Initial commit: dial — interactive SSH host picker

A fast, read-only ~/.ssh/config picker that exec's the system ssh client.
Includes: static high-contrast picker with recency/frequency/name sort and
tag grouping, `dial keygen` (native ed25519/RSA + optional config entry), and
an optional offline YubiKey launch gate with one-time recovery codes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/keygen/keygen_test.go

@@ -0,0 +1,129 @@
+package keygen
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"golang.org/x/crypto/ssh"
+)
+
+func TestGenerateED25519(t *testing.T) {
+	r, err := Generate(AlgoED25519, "test@dial", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Private key must parse back as an OpenSSH key.
+	if _, err := ssh.ParseRawPrivateKey(r.PrivatePEM); err != nil {
+		t.Fatalf("private key does not parse: %v", err)
+	}
+	// Public line must parse and carry the comment.
+	pk, comment, _, _, err := ssh.ParseAuthorizedKey(r.PublicLine)
+	if err != nil {
+		t.Fatalf("public key does not parse: %v", err)
+	}
+	if pk.Type() != ssh.KeyAlgoED25519 {
+		t.Errorf("expected ed25519, got %s", pk.Type())
+	}
+	if comment != "test@dial" {
+		t.Errorf("comment = %q, want test@dial", comment)
+	}
+}
+
+func TestGenerateWithPassphrase(t *testing.T) {
+	r, err := Generate(AlgoED25519, "c", []byte("hunter2"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := ssh.ParseRawPrivateKey(r.PrivatePEM); err == nil {
+		t.Error("encrypted key should not parse without passphrase")
+	}
+	if _, err := ssh.ParseRawPrivateKeyWithPassphrase(r.PrivatePEM, []byte("hunter2")); err != nil {
+		t.Errorf("key should parse with passphrase: %v", err)
+	}
+}
+
+func TestGenerateRSA(t *testing.T) {
+	r, err := Generate(AlgoRSA, "c", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pk, _, _, _, err := ssh.ParseAuthorizedKey(r.PublicLine)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if pk.Type() != ssh.KeyAlgoRSA {
+		t.Errorf("expected rsa, got %s", pk.Type())
+	}
+}
+
+func TestWriteKeyPairPermsAndNoOverwrite(t *testing.T) {
+	dir := t.TempDir()
+	r, _ := Generate(AlgoED25519, "c", nil)
+	priv, pub, err := WriteKeyPair(dir, "mykey", r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	fi, _ := os.Stat(priv)
+	if fi.Mode().Perm() != 0o600 {
+		t.Errorf("private key perms = %o, want 600", fi.Mode().Perm())
+	}
+	pfi, _ := os.Stat(pub)
+	if pfi.Mode().Perm() != 0o644 {
+		t.Errorf("public key perms = %o, want 644", pfi.Mode().Perm())
+	}
+	// Second write must refuse to overwrite.
+	if _, _, err := WriteKeyPair(dir, "mykey", r); err == nil {
+		t.Error("expected refusal to overwrite existing key")
+	}
+}
+
+func TestAppendHostEntryBackupAndDup(t *testing.T) {
+	dir := t.TempDir()
+	cfg := filepath.Join(dir, "config")
+	if err := os.WriteFile(cfg, []byte("Host existing\n    HostName e\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	backup, err := AppendHostEntry(cfg, HostEntry{
+		Alias: "newhost", HostName: "10.0.0.1", User: "ben", Port: "22",
+		IdentityFile: "~/.ssh/mykey", Tags: []string{"prod"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if backup == "" {
+		t.Error("expected a backup path")
+	}
+	if _, err := os.Stat(backup); err != nil {
+		t.Errorf("backup not written: %v", err)
+	}
+	b, _ := os.ReadFile(cfg)
+	got := string(b)
+	for _, want := range []string{"# tag: prod", "Host newhost", "HostName 10.0.0.1", "IdentitiesOnly yes"} {
+		if !strings.Contains(got, want) {
+			t.Errorf("config missing %q\n%s", want, got)
+		}
+	}
+	// Port 22 is the default and should be omitted.
+	if strings.Contains(got, "Port 22") {
+		t.Error("default port 22 should not be written")
+	}
+
+	// Appending the same alias must be refused.
+	if _, err := AppendHostEntry(cfg, HostEntry{Alias: "newhost", HostName: "x"}); err == nil {
+		t.Error("expected duplicate-alias refusal")
+	}
+}
+
+func TestValidateRejectsInjection(t *testing.T) {
+	dir := t.TempDir()
+	cfg := filepath.Join(dir, "config")
+	if _, err := AppendHostEntry(cfg, HostEntry{Alias: "a b"}); err == nil {
+		t.Error("alias with space should be rejected")
+	}
+	if _, err := AppendHostEntry(cfg, HostEntry{Alias: "ok", HostName: "x\n    ProxyCommand evil"}); err == nil {
+		t.Error("newline injection should be rejected")
+	}
+}