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Add signature/decryption support for PGP RSA encrypted session key #418

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merged 1 commit into from
Nov 8, 2019
Merged

Add signature/decryption support for PGP RSA encrypted session key #418

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100 changes: 100 additions & 0 deletions src/binwalk/magic/crypto
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -129,3 +129,103 @@
>72 string sha256 %s
>72 string sha512 %s
>72 string ripemd160 %s

# magic signatures to detect PGP crypto material (from stef)
# detects and extracts metadata from:
# - symmetric encrypted packet header
# - RSA (e=65537) secret (sub-)keys

# 1024b RSA encrypted data

0 string \x84\x8c\x03 PGP RSA encrypted session key -
>3 ubelong x keyid: %X
>7 ubelong x %X
>11 byte <0x01 {invalid}
>11 byte >0x02 {invalid}
>11 byte 0x01 RSA (Encrypt or Sign) 1024b
>11 byte 0x02 RSA Encrypt-Only 1024b
>12 string \x04\x00
>12 string \x03\xff
>12 string \x03\xfe
>12 string \x03\xfd
>12 string \x03\xfc
>12 string \x03\xfb
>12 string \x03\xfa
>12 string \x03\xf9
>142 byte 0xd2

# 2048b RSA encrypted data

0 string \x85\x01\x0c\x03 PGP RSA encrypted session key -
>4 ubelong x keyid: %X
>8 ubelong x %X
>12 byte <0x01 {invalid}
>12 byte >0x02 {invalid}
>12 byte 0x01 RSA (Encrypt or Sign) 2048b
>12 byte 0x02 RSA Encrypt-Only 2048b
>13 string \x08\x00
>13 string \x07\xff
>13 string \x07\xfe
>13 string \x07\xfd
>13 string \x07\xfc
>13 string \x07\xfb
>13 string \x07\xfa
>13 string \x07\xf9
>271 byte 0xd2

# 3072b RSA encrypted data

0 string \x85\x01\x8c\x03 PGP RSA encrypted session key -
>4 ubelong x keyid: %X
>8 ubelong x %X
>12 byte <0x01 {invalid}
>12 byte >0x02 {invalid}
>12 byte 0x01 RSA (Encrypt or Sign) 3072b
>12 byte 0x02 RSA Encrypt-Only 3072b
>13 string \x0c\x00
>13 string \x0b\xff
>13 string \x0b\xfe
>13 string \x0b\xfd
>13 string \x0b\xfc
>13 string \x0b\xfb
>13 string \x0b\xfa
>13 string \x0b\xf9
>399 byte 0xd2

# 3072b RSA encrypted data

0 string \x85\x02\x0c\x03 PGP RSA encrypted session key -
>4 ubelong x keyid: %X
>8 ubelong x %X
>12 byte <0x01 {invalid}
>12 byte >0x02 {invalid}
>12 byte 0x01 RSA (Encrypt or Sign) 4096b
>12 byte 0x02 RSA Encrypt-Only 4096b
>13 string \x10\x00
>13 string \x0f\xff
>13 string \x0f\xfe
>13 string \x0f\xfd
>13 string \x0f\xfc
>13 string \x0f\xfb
>13 string \x0f\xfa
>13 string \x0f\xf9
>527 byte 0xd2

# 4096b RSA encrypted data

0 string \x85\x04\x0c\x03 PGP RSA encrypted session key -
>4 ubelong x keyid: %X
>8 ubelong x %X
>12 byte <0x01 {invalid}
>12 byte >0x02 {invalid}
>12 byte 0x01 RSA (Encrypt or Sign) 8129b
>12 byte 0x02 RSA Encrypt-Only 8129b
>13 string \x20\x00
>13 string \x1f\xff
>13 string \x1f\xfe
>13 string \x1f\xfd
>13 string \x1f\xfc
>13 string \x1f\xfb
>13 string \x1f\xfa
>13 string \x1f\xf9
>1039 byte 0xd2
204 changes: 204 additions & 0 deletions src/binwalk/plugins/pgp.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,204 @@
#!/usr/bin/env python

import errno
import shutil
import tempfile
import binwalk.core.plugin
import binwalk.core.compat
import binwalk.core.common
try:
# Requires the python-gnupg library
from gnupg import GPG
except ImportError as e:
GPG = None


class PgpDecryptor(binwalk.core.plugin.Plugin):

'''
Plugin to decrypt, validate, and extract PGP encrypted firmware.
'''
MODULES = ["Signature"]

EDDA2E82EDC7030C_KEY = """-----BEGIN PGP PRIVATE KEY BLOCK-----

lQOYBFLP6aQBCACpXewcfz5tFjCA+HaeTafYE8mhvtSab3D1eYqCJTcDdqC8wJEw
9bbUR1cGqZYev9oRjTG/gGUGbbToqqmAAneEi5+1i0ABHT8ThvF34G2nAa528dww
9kfOt842d82ojxhF7kx/KjeLDSaoPaYXbgpKyK8S4CcJM3CObvbxYafZAiGfHLQC
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rpNdLebx+4NTULnUhp2legPDXLKVQsbgNE2z0ev7GDWhBADlT8AUE4U3xsI8wa4n
dTPl9M8Eua9xnuKNb/fYKhN34J/FXXR9rDfzCXCH4C9zT58UxTKTe9MEEimlvuHY
Cts5RImcGp/g4xqzV7y4bQ9LR8BZseoWpMdhdfolUdy972/ZqMtElQtDgla0DBGX
id9d9hdIpDBmKNKKOSkndQLMcQQA6C4ylHUCNMC4tQVTmzylFaYyTre3OIxad8Xp
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GnQu4GBXuRLNl+tXy7UcVw3Z53jEWnmqDkNwCc3ozJD7Rew/0X0briNecSwKsxJq
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azYsg+Zy1uG+NO2j5NvmJwSKChV4gI5J66qHDLRAWbT7XGeukb3rgXu2uhsx4NRj
GAGkfAqRnKmtgIVyDuqqtW4vRSmzLhIjMd2QDCaMfSyAtb+9MltoPseJAR8EGAEC
AAkFAlLP6aQCGwwACgkQq8dIUWZiduX8EAf+Lrc3Zify4tiQU7mzjknYcZYBWVrj
6F+3FOnka+Zg7uwKcBK6fHQajClCXgLmPmLTNyYawaj2tM57TLYX9SsbdCA9Ng3b
0iMyCixOHY2OunTQv4wCYimGWs6WUXkUwlCFhnGGaPqLHkxXWEgiqu8IKgjaA2UN
B/kLChLVgnxqklAMC2AWT1mT4rmfjY6efWozEjeHOGNTagxT0efN3Sw01xitoekF
b1+jvE5K0EAKddMxSUbpv5V4kuBQ9gomZei6hl2xeYqjlbOAohXjXY1ViTiez3IE
MtbF9y9d0+OoaniAmZVWsufxjaf27n6DdT/S+7Jt1fTqTY9QYAJVd73Kog==
=c6nn
-----END PGP PRIVATE KEY BLOCK-----"""

F18B47DF3F881C75_KEY = """-----BEGIN PGP PRIVATE KEY BLOCK-----

lQOXBFUrhvcBCACYLresTT4+S7YAoqctW3VWXtoiFFc/hR+kHZvhpKdQjYirorRy
aYv9xCYc5Y+6Rh/mpQFYIbZoMqxtTZ5kf02kQyXXR7mDhiWu0b3S8q4dUJ/hyy4E
Q1oYZDMX9t9El60AeiB9AEzEpiPlOrT2s77PfexR34e4uQ5GIMZVoSM5WB734ZUW
qumyhPeGg3108m4NpuMitSoRUJW683J0oWFf/b/rXEle+onYaafeAAuZTkFwD8s3
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FTMsIxkM1SuitfgTlhdaxuTm8Ys7tIDm+yd5918p4MFlXP/CUPFqqgp4Rtn+DBAh
e/iZxfUBjXOWF1Z8A+KuCiZno4Z1iXPICwoYZxF10sX7pYldFBDNEZXj6EZdN1AO
s6VD0w7Oe1Z4yBOeUqFXwF+nifN81GwyO3RnUWIpbmeEE94Vz9U/cSnyxwXywChm
dQ8NT+CEP0o+ypkcf1v2KNIcUdrgJ995Z3sLVhsqOc8X+fWfW04HQuEpIX2bLF6+
lQdKKbF0oK15Zf/8FmmGrh9Uh07n87kwDXNpGtDiTNsQgOngYNqL6iPytLKv6xAJ
hiEEAMN2o5RcHwX1y4djcMvNUumfSsmACpnDPBA3mPfwXcmzi5DhWWnWav/waIAC
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KjN9HiHVNBWJakFTAcTsDrCVm3WpTKZkDLS0IQTps/eB46vF7V97AIQ6
=UtFV
-----END PGP PRIVATE KEY BLOCK-----"""

EDDA2E82EDC7030C_SIGNATURE_DESCRIPTION = "PGP RSA encrypted session key - keyid: EDDA2E82 EDC7030C RSA".lower()

F18B47DF3F881C75_SIGNATURE_DESCRIPTION = "PGP RSA encrypted session key - keyid: F18B47DF 3F881C75 RSA".lower()

def init(self):
if GPG is None:
self.enabled = False
else:
self.enabled = True

if self.enabled is True and self.module.extractor.enabled is True:
# Add extraction rules for encrypted PGP firmware signature
# results
self.module.extractor.add_rule(txtrule=None,
regex="^%s" % self.EDDA2E82EDC7030C_SIGNATURE_DESCRIPTION,
extension="gpg",
cmd=self._decrypt_and_extract_EDDA2E82EDC7030C)
self.module.extractor.add_rule(txtrule=None,
regex="^%s" % self.F18B47DF3F881C75_SIGNATURE_DESCRIPTION,
extension="gpg",
cmd=self._decrypt_and_extract_F18B47DF3F881C75)

def _decrypt_and_extract_EDDA2E82EDC7030C(self, fname):
return self._decrypt_and_extract(fname, self.EDDA2E82EDC7030C_KEY)

def _decrypt_and_extract_F18B47DF3F881C75(self, fname):
return self._decrypt_and_extract(fname, self.F18B47DF3F881C75_KEY)

def _decrypt_and_extract(self, fname, key):
'''
This does the extraction (e.g., it decrypts the image and writes it to a new file on disk).
'''
with open(fname, "rb") as fp_in:
encrypted_data = fp_in.read()

decrypted_data = self._pgp_decrypt(encrypted_data, key)

with open(binwalk.core.common.unique_file_name(fname[:-4], "dec"), "wb") as fp_out:
fp_out.write(decrypted_data)
return True

def _pgp_decrypt(self, encrypted_firmware, key):
'''
This does the actual decryption.
'''
try:
tmp_dir = tempfile.mkdtemp()
gpg = GPG(gnupghome=tmp_dir)
gpg.import_keys(key)
decrypted_data = gpg.decrypt(encrypted_firmware)
finally:
try:
shutil.rmtree(tmp_dir)
except OSError as exc:
if exc.errno != errno.ENOENT:
raise

return bytes(decrypted_data.data)

def scan(self, result):
'''
Validate signature results.
'''
if result.valid is True:
if result.description.lower().startswith(self.EDDA2E82EDC7030C_SIGNATURE_DESCRIPTION) is True:
result.description += ", Verizon BHR4 <[email protected]>"
elif result.description.lower().startswith(self.F18B47DF3F881C75_SIGNATURE_DESCRIPTION) is True:
result.description += ", Verizon BHR4 <[email protected]>"