felhom-agent/cmd/felhom-opsign/main.go

// Command felhom-opsign is the OPERATOR's offline signing CLI for destructive ops (slice 10B,
// decision (a): offline operator key + signing CLI, hardware-key-ready).
//
// It constructs the canonical OpBlob bytes by REUSING internal/authz.CanonicalBlob — the exact
// production path the agent's verifier authenticates over — so signer and verifier can never drift.
// It signs that canonical message with the operator's key via `ssh-keygen -Y sign`, which makes it
// hardware-ready: an `sk-`/YubiKey key works through ssh-keygen unchanged. The output is a signed-op
// envelope { op_blob_b64, sig_armored } to hand to the hub's jobs queue (optionally uploaded with
// --upload). This CLI touches ONLY the operator's signing key — never the hub's or agent's keys.
//
// Example — sign a data-bearing wipe (closing the 8C pending_signature gap):
//
//	felhom-opsign -op storage_wipe -host demo-felhom-01 \
//	   -durable-id byid:wwn-0x5000c500abcd1234 -fstype ext4 \
//	   -key-id ops-key-1 -key ~/.ssh/felhom_op_ed25519 -ttl 30m
package main

import (
	"bytes"
	"crypto/rand"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"gitea.dooplex.hu/admin/felhom-agent/internal/authz"
)

func main() {
	if err := run(); err != nil {
		fmt.Fprintln(os.Stderr, "felhom-opsign:", err)
		os.Exit(1)
	}
}

func run() error {
	var (
		op        = flag.String("op", "", "op class to sign, e.g. storage_wipe | guest_destroy | decommission")
		host      = flag.String("host", "", "target host_id (anti-retarget — the op runs ONLY on this host)")
		guest     = flag.String("guest", "", "target guest_id (\"\" = host-scoped op)")
		keyID     = flag.String("key-id", "", "key id of the signing key (must match a pinned agent signer)")
		paramsRaw = flag.String("params", "", "op params as JSON (overrides -durable-id/-fstype)")
		durableID = flag.String("durable-id", "", "for storage_wipe: the DURABLE device id (byid:…|byuuid:…)")
		fstype    = flag.String("fstype", "ext4", "for storage_wipe: the filesystem to mkfs after wipe")
		keyFile   = flag.String("key", "", "operator signing key (ssh private key / sk- key handle) for ssh-keygen -Y sign")
		ttl       = flag.Duration("ttl", 30*time.Minute, "validity window from now (issued_at..expires_at)")
		nonce     = flag.String("nonce", "", "explicit nonce (default: a fresh 128-bit random nonce)")
		uploadURL = flag.String("upload", "", "optional hub base URL to POST the signed op to the jobs queue")
		hubKey    = flag.String("hub-key", "", "hub bearer key for --upload (operator's hub key — NOT a signing key)")
		out       = flag.String("o", "", "write the envelope JSON to this file (default: stdout)")
	)
	flag.Parse()

	if *op == "" || *host == "" || *keyID == "" || *keyFile == "" {
		return fmt.Errorf("-op, -host, -key-id and -key are required")
	}

	// Params: explicit JSON, or built from the wipe convenience flags.
	params := strings.TrimSpace(*paramsRaw)
	if params == "" {
		if *op == "storage_wipe" {
			if *durableID == "" {
				return fmt.Errorf("storage_wipe needs -durable-id (byid:…|byuuid:…) — a path-only binding is refused by the agent")
			}
			pj, _ := json.Marshal(map[string]string{"durable_id": *durableID, "fstype": *fstype})
			params = string(pj)
		} else {
			params = "{}"
		}
	}

	n := *nonce
	if n == "" {
		var b [16]byte
		if _, err := rand.Read(b[:]); err != nil {
			return fmt.Errorf("generating nonce: %w", err)
		}
		n = hex.EncodeToString(b[:])
	}

	now := time.Now().UTC()
	issued := now
	expires := now.Add(*ttl)

	// Canonical OpBlob bytes — the EXACT bytes the agent verifier authenticates over.
	blob, err := authz.CanonicalBlob(*op, *host, *guest, *keyID, n, params, issued, expires)
	if err != nil {
		return err
	}

	sigArmored, err := signWithSSHKeygen(blob, *keyFile)
	if err != nil {
		return err
	}

	env := map[string]string{
		"op_blob_b64": base64.StdEncoding.EncodeToString(blob),
		"sig_armored": sigArmored,
	}
	envJSON, _ := json.Marshal(env)

	// Emit the envelope (stdout or file). Also print the human summary to stderr (never the key).
	fmt.Fprintf(os.Stderr, "signed: op=%s host=%s guest=%q key_id=%s nonce=%s expires=%s\n",
		*op, *host, *guest, *keyID, n, expires.Format(time.RFC3339))
	if *out != "" {
		if err := os.WriteFile(*out, envJSON, 0o600); err != nil {
			return err
		}
		fmt.Fprintln(os.Stderr, "wrote envelope to", *out)
	} else {
		fmt.Println(string(envJSON))
	}

	if *uploadURL != "" {
		if *hubKey == "" {
			return fmt.Errorf("--upload needs --hub-key (the operator's hub bearer key)")
		}
		if err := upload(*uploadURL, *hubKey, *host, envJSON); err != nil {
			return fmt.Errorf("upload to hub: %w", err)
		}
		fmt.Fprintln(os.Stderr, "uploaded signed op to the hub jobs queue")
	}
	return nil
}

// signWithSSHKeygen signs `message` with `ssh-keygen -Y sign -n <namespace>`, the hardware-ready
// path (sk-/YubiKey keys work unchanged). It writes the message to a temp file, runs ssh-keygen,
// and reads the armored SSHSIG it produces. The namespace is the agent's FIXED domain separator.
func signWithSSHKeygen(message []byte, keyFile string) (string, error) {
	dir, err := os.MkdirTemp("", "felhom-opsign-")
	if err != nil {
		return "", err
	}
	defer os.RemoveAll(dir)
	msgPath := filepath.Join(dir, "op.blob")
	if err := os.WriteFile(msgPath, message, 0o600); err != nil {
		return "", err
	}
	cmd := exec.Command("ssh-keygen", "-Y", "sign", "-n", authz.Namespace, "-f", keyFile, msgPath)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		return "", fmt.Errorf("ssh-keygen -Y sign: %w: %s", err, strings.TrimSpace(stderr.String()))
	}
	sig, err := os.ReadFile(msgPath + ".sig")
	if err != nil {
		return "", fmt.Errorf("reading produced signature: %w", err)
	}
	return string(sig), nil
}

// upload POSTs the signed-op envelope to the hub's jobs queue (POST /api/v1/admin/hosts/{id}/jobs).
// The queued blob is base64(envelope JSON); the hub stores it opaquely (it cannot forge or open it).
func upload(baseURL, hubKey, hostID string, envJSON []byte) error {
	body, _ := json.Marshal(map[string]string{
		"blob_b64": base64.StdEncoding.EncodeToString(envJSON),
	})
	// 10A's enqueue lives under /admin/hosts/{id}/jobs (operator/global key). The queued blob is
	// base64(envelope JSON); the hub stores it opaquely.
	url := strings.TrimRight(baseURL, "/") + "/api/v1/admin/hosts/" + hostID + "/jobs"
	req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+hubKey)
	req.Header.Set("Content-Type", "application/json")
	hc := &http.Client{Timeout: 15 * time.Second}
	resp, err := hc.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 4<<10))
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(raw)))
	}
	return nil
}