chrome-session-dump.go

package main

//Written by Aetnaeus
//Original Source: https://github.com/lemnos/chrome-session-dump

import (
	"bytes"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path"
	"sort"
	"strings"
	"unicode/utf16"
)

//Rather than storing session state directly chrome appends a pickled command to a
//session file as tabs are manipulated. These commands are subsequently used to
//reconstruct the session when the browser is restarted. Thus obtaining the
//working tab set involves attemping to simulate the reconstruction process
//performed by chrome (which is an implementation detail liable to change).

//A file has the following format:

//"SNSS"
//int32 version number (should be 1)
//<command>...

//Where each command has the following format

//<int16(size)><int8(type id)><payload (size-1 bytes)>...

//Where payload is a pickled struct containing data of the
//given type.

//See https://source.chromium.org/chromium/chromium/src/+/master:components/sessions/core/session_service_commands.cc;bpv=1;bpt=1?q=kCommandUpdateTabNavigation&ss=chromium%2Fchromium%2Fsrc

//Source:
//https://source.chromium.org/chromium/chromium/src/+/master:components/sessions/core/session_service_commands.cc;drc=948de71be4a38bc27197146904266867c509f4c0;bpv=1;bpt=1;l=25

const (
	kCommandUpdateTabNavigation        = 6
	kCommandSetSelectedTabInIndex      = 8
	kCommandSetTabWindow               = 0
	kCommandSetTabGroup                = 25
	kCommandSetTabGroupMetadata2       = 27
	kCommandSetSelectedNavigationIndex = 7
	kCommandTabClosed                  = 16
	kCommandWindowClosed               = 17
	kCommandSetTabIndexInWindow        = 2
	kCommandSetActiveWindow            = 20
	kCommandLastActiveTime             = 21
)

type group struct {
	high uint64
	low  uint64
	name string
}

type window struct {
	activeTabIdx uint32
	id           uint32
	deleted      bool
	tabs         []*tab
}

type histItem struct {
	idx   uint32
	url   string
	title string
}

type tab struct {
	id                uint32
	history           []*histItem
	idx               uint32 //The tab position in the window (a relative value)
	win               uint32 //the id of the window to which the tab belongs
	deleted           bool
	currentHistoryIdx uint32
	group             *group //May be null
}

//indexed by id
var tabs = map[uint32]*tab{}
var windows = map[uint32]*window{}
var groups = map[string]*group{}

func getWindow(id uint32) *window {
	if _, ok := windows[id]; !ok {
		windows[id] = &window{id: id}
	}

	return windows[id]
}

func getGroup(high uint64, low uint64) *group {
	key := fmt.Sprintf("%x%x", high, low)
	if _, ok := groups[key]; !ok {
		groups[key] = &group{high, low, ""}
	}

	return groups[key]
}

func getTab(id uint32) *tab {
	if _, ok := tabs[id]; !ok {
		tabs[id] = &tab{id: id}
	}

	return tabs[id]
}

func readUint8(r io.Reader) uint8 {
	var b [1]byte
	if n, err := r.Read(b[:]); err != nil || n != 1 {
		if err != nil {
			panic(err)
		}
		panic(fmt.Errorf("Failed to read int8."))
	}

	return uint8(b[0])
}

func readUint16(r io.Reader) uint16 {
	var b [2]byte
	if n, err := r.Read(b[:]); err != nil || n != 2 {
		if err != nil {
			panic(err)
		}
		panic(fmt.Errorf("Failed to read int16."))
	}

	return uint16(b[0]) | uint16(b[1])<<8
}

func readUint32(r io.Reader) uint32 {
	var b [4]byte
	if n, err := r.Read(b[:]); err != nil || n != 4 {
		if err != nil {
			panic(err)
		}

		panic(fmt.Errorf("Failed to read uint32."))
	}

	return uint32(b[3])<<24 | uint32(b[2])<<16 | uint32(b[1])<<8 | uint32(b[0])
}

func readUint64(r io.Reader) uint64 {
	var b [8]byte
	if n, err := r.Read(b[:]); err != nil || n != 8 {
		if err != nil {
			panic(err)
		}

		panic(fmt.Errorf("Failed to read uint64."))
	}

	return uint64(b[7])<<56 |
		uint64(b[6])<<48 |
		uint64(b[5])<<40 |
		uint64(b[4])<<32 |
		uint64(b[3])<<24 |
		uint64(b[2])<<16 |
		uint64(b[1])<<8 |
		uint64(b[0])
}

func readString(r io.Reader) string {
	sz := readUint32(r)
	rsz := sz
	if rsz%4 != 0 { //Chrome 32bit aligns pickled data
		rsz += 4 - (rsz % 4)
	}

	b := make([]byte, rsz)

	if n, err := io.ReadFull(r, b); err != nil {
		panic(err)
	} else if n != len(b) {
		panic(fmt.Errorf("Failed to read string"))
	}

	return string(b[:sz]) //don't return padding
}

//Reads a pickled 16 bit string: NOTE: chrome appears to store the internal c++ std representation
//which is not guaranteed to be UTF16 and may vary by platform and locale (aka this works on
//MY machine :P).

func readString16(r io.Reader) string {
	sz := readUint32(r)
	rsz := sz * 2
	if rsz%4 != 0 { //Chrome 32bit aligns pickled data
		rsz += 4 - (rsz % 4)
	}

	b := make([]byte, rsz)

	if n, err := io.ReadFull(r, b); err != nil {
		panic(err)
	} else if n != len(b) {
		panic(fmt.Errorf("Failed to read string"))
	}

	var s []uint16
	for i := 0; i < int(sz*2); i += 2 {
		s = append(s, uint16(b[i+1])<<8|uint16(b[i]))
	}

	return string(utf16.Decode(s))
}

//Normalized output structures (as distinct from the lower case internal ones which correspond to SNSS structures)

type Result struct {
	Windows []*Window `json:"windows"`
}

type Tab struct {
	Active  bool           `json:"active"`
	History []*HistoryItem `json:"history"`
	Url     string         `json:"url"`
	Title   string         `json:"title"`
	Deleted bool           `json:"deleted"`
	Group   string         `json:"group"`
}

type Window struct {
	Tabs    []*Tab `json:"tabs"`
	Active  bool   `json:"active"`
	Deleted bool   `json:"deleted"`
}

type HistoryItem struct {
	Url   string `json:"url"`
	Title string `json:"title"`
}

func parse(path string) Result {
	fh, err := os.Open(path)
	if err != nil {
		panic(err)
	}

	var magic [4]byte

	if n, err := fh.Read(magic[:4]); err != nil || n != 4 {
		panic(err)
	}

	ver := readUint32(fh)

	if magic != [4]byte{0x53, 0x4E, 0x53, 0x53} || //0x534E5353 == "SNSS"
		(ver != 1 && ver != 3) { //TODO (hotfix): Review https://source.chromium.org/chromium/chromium/src/+/807acce36a4baa1004d23ae896b07e2148ea1533 and implement neccesary changes.

		panic(fmt.Errorf("Invalid SNSS file: (version %d)", ver))
	}

	var activeWindow *window

	readCommand := func() (typ uint8, data io.Reader, eof bool) {
		defer func() {
			if e := recover(); e == io.EOF {
				eof = true
				return
			} else if e != nil {
				panic(err)
			}
		}()

		sz := int(readUint16(fh)) - 1

		typ = readUint8(fh)
		buf := make([]byte, sz)

		if n, err := fh.Read(buf); err != nil {
			panic(err)
		} else if n != sz {
			panic(fmt.Errorf("Failed to read %d bytes", n))
		}

		return typ, bytes.NewBuffer(buf), false
	}

	for {
		typ, data, eof := readCommand()
		if eof {
			break
		}

		//Note: Some commands are pickled whilst others are raw struct
		//dumps from memory, the former have a 32 bit size header whilst the
		//latter may include padding between members.

		switch typ {
		case kCommandUpdateTabNavigation:
			readUint32(data) //size of the data (again)

			id := readUint32(data)
			histIdx := readUint32(data)
			url := readString(data)
			title := readString16(data)

			t := getTab(id)

			var item *histItem
			for _, h := range t.history {
				if h.idx == histIdx {
					item = h
					break
				}
			}

			if item == nil {
				item = &histItem{idx: histIdx}
				t.history = append(t.history, item)
			}

			item.url = url
			item.title = title
		case kCommandSetSelectedTabInIndex: //Sets the active tab index in window, note that 'tab index' is a derived value and not present in any data.
			id := readUint32(data)
			idx := readUint32(data)

			getWindow(id).activeTabIdx = idx
		case kCommandSetTabGroupMetadata2:
			readUint32(data) //Size

			high := readUint64(data)
			low := readUint64(data)

			name := readString16(data)
			getGroup(high, low).name = name
		case kCommandSetTabGroup:
			id := readUint32(data)
			readUint32(data) //Struct padding

			high := readUint64(data)
			low := readUint64(data)

			getTab(id).group = getGroup(high, low)
		case kCommandSetTabWindow:
			win := readUint32(data)
			id := readUint32(data)

			getTab(id).win = win
		case kCommandWindowClosed:
			id := readUint32(data)

			getWindow(id).deleted = true
		case kCommandTabClosed:
			id := readUint32(data)

			getTab(id).deleted = true
		case kCommandSetTabIndexInWindow:
			id := readUint32(data)
			index := readUint32(data)

			getTab(id).idx = index
		case kCommandSetActiveWindow:
			id := readUint32(data)

			activeWindow = getWindow(id)
		case kCommandLastActiveTime: //TODO implement properly
			//id := readUint32(data)
			//time := readUint64(data)

			//getTab(id)._lastActiveTime = time //figure out how to interpret this.
		case kCommandSetSelectedNavigationIndex:
			id := readUint32(data)
			idx := readUint32(data) //The current position within history

			getTab(id).currentHistoryIdx = idx
		}
	}

	for _, t := range tabs {
		sort.Slice(t.history, func(i, j int) bool {
			return t.history[i].idx < t.history[j].idx
		})

		w := getWindow(t.win)
		w.tabs = append(w.tabs, t)
	}

	for _, w := range windows {
		sort.Slice(w.tabs, func(i, j int) bool {
			return w.tabs[i].idx < w.tabs[j].idx
		})
	}

	var Windows []*Window

	for _, w := range windows {
		W := &Window{Active: w == activeWindow, Deleted: w.deleted}

		idx := 0
		for _, t := range w.tabs {
			groupName := ""
			if t.group != nil {
				groupName = t.group.name
			}

			T := &Tab{Active: idx == int(w.activeTabIdx), Deleted: t.deleted, Group: groupName}

			for _, h := range t.history {
				T.History = append(T.History, &HistoryItem{h.url, h.title})
				if h.idx == t.currentHistoryIdx { //Truncate history to avoid having to deal with trees TODO: find a better way to export this.
					T.Url = h.url
					T.Title = h.title
					break
				}
			}

			W.Tabs = append(W.Tabs, T)
			if !t.deleted {
				idx++
			}
		}

		Windows = append(Windows, W)
	}

	return Result{Windows}
}

func findSession(_path string) string {
	var cfile = ""

	ents, err := ioutil.ReadDir(_path)
	if err != nil {
		panic(err)
	}

	cmp := func(candidate string) {
		if cfile != "" {
			info1, err := os.Stat(candidate)
			if err != nil {
				panic(err)
			}

			info2, err := os.Stat(cfile)
			if err != nil {
				panic(err)
			}
			if info1.ModTime().Sub(info2.ModTime()) > 0 {
				cfile = candidate
			}
		} else {
			cfile = candidate
		}
	}

	for _, ent := range ents {
		if ent.IsDir() {
			if cand := findSession(path.Join(_path, ent.Name())); cand != "" {
				cmp(cand)
			}
		} else if strings.Index(ent.Name(), "Session_") == 0 {
			cmp(path.Join(_path, ent.Name()))
		}
	}

	return cfile
}

func tabPrintf(format string, tab *Tab, includeHistory bool) {
	if includeHistory {
		for _, item := range tab.History {
			s := strings.Replace(format, "%u", item.Url, -1)
			s = strings.Replace(s, "%g", tab.Group, -1)
			s = strings.Replace(s, "%t", item.Title, -1)
			s = strings.Replace(s, "\\n", "\n", -1)
			s = strings.Replace(s, "\\t", "\t", -1)
			s = strings.Replace(s, "\\0", "\x00", -1)

			os.Stdout.Write([]byte(s))
		}
	} else {
		s := strings.Replace(format, "%u", tab.Url, -1)
		s = strings.Replace(s, "%g", tab.Group, -1)
		s = strings.Replace(s, "%t", tab.Title, -1)
		s = strings.Replace(s, "\\n", "\n", -1)
		s = strings.Replace(s, "\\t", "\t", -1)
		s = strings.Replace(s, "\\0", "\x00", -1)

		os.Stdout.Write([]byte(s))
	}
}

func main() {
	var jsonFlag bool
	var activeFlag bool
	var deletedFlag bool
	var historyFlag bool
	var outputFmt string

	flag.BoolVar(&jsonFlag, "json", false, "Produce json formatted output. Note that this includes all tabs along with their history and any corresponding metadata. Useful for other scripts.")
	flag.BoolVar(&activeFlag, "active", false, "Print the currently active tab.")
	flag.StringVar(&outputFmt, "printf", "%u\n", "The output format for tabs if -json is not specified (%u = url, %t = title, %g = group).")

	flag.BoolVar(&deletedFlag, "deleted", false, "Include tabs which have been deleted.")
	flag.BoolVar(&historyFlag, "history", false, "Include the history of each tab in the output.")

	flag.Usage = func() {
		fmt.Printf("Usage: 
			   -session-dump [options] ([session file] | [chrome dir])\n\n")
		fmt.Printf(`If a chrome directory is supplied the most recent session file
contained within it is used. If neither a directory or file 
is supplied then the program will use ~/.config/chrome by 
default

`)

		flag.PrintDefaults()
	}

	flag.Parse()

	target := os.ExpandEnv("$HOME/.config/chromium")

	if _, err := os.Stat(target); os.IsNotExist(err) {
		target = os.ExpandEnv("$HOME/.config/google-chrome")
	}

	if _, err := os.Stat(target); os.IsNotExist(err) {
		target = os.ExpandEnv("$HOME/.config/chrome")
	}

	if len(flag.Args()) >= 1 {
		target = flag.Args()[0]
	}

	if info, err := os.Stat(target); err == nil && info.IsDir() {
		target = findSession(target)
	}

	if target == "" {
		panic(fmt.Errorf("Unable to find session file."))
	}

	data := parse(target)

	if jsonFlag {
		b, err := json.Marshal(data)
		if err != nil {
			panic(err)
		}

		fmt.Println(string(b))
	} else if activeFlag {
		for _, win := range data.Windows {
			if win.Active {
				for _, tab := range win.Tabs {
					if tab.Active {
						tabPrintf(outputFmt, tab, historyFlag)
					}
				}
			}
		}
	} else {
		for _, win := range data.Windows {
			if deletedFlag || !win.Deleted {
				for _, tab := range win.Tabs {
					if deletedFlag || !tab.Deleted {
						tabPrintf(outputFmt, tab, historyFlag)
					}
				}
			}
		}
	}
}