From 44e74b5d0cc39b7f0b1cb223b401392e6d8e778d Mon Sep 17 00:00:00 2001
From: Yorick van Pelt <yorick@yorickvanpelt.nl>
Date: Sun, 30 Apr 2023 21:38:30 +0200
Subject: [PATCH] passwords: add version field, more constants for params

---
 internal/db/user.go | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/internal/db/user.go b/internal/db/user.go
index d1de281..54dcf1b 100644
--- a/internal/db/user.go
+++ b/internal/db/user.go
@@ -69,11 +69,21 @@ func Authenticate(db *gorm.DB, username string, password string) (*User, error)
 const (
 	pwdSaltSize = 16
 	pwdHashSize = 32
-	pwdParams   = "m=65536,t=2,p=1"
+
+	// chosen from https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html
+	pwdMemory   = 64 * 1024
+	pwdThreads  = 1
+	pwdIterations = 2
+	pwdParams   = "m=65536,t=2,p=1,v=19"
+	pwdVersion  = "v=19"
 	pwdAlgo     = "argon2id"
 )
 
 func HashPassword(password string) (string, error) {
+	if argon2.Version != 19 {
+		// go has no static asserts
+		panic("Unexpected argon2 version")
+	}
 	// Generate a salt for the password hash
 	salt := make([]byte, pwdSaltSize)
 	if _, err := rand.Read(salt); err != nil {
@@ -81,22 +91,22 @@ func HashPassword(password string) (string, error) {
 	}
 
 	// Hash the password using argon2id
-	hash := argon2.IDKey([]byte(password), salt, 2, 64*1024, 1, pwdHashSize)
+	hash := argon2.IDKey([]byte(password), salt, pwdIterations, pwdMemory, pwdThreads, pwdHashSize)
 
 	// Encode the salt and hash as a string in PHC format
 	encodedSalt := base64.RawStdEncoding.EncodeToString(salt)
 	encodedHash := base64.RawStdEncoding.EncodeToString(hash)
-	return fmt.Sprintf("$%s$%s$%s$%s", pwdAlgo, pwdParams, encodedSalt, encodedHash), nil
+	return fmt.Sprintf("$%s$%s$%s$%s$%s", pwdAlgo, pwdVersion, pwdParams, encodedSalt, encodedHash), nil
 }
 
 var errInvalidDBPasswordFormat = errors.New("invalid password format in db")
 func comparePassword(hashedPassword string, password string) (bool, error) {
 	// Extract the salt and hash from the hashed password string
 	fields := strings.Split(hashedPassword, "$")
-	if len(fields) != 5 || fields[1] != pwdAlgo || fields[2] != pwdParams {
+	if len(fields) != 6 || fields[1] != pwdAlgo || fields[2] != pwdVersion || fields[3] != pwdParams {
 		return false, errInvalidDBPasswordFormat
 	}
-	encodedSalt, encodedHash := fields[3], fields[4]
+	encodedSalt, encodedHash := fields[4], fields[5]
 
 	// Decode the salt and hash from base64
 	salt, err := base64.RawStdEncoding.DecodeString(encodedSalt)
@@ -109,7 +119,7 @@ func comparePassword(hashedPassword string, password string) (bool, error) {
 	}
 
 	// Hash the password using the extracted salt and parameters
-	computedHash := argon2.IDKey([]byte(password), salt, 2, 64*1024, 1, pwdHashSize)
+	computedHash := argon2.IDKey([]byte(password), salt, pwdIterations, pwdMemory, pwdThreads, pwdHashSize)
 
 	// Compare the computed hash with the stored hash
 	return subtle.ConstantTimeCompare(hash, computedHash) == 1, nil