Firepwd.py, an open source tool to decrypt Mozilla protected passwords

31oct2025

Introduction

This educational tool was written to illustrate how Mozilla passwords (Firefox, Thunderbird) are protected using contents of files key4.db (or key3.db), logins.json (or signons.sqlite).

NSS library is NOT used. Only python is used (PyCryptodome, pyasn1)

This code is released under GPL license.

Now part of LaZagne project: https://github.com/AlessandroZ/LaZagne

You can also read the related article, in french: http://connect.ed-diamond.com/MISC/MISC-069/Protection-des-mots-de-passe-par-Firefox-et-Thunderbird-analyse-par-la-pratique

or this poster for the password crypto of key3.db and signons.sqlite.

Versions supported

• Firefox <32 (key3.db, signons.sqlite)
• Firefox >=32 (key3.db, logins.json)
• Firefox >=58.0.2 (key4.db, logins.json)
• Firefox >=75.0 (sha1 pbkdf2 sha256 aes256 cbc used by key4.db, logins.json)
• Firefox >=144.0 (https://github.com/lclevy/firepwd/pull/29) for logins.json using aes256 instead of 3des
• at least Thunderbird 68.7.0, likely other versions

key3.db is read directly, the 3rd party bsddb python module is NOT needed.

Warning

File firepwd.py is detected as "HackTool:Python/Stealer!AMTB" by Microsoft Defender, which is NOT a false positive.

Usage

By default, firepwd.py processes key3.db (or key4.db) and signons.sqlite (logins.json) files in current directory, but an alternative directory can be provided using the -d option. Do not forget the '/' at the end.

If a master password has been set, provide it using the -p option.

Valid verbose levels (-v) are from 0 (default) to 2.

$ python firepwd.py -h
Usage: firepwd.py [options] 

Options:
  -h, --help            show this help message and exit
  -v VERBOSE, --verbose=VERBOSE
                        verbose level
  -p MASTERPASSWORD, --password=MASTERPASSWORD
                        masterPassword
  -d DIRECTORY, --dir=DIRECTORY
                        directory
						
$ python firepwd.py -d /c/Users/lclevy/AppData/Roaming/Mozilla/Firefox/Profiles/o8syoe2h.default/
no stored passwords

$ python firepwd.py -p 'MISC*' -d mozilla_db/
 SEQUENCE {
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.12.5.1.3
     SEQUENCE {
       OCTETSTRING a8db682ac51cfad8c06664fe9deb5283073b33ee
       INTEGER 01
     }
   }
   OCTETSTRING 72d5636049d4af9eeadaf7eb0dc1710a62d5362fe4086dcc0495e5ec8e96c23c56b72a552e17756141ae80854d6fd03ecdc2c8f83d2c02d4c3f36e7e2b906f2c70a8cf571a06666e53f241780f9e39815e7d840e97e434614ac20ec09002e861
 }
decrypting privKeyData
 SEQUENCE {
   INTEGER 00
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.1.1
     NULL 0
   }
   OCTETSTRING 3042020100021100f8000000000000000000000000000001020100021813c1e53d51a1e60bc79419f7d59107ef97976d075832a45b020100020100020100020100020115
 }
decoding 3042020100021100f8000000000000000000000000000001020100021813c1e53d51a1e60bc79419f7d59107ef97976d075832a45b020100020100020100020100020115
 SEQUENCE {
   INTEGER 00
   INTEGER 00f8000000000000000000000000000001
   INTEGER 00
   INTEGER 13c1e53d51a1e60bc79419f7d59107ef97976d075832a45b
   INTEGER 00
   INTEGER 00
   INTEGER 00
   INTEGER 00
   INTEGER 15
 }
decrypting login/password pairs
http://challenge01.root-me.org: 'login\x03\x03\x03' , 'password\x08\x08\x08\x08\x08\x08\x08\x08'

$ python firepwd.py -d /c/Users/laurent/AppData/Roaming/Thunderbird/Profiles/3luvewzm.default/
 SEQUENCE {
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.12.5.1.3
     SEQUENCE {
       OCTETSTRING 10540ef85fb7e198d41884c8c9c90cf3bc065482
       INTEGER 01
     }
   }
   OCTETSTRING 082fe34f23eae209334d53be2c85ea62d0242a722d452da5b0f27e39dd2733f177c0dc55dd22635d6c8e61fc3e7dc44fe2f1cccef58a8f3138b2822b5a1db3bc39ee8e57c5f4bf05aaed8073eeaf2cd7fddffd6fbc1f5d05ee870f353861c952
 }
decrypting privKeyData
 SEQUENCE {
   INTEGER 00
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.1.1
     NULL 0
   }
   OCTETSTRING 3042020100021100f8000000000000000000000000000001020100021875a873cdb39783ecf1fedcea3d010dd9732a01a8b30451e9020100020100020100020100020115
 }
decoding 3042020100021100f8000000000000000000000000000001020100021875a873cdb39783ecf1fedcea3d010dd9732a01a8b30451e9020100020100020100020100020115
 SEQUENCE {
   INTEGER 00
   INTEGER 00f8000000000000000000000000000001
   INTEGER 00
   INTEGER 75a873cdb39783ecf1fedcea3d010dd9732a01a8b30451e9
   INTEGER 00
   INTEGER 00
   INTEGER 00
   INTEGER 00
   INTEGER 15
 }
decrypting login/password pairs
[censored]


$ python firepwd.py -d /c/Users/laurent/AppData/Roaming/Mozilla/Firefox/Profiles/77l7qxfi.default/
 SEQUENCE {
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.12.5.1.3
     SEQUENCE {
       OCTETSTRING c6581e1fbdb50b4265ab11f54861fdbb62cb4abd
       INTEGER 01
     }
   }
   OCTETSTRING cecb819cb612dccfc2265121aa38ed5d4b7cfc6f06f92f4fb48305f1afb3234f02e25fcb8f3029c0d4aa8c9be7ef292fc3c7d2d446e33f7f80d03a1df35aecb72f843463907786777da8bf1fd47a955fad9eb23e65e0ddff6d1ed0463cc69ed4
 }
decrypting privKeyData
[...]

>python firepwd.py -v 2 -p MISC* -d ff50\
globalSalt: b'5ed0adce15d896b84115f530be4e259f72beda91'
 SEQUENCE {
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.5.13 pkcs5 pbes2
     SEQUENCE {
       SEQUENCE {
         OBJECTIDENTIFIER 1.2.840.113549.1.5.12 pkcs5 PBKDF2
         SEQUENCE {
           OCTETSTRING b'f92dde91809b8b00c6607b73f3d0321c80f930aa13f13da5293aede76ee92048'
           INTEGER b'01'
           INTEGER b'20'
           SEQUENCE {
             OBJECTIDENTIFIER 1.2.840.113549.2.9 hmacWithSHA256
           }
         }
       }
       SEQUENCE {
         OBJECTIDENTIFIER 2.16.840.1.101.3.4.1.42 aes256-CBC
         OCTETSTRING b'd7f6eef452a0becb5227af2e175c'
       }
     }
   }
   OCTETSTRING b'9ef5288ba19326df7188f1f0d1811c2a'
 }
clearText b'70617373776f72642d636865636b0202'
password check? True
 SEQUENCE {
   SEQUENCE {
     OBJECTIDENTIFIER 1.2.840.113549.1.5.13 pkcs5 pbes2
     SEQUENCE {
       SEQUENCE {
         OBJECTIDENTIFIER 1.2.840.113549.1.5.12 pkcs5 PBKDF2
         SEQUENCE {
           OCTETSTRING b'86535fdbbc242465d6e8477094b93221c9cc45bb363141e177ae2801e1972b32'
           INTEGER b'01'
           INTEGER b'20'
           SEQUENCE {
             OBJECTIDENTIFIER 1.2.840.113549.2.9 hmacWithSHA256
           }
         }
       }
       SEQUENCE {
         OBJECTIDENTIFIER 2.16.840.1.101.3.4.1.42 aes256-CBC
         OCTETSTRING b'4de278f3bc4cf8e503ce0b8672ec'
       }
     }
   }
   OCTETSTRING b'62093ca8bb60c0416b5e7bee18402b99c21e780985ff75737fb8a493a858aaf2'
 }
clearText b'7f914a642a4552b0e0c7a87061fe5d9437a41968c4a7d35e0808080808080808'
decrypting login/password pairs
[...]

Installation

pip install -r requirements.txt

Tested with python 3.7.3, PyCryptodome 3.9.0 and pyasn 0.4.8

Modules required:

• pyasn1, https://pypi.python.org/pypi/pyasn1/, for ASN1 decoding
• PyCryptodome, https://www.pycryptodome.org/en/latest/, for 3DES and AES decryption

Fork: firepwd-ng.py

A simplified script to decrypt Firefox passwords stored in the 'logins.json' file, using the master_key from 'key4.db'.

This script is based on the original work by @lclevy but has been refactored for clarity and simplicity, focusing only on modern Firefox versions that use key4.db and logins.json.

Reference documents

• Into the Black Box: A Case Study in Obtaining Visibility into Commercial Software, D. Plakosh, S. Hissam, K. Wallnau, March 1999, Carnegie Mellon University : http://www.sei.cmu.edu/library/abstracts/reports/99tn010.cfm
• Dr. Stephen Henson, August 4th 1999 : http://arc.info/?l=openssl-dev&m=93378860132031&w=2