feat: Decrypt the browser master key on macOS via CVE-2025-24204 (#494)

* feat: Decrypt the browser master key on macOS via CVE-2025-24204

* fix: resolve lint warnings and stabilize tests

* feat: default to gcoredump key extraction on macOS
This commit is contained in:
zznQ
2025-11-27 17:13:07 +08:00
committed by GitHub
parent 1a04abb81a
commit f2b0e4bf47
5 changed files with 971 additions and 1 deletions
+695
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@@ -0,0 +1,695 @@
package chainbreaker
// Logic ported from https://github.com/n0fate/chainbreaker
import (
"bytes"
"crypto/cipher"
"crypto/des"
"encoding/base64"
"encoding/binary"
"encoding/hex"
"errors"
"fmt"
"os"
"strings"
"time"
"unicode/utf8"
)
const (
atomSize = 4
headerSize = 20
schemaSize = 8
tableHeaderSize = 28
keyBlobRecordHeaderSize = 132
keyBlobStructSize = 24
genericPasswordHeaderSize = 22 * 4
blockSize = 8
keyLength = 24
metadataOffsetAdjustment = 0x38
keyBlobMagic uint32 = 0xFADE0711
keychainSignature = "kych"
secureStorageGroup = "ssgp"
keychainLockedSignature = "[Invalid Password / Keychain Locked]"
)
const (
cssmDBRecordTypeAppDefinedStart uint32 = 0x80000000
cssmGenericPassword = cssmDBRecordTypeAppDefinedStart + 0
cssmMetadata = cssmDBRecordTypeAppDefinedStart + 0x8000
cssmDBRecordTypeOpenGroupStart uint32 = 0x0000000A
cssmSymmetricKey = cssmDBRecordTypeOpenGroupStart + 7
)
const dbBlobSize = 92
var magicCMSIV = []byte{0x4a, 0xdd, 0xa2, 0x2c, 0x79, 0xe8, 0x21, 0x05}
type Keychain struct {
buf []byte
header applDBHeader
tableList []uint32
tableEnum map[uint32]int
dbblob dbBlob
baseAddr int
dbKey []byte
keyList map[string][]byte
}
type applDBHeader struct {
Signature [4]byte
Version uint32
HeaderSize uint32
SchemaOffset uint32
AuthOffset uint32
}
type applDBSchema struct {
SchemaSize uint32
TableCount uint32
}
type tableHeader struct {
TableSize uint32
TableID uint32
RecordCount uint32
Records uint32
IndexesOffset uint32
FreeListHead uint32
RecordNumbersCount uint32
}
type dbBlob struct {
StartCryptoBlob uint32
TotalLength uint32
Salt []byte
IV []byte
}
type keyBlobRecordHeader struct {
RecordSize uint32
}
type keyBlob struct {
Magic uint32
StartCryptoBlob uint32
TotalLength uint32
IV []byte
}
type genericPasswordHeader struct {
RecordSize uint32
SSGPArea uint32
CreationDate uint32
ModDate uint32
Description uint32
Comment uint32
Creator uint32
Type uint32
PrintName uint32
Alias uint32
Account uint32
Service uint32
}
type ssgpBlock struct {
Magic []byte
Label []byte
IV []byte
EncryptedPassword []byte
}
type genericPassword struct {
Description string
Creator string
Type string
PrintName string
Alias string
Account string
Service string
Created string
LastModified string
Password string
PasswordBase64 bool
}
func New(path, unlockHex string) (*Keychain, error) {
buf, err := os.ReadFile(path)
if err != nil {
return nil, err
}
hdr, err := parseHeader(buf)
if err != nil {
return nil, err
}
if string(hdr.Signature[:]) != keychainSignature {
return nil, fmt.Errorf("invalid keychain signature: %q", hdr.Signature)
}
schema, tableList, err := parseSchema(buf, hdr.SchemaOffset)
if err != nil {
return nil, err
}
if schema.TableCount == 0 {
return nil, errors.New("schema does not list any tables")
}
kc := &Keychain{
buf: buf,
header: hdr,
tableList: tableList,
tableEnum: make(map[uint32]int),
keyList: make(map[string][]byte),
}
if err := kc.buildTableIndex(); err != nil {
return nil, err
}
metaOffset, err := kc.getTableOffset(cssmMetadata)
if err != nil {
return nil, err
}
kc.baseAddr = headerSize + int(metaOffset) + metadataOffsetAdjustment
if kc.baseAddr+dbBlobSize > len(kc.buf) {
return nil, errors.New("db blob exceeds file size")
}
blob, err := parseDBBlob(kc.buf[kc.baseAddr : kc.baseAddr+dbBlobSize])
if err != nil {
return nil, err
}
kc.dbblob = blob
masterKey, err := decodeUnlockKey(unlockHex)
if err != nil {
return nil, err
}
dbKey, err := kc.findWrappingKey(masterKey)
if err != nil {
return nil, err
}
kc.dbKey = dbKey
if err := kc.generateKeyList(); err != nil {
return nil, err
}
return kc, nil
}
func parseHeader(buf []byte) (applDBHeader, error) {
if len(buf) < headerSize {
return applDBHeader{}, errors.New("file too small for header")
}
hdr := applDBHeader{}
copy(hdr.Signature[:], buf[:4])
hdr.Version = binary.BigEndian.Uint32(buf[4:8])
hdr.HeaderSize = binary.BigEndian.Uint32(buf[8:12])
hdr.SchemaOffset = binary.BigEndian.Uint32(buf[12:16])
hdr.AuthOffset = binary.BigEndian.Uint32(buf[16:20])
return hdr, nil
}
func parseSchema(buf []byte, offset uint32) (applDBSchema, []uint32, error) {
if int(offset)+schemaSize > len(buf) {
return applDBSchema{}, nil, errors.New("schema offset exceeds file size")
}
schema := applDBSchema{}
start := int(offset)
schema.SchemaSize = binary.BigEndian.Uint32(buf[start : start+4])
schema.TableCount = binary.BigEndian.Uint32(buf[start+4 : start+8])
baseAddr := headerSize + schemaSize
tableList := make([]uint32, schema.TableCount)
for i := 0; i < int(schema.TableCount); i++ {
pos := baseAddr + i*atomSize
if pos+atomSize > len(buf) {
return applDBSchema{}, nil, errors.New("table list exceeds file size")
}
tableList[i] = binary.BigEndian.Uint32(buf[pos : pos+atomSize])
}
return schema, tableList, nil
}
func parseDBBlob(buf []byte) (dbBlob, error) {
if len(buf) < dbBlobSize {
return dbBlob{}, errors.New("db blob buffer too small")
}
blob := dbBlob{}
blob.StartCryptoBlob = binary.BigEndian.Uint32(buf[8:12])
blob.TotalLength = binary.BigEndian.Uint32(buf[12:16])
// Salt and IV are located after the random signature (16 bytes), sequence (4 bytes),
// and DB parameters (8 bytes) inside the blob structure.
blob.Salt = append([]byte{}, buf[44:64]...)
blob.IV = append([]byte{}, buf[64:72]...)
return blob, nil
}
func decodeUnlockKey(hexKey string) ([]byte, error) {
cleaned := strings.TrimSpace(hexKey)
cleaned = strings.TrimPrefix(cleaned, "0x")
key, err := hex.DecodeString(cleaned)
if err != nil {
return nil, fmt.Errorf("unable to decode unlock key: %w", err)
}
if len(key) != keyLength {
return nil, fmt.Errorf("unlock key must be %d bytes (got %d)", keyLength, len(key))
}
return key, nil
}
func (kc *Keychain) buildTableIndex() error {
for idx, offset := range kc.tableList {
if offset == 0 {
continue
}
meta, _, err := kc.getTable(offset)
if err != nil {
continue
}
if _, exists := kc.tableEnum[meta.TableID]; !exists {
kc.tableEnum[meta.TableID] = idx
}
}
if len(kc.tableEnum) == 0 {
return errors.New("unable to derive table index")
}
return nil
}
func (kc *Keychain) getTableOffset(tableID uint32) (uint32, error) {
idx, ok := kc.tableEnum[tableID]
if !ok || idx >= len(kc.tableList) {
return 0, fmt.Errorf("table id %d not present", tableID)
}
return kc.tableList[idx], nil
}
func (kc *Keychain) getTableFromType(tableID uint32) (tableHeader, []uint32, error) {
offset, err := kc.getTableOffset(tableID)
if err != nil {
return tableHeader{}, nil, err
}
return kc.getTable(offset)
}
func (kc *Keychain) getTable(offset uint32) (tableHeader, []uint32, error) {
base := headerSize + int(offset)
if base < 0 || base+tableHeaderSize > len(kc.buf) {
return tableHeader{}, nil, errors.New("table header exceeds file size")
}
meta := tableHeader{}
data := kc.buf[base : base+tableHeaderSize]
meta.TableSize = binary.BigEndian.Uint32(data[0:4])
meta.TableID = binary.BigEndian.Uint32(data[4:8])
meta.RecordCount = binary.BigEndian.Uint32(data[8:12])
meta.Records = binary.BigEndian.Uint32(data[12:16])
meta.IndexesOffset = binary.BigEndian.Uint32(data[16:20])
meta.FreeListHead = binary.BigEndian.Uint32(data[20:24])
meta.RecordNumbersCount = binary.BigEndian.Uint32(data[24:28])
recordBase := base + tableHeaderSize
recordList := make([]uint32, 0, meta.RecordCount)
for idx := 0; idx < int(meta.RecordCount); idx++ {
pos := recordBase + idx*atomSize
if pos+atomSize > len(kc.buf) {
return meta, recordList, errors.New("record offset exceeds file size")
}
value := binary.BigEndian.Uint32(kc.buf[pos : pos+atomSize])
if value != 0 && value%4 == 0 {
recordList = append(recordList, value)
}
}
return meta, recordList, nil
}
func (kc *Keychain) findWrappingKey(master []byte) ([]byte, error) {
start := kc.baseAddr + int(kc.dbblob.StartCryptoBlob)
end := kc.baseAddr + int(kc.dbblob.TotalLength)
if start < 0 || end > len(kc.buf) || start >= end {
return nil, errors.New("db blob cipher bounds invalid")
}
plain, err := kcdecrypt(master, kc.dbblob.IV, kc.buf[start:end])
if err != nil {
return nil, err
}
if len(plain) < keyLength {
return nil, errors.New("db key shorter than expected")
}
return append([]byte{}, plain[:keyLength]...), nil
}
func (kc *Keychain) generateKeyList() error {
_, records, err := kc.getTableFromType(cssmSymmetricKey)
if err != nil {
return err
}
for _, recordOffset := range records {
index, ciphertext, iv, err := kc.getKeyblobRecord(recordOffset)
if err != nil {
continue
}
key, err := keyblobDecryption(ciphertext, iv, kc.dbKey)
if err != nil || len(key) == 0 {
continue
}
kc.keyList[string(index)] = key
}
if len(kc.keyList) == 0 {
return errors.New("no symmetric keys recovered")
}
return nil
}
func (kc *Keychain) getKeyblobRecord(recordOffset uint32) ([]byte, []byte, []byte, error) {
base, err := kc.getBaseAddress(cssmSymmetricKey, recordOffset)
if err != nil {
return nil, nil, nil, err
}
if base+keyBlobRecordHeaderSize > len(kc.buf) {
return nil, nil, nil, errors.New("keyblob header exceeds file size")
}
hdr := keyBlobRecordHeader{}
hdr.RecordSize = binary.BigEndian.Uint32(kc.buf[base : base+4])
_ = binary.BigEndian.Uint32(kc.buf[base+4 : base+8]) // Skip RecordCount
recordStart := base + keyBlobRecordHeaderSize
recordEnd := base + int(hdr.RecordSize)
if recordEnd > len(kc.buf) {
return nil, nil, nil, errors.New("keyblob record exceeds file size")
}
record := kc.buf[recordStart:recordEnd]
if len(record) < keyBlobStructSize {
return nil, nil, nil, errors.New("keyblob structure incomplete")
}
blob, err := parseKeyBlob(record[:keyBlobStructSize])
if err != nil {
return nil, nil, nil, err
}
if blob.Magic != keyBlobMagic {
return nil, nil, nil, errors.New("unexpected keyblob magic")
}
if secureStorageGroup != readASCII(record, int(blob.TotalLength)+8, 4) {
return nil, nil, nil, errors.New("keyblob not part of secure storage group")
}
cipherStart := int(blob.StartCryptoBlob)
cipherEnd := int(blob.TotalLength)
if cipherEnd > len(record) || cipherStart >= cipherEnd {
return nil, nil, nil, errors.New("invalid cipher bounds")
}
cipherText := append([]byte{}, record[cipherStart:cipherEnd]...)
indexStart := int(blob.TotalLength) + 8
indexEnd := indexStart + 20
if indexEnd > len(record) {
return nil, nil, nil, errors.New("key index exceeds record length")
}
index := append([]byte{}, record[indexStart:indexEnd]...)
iv := append([]byte{}, blob.IV...)
return index, cipherText, iv, nil
}
func parseKeyBlob(buf []byte) (keyBlob, error) {
if len(buf) < keyBlobStructSize {
return keyBlob{}, errors.New("key blob buffer too small")
}
kb := keyBlob{}
kb.Magic = binary.BigEndian.Uint32(buf[0:4])
kb.StartCryptoBlob = binary.BigEndian.Uint32(buf[8:12])
kb.TotalLength = binary.BigEndian.Uint32(buf[12:16])
kb.IV = append([]byte{}, buf[16:24]...)
return kb, nil
}
func (kc *Keychain) getBaseAddress(tableID uint32, offset uint32) (int, error) {
switch tableID {
case 23972, 30912:
tableID = 16
}
tableOffset, err := kc.getTableOffset(tableID)
if err != nil {
return 0, err
}
base := headerSize + int(tableOffset)
if offset != 0 {
base += int(offset)
}
if base > len(kc.buf) {
return 0, errors.New("base address exceeds buffer")
}
return base, nil
}
func keyblobDecryption(encryptedblob, iv, dbkey []byte) ([]byte, error) {
plain, err := kcdecrypt(dbkey, magicCMSIV, encryptedblob)
if err != nil {
return nil, err
}
if len(plain) == 0 {
return nil, errors.New("empty plain blob")
}
if len(plain) < 32 {
return nil, errors.New("wrapped blob too short")
}
rev := make([]byte, 32)
for i := 0; i < 32; i++ {
rev[i] = plain[31-i]
}
finalPlain, err := kcdecrypt(dbkey, iv, rev)
if err != nil {
return nil, err
}
if len(finalPlain) < 4 {
return nil, errors.New("final plain too short")
}
key := finalPlain[4:]
if len(key) != keyLength {
return nil, errors.New("invalid unwrapped key length")
}
return append([]byte{}, key...), nil
}
func kcdecrypt(key, iv, data []byte) ([]byte, error) {
if len(data) == 0 {
return nil, errors.New("ciphertext is empty")
}
if len(data)%blockSize != 0 {
return nil, errors.New("ciphertext not aligned to block size")
}
block, err := des.NewTripleDESCipher(key)
if err != nil {
return nil, err
}
if len(iv) != blockSize {
return nil, errors.New("invalid IV length")
}
plain := make([]byte, len(data))
cipher.NewCBCDecrypter(block, iv).CryptBlocks(plain, data)
pad := int(plain[len(plain)-1])
if pad == 0 || pad > blockSize {
return nil, errors.New("invalid padding value")
}
for _, b := range plain[len(plain)-pad:] {
if int(b) != pad {
return nil, errors.New("padding verification failed")
}
}
return plain[:len(plain)-pad], nil
}
func (kc *Keychain) DumpGenericPasswords() ([]genericPassword, error) {
_, records, err := kc.getTableFromType(cssmGenericPassword)
if err != nil {
return nil, err
}
results := make([]genericPassword, 0, len(records))
for _, offset := range records {
rec, err := kc.parseGenericPasswordRecord(offset)
if err != nil {
continue
}
results = append(results, rec)
}
return results, nil
}
func (kc *Keychain) parseGenericPasswordRecord(recordOffset uint32) (genericPassword, error) {
base, err := kc.getBaseAddress(cssmGenericPassword, recordOffset)
if err != nil {
return genericPassword{}, err
}
if base+genericPasswordHeaderSize > len(kc.buf) {
return genericPassword{}, errors.New("generic password header exceeds file size")
}
header, err := parseGenericPasswordHeader(kc.buf[base : base+genericPasswordHeaderSize])
if err != nil {
return genericPassword{}, err
}
recordEnd := base + int(header.RecordSize)
if recordEnd > len(kc.buf) {
return genericPassword{}, errors.New("generic password record exceeds file size")
}
buffer := kc.buf[base+genericPasswordHeaderSize : recordEnd]
ssgp, dbkey := kc.extractSSGP(header, buffer)
password, base64Encoded := decryptSSGP(ssgp, dbkey)
rec := genericPassword{
Description: kc.readLV(base, header.Description),
Creator: kc.readFourChar(base, header.Creator),
Type: kc.readFourChar(base, header.Type),
PrintName: kc.readLV(base, header.PrintName),
Alias: kc.readLV(base, header.Alias),
Account: kc.readLV(base, header.Account),
Service: kc.readLV(base, header.Service),
Created: kc.readKeychainTime(base, header.CreationDate),
LastModified: kc.readKeychainTime(base, header.ModDate),
Password: password,
PasswordBase64: base64Encoded,
}
return rec, nil
}
func parseGenericPasswordHeader(buf []byte) (genericPasswordHeader, error) {
if len(buf) < genericPasswordHeaderSize {
return genericPasswordHeader{}, errors.New("generic password header too small")
}
vals := make([]uint32, 22)
for i := 0; i < 22; i++ {
start := i * 4
vals[i] = binary.BigEndian.Uint32(buf[start : start+4])
}
hdr := genericPasswordHeader{
RecordSize: vals[0],
SSGPArea: vals[4],
CreationDate: vals[6],
ModDate: vals[7],
Description: vals[8],
Comment: vals[9],
Creator: vals[10],
Type: vals[11],
PrintName: vals[13],
Alias: vals[14],
Account: vals[19],
Service: vals[20],
}
return hdr, nil
}
func (kc *Keychain) extractSSGP(header genericPasswordHeader, buffer []byte) (*ssgpBlock, []byte) {
if header.SSGPArea == 0 || int(header.SSGPArea) > len(buffer) {
return nil, nil
}
block, err := parseSSGP(buffer[:header.SSGPArea])
if err != nil {
return nil, nil
}
keyIndex := make([]byte, 0, len(block.Magic)+len(block.Label))
keyIndex = append(keyIndex, block.Magic...)
keyIndex = append(keyIndex, block.Label...)
dbkey, ok := kc.keyList[string(keyIndex)]
if !ok {
return block, nil
}
return block, dbkey
}
func parseSSGP(buf []byte) (*ssgpBlock, error) {
if len(buf) < 28 {
return nil, errors.New("ssgp buffer too small")
}
block := &ssgpBlock{
Magic: append([]byte{}, buf[0:4]...),
Label: append([]byte{}, buf[4:20]...),
IV: append([]byte{}, buf[20:28]...),
EncryptedPassword: append([]byte{}, buf[28:]...),
}
return block, nil
}
func decryptSSGP(block *ssgpBlock, dbkey []byte) (string, bool) {
if block == nil || len(dbkey) == 0 {
return keychainLockedSignature, false
}
plain, err := kcdecrypt(dbkey, block.IV, block.EncryptedPassword)
if err != nil || len(plain) == 0 {
return keychainLockedSignature, false
}
if utf8.Valid(plain) {
return string(plain), false
}
return base64.StdEncoding.EncodeToString(plain), true
}
func (kc *Keychain) readKeychainTime(base int, ptr uint32) string {
if ptr == 0 {
return ""
}
offset := base + maskedPointer(ptr)
if offset < 0 || offset+16 > len(kc.buf) {
return ""
}
raw := bytes.TrimRight(kc.buf[offset:offset+16], "\x00")
if len(raw) == 0 {
return ""
}
parsed, err := time.Parse("20060102150405Z", string(raw))
if err != nil {
return string(raw)
}
return parsed.Format(time.RFC3339)
}
func (kc *Keychain) readFourChar(base int, ptr uint32) string {
if ptr == 0 {
return ""
}
offset := base + maskedPointer(ptr)
if offset < 0 || offset+4 > len(kc.buf) {
return ""
}
return strings.TrimRight(string(kc.buf[offset:offset+4]), "\x00")
}
func (kc *Keychain) readLV(base int, ptr uint32) string {
if ptr == 0 {
return ""
}
offset := base + maskedPointer(ptr)
if offset < 0 || offset+4 > len(kc.buf) {
return ""
}
length := int(binary.BigEndian.Uint32(kc.buf[offset : offset+4]))
padded := alignToWord(length)
start := offset + 4
end := start + padded
if end > len(kc.buf) {
return ""
}
data := kc.buf[start : start+length]
data = bytes.TrimRight(data, "\x00")
return string(data)
}
func maskedPointer(value uint32) int {
return int(value & 0xFFFFFFFE)
}
func alignToWord(value int) int {
if value%4 == 0 {
return value
}
return ((value / 4) + 1) * 4
}
func readASCII(buf []byte, start, length int) string {
if start < 0 || start+length > len(buf) {
return ""
}
return string(buf[start : start+length])
}
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@@ -0,0 +1,30 @@
package chainbreaker
import (
"testing"
)
func TestUnlockKeychain(t *testing.T) {
keychain, err := New("./testdata/test.keychain-db", "6d43376c0d257bbaca2c41eded65b3b34a1a96bd19979bde")
if err != nil {
t.Fatalf("Failed to unlock keychain: %v", err)
}
records, err := keychain.DumpGenericPasswords()
if err != nil {
t.Fatal(err)
}
for _, rec := range records {
t.Log("[+] Generic Password Record")
t.Logf(" [-] Service: %s\n", rec.Service)
t.Logf(" [-] Account: %s\n", rec.Account)
t.Logf(" [-] Description: %s\n", rec.Description)
t.Logf(" [-] Created: %s\n", rec.Created)
t.Logf(" [-] Last Modified: %s\n", rec.LastModified)
if rec.PasswordBase64 {
t.Logf(" [-] Base64 Password: %s\n", rec.Password)
} else {
t.Logf(" [-] Password: %s\n", rec.Password)
}
}
}
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