Merge pull request #30 from ifanchu/topic/ifanchu/parse_logins_bad

Issue 29: Parse logins.bad

bad_logins.go

@@ -0,0 +1,163 @@
+package bbs
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"time"
+)
+
+// logins.bad 有兩種，一個在BBSHOME，一個在User下面
+// https://github.com/ptt/pttbbs/blob/master/include/common.h#L56
+// https://github.com/ptt/pttbbs/blob/master/common/bbs/passwd.c#L255
+//
+// BBSHOME/logins.bad: 這個檔裡有每個 user的login attempt且包含成功與失敗。第一個字元若是"-"代表失敗。
+//
+//  test03      [01/01/2021 10:11:45 Fri] [email protected]
+//  test04      [01/01/2021 10:13:35 Fri] [email protected]
+//  test05      [01/01/2021 10:13:45 Fri] [email protected]
+//  SYSOP       [01/01/2021 10:13:53 Fri] [email protected]
+//  test06      [01/01/2021 10:14:38 Fri] [email protected]
+//  SYSOP       [01/01/2021 10:14:46 Fri] [email protected]
+// -test01      [01/01/2021 10:15:16 Fri] [email protected]
+// -test02      [01/01/2021 10:15:19 Fri] [email protected]
+// -test03      [01/01/2021 10:15:22 Fri] [email protected]
+//  test04      [01/01/2021 10:15:38 Fri] [email protected]
+//
+// BBSHOME/home/<x>/<user>/logins.bad: 這個檔裡只有該user的 失敗 login attempt
+//
+// ╰─➤  cat home/T/test01/logins.bad
+// [01/01/2021 10:15:16 Fri] 172.22.0.1
+//
+// 目前想法是用同一個struct來parse這2種logins.bad
+//
+// type LoginAttempt struct {
+// 	Success        bool
+// 	UserId         string
+// 	LoginStartTime time.Time
+// 	FromHost       string
+// }
+// For BBSHOME/logins.bad ，這個檔裡四個field都有，所以沒問題。
+// 但在user/logins.bad，缺少 UserId ，所以parse出來的struct就沒有 UserId，需要caller assign
+
+const (
+	// UserIdLength is fixed to 12
+	UserIdLength = 12
+	// FromHostPrefix is a prefix affixed to ip only in BBSHOME/logins.bad
+	fromHostPrefix             = "?@"
+	loginStartTimeFormatString = "[01/02/2006 15:04:05 Mon]"
+)
+
+var (
+	InvalidLoginsBadFormat = errors.New("Invalid logins.bad line format")
+)
+
+// LoginAttempt represents an entry in logins.bad file to indicate a successful or failed login
+// attempt for a UserId. Note that UserId could be empty if the logins.bad is under user dir.
+type LoginAttempt struct {
+	Success        bool
+	UserId         string
+	LoginStartTime time.Time
+	FromHost       string
+}
+
+// OpenBadLoginFile opens logins.bad file and returns a slice of LoginAttempt.
+// Note that depending on different format of logins.bad as descirbed above, each LoginAttempt
+// might not have LoginAttempt.UserId field
+func OpenBadLoginFile(filename string) ([]*LoginAttempt, error) {
+	file, err := os.Open(filename)
+	if err != nil {
+		log.Println(err)
+		return nil, err
+	}
+
+	var ret []*LoginAttempt
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		a := &LoginAttempt{}
+		err = a.UnmarshalText(line)
+		if err != nil {
+			return nil, err
+		}
+		ret = append(ret, a)
+	}
+	return ret, nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler to unmarshal text to the receiver
+func (l *LoginAttempt) UnmarshalText(text []byte) error {
+	str := string(text)
+
+	idx := 0 // current index of str
+	// Handle Success and UserId
+	switch str[idx] {
+	case ' ':
+		idx += 1
+		l.Success = true
+		// Next 12 is UserId
+		l.UserId = str[idx : idx+UserIdLength]
+		idx += UserIdLength
+	case '-':
+		idx += 1
+		l.Success = false
+		l.UserId = str[idx : idx+UserIdLength]
+		idx += UserIdLength
+	case '[':
+		// This indicates this line has no Success and UserId, set Success to false
+		l.Success = false
+		l.UserId = ""
+	default:
+		return InvalidLoginsBadFormat
+	}
+	l.UserId = strings.TrimSpace(l.UserId)
+	// Now idx points to the start of time
+	// TODO: do we need to consider timezone? This Parse returns UTC
+	t, err := time.Parse(loginStartTimeFormatString, str[idx:idx+len(loginStartTimeFormatString)])
+	if err != nil {
+		return err
+	}
+	l.LoginStartTime = t
+	idx += len(loginStartTimeFormatString)
+
+	l.FromHost = strings.TrimLeft(str[idx+1:], fromHostPrefix)
+	return nil
+}
+
+// MarshalText implements encoding.TextMarshaler to marshal receiver to text
+func (l *LoginAttempt) MarshalText() ([]byte, error) {
+	var sb strings.Builder
+	if l.IsUnderBbsHome() {
+		if l.Success {
+			sb.WriteRune(' ')
+		} else {
+			sb.WriteRune('-')
+		}
+		// Right padding UserId
+		sb.WriteString(fmt.Sprintf("%-*s", UserIdLength, l.UserId))
+	}
+	// time
+	formatted := ""
+	// TODO: consider timezone?
+	formatted = l.LoginStartTime.Format(loginStartTimeFormatString)
+	sb.WriteString(formatted)
+	sb.WriteRune(' ')
+	// ip
+	if l.IsUnderBbsHome() {
+		sb.WriteString(fromHostPrefix)
+	}
+	sb.WriteString(l.FromHost)
+
+	return []byte(sb.String()), nil
+}
+
+// IsUnderBbsHome return true if this LoginAttempt was read from logins.bad from under BBSHOME.
+// The difference between logins.bad between under BBSHOME and under User Dir is whether it contains
+// UserId
+func (l *LoginAttempt) IsUnderBbsHome() bool {
+	return len(l.UserId) > 1
+}

bad_logins_test.go

@@ -0,0 +1,68 @@
+package bbs
+
+import (
+	"testing"
+)
+
+func TestOpenBadLoginFile(t *testing.T) {
+	type testCase struct {
+		filename string
+		expected []*LoginAttempt
+	}
+	testCases := []*testCase{
+		{
+			filename: "testcase/bad_logins/logins.bad",
+			expected: nil,
+		},
+		{
+			filename: "testcase/bad_logins/test01/logins.bad",
+			expected: nil,
+		},
+	}
+
+	for _, c := range testCases {
+		attemps, err := OpenBadLoginFile(c.filename)
+		if err != nil {
+			t.Errorf("Failed to open logins.bad. Err %v", err)
+		}
+		for _, l := range attemps {
+			if l.FromHost == "" {
+				t.Error("FromHost should never be empty")
+			}
+			if l.LoginStartTime.IsZero() {
+				t.Error("LoginStartTime should not be zero")
+			}
+			if l.UserId == "" && l.Success {
+				t.Error("If UserId is empty, Success must be false")
+			}
+		}
+	}
+}
+
+func TestLoginAttempt(t *testing.T) {
+	testLines := []string{
+		" SYSOP       [01/01/2021 10:08:56 Fri] [email protected]",
+		"-test03      [01/12/2021 13:14:15 Tue] [email protected]",
+		" test03      [12/30/2021 21:55:59 Thu] [email protected]",
+		" abc123456789[01/01/2021 10:11:09 Fri] [email protected]",
+		"-abc123456789[01/01/2021 10:11:09 Fri] [email protected]",
+		"[01/01/2021 01:02:03 Fri] 1.2.3.4",
+		"[01/12/2021 13:14:15 Tue] 255.255.255.255",
+		"[12/30/2021 21:55:59 Thu] 100.100.100.100",
+	}
+
+	for _, line := range testLines {
+		attempt := &LoginAttempt{}
+		err := attempt.UnmarshalText([]byte(line))
+		if err != nil {
+			t.Errorf("Failed to unmarshal line %s. Err %v", line, err)
+		}
+		formatted, err := attempt.MarshalText()
+		if err != nil {
+			t.Errorf("Failed to marshal LoginAttempt. Err %v", err)
+		}
+		if string(formatted) != line {
+			t.Errorf("Marshaled != original. Original: '%s'. Marshaled: '%s'.", line, string(formatted))
+		}
+	}
+}

testcase/bad_logins/logins.bad

@@ -0,0 +1,15 @@
+ SYSOP       [01/01/2021 10:08:56 Fri] [email protected]
+ SYSOP       [01/01/2021 10:10:50 Fri] [email protected]
+ abc123456789[01/01/2021 10:11:09 Fri] [email protected]
+ test01      [01/01/2021 10:11:23 Fri] [email protected]
+ test02      [01/01/2021 10:11:35 Fri] [email protected]
+ test03      [01/01/2021 10:11:45 Fri] [email protected]
+ test04      [01/01/2021 10:13:35 Fri] [email protected]
+ test05      [01/01/2021 10:13:45 Fri] [email protected]
+ SYSOP       [01/01/2021 10:13:53 Fri] [email protected]
+ test06      [01/01/2021 10:14:38 Fri] [email protected]
+ SYSOP       [01/01/2021 10:14:46 Fri] [email protected]
+-test01      [01/01/2021 10:15:16 Fri] [email protected]
+-test02      [01/01/2021 10:15:19 Fri] [email protected]
+-test03      [01/01/2021 10:15:22 Fri] [email protected]
+ test04      [01/01/2021 10:15:38 Fri] [email protected]

testcase/bad_logins/test01/logins.bad

@@ -0,0 +1 @@
+[01/01/2021 10:15:16 Fri] 172.22.0.1