From 0143b6e4cb7c31abee7d71a2dbd713abcc98936d Mon Sep 17 00:00:00 2001
From: xengineering <me@xengineering.eu>
Date: Fri, 5 Jun 2026 22:45:01 +0200
Subject: Add Register()

This function creates a new user and sets the username and bcrypt-hashed
password.
---
 meson.build      |  1 +
 password.go      | 26 ++++++++++++++++++++++++++
 password_test.go | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 password.go
 create mode 100644 password_test.go

diff --git a/meson.build b/meson.build
index ba66106..7955190 100644
--- a/meson.build
+++ b/meson.build
@@ -12,6 +12,7 @@ finserv_linux_amd64 = custom_target(
     meson.current_source_dir() / 'main.go',
     meson.current_source_dir() / 'handlers.go',
     meson.current_source_dir() / 'database.go',
+    meson.current_source_dir() / 'password.go',
   ],
   output : 'finserv-linux-amd64',
   env : {'GOOS': 'linux', 'GOARCH': 'amd64'},
diff --git a/password.go b/password.go
new file mode 100644
index 0000000..ae11968
--- /dev/null
+++ b/password.go
@@ -0,0 +1,26 @@
+package main
+
+import (
+	"database/sql"
+
+	"golang.org/x/crypto/bcrypt"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+const (
+	bcryptCost = 12
+)
+
+func Register(db *sql.DB, username, password string) error {
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcryptCost)
+	if err != nil {
+		return err
+	}
+
+	err = Transaction(db, func(tx *sql.Tx) error {
+		_, err := tx.Exec(`INSERT INTO users (username, password_bcrypt) VALUES(?, ?);`, username, hash)
+		return err
+	})
+
+	return err
+}
diff --git a/password_test.go b/password_test.go
new file mode 100644
index 0000000..f540cc4
--- /dev/null
+++ b/password_test.go
@@ -0,0 +1,57 @@
+package main
+
+import (
+	"testing"
+
+	"golang.org/x/crypto/bcrypt"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+var passwords = []struct {
+	description string
+	username    string
+	password    string
+}{
+	{"basic", "testuser", "mypassword"},
+	{"password-characterset", "testuser", "mypSDFäÖ$🚧"},
+	{"user-characterset", "mypSDFäÖ$🚧", "mypassword"},
+}
+
+func TestRegister(t *testing.T) {
+	for _, p := range passwords {
+		t.Run(p.description, func(t *testing.T) {
+			db, _ := emptyDB(t)
+
+			err := MigrateToLatest(db)
+			if err != nil {
+				t.Fatalf("Could not execute function to test: %v", err)
+			}
+
+			err = Register(db, p.username, p.password)
+			if err != nil {
+				t.Fatalf("Could not register user: %v", err)
+			}
+
+			row := db.QueryRow(
+				`SELECT password_bcrypt FROM users WHERE username=?;`,
+				p.username,
+			)
+
+			var hash []byte
+			err = row.Scan(&hash)
+			if err != nil {
+				t.Fatalf("Could not scan for password: %v", err)
+			}
+
+			err = bcrypt.CompareHashAndPassword(hash, []byte(p.password))
+			if err != nil {
+				t.Fatalf("Password not valid after registration: %v", err)
+			}
+
+			err = bcrypt.CompareHashAndPassword(hash, []byte(""))
+			if err == nil {
+				t.Fatalf("Empty password is valid after registration.")
+			}
+		})
+	}
+}
-- 
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