# This file is part of Scapy # Copyright (C) 2008 Arnaud Ebalard # # 2015, 2016, 2017 Maxence Tury # This program is published under a GPLv2 license """ High-level methods for PKI objects (X.509 certificates, CRLs, asymmetric keys). Supports both RSA and ECDSA objects. The classes below are wrappers for the ASN.1 objects defined in x509.py. By collecting their attributes, we bypass the ASN.1 structure, hence there is no direct method for exporting a new full DER-encoded version of a Cert instance after its serial has been modified (for example). If you need to modify an import, just use the corresponding ASN1_Packet. For instance, here is what you could do in order to modify the serial of 'cert' and then resign it with whatever 'key':: f = open('cert.der') c = X509_Cert(f.read()) c.tbsCertificate.serialNumber = 0x4B1D k = PrivKey('key.pem') new_x509_cert = k.resignCert(c) No need for obnoxious openssl tweaking anymore. :) """ from __future__ import absolute_import from __future__ import print_function import base64 import os import time from scapy.config import conf, crypto_validator import scapy.modules.six as six from scapy.modules.six.moves import range from scapy.error import warning from scapy.utils import binrepr from scapy.asn1.asn1 import ASN1_BIT_STRING from scapy.asn1.mib import hash_by_oid from scapy.layers.x509 import (X509_SubjectPublicKeyInfo, RSAPublicKey, RSAPrivateKey, ECDSAPublicKey, ECDSAPrivateKey, RSAPrivateKey_OpenSSL, ECDSAPrivateKey_OpenSSL, X509_Cert, X509_CRL) from scapy.layers.tls.crypto.pkcs1 import pkcs_os2ip, _get_hash, \ _EncryptAndVerifyRSA, _DecryptAndSignRSA from scapy.compat import raw, bytes_encode if conf.crypto_valid: from cryptography.hazmat.backends import default_backend from cryptography.hazmat.primitives import serialization from cryptography.hazmat.primitives.asymmetric import rsa, ec from cryptography.hazmat.backends.openssl.ec import InvalidSignature # Maximum allowed size in bytes for a certificate file, to avoid # loading huge file when importing a cert _MAX_KEY_SIZE = 50 * 1024 _MAX_CERT_SIZE = 50 * 1024 _MAX_CRL_SIZE = 10 * 1024 * 1024 # some are that big ##################################################################### # Some helpers ##################################################################### @conf.commands.register def der2pem(der_string, obj="UNKNOWN"): """Convert DER octet string to PEM format (with optional header)""" # Encode a byte string in PEM format. Header advertizes type. pem_string = ("-----BEGIN %s-----\n" % obj).encode() base64_string = base64.b64encode(der_string) chunks = [base64_string[i:i + 64] for i in range(0, len(base64_string), 64)] # noqa: E501 pem_string += b'\n'.join(chunks) pem_string += ("\n-----END %s-----\n" % obj).encode() return pem_string @conf.commands.register def pem2der(pem_string): """Convert PEM string to DER format""" # Encode all lines between the first '-----\n' and the 2nd-to-last '-----'. pem_string = pem_string.replace(b"\r", b"") first_idx = pem_string.find(b"-----\n") + 6 if pem_string.find(b"-----BEGIN", first_idx) != -1: raise Exception("pem2der() expects only one PEM-encoded object") last_idx = pem_string.rfind(b"-----", 0, pem_string.rfind(b"-----")) base64_string = pem_string[first_idx:last_idx] base64_string.replace(b"\n", b"") der_string = base64.b64decode(base64_string) return der_string def split_pem(s): """ Split PEM objects. Useful to process concatenated certificates. """ pem_strings = [] while s != b"": start_idx = s.find(b"-----BEGIN") if start_idx == -1: break end_idx = s.find(b"-----END") end_idx = s.find(b"\n", end_idx) + 1 pem_strings.append(s[start_idx:end_idx]) s = s[end_idx:] return pem_strings class _PKIObj(object): def __init__(self, frmt, der, pem): # Note that changing attributes of the _PKIObj does not update these # values (e.g. modifying k.modulus does not change k.der). # XXX use __setattr__ for this self.frmt = frmt self.der = der self.pem = pem def __str__(self): return self.der class _PKIObjMaker(type): def __call__(cls, obj_path, obj_max_size, pem_marker=None): # This enables transparent DER and PEM-encoded data imports. # Note that when importing a PEM file with multiple objects (like ECDSA # private keys output by openssl), it will concatenate every object in # order to create a 'der' attribute. When converting a 'multi' DER file # into a PEM file, though, the PEM attribute will not be valid, # because we do not try to identify the class of each object. error_msg = "Unable to import data" if obj_path is None: raise Exception(error_msg) obj_path = bytes_encode(obj_path) if (b'\x00' not in obj_path) and os.path.isfile(obj_path): _size = os.path.getsize(obj_path) if _size > obj_max_size: raise Exception(error_msg) try: with open(obj_path, "rb") as f: _raw = f.read() except Exception: raise Exception(error_msg) else: _raw = obj_path try: if b"-----BEGIN" in _raw: frmt = "PEM" pem = _raw der_list = split_pem(_raw) der = b''.join(map(pem2der, der_list)) else: frmt = "DER" der = _raw pem = "" if pem_marker is not None: pem = der2pem(_raw, pem_marker) # type identification may be needed for pem_marker # in such case, the pem attribute has to be updated except Exception: raise Exception(error_msg) p = _PKIObj(frmt, der, pem) return p ##################################################################### # PKI objects wrappers ##################################################################### ############### # Public Keys # ############### class _PubKeyFactory(_PKIObjMaker): """ Metaclass for PubKey creation. It casts the appropriate class on the fly, then fills in the appropriate attributes with import_from_asn1pkt() submethod. """ def __call__(cls, key_path=None): if key_path is None: obj = type.__call__(cls) if cls is PubKey: cls = PubKeyRSA obj.__class__ = cls obj.frmt = "original" obj.fill_and_store() return obj # This deals with the rare RSA 'kx export' call. if isinstance(key_path, tuple): obj = type.__call__(cls) obj.__class__ = PubKeyRSA obj.frmt = "tuple" obj.import_from_tuple(key_path) return obj # Now for the usual calls, key_path may be the path to either: # _an X509_SubjectPublicKeyInfo, as processed by openssl; # _an RSAPublicKey; # _an ECDSAPublicKey. obj = _PKIObjMaker.__call__(cls, key_path, _MAX_KEY_SIZE) try: spki = X509_SubjectPublicKeyInfo(obj.der) pubkey = spki.subjectPublicKey if isinstance(pubkey, RSAPublicKey): obj.__class__ = PubKeyRSA obj.import_from_asn1pkt(pubkey) elif isinstance(pubkey, ECDSAPublicKey): obj.__class__ = PubKeyECDSA try: obj.import_from_der(obj.der) except ImportError: pass else: raise marker = b"PUBLIC KEY" except Exception: try: pubkey = RSAPublicKey(obj.der) obj.__class__ = PubKeyRSA obj.import_from_asn1pkt(pubkey) marker = b"RSA PUBLIC KEY" except Exception: # We cannot import an ECDSA public key without curve knowledge raise Exception("Unable to import public key") if obj.frmt == "DER": obj.pem = der2pem(obj.der, marker) return obj class PubKey(six.with_metaclass(_PubKeyFactory, object)): """ Parent class for both PubKeyRSA and PubKeyECDSA. Provides a common verifyCert() method. """ def verifyCert(self, cert): """ Verifies either a Cert or an X509_Cert. """ tbsCert = cert.tbsCertificate sigAlg = tbsCert.signature h = hash_by_oid[sigAlg.algorithm.val] sigVal = raw(cert.signatureValue) return self.verify(raw(tbsCert), sigVal, h=h, t='pkcs') class PubKeyRSA(PubKey, _EncryptAndVerifyRSA): """ Wrapper for RSA keys based on _EncryptAndVerifyRSA from crypto/pkcs1.py Use the 'key' attribute to access original object. """ @crypto_validator def fill_and_store(self, modulus=None, modulusLen=None, pubExp=None): pubExp = pubExp or 65537 if not modulus: real_modulusLen = modulusLen or 2048 private_key = rsa.generate_private_key(public_exponent=pubExp, key_size=real_modulusLen, backend=default_backend()) self.pubkey = private_key.public_key() else: real_modulusLen = len(binrepr(modulus)) if modulusLen and real_modulusLen != modulusLen: warning("modulus and modulusLen do not match!") pubNum = rsa.RSAPublicNumbers(n=modulus, e=pubExp) self.pubkey = pubNum.public_key(default_backend()) # Lines below are only useful for the legacy part of pkcs1.py pubNum = self.pubkey.public_numbers() self._modulusLen = real_modulusLen self._modulus = pubNum.n self._pubExp = pubNum.e @crypto_validator def import_from_tuple(self, tup): # this is rarely used e, m, mLen = tup if isinstance(m, bytes): m = pkcs_os2ip(m) if isinstance(e, bytes): e = pkcs_os2ip(e) self.fill_and_store(modulus=m, pubExp=e) self.pem = self.pubkey.public_bytes( encoding=serialization.Encoding.PEM, format=serialization.PublicFormat.SubjectPublicKeyInfo) self.der = pem2der(self.pem) def import_from_asn1pkt(self, pubkey): modulus = pubkey.modulus.val pubExp = pubkey.publicExponent.val self.fill_and_store(modulus=modulus, pubExp=pubExp) def encrypt(self, msg, t="pkcs", h="sha256", mgf=None, L=None): # no ECDSA encryption support, hence no ECDSA specific keywords here return _EncryptAndVerifyRSA.encrypt(self, msg, t=t, h=h, mgf=mgf, L=L) def verify(self, msg, sig, t="pkcs", h="sha256", mgf=None, L=None): return _EncryptAndVerifyRSA.verify( self, msg, sig, t=t, h=h, mgf=mgf, L=L) class PubKeyECDSA(PubKey): """ Wrapper for ECDSA keys based on the cryptography library. Use the 'key' attribute to access original object. """ @crypto_validator def fill_and_store(self, curve=None): curve = curve or ec.SECP256R1 private_key = ec.generate_private_key(curve(), default_backend()) self.pubkey = private_key.public_key() @crypto_validator def import_from_der(self, pubkey): # No lib support for explicit curves nor compressed points. self.pubkey = serialization.load_der_public_key(pubkey, backend=default_backend()) # noqa: E501 def encrypt(self, msg, h="sha256", **kwargs): # cryptography lib does not support ECDSA encryption raise Exception("No ECDSA encryption support") @crypto_validator def verify(self, msg, sig, h="sha256", **kwargs): # 'sig' should be a DER-encoded signature, as per RFC 3279 try: self.pubkey.verify(sig, msg, ec.ECDSA(_get_hash(h))) return True except InvalidSignature: return False ################ # Private Keys # ################ class _PrivKeyFactory(_PKIObjMaker): """ Metaclass for PrivKey creation. It casts the appropriate class on the fly, then fills in the appropriate attributes with import_from_asn1pkt() submethod. """ def __call__(cls, key_path=None): """ key_path may be the path to either: _an RSAPrivateKey_OpenSSL (as generated by openssl); _an ECDSAPrivateKey_OpenSSL (as generated by openssl); _an RSAPrivateKey; _an ECDSAPrivateKey. """ if key_path is None: obj = type.__call__(cls) if cls is PrivKey: cls = PrivKeyECDSA obj.__class__ = cls obj.frmt = "original" obj.fill_and_store() return obj obj = _PKIObjMaker.__call__(cls, key_path, _MAX_KEY_SIZE) multiPEM = False try: privkey = RSAPrivateKey_OpenSSL(obj.der) privkey = privkey.privateKey obj.__class__ = PrivKeyRSA marker = b"PRIVATE KEY" except Exception: try: privkey = ECDSAPrivateKey_OpenSSL(obj.der) privkey = privkey.privateKey obj.__class__ = PrivKeyECDSA marker = b"EC PRIVATE KEY" multiPEM = True except Exception: try: privkey = RSAPrivateKey(obj.der) obj.__class__ = PrivKeyRSA marker = b"RSA PRIVATE KEY" except Exception: try: privkey = ECDSAPrivateKey(obj.der) obj.__class__ = PrivKeyECDSA marker = b"EC PRIVATE KEY" except Exception: raise Exception("Unable to import private key") try: obj.import_from_asn1pkt(privkey) except ImportError: pass if obj.frmt == "DER": if multiPEM: # this does not restore the EC PARAMETERS header obj.pem = der2pem(raw(privkey), marker) else: obj.pem = der2pem(obj.der, marker) return obj class _Raw_ASN1_BIT_STRING(ASN1_BIT_STRING): """A ASN1_BIT_STRING that ignores BER encoding""" def __bytes__(self): return self.val_readable __str__ = __bytes__ class PrivKey(six.with_metaclass(_PrivKeyFactory, object)): """ Parent class for both PrivKeyRSA and PrivKeyECDSA. Provides common signTBSCert() and resignCert() methods. """ def signTBSCert(self, tbsCert, h="sha256"): """ Note that this will always copy the signature field from the tbsCertificate into the signatureAlgorithm field of the result, regardless of the coherence between its contents (which might indicate ecdsa-with-SHA512) and the result (e.g. RSA signing MD2). There is a small inheritance trick for the computation of sigVal below: in order to use a sign() method which would apply to both PrivKeyRSA and PrivKeyECDSA, the sign() methods of the subclasses accept any argument, be it from the RSA or ECDSA world, and then they keep the ones they're interested in. Here, t will be passed eventually to pkcs1._DecryptAndSignRSA.sign(). """ sigAlg = tbsCert.signature h = h or hash_by_oid[sigAlg.algorithm.val] sigVal = self.sign(raw(tbsCert), h=h, t='pkcs') c = X509_Cert() c.tbsCertificate = tbsCert c.signatureAlgorithm = sigAlg c.signatureValue = _Raw_ASN1_BIT_STRING(sigVal, readable=True) return c def resignCert(self, cert): """ Rewrite the signature of either a Cert or an X509_Cert. """ return self.signTBSCert(cert.tbsCertificate) def verifyCert(self, cert): """ Verifies either a Cert or an X509_Cert. """ tbsCert = cert.tbsCertificate sigAlg = tbsCert.signature h = hash_by_oid[sigAlg.algorithm.val] sigVal = raw(cert.signatureValue) return self.verify(raw(tbsCert), sigVal, h=h, t='pkcs') class PrivKeyRSA(PrivKey, _EncryptAndVerifyRSA, _DecryptAndSignRSA): """ Wrapper for RSA keys based on _DecryptAndSignRSA from crypto/pkcs1.py Use the 'key' attribute to access original object. """ @crypto_validator def fill_and_store(self, modulus=None, modulusLen=None, pubExp=None, prime1=None, prime2=None, coefficient=None, exponent1=None, exponent2=None, privExp=None): pubExp = pubExp or 65537 if None in [modulus, prime1, prime2, coefficient, privExp, exponent1, exponent2]: # note that the library requires every parameter # in order to call RSAPrivateNumbers(...) # if one of these is missing, we generate a whole new key real_modulusLen = modulusLen or 2048 self.key = rsa.generate_private_key(public_exponent=pubExp, key_size=real_modulusLen, backend=default_backend()) self.pubkey = self.key.public_key() else: real_modulusLen = len(binrepr(modulus)) if modulusLen and real_modulusLen != modulusLen: warning("modulus and modulusLen do not match!") pubNum = rsa.RSAPublicNumbers(n=modulus, e=pubExp) privNum = rsa.RSAPrivateNumbers(p=prime1, q=prime2, dmp1=exponent1, dmq1=exponent2, iqmp=coefficient, d=privExp, public_numbers=pubNum) self.key = privNum.private_key(default_backend()) self.pubkey = self.key.public_key() # Lines below are only useful for the legacy part of pkcs1.py pubNum = self.pubkey.public_numbers() self._modulusLen = real_modulusLen self._modulus = pubNum.n self._pubExp = pubNum.e def import_from_asn1pkt(self, privkey): modulus = privkey.modulus.val pubExp = privkey.publicExponent.val privExp = privkey.privateExponent.val prime1 = privkey.prime1.val prime2 = privkey.prime2.val exponent1 = privkey.exponent1.val exponent2 = privkey.exponent2.val coefficient = privkey.coefficient.val self.fill_and_store(modulus=modulus, pubExp=pubExp, privExp=privExp, prime1=prime1, prime2=prime2, exponent1=exponent1, exponent2=exponent2, coefficient=coefficient) def verify(self, msg, sig, t="pkcs", h="sha256", mgf=None, L=None): # Let's copy this from PubKeyRSA instead of adding another baseclass :) return _EncryptAndVerifyRSA.verify( self, msg, sig, t=t, h=h, mgf=mgf, L=L) def sign(self, data, t="pkcs", h="sha256", mgf=None, L=None): return _DecryptAndSignRSA.sign(self, data, t=t, h=h, mgf=mgf, L=L) class PrivKeyECDSA(PrivKey): """ Wrapper for ECDSA keys based on SigningKey from ecdsa library. Use the 'key' attribute to access original object. """ @crypto_validator def fill_and_store(self, curve=None): curve = curve or ec.SECP256R1 self.key = ec.generate_private_key(curve(), default_backend()) self.pubkey = self.key.public_key() @crypto_validator def import_from_asn1pkt(self, privkey): self.key = serialization.load_der_private_key(raw(privkey), None, backend=default_backend()) # noqa: E501 self.pubkey = self.key.public_key() @crypto_validator def verify(self, msg, sig, h="sha256", **kwargs): # 'sig' should be a DER-encoded signature, as per RFC 3279 try: self.pubkey.verify(sig, msg, ec.ECDSA(_get_hash(h))) return True except InvalidSignature: return False @crypto_validator def sign(self, data, h="sha256", **kwargs): return self.key.sign(data, ec.ECDSA(_get_hash(h))) ################ # Certificates # ################ class _CertMaker(_PKIObjMaker): """ Metaclass for Cert creation. It is not necessary as it was for the keys, but we reuse the model instead of creating redundant constructors. """ def __call__(cls, cert_path): obj = _PKIObjMaker.__call__(cls, cert_path, _MAX_CERT_SIZE, "CERTIFICATE") obj.__class__ = Cert try: cert = X509_Cert(obj.der) except Exception: raise Exception("Unable to import certificate") obj.import_from_asn1pkt(cert) return obj class Cert(six.with_metaclass(_CertMaker, object)): """ Wrapper for the X509_Cert from layers/x509.py. Use the 'x509Cert' attribute to access original object. """ def import_from_asn1pkt(self, cert): error_msg = "Unable to import certificate" self.x509Cert = cert tbsCert = cert.tbsCertificate self.tbsCertificate = tbsCert if tbsCert.version: self.version = tbsCert.version.val + 1 else: self.version = 1 self.serial = tbsCert.serialNumber.val self.sigAlg = tbsCert.signature.algorithm.oidname self.issuer = tbsCert.get_issuer() self.issuer_str = tbsCert.get_issuer_str() self.issuer_hash = hash(self.issuer_str) self.subject = tbsCert.get_subject() self.subject_str = tbsCert.get_subject_str() self.subject_hash = hash(self.subject_str) self.authorityKeyID = None self.notBefore_str = tbsCert.validity.not_before.pretty_time notBefore = tbsCert.validity.not_before.val if notBefore[-1] == "Z": notBefore = notBefore[:-1] try: _format = tbsCert.validity.not_before._format self.notBefore = time.strptime(notBefore, _format) except Exception: raise Exception(error_msg) self.notBefore_str_simple = time.strftime("%x", self.notBefore) self.notAfter_str = tbsCert.validity.not_after.pretty_time notAfter = tbsCert.validity.not_after.val if notAfter[-1] == "Z": notAfter = notAfter[:-1] try: _format = tbsCert.validity.not_after._format self.notAfter = time.strptime(notAfter, _format) except Exception: raise Exception(error_msg) self.notAfter_str_simple = time.strftime("%x", self.notAfter) self.pubKey = PubKey(raw(tbsCert.subjectPublicKeyInfo)) if tbsCert.extensions: for extn in tbsCert.extensions: if extn.extnID.oidname == "basicConstraints": self.cA = False if extn.extnValue.cA: self.cA = not (extn.extnValue.cA.val == 0) elif extn.extnID.oidname == "keyUsage": self.keyUsage = extn.extnValue.get_keyUsage() elif extn.extnID.oidname == "extKeyUsage": self.extKeyUsage = extn.extnValue.get_extendedKeyUsage() elif extn.extnID.oidname == "authorityKeyIdentifier": self.authorityKeyID = extn.extnValue.keyIdentifier.val self.signatureValue = raw(cert.signatureValue) self.signatureLen = len(self.signatureValue) def isIssuerCert(self, other): """ True if 'other' issued 'self', i.e.: - self.issuer == other.subject - self is signed by other """ if self.issuer_hash != other.subject_hash: return False return other.pubKey.verifyCert(self) def isSelfSigned(self): """ Return True if the certificate is self-signed: - issuer and subject are the same - the signature of the certificate is valid. """ if self.issuer_hash == self.subject_hash: return self.isIssuerCert(self) return False def encrypt(self, msg, t="pkcs", h="sha256", mgf=None, L=None): # no ECDSA *encryption* support, hence only RSA specific keywords here return self.pubKey.encrypt(msg, t=t, h=h, mgf=mgf, L=L) def verify(self, msg, sig, t="pkcs", h="sha256", mgf=None, L=None): return self.pubKey.verify(msg, sig, t=t, h=h, mgf=mgf, L=L) def remainingDays(self, now=None): """ Based on the value of notAfter field, returns the number of days the certificate will still be valid. The date used for the comparison is the current and local date, as returned by time.localtime(), except if 'now' argument is provided another one. 'now' argument can be given as either a time tuple or a string representing the date. Accepted format for the string version are: - '%b %d %H:%M:%S %Y %Z' e.g. 'Jan 30 07:38:59 2008 GMT' - '%m/%d/%y' e.g. '01/30/08' (less precise) If the certificate is no more valid at the date considered, then a negative value is returned representing the number of days since it has expired. The number of days is returned as a float to deal with the unlikely case of certificates that are still just valid. """ if now is None: now = time.localtime() elif isinstance(now, str): try: if '/' in now: now = time.strptime(now, '%m/%d/%y') else: now = time.strptime(now, '%b %d %H:%M:%S %Y %Z') except Exception: warning("Bad time string provided, will use localtime() instead.") # noqa: E501 now = time.localtime() now = time.mktime(now) nft = time.mktime(self.notAfter) diff = (nft - now) / (24. * 3600) return diff def isRevoked(self, crl_list): """ Given a list of trusted CRL (their signature has already been verified with trusted anchors), this function returns True if the certificate is marked as revoked by one of those CRL. Note that if the Certificate was on hold in a previous CRL and is now valid again in a new CRL and bot are in the list, it will be considered revoked: this is because _all_ CRLs are checked (not only the freshest) and revocation status is not handled. Also note that the check on the issuer is performed on the Authority Key Identifier if available in _both_ the CRL and the Cert. Otherwise, the issuers are simply compared. """ for c in crl_list: if (self.authorityKeyID is not None and c.authorityKeyID is not None and self.authorityKeyID == c.authorityKeyID): return self.serial in (x[0] for x in c.revoked_cert_serials) elif self.issuer == c.issuer: return self.serial in (x[0] for x in c.revoked_cert_serials) return False def export(self, filename, fmt="DER"): """ Export certificate in 'fmt' format (DER or PEM) to file 'filename' """ with open(filename, "wb") as f: if fmt == "DER": f.write(self.der) elif fmt == "PEM": f.write(self.pem) def show(self): print("Serial: %s" % self.serial) print("Issuer: " + self.issuer_str) print("Subject: " + self.subject_str) print("Validity: %s to %s" % (self.notBefore_str, self.notAfter_str)) def __repr__(self): return "[X.509 Cert. Subject:%s, Issuer:%s]" % (self.subject_str, self.issuer_str) # noqa: E501 ################################ # Certificate Revocation Lists # ################################ class _CRLMaker(_PKIObjMaker): """ Metaclass for CRL creation. It is not necessary as it was for the keys, but we reuse the model instead of creating redundant constructors. """ def __call__(cls, cert_path): obj = _PKIObjMaker.__call__(cls, cert_path, _MAX_CRL_SIZE, "X509 CRL") obj.__class__ = CRL try: crl = X509_CRL(obj.der) except Exception: raise Exception("Unable to import CRL") obj.import_from_asn1pkt(crl) return obj class CRL(six.with_metaclass(_CRLMaker, object)): """ Wrapper for the X509_CRL from layers/x509.py. Use the 'x509CRL' attribute to access original object. """ def import_from_asn1pkt(self, crl): error_msg = "Unable to import CRL" self.x509CRL = crl tbsCertList = crl.tbsCertList self.tbsCertList = raw(tbsCertList) if tbsCertList.version: self.version = tbsCertList.version.val + 1 else: self.version = 1 self.sigAlg = tbsCertList.signature.algorithm.oidname self.issuer = tbsCertList.get_issuer() self.issuer_str = tbsCertList.get_issuer_str() self.issuer_hash = hash(self.issuer_str) self.lastUpdate_str = tbsCertList.this_update.pretty_time lastUpdate = tbsCertList.this_update.val if lastUpdate[-1] == "Z": lastUpdate = lastUpdate[:-1] try: self.lastUpdate = time.strptime(lastUpdate, "%y%m%d%H%M%S") except Exception: raise Exception(error_msg) self.lastUpdate_str_simple = time.strftime("%x", self.lastUpdate) self.nextUpdate = None self.nextUpdate_str_simple = None if tbsCertList.next_update: self.nextUpdate_str = tbsCertList.next_update.pretty_time nextUpdate = tbsCertList.next_update.val if nextUpdate[-1] == "Z": nextUpdate = nextUpdate[:-1] try: self.nextUpdate = time.strptime(nextUpdate, "%y%m%d%H%M%S") except Exception: raise Exception(error_msg) self.nextUpdate_str_simple = time.strftime("%x", self.nextUpdate) if tbsCertList.crlExtensions: for extension in tbsCertList.crlExtensions: if extension.extnID.oidname == "cRLNumber": self.number = extension.extnValue.cRLNumber.val revoked = [] if tbsCertList.revokedCertificates: for cert in tbsCertList.revokedCertificates: serial = cert.serialNumber.val date = cert.revocationDate.val if date[-1] == "Z": date = date[:-1] try: time.strptime(date, "%y%m%d%H%M%S") except Exception: raise Exception(error_msg) revoked.append((serial, date)) self.revoked_cert_serials = revoked self.signatureValue = raw(crl.signatureValue) self.signatureLen = len(self.signatureValue) def isIssuerCert(self, other): # This is exactly the same thing as in Cert method. if self.issuer_hash != other.subject_hash: return False return other.pubKey.verifyCert(self) def verify(self, anchors): # Return True iff the CRL is signed by one of the provided anchors. return any(self.isIssuerCert(a) for a in anchors) def show(self): print("Version: %d" % self.version) print("sigAlg: " + self.sigAlg) print("Issuer: " + self.issuer_str) print("lastUpdate: %s" % self.lastUpdate_str) print("nextUpdate: %s" % self.nextUpdate_str) ###################### # Certificate chains # ###################### class Chain(list): """ Basically, an enhanced array of Cert. """ def __init__(self, certList, cert0=None): """ Construct a chain of certificates starting with a self-signed certificate (or any certificate submitted by the user) and following issuer/subject matching and signature validity. If there is exactly one chain to be constructed, it will be, but if there are multiple potential chains, there is no guarantee that the retained one will be the longest one. As Cert and CRL classes both share an isIssuerCert() method, the trailing element of a Chain may alternatively be a CRL. Note that we do not check AKID/{SKID/issuer/serial} matching, nor the presence of keyCertSign in keyUsage extension (if present). """ list.__init__(self, ()) if cert0: self.append(cert0) else: for root_candidate in certList: if root_candidate.isSelfSigned(): self.append(root_candidate) certList.remove(root_candidate) break if len(self) > 0: while certList: tmp_len = len(self) for c in certList: if c.isIssuerCert(self[-1]): self.append(c) certList.remove(c) break if len(self) == tmp_len: # no new certificate appended to self break def verifyChain(self, anchors, untrusted=None): """ Perform verification of certificate chains for that certificate. A list of anchors is required. The certificates in the optional untrusted list may be used as additional elements to the final chain. On par with chain instantiation, only one chain constructed with the untrusted candidates will be retained. Eventually, dates are checked. """ untrusted = untrusted or [] for a in anchors: chain = Chain(self + untrusted, a) if len(chain) == 1: # anchor only continue # check that the chain does not exclusively rely on untrusted if any(c in chain[1:] for c in self): for c in chain: if c.remainingDays() < 0: break if c is chain[-1]: # we got to the end of the chain return chain return None def verifyChainFromCAFile(self, cafile, untrusted_file=None): """ Does the same job as .verifyChain() but using the list of anchors from the cafile. As for .verifyChain(), a list of untrusted certificates can be passed (as a file, this time). """ try: with open(cafile, "rb") as f: ca_certs = f.read() except Exception: raise Exception("Could not read from cafile") anchors = [Cert(c) for c in split_pem(ca_certs)] untrusted = None if untrusted_file: try: with open(untrusted_file, "rb") as f: untrusted_certs = f.read() except Exception: raise Exception("Could not read from untrusted_file") untrusted = [Cert(c) for c in split_pem(untrusted_certs)] return self.verifyChain(anchors, untrusted) def verifyChainFromCAPath(self, capath, untrusted_file=None): """ Does the same job as .verifyChainFromCAFile() but using the list of anchors in capath directory. The directory should (only) contain certificates files in PEM format. As for .verifyChainFromCAFile(), a list of untrusted certificates can be passed as a file (concatenation of the certificates in PEM format). """ try: anchors = [] for cafile in os.listdir(capath): with open(os.path.join(capath, cafile), "rb") as fd: anchors.append(Cert(fd.read())) except Exception: raise Exception("capath provided is not a valid cert path") untrusted = None if untrusted_file: try: with open(untrusted_file, "rb") as f: untrusted_certs = f.read() except Exception: raise Exception("Could not read from untrusted_file") untrusted = [Cert(c) for c in split_pem(untrusted_certs)] return self.verifyChain(anchors, untrusted) def __repr__(self): llen = len(self) - 1 if llen < 0: return "" c = self[0] s = "__ " if not c.isSelfSigned(): s += "%s [Not Self Signed]\n" % c.subject_str else: s += "%s [Self Signed]\n" % c.subject_str idx = 1 while idx <= llen: c = self[idx] s += "%s_ %s" % (" " * idx * 2, c.subject_str) if idx != llen: s += "\n" idx += 1 return s