1 package mailmux
2 
3 import (
4 	"database/sql"
5 	"errors"
6 	"fmt"
7 	"net/mail"
8 	"os"
9 	"path"
10 	"time"
11 
12 	_ "github.com/mattn/go-sqlite3"
13 	"golang.org/x/crypto/bcrypt"
14 )
15 
16 // maxUsernameSize defines a reasonable maximum length for an email address.
17 const maxUsernameLength = 255
18 
19 // UserDB is an implementation of UserStore backed by a SQLite3 database.
20 // Users are fully authenticated after confirming ownership of their
21 // email address by supplying a matching ticket to a generated ticket file.
22 type UserDB struct {
23 	*sql.DB
24 	TicketDir string
25 }
26 
27 // CreateUserDB creates the named user database file and ticket directory.
28 // If the database file already exists, it is truncated. If successfullly created,
29 // the database's tables are initialised so the database is ready to use.
30 func CreateUserDB(name, ticketDir string) (*UserDB, error) {
31 	_, err := os.Create(name)
32 	if err != nil {
33 		return nil, err
34 	}
35 	if err := os.MkdirAll(ticketDir, 0666); err != nil {
36 		return nil, fmt.Errorf("create user db: %w", err)
37 	}
38 	db, err := OpenUserDB(name, ticketDir)
39 	if err != nil {
40 		return nil, fmt.Errorf("create user db: %w", err)
41 	}
42 	return db, initialiseUserDB(db.DB)
43 }
44 
45 // OpenUserDB opens the named user database file and ticket directory.
46 // If the database does not exist, it is created and its tables are 
47 // initialised ready for use.
48 func OpenUserDB(name, dir string) (*UserDB, error) {
49 	db, err := sql.Open("sqlite3", name)
50 	if err != nil {
51 		return nil, err
52 	}
53 	if err := initialiseUserDB(db); err != nil {
54 		return nil, err
55 	}
56 	return &UserDB{db, dir}, db.Ping()
57 }
58 
59 func initialiseUserDB(db *sql.DB) error {
60 	stmt := `CREATE TABLE IF NOT EXISTS users (
61 	username TEXT PRIMARY KEY,
62 	password BLOB NOT NULL,
63 	modtime INTEGER NOT NULL
64 );`
65 	_, err := db.Exec(stmt)
66 	return err
67 }
68 
69 func (db *UserDB) Lookup(name string) (User, error) {
70 	var u User
71 	row := db.QueryRow("SELECT username, password FROM users WHERE username = ?", name)
72 	if err := row.Scan(&u.name, &u.password); err != nil {
73 		if errors.Is(err, sql.ErrNoRows) {
74 			return User{}, ErrUnknownUser
75 		}
76 		return User{}, err
77 	}
78 	return u, nil
79 }
80 
81 func (db *UserDB) add(username string, pw Password) error {
82 	if len(username) > maxUsernameLength {
83 		return fmt.Errorf("add %s: invalid username: too long", username)
84 	}
85 	addr, err := mail.ParseAddress(username)
86 	if err != nil {
87 		return fmt.Errorf("add %s: invalid username: %w", username, err)
88 	}
89 	if addr.Name != "" {
90 		return fmt.Errorf("add %s: proper name present", username)
91 	}
92 
93 	hashed, err := bcrypt.GenerateFromPassword(pw, bcrypt.DefaultCost)
94 	if err != nil {
95 		return fmt.Errorf("add %s: %w", username, err)
96 	}
97 	_, err = db.Exec("INSERT INTO users (username, password, modtime) VALUES (?, ?, ?)", username, hashed, time.Now().Unix())
98 	if err != nil {
99 		return fmt.Errorf("add %s: %w", username, err)
100 	}
101 	if err := createTicket(db.TicketDir, username, pw); err != nil {
102 		return fmt.Errorf("add %s: create ticket: %w", username, err)
103 	}
104 	return nil
105 }
106 
107 func (db *UserDB) Change(name string, new Password) error {
108 	_, err := db.Lookup(name)
109 	if errors.Is(err, ErrUnknownUser) {
110 		return db.add(name, new)
111 	}
112 	if err != nil {
113 		return fmt.Errorf("lookup %s: %w", name, err)
114 	}
115 
116 	hashed, err := bcrypt.GenerateFromPassword(new, bcrypt.DefaultCost)
117 	if err != nil {
118 		return fmt.Errorf("generate hash: %w", err)
119 	}
120 	_, err = db.Exec("UPDATE users SET password = ?, modtime = ? WHERE username = ?", hashed, time.Now().Unix(), name)
121 	return err
122 }
123 
124 func (db *UserDB) Delete(name string) error {
125 	_, err := db.Lookup(name)
126 	if err != nil {
127 		return fmt.Errorf("delete %s: %w", name, err)
128 	}
129 	_, err = db.Exec("DELETE FROM users WHERE username = ?", name)
130 	if err != nil {
131 		return fmt.Errorf("delete %s: %w", name, err)
132 	}
133 	return nil
134 }
135 
136 func (db *UserDB) Authenticate(name string, pw Password) error {
137 	u, err := db.Lookup(name)
138 	if err != nil {
139 		return fmt.Errorf("authenticate %s: %w", name, err)
140 	}
141 	if err := bcrypt.CompareHashAndPassword(u.password, pw); err != nil {
142 		return fmt.Errorf("authenticate %s: %w", name, err)
143 	}
144 	return nil
145 }
146 
147 // TODO tickets aren't implemented yet
148 func createTicket(dir, username string, pw Password) error {
149 	f, err := os.Create(path.Join(dir, username))
150 	if err != nil {
151 		return err
152 	}
153 	defer f.Close()
154 
155 	// TODO hash username, password, random bytes
156 	// _, err := f.Write(b)
157 	if _, err := f.Write(testTicket); err != nil {
158 		return err
159 	}
160 	return nil
161 }