Foundation: config, schema/migrations, auth, stable IDs, metadata probing

internal/auth/password.go

@@ -0,0 +1,87 @@
+// Package auth handles password hashing, cookie sessions, CSRF
+// protection, and optional trusted-reverse-proxy external authentication.
+package auth
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strings"
+
+	"golang.org/x/crypto/argon2"
+)
+
+// Argon2id parameters, tuned for a self-hosted single/small-household
+// server rather than a high-throughput multi-tenant service.
+const (
+	argonTime    = 1
+	argonMemory  = 64 * 1024 // KiB
+	argonThreads = 4
+	argonKeyLen  = 32
+	saltLen      = 16
+)
+
+var ErrInvalidHash = errors.New("invalid password hash format")
+
+// HashPassword returns an encoded argon2id hash in the standard
+// $argon2id$v=19$m=...,t=...,p=...$salt$hash format.
+func HashPassword(password string) (string, error) {
+	salt := make([]byte, saltLen)
+	if _, err := rand.Read(salt); err != nil {
+		return "", err
+	}
+	hash := argon2.IDKey([]byte(password), salt, argonTime, argonMemory, argonThreads, argonKeyLen)
+	b64Salt := base64.RawStdEncoding.EncodeToString(salt)
+	b64Hash := base64.RawStdEncoding.EncodeToString(hash)
+	return fmt.Sprintf("$argon2id$v=%d$m=%d,t=%d,p=%d$%s$%s", argon2.Version, argonMemory, argonTime, argonThreads, b64Salt, b64Hash), nil
+}
+
+// VerifyPassword checks password against an encoded hash produced by
+// HashPassword, using constant-time comparison.
+func VerifyPassword(password, encoded string) (bool, error) {
+	parts := strings.Split(encoded, "$")
+	if len(parts) != 6 || parts[1] != "argon2id" {
+		return false, ErrInvalidHash
+	}
+	var version int
+	if _, err := fmt.Sscanf(parts[2], "v=%d", &version); err != nil {
+		return false, ErrInvalidHash
+	}
+	var memory, timeCost uint32
+	var threads uint8
+	if _, err := fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &timeCost, &threads); err != nil {
+		return false, ErrInvalidHash
+	}
+	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
+	if err != nil {
+		return false, ErrInvalidHash
+	}
+	want, err := base64.RawStdEncoding.DecodeString(parts[5])
+	if err != nil {
+		return false, ErrInvalidHash
+	}
+	got := argon2.IDKey([]byte(password), salt, timeCost, memory, threads, uint32(len(want)))
+	return subtle.ConstantTimeCompare(got, want) == 1, nil
+}
+
+// GenerateRandomPassword returns a strong, human-typeable temporary
+// password for the first-run administrator account.
+func GenerateRandomPassword() (string, error) {
+	b := make([]byte, 18)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}
+
+// GenerateAPIKey returns a random API key and its SHA-256 hash for
+// storage (the raw key is shown to the user only once).
+func GenerateAPIKey() (raw string, err error) {
+	b := make([]byte, 32)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	return "vs_" + base64.RawURLEncoding.EncodeToString(b), nil
+}