Replace SSH shell-outs with Go implementation

internal/ssh/host_scan.go

@@ -0,0 +1,47 @@
+package ssh
+
+import (
+	"encoding/base64"
+	"fmt"
+	"net"
+
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/knownhosts"
+)
+
+func ScanHostKey(host string, user string, pair *KeyPair) ([]byte, error) {
+	signer, err := ssh.ParsePrivateKey(pair.PrivateKey)
+	if err != nil {
+		return nil, err
+	}
+	col := &collector{}
+	config := &ssh.ClientConfig{
+		User: user,
+		Auth: []ssh.AuthMethod{
+			ssh.PublicKeys(signer),
+		},
+		HostKeyCallback: col.StoreKey(),
+	}
+	client, err := ssh.Dial("tcp", host, config)
+	if err == nil {
+		defer client.Close()
+	}
+	if len(col.knownKeys) > 0 {
+		return col.knownKeys, nil
+	}
+	return col.knownKeys, err
+}
+
+type collector struct {
+	knownKeys []byte
+}
+
+func (c *collector) StoreKey() ssh.HostKeyCallback {
+	return func(hostname string, remote net.Addr, key ssh.PublicKey) error {
+		c.knownKeys = append(
+			c.knownKeys,
+			fmt.Sprintf("%s %s %s\n", knownhosts.Normalize(hostname), key.Type(), base64.StdEncoding.EncodeToString(key.Marshal()))...,
+		)
+		return nil
+	}
+}

internal/ssh/key_pair.go

@@ -0,0 +1,89 @@
+package ssh
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+
+	"golang.org/x/crypto/ssh"
+)
+
+type KeyPair struct {
+	PublicKey  []byte
+	PrivateKey []byte
+}
+
+type KeyPairGenerator interface {
+	Generate() (*KeyPair, error)
+}
+
+type RSAGenerator struct {
+	bits int
+}
+
+func NewRSAGenerator(bits int) KeyPairGenerator {
+	return &RSAGenerator{bits}
+}
+
+func (g *RSAGenerator) Generate() (*KeyPair, error) {
+	pk, err := rsa.GenerateKey(rand.Reader, g.bits)
+	if err != nil {
+		return nil, err
+	}
+	err = pk.Validate()
+	if err != nil {
+		return nil, err
+	}
+	pub, err := generatePublicKey(&pk.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+	return &KeyPair{
+		PublicKey:  pub,
+		PrivateKey: encodePrivateKeyToPEM(pk),
+	}, nil
+}
+
+type ECDSAGenerator struct {
+	c elliptic.Curve
+}
+
+func NewECDSAGenerator(c elliptic.Curve) KeyPairGenerator {
+	return &ECDSAGenerator{c}
+}
+
+func (g *ECDSAGenerator) Generate() (*KeyPair, error) {
+	pk, err := ecdsa.GenerateKey(g.c, rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+	pub, err := generatePublicKey(&pk.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+	return &KeyPair{
+		PublicKey:  pub,
+		PrivateKey: encodePrivateKeyToPEM(pk),
+	}, nil
+}
+
+func generatePublicKey(pk interface{}) ([]byte, error) {
+	b, err := ssh.NewPublicKey(pk)
+	if err != nil {
+		return nil, err
+	}
+	k := ssh.MarshalAuthorizedKey(b)
+	return k, nil
+}
+
+func encodePrivateKeyToPEM(pk interface{}) []byte {
+	b, _ := x509.MarshalPKCS8PrivateKey(pk)
+	block := pem.Block{
+		Type:  "PRIVATE KEY",
+		Bytes: b,
+	}
+	return pem.EncodeToMemory(&block)
+}