4 files changed, 395 insertions, 0 deletions
diff --git a/internal/identity/cli.go b/internal/identity/cli.go
new file mode 100644
index 0000000..85408c8
--- /dev/null
+++ b/internal/identity/cli.go
@@ -0,0 +1,147 @@
+// Package identity integrates the existing identicon-cli program without
+// copying its GUI or reimplementing its rendering algorithm.
+package identity
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+var cliCandidates = []string{
+	"/home/gabriel1/Projects/identicons/identicons-cli",
+	"/home/gabriel1/Workspace/Projects/identicons/identicons",
+	"/usr/local/bin/identicon-cli",
+	"/usr/bin/identicon-cli",
+	"/SDCard/identicon-cli",
+	"/Shared/identicon-cli",
+}
+
+// FindCLI returns the configured or locally installed identicon-cli binary.
+func FindCLI() (string, error) {
+	if configured := strings.TrimSpace(os.Getenv("AEGIS_IDENTICON_CLI")); configured != "" {
+		if isExecutable(configured) {
+			return configured, nil
+		}
+		return "", fmt.Errorf("AEGIS_IDENTICON_CLI is not executable: %s", configured)
+	}
+	for _, candidate := range cliCandidates {
+		if isExecutable(candidate) {
+			return candidate, nil
+		}
+	}
+	return "", errors.New("identicon-cli executable not found")
+}
+
+func isExecutable(path string) bool {
+	info, err := os.Stat(path)
+	return err == nil && info.Mode().IsRegular() && info.Mode()&0o111 != 0
+}
+
+// GenerateFace delegates to identicon-cli with its existing 48px rendering
+// and returns the base64 PNG payload used in a Face header.
+func GenerateFace(seed string) (string, error) {
+	if strings.TrimSpace(seed) == "" {
+		return "", errors.New("identicon seed is required")
+	}
+	return generateFace(seed, 48)
+}
+
+func generateFace(seed string, size int) (string, error) {
+	if strings.TrimSpace(seed) == "" {
+		return "", errors.New("identicon seed is required")
+	}
+	if size <= 0 {
+		return "", errors.New("identicon size must be positive")
+	}
+	executable, err := FindCLI()
+	if err != nil {
+		return "", err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	command := exec.CommandContext(ctx, executable, "-input", seed, "-format", "base64", "-size", fmt.Sprintf("%d", size), "-transparent")
+	var stdout, stderr bytes.Buffer
+	command.Stdout = &stdout
+	command.Stderr = &stderr
+	if err := command.Run(); err != nil {
+		return "", fmt.Errorf("run identicon-cli: %w: %s", err, strings.TrimSpace(stderr.String()))
+	}
+	value := strings.TrimSpace(stdout.String())
+	if _, err := pngImageFromBase64(value, size); err != nil {
+		return "", fmt.Errorf("identicon-cli returned invalid Face data: %w", err)
+	}
+	return value, nil
+}
+
+func decodeFacePNG(value string) ([]byte, error) {
+	return pngBytes(value, 48)
+}
+
+func pngBytes(value string, size int) ([]byte, error) {
+	data, err := base64.StdEncoding.DecodeString(value)
+	if err != nil {
+		return nil, fmt.Errorf("decode base64: %w", err)
+	}
+	if _, err := pngImage(data, size); err != nil {
+		return nil, err
+	}
+	return data, nil
+}
+
+func pngImageFromBase64(value string, size int) (image.Image, error) {
+	data, err := pngBytes(value, size)
+	if err != nil {
+		return nil, err
+	}
+	return pngImage(data, size)
+}
+
+func pngImage(data []byte, size int) (image.Image, error) {
+	img, err := png.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("decode PNG: %w", err)
+	}
+	if img.Bounds().Dx() != size || img.Bounds().Dy() != size {
+		return nil, fmt.Errorf("PNG dimensions are %dx%d, want %dx%d", img.Bounds().Dx(), img.Bounds().Dy(), size, size)
+	}
+	return img, nil
+}
+
+// FormatFaceHeader folds the Face value in the same 70/75-byte pattern used
+// by the existing identicon-cli output files.
+func FormatFaceHeader(value string) string {
+	if len(value) <= 70 {
+		return "Face: " + value
+	}
+	var out strings.Builder
+	out.WriteString("Face: ")
+	out.WriteString(value[:70])
+	for position := 70; position < len(value); position += 75 {
+		end := position + 75
+		if end > len(value) {
+			end = len(value)
+		}
+		out.WriteString("\r\n ")
+		out.WriteString(value[position:end])
+	}
+	return out.String()
+}
+
+// CLIPathForDisplay returns a stable path label without exposing environment
+// secrets or invoking a shell.
+func CLIPathForDisplay(path string) string {
+	if path == "" {
+		return ""
+	}
+	return filepath.Clean(path)
+}
diff --git a/internal/identity/cli_test.go b/internal/identity/cli_test.go
new file mode 100644
index 0000000..e096fe4
--- /dev/null
+++ b/internal/identity/cli_test.go
@@ -0,0 +1,62 @@
+package identity
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"strings"
+	"testing"
+)
+
+func TestFormatFaceHeader(t *testing.T) {
+	header := FormatFaceHeader(strings.Repeat("A", 200))
+	for _, line := range strings.Split(header, "\r\n") {
+		if len(line) > 76 {
+			t.Fatalf("folded line length = %d", len(line))
+		}
+	}
+}
+
+func TestGenerateFaceUsesExistingCLI(t *testing.T) {
+	if _, err := FindCLI(); err != nil {
+		t.Skip(err)
+	}
+	value, err := GenerateFace("reader@example.org")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := decodeFacePNG(value); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGenerateVFaceBindsUsernameEmailAndPublicKey(t *testing.T) {
+	if _, err := FindCLI(); err != nil {
+		t.Skip(err)
+	}
+	public, _, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	publicKey := base64.StdEncoding.EncodeToString(public)
+	profile, err := GenerateVFace("pseudonym", "reader@example.org", publicKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	input := "pseudonym|reader@example.org|" + publicKey
+	identityHash := sha256.Sum256([]byte(input))
+	if profile.Input != input || profile.IdentityHash != hex.EncodeToString(identityHash[:]) {
+		t.Fatalf("unexpected VFace identity: %#v", profile)
+	}
+	if profile.PNGHash == "" || profile.FaceBase64 == "" {
+		t.Fatalf("VFace image metadata is incomplete: %#v", profile)
+	}
+	headers := strings.Join(profile.Headers(), "\n")
+	for _, want := range []string{"X-VFace-Version: 1", "X-Ed25519-Pub: " + publicKey, "Identity-Hash: " + profile.IdentityHash, "X-VFace-Hash: sha256:" + profile.IdentityHash, "X-VFace-Verify: " + VFaceVerificationURL} {
+		if !strings.Contains(headers, want) {
+			t.Fatalf("VFace headers missing %q: %s", want, headers)
+		}
+	}
+}
diff --git a/internal/identity/verify.go b/internal/identity/verify.go
new file mode 100644
index 0000000..e337e07
--- /dev/null
+++ b/internal/identity/verify.go
@@ -0,0 +1,92 @@
+package identity
+
+import (
+	"crypto/ed25519"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"net/mail"
+	"strings"
+
+	"aegis/internal/cryptokit"
+)
+
+type VerificationResult struct {
+	VFaceValid        bool
+	IdentityHashValid bool
+	FaceValid         bool
+	SignaturePresent  bool
+	SignatureValid    bool
+	PublicKey         string
+	IdentityHash      string
+	PNGHash           string
+	Error             error
+}
+
+func VerifyArticle(article string) VerificationResult {
+	message, err := mail.ReadMessage(strings.NewReader(article))
+	if err != nil {
+		return VerificationResult{Error: fmt.Errorf("parse article: %w", err)}
+	}
+	from, err := mail.ParseAddress(message.Header.Get("From"))
+	if err != nil {
+		return VerificationResult{Error: fmt.Errorf("parse From: %w", err)}
+	}
+	publicKey := strings.TrimSpace(message.Header.Get("X-Ed25519-Pub"))
+	result := VerificationResult{PublicKey: publicKey, IdentityHash: strings.TrimSpace(message.Header.Get("Identity-Hash")), PNGHash: strings.TrimSpace(message.Header.Get("X-VFace-PNG-SHA256"))}
+	profile, profileErr := GenerateVFace(from.Name, from.Address, publicKey)
+	if profileErr != nil {
+		result.Error = profileErr
+		return result
+	}
+	result.IdentityHashValid = strings.EqualFold(strings.TrimPrefix(result.IdentityHash, "sha256:"), profile.IdentityHash)
+	result.FaceValid = strings.TrimSpace(message.Header.Get("Face")) == profile.FaceBase64
+	result.VFaceValid = result.IdentityHashValid && result.FaceValid
+	if result.PNGHash != "" && !strings.EqualFold(strings.TrimPrefix(result.PNGHash, "sha256:"), profile.PNGHash) {
+		result.VFaceValid = false
+	}
+	signature := strings.TrimSpace(message.Header.Get("X-Ed25519-Sig"))
+	if signature == "" {
+		value := strings.TrimSpace(message.Header.Get("X-Aegis-Signature"))
+		if parts := strings.SplitN(value, ";", 2); len(parts) == 2 && strings.EqualFold(strings.TrimSpace(parts[0]), "ed25519") {
+			signature = strings.TrimSpace(parts[1])
+		}
+	}
+	if signature == "" {
+		return result
+	}
+	result.SignaturePresent = true
+	signatureBytes, decodeErr := base64.StdEncoding.DecodeString(signature)
+	if decodeErr != nil || len(signatureBytes) != ed25519.SignatureSize {
+		result.Error = errors.New("invalid Ed25519 signature encoding")
+		return result
+	}
+	body, readErr := io.ReadAll(io.LimitReader(message.Body, 16<<20))
+	if readErr != nil {
+		result.Error = fmt.Errorf("read article body: %w", readErr)
+		return result
+	}
+	key, keyErr := decodePublicKey(publicKey)
+	if keyErr != nil {
+		result.Error = keyErr
+		return result
+	}
+	result.SignatureValid = ed25519.Verify(key, body, signatureBytes)
+	if !result.SignatureValid {
+		result.Error = errors.New("Ed25519 signature verification failed")
+	}
+	return result
+}
+
+func decodePublicKey(value string) (ed25519.PublicKey, error) {
+	canonicalText, err := cryptokit.CanonicalEd25519PublicKey(value)
+	if err != nil {
+		return nil, err
+	}
+	canonical, err := base64.StdEncoding.DecodeString(canonicalText)
+	if err != nil {
+		return nil, fmt.Errorf("decode Ed25519 public key: %w", err)
+	}
+	return ed25519.PublicKey(canonical), nil
+}
diff --git a/internal/identity/vface.go b/internal/identity/vface.go
new file mode 100644
index 0000000..a5dcef5
--- /dev/null
+++ b/internal/identity/vface.go
@@ -0,0 +1,94 @@
+package identity
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"image"
+	"strings"
+
+	"aegis/internal/cryptokit"
+)
+
+const VFaceVerificationURL = "https://identicons.virebent.art"
+
+// VFace is the deterministic public profile derived from the three identity
+// fields username, email and Ed25519 public key. The private key is never part
+// of this structure.
+type VFace struct {
+	Username        string
+	Email           string
+	PublicKey       string
+	Input           string
+	IdentityHash    string
+	PNGHash         string
+	FaceBase64      string
+	VerificationURL string
+}
+
+// GenerateVFace creates the optional 48x48 transparent PNG used by Face and
+// the profile preview. The seed is exactly username|email|public-key, matching
+// the VFace implementation used by M2Usenet and N2Usenet.
+func GenerateVFace(username, email, publicKey string) (VFace, error) {
+	username = strings.TrimSpace(username)
+	email = strings.TrimSpace(email)
+	if username == "" || email == "" {
+		return VFace{}, errors.New("VFace requires a username and email address")
+	}
+	if strings.ContainsAny(username+email, "\r\n|") {
+		return VFace{}, errors.New("VFace identity fields contain forbidden characters")
+	}
+	canonicalKey, err := cryptokit.CanonicalEd25519PublicKey(publicKey)
+	if err != nil {
+		return VFace{}, fmt.Errorf("canonicalize VFace public key: %w", err)
+	}
+	input := username + "|" + email + "|" + canonicalKey
+	faceBase64, err := generateFace(input, 48)
+	if err != nil {
+		return VFace{}, fmt.Errorf("generate VFace identicon: %w", err)
+	}
+	pngBytes, err := base64.StdEncoding.DecodeString(faceBase64)
+	if err != nil {
+		return VFace{}, fmt.Errorf("decode VFace PNG: %w", err)
+	}
+	if _, err := pngImage(pngBytes, 48); err != nil {
+		return VFace{}, err
+	}
+	identityDigest := sha256.Sum256([]byte(input))
+	pngDigest := sha256.Sum256(pngBytes)
+	return VFace{
+		Username:        username,
+		Email:           email,
+		PublicKey:       canonicalKey,
+		Input:           input,
+		IdentityHash:    hex.EncodeToString(identityDigest[:]),
+		PNGHash:         hex.EncodeToString(pngDigest[:]),
+		FaceBase64:      faceBase64,
+		VerificationURL: VFaceVerificationURL,
+	}, nil
+}
+
+// Headers returns the interoperable VFace headers for an article or email.
+// The Face value is folded according to the existing identicon convention.
+func (v VFace) Headers() []string {
+	return []string{
+		FormatFaceHeader(v.FaceBase64),
+		"X-VFace-Version: 1",
+		"X-Ed25519-Pub: " + v.PublicKey,
+		"Identity-Hash: " + v.IdentityHash,
+		"X-VFace-Hash: sha256:" + v.IdentityHash,
+		"X-VFace-PNG-SHA256: " + v.PNGHash,
+		"X-VFace-Verify: " + v.VerificationURL,
+	}
+}
+
+// DecodeFacePNG decodes a generated VFace image for a GUI preview.
+func DecodeFacePNG(value string) (image.Image, error) {
+	data, err := base64.StdEncoding.DecodeString(strings.TrimSpace(value))
+	if err != nil {
+		return nil, fmt.Errorf("decode Face base64: %w", err)
+	}
+	return pngImage(data, 48)
+}