+			got, err := PublicKeyFromPrivate(tt.privKey)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if diff := cmp.Diff(got, tt.pubKey); diff != "" {
+				t.Errorf("wrong PublicKeyFromPrivate(): %s", diff)
+			}
+		})
+	}
+}

communicator/step_ssh_keygen.go

@@ -31,7 +31,13 @@ func (s *StepSSHKeyGen) Run(ctx context.Context, state multistep.StateBag) multi
 		}
 
 		comm.SSHPrivateKey = privateKeyBytes
-		comm.SSHPublicKey = nil
+
+		publicKeyBytes, err := sshkey.PublicKeyFromPrivate(privateKeyBytes)
+		if err != nil {
+			state.Put("error", err)
+			return multistep.ActionHalt
+		}
+		comm.SSHPublicKey = publicKeyBytes
 
 		return multistep.ActionContinue
 	}