v0.1.0 initial commit, auth features exatracted from logwisp to be a standalone utility package

argon2.go

@@ -0,0 +1,110 @@
+// FILE: auth/argon2.go
+package auth
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"fmt"
+	"strings"
+
+	"golang.org/x/crypto/argon2"
+)
+
+// Default Argon2id parameters
+const (
+	DefaultArgonTime    = 3         // iterations (reduce for faster but less secure auth)
+	DefaultArgonMemory  = 64 * 1024 // 64 MB
+	DefaultArgonThreads = 4
+	DefaultArgonSaltLen = 16
+	DefaultArgonKeyLen  = 32
+)
+
+// HashPassword creates an Argon2id PHC-format hash
+func (a *Authenticator) HashPassword(password string) (string, error) {
+	if len(password) < 8 {
+		return "", ErrWeakPassword
+	}
+
+	// Generate salt
+	salt := make([]byte, DefaultArgonSaltLen)
+	if _, err := rand.Read(salt); err != nil {
+		return "", fmt.Errorf("%w: %v", ErrSaltGenerationFailed, err)
+	}
+
+	// Derive key using Argon2id
+	hash := argon2.IDKey([]byte(password), salt, a.argonTime, a.argonMemory, a.argonThreads, DefaultArgonKeyLen)
+
+	// Construct PHC format
+	saltB64 := base64.RawStdEncoding.EncodeToString(salt)
+	hashB64 := base64.RawStdEncoding.EncodeToString(hash)
+	phcHash := fmt.Sprintf("$argon2id$v=%d$m=%d,t=%d,p=%d$%s$%s",
+		argon2.Version, a.argonMemory, a.argonTime, a.argonThreads, saltB64, hashB64)
+
+	return phcHash, nil
+}
+
+// VerifyPassword checks password against PHC-format hash
+func (a *Authenticator) VerifyPassword(password, phcHash string) error {
+	// Parse PHC format
+	parts := strings.Split(phcHash, "$")
+	if len(parts) != 6 || parts[1] != "argon2id" {
+		return ErrPHCInvalidFormat
+	}
+
+	var memory, time uint32
+	var threads uint8
+	fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &time, &threads)
+
+	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrPHCInvalidSalt, err)
+	}
+
+	expectedHash, err := base64.RawStdEncoding.DecodeString(parts[5])
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrPHCInvalidHash, err)
+	}
+
+	// Compute hash with same parameters
+	computedHash := argon2.IDKey([]byte(password), salt, time, memory, threads, uint32(len(expectedHash)))
+
+	// Constant-time comparison
+	if subtle.ConstantTimeCompare(computedHash, expectedHash) != 1 {
+		return ErrInvalidCredentials
+	}
+
+	return nil
+}
+
+// MigrateFromPHC converts existing Argon2 PHC hash to SCRAM credential
+func MigrateFromPHC(username, password, phcHash string) (*Credential, error) {
+	// Parse PHC format
+	parts := strings.Split(phcHash, "$")
+	if len(parts) != 6 || parts[1] != "argon2id" {
+		return nil, ErrPHCInvalidFormat
+	}
+
+	var memory, time uint32
+	var threads uint8
+	fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &time, &threads)
+
+	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
+	if err != nil {
+		return nil, ErrPHCInvalidSalt
+	}
+
+	expectedHash, err := base64.RawStdEncoding.DecodeString(parts[5])
+	if err != nil {
+		return nil, ErrPHCInvalidHash
+	}
+
+	// Verify password against hash
+	computedHash := argon2.IDKey([]byte(password), salt, time, memory, threads, uint32(len(expectedHash)))
+	if subtle.ConstantTimeCompare(computedHash, expectedHash) != 1 {
+		return nil, ErrInvalidCredentials
+	}
+
+	// Derive SCRAM credential with same parameters
+	return DeriveCredential(username, password, salt, time, memory, threads)
+}