From 215d40d96a7608c886216d0acc4312499373ea6c Mon Sep 17 00:00:00 2001 From: abhishekram Date: Tue, 25 Jun 2019 15:50:08 +0530 Subject: [PATCH] handle exceptions with parsing signed attributes and more debug logging --- pyas2lib/as2.py | 154 +++++++++++++++++++------------------ pyas2lib/cms.py | 14 ++-- pyas2lib/tests/test_mdn.py | 32 ++++++++ pyas2lib/utils.py | 16 ++-- 4 files changed, 132 insertions(+), 84 deletions(-) diff --git a/pyas2lib/as2.py b/pyas2lib/as2.py index 8173f5d..7042dda 100644 --- a/pyas2lib/as2.py +++ b/pyas2lib/as2.py @@ -368,7 +368,7 @@ def build(self, data, filename=None, subject='AS2 Message', self.payload = compressed_message logger.debug( - f'Compressed message {self.message_id} payload as:\n{self.payload.as_string()}') + f'Compressed message {self.message_id} payload as:\n{mime_to_bytes(self.payload)}') if self.receiver.sign: self.signed, self.digest_alg = True, self.receiver.digest_alg @@ -415,7 +415,7 @@ def build(self, data, filename=None, subject='AS2 Message', self.payload = encrypted_message logger.debug( - f'Encrypted message {self.message_id} payload as:\n{self.payload.as_string()}') + f'Encrypted message {self.message_id} payload as:\n{mime_to_bytes(self.payload)}') if self.receiver.mdn_mode: as2_headers['disposition-notification-to'] = disposition_notification_to @@ -439,10 +439,11 @@ def build(self, data, filename=None, subject='AS2 Message', if self.payload.is_multipart(): self.payload.set_boundary(make_mime_boundary()) - @staticmethod - def _decompress_data(payload): + def _decompress_data(self, payload): if payload.get_content_type() == 'application/pkcs7-mime' \ and payload.get_param('smime-type') == 'compressed-data': + logger.debug(f'Decompressing message {self.message_id} payload :\n' + f'{mime_to_bytes(self.payload)}') compressed_data = payload.get_payload(decode=True) decompressed_data = decompress_message(compressed_data) return True, parse_mime(decompressed_data) @@ -513,8 +514,8 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, if self.payload.get_content_type() == 'application/pkcs7-mime' \ and self.payload.get_param('smime-type') == 'enveloped-data': - logger.debug( - f'Decrypting message {self.message_id} payload :\n{self.payload.as_string()}') + logger.debug(f'Decrypting message {self.message_id} payload :\n' + f'{mime_to_bytes(self.payload)}') self.encrypted = True encrypted_data = self.payload.get_payload(decode=True) @@ -537,9 +538,8 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, f'but signed message not found.') if self.payload.get_content_type() == 'multipart/signed': - logger.debug( - f'Verifying signed message {self.message_id} ' - f'payload: \n{self.payload.as_string()}') + logger.debug(f'Verifying signed message {self.message_id} payload: \n' + f'{mime_to_bytes(self.payload)}') self.signed = True # Split the message into signature and signed message @@ -555,8 +555,7 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, # then convert to canonical form and try again mic_content = canonicalize(self.payload) verify_cert = self.sender.load_verify_cert() - self.digest_alg = verify_message( - mic_content, signature, verify_cert) + self.digest_alg = verify_message(mic_content, signature, verify_cert) # Calculate the MIC Hash of the message to be verified digest_func = hashlib.new(self.digest_alg) @@ -590,6 +589,9 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, digest_alg = as2_headers.get('disposition-notification-options') if digest_alg: digest_alg = digest_alg.split(';')[-1].split(',')[-1].strip() + + logger.debug(f'Building the MDN for message {self.message_id} with status {status} ' + f'and detailed-status {detailed_status}.') mdn = Mdn(mdn_mode=mdn_mode, mdn_url=mdn_url, digest_alg=digest_alg) mdn.build(message=self, status=status, detailed_status=detailed_status) @@ -709,14 +711,13 @@ def build(self, message, status, detailed_status=None, confirmation_text=MDN_CON self.payload.attach(mdn_base) logger.debug( - f'MDN for message {message.message_id} created:\n{mdn_base.as_string()}') + f'MDN report for message {message.message_id} created:\n{mime_to_bytes(mdn_base)}') # Sign the MDN if it is requested by the sender if message.headers.get('disposition-notification-options') and \ message.receiver and message.receiver.sign_key: - self.digest_alg = \ - message.headers['disposition-notification-options'].\ - split(';')[-1].split(',')[-1].strip().replace('-', '') + self.digest_alg = message.headers['disposition-notification-options'].\ + split(';')[-1].split(',')[-1].strip().replace('-', '') signed_mdn = MIMEMultipart('signed', protocol="application/pkcs7-signature") del signed_mdn['MIME-Version'] signed_mdn.attach(self.payload) @@ -739,8 +740,7 @@ def build(self, message, status, detailed_status=None, confirmation_text=MDN_CON signed_mdn.attach(signature) self.payload = signed_mdn - logger.debug( - f'Signature for MDN {message.message_id} created:\n{signature.as_string()}') + logger.debug(f'Signing the MDN for message {message.message_id}') # Update the headers of the final payload and set message boundary for k, v in mdn_headers.items(): @@ -749,6 +749,8 @@ def build(self, message, status, detailed_status=None, confirmation_text=MDN_CON else: self.payload.add_header(k, v) self.payload.set_boundary(make_mime_boundary()) + logger.debug(f'MDN generated for message {message.message_id} with ' + f'content:\n {mime_to_bytes(self.payload)}') def parse(self, raw_content, find_message_cb): """Function parses the RAW AS2 MDN, verifies it and extracts the @@ -770,68 +772,74 @@ def parse(self, raw_content, find_message_cb): """ status, detailed_status = None, None - self.payload = parse_mime(raw_content) - self.orig_message_id, orig_recipient = self.detect_mdn() - - # Call the find message callback which should return a Message instance - orig_message = find_message_cb(self.orig_message_id, orig_recipient) + try: + self.payload = parse_mime(raw_content) + self.orig_message_id, orig_recipient = self.detect_mdn() + + # Call the find message callback which should return a Message instance + orig_message = find_message_cb(self.orig_message_id, orig_recipient) + + # Extract the headers and save it + mdn_headers = {} + for k, v in self.payload.items(): + k = k.lower() + if k == 'message-id': + self.message_id = v.lstrip('<').rstrip('>') + mdn_headers[k] = v + + if orig_message.receiver.mdn_digest_alg \ + and self.payload.get_content_type() != 'multipart/signed': + status = 'failed/Failure' + detailed_status = 'Expected signed MDN but unsigned MDN returned' + return status, detailed_status - # Extract the headers and save it - mdn_headers = {} - for k, v in self.payload.items(): - k = k.lower() - if k == 'message-id': - self.message_id = v.lstrip('<').rstrip('>') - mdn_headers[k] = v + if self.payload.get_content_type() == 'multipart/signed': + logger.debug(f'Verifying signed MDN: \n{mime_to_bytes(self.payload)}') + message_boundary = ('--' + self.payload.get_boundary()).encode('utf-8') - if orig_message.receiver.mdn_digest_alg \ - and self.payload.get_content_type() != 'multipart/signed': - status = 'failed/Failure' - detailed_status = 'Expected signed MDN but unsigned MDN returned' - return status, detailed_status + # Extract the signature and the signed payload + signature = None + signature_types = ['application/pkcs7-signature', 'application/x-pkcs7-signature'] + for part in self.payload.walk(): + if part.get_content_type() in signature_types: + signature = part.get_payload(decode=True) + elif part.get_content_type() == 'multipart/report': + self.payload = part - if self.payload.get_content_type() == 'multipart/signed': - message_boundary = ('--' + self.payload.get_boundary()).encode('utf-8') + # Verify the message, first using raw message and if it fails + # then convert to canonical form and try again + mic_content = extract_first_part(raw_content, message_boundary) + verify_cert = orig_message.receiver.load_verify_cert() + try: + self.digest_alg = verify_message(mic_content, signature, verify_cert) + except IntegrityError: + mic_content = canonicalize(self.payload) + self.digest_alg = verify_message(mic_content, signature, verify_cert) - # Extract the signature and the signed payload - signature = None - signature_types = ['application/pkcs7-signature', - 'application/x-pkcs7-signature'] for part in self.payload.walk(): - if part.get_content_type() in signature_types: - signature = part.get_payload(decode=True) - elif part.get_content_type() == 'multipart/report': - self.payload = part - - # Verify the message, first using raw message and if it fails - # then convert to canonical form and try again - mic_content = extract_first_part(raw_content, message_boundary) - verify_cert = orig_message.receiver.load_verify_cert() - try: - self.digest_alg = verify_message(mic_content, signature, verify_cert) - except IntegrityError: - mic_content = canonicalize(self.payload) - self.digest_alg = verify_message(mic_content, signature, verify_cert) + if part.get_content_type() == 'message/disposition-notification': + logger.debug( + f'MDN report for message {orig_message.message_id}:\n{part.as_string()}') + + mdn = part.get_payload()[-1] + mdn_status = mdn['Disposition'].split(';').pop().strip().split(':') + status = mdn_status[0] + if status == 'processed': + mdn_mic = mdn.get('Received-Content-MIC', '').split(',')[0] + + # TODO: Check MIC for all cases + if mdn_mic and orig_message.mic and mdn_mic != orig_message.mic.decode(): + status = 'processed/warning' + detailed_status = 'Message Integrity check failed.' + else: + detailed_status = ' '.join(mdn_status[1:]).strip() + except Exception as e: + status = 'failed/Failure' + detailed_status = f'Failed to parse received MDN. {e}' + logger.error(f'Failed to parse AS2 MDN\n: {traceback.format_exc()}') - for part in self.payload.walk(): - if part.get_content_type() == 'message/disposition-notification': - logger.debug( - f'Found MDN report for message {orig_message.message_id}:\n{part.as_string()}') - - mdn = part.get_payload()[-1] - mdn_status = mdn['Disposition'].split(';').pop().strip().split(':') - status = mdn_status[0] - if status == 'processed': - mdn_mic = mdn.get('Received-Content-MIC', '').split(',')[0] - - # TODO: Check MIC for all cases - if mdn_mic and orig_message.mic and mdn_mic != orig_message.mic.decode(): - status = 'processed/warning' - detailed_status = 'Message Integrity check failed.' - else: - detailed_status = ' '.join(mdn_status[1:]).strip() - - return status, detailed_status + finally: + return status, detailed_status def detect_mdn(self): """ Function checks if the received raw message is an AS2 MDN or not. diff --git a/pyas2lib/cms.py b/pyas2lib/cms.py index 0c37763..72bb141 100644 --- a/pyas2lib/cms.py +++ b/pyas2lib/cms.py @@ -343,11 +343,10 @@ def verify_message(data_to_verify, signature, verify_cert): cms_content = cms.ContentInfo.load(signature) digest_alg = None if cms_content['content_type'].native == 'signed_data': + for signer in cms_content['content']['signer_infos']: - signed_attributes = signer['signed_attrs'].copy() digest_alg = signer['digest_algorithm']['algorithm'].native - if digest_alg not in DIGEST_ALGORITHMS: raise Exception('Unsupported Digest Algorithm') @@ -355,10 +354,13 @@ def verify_message(data_to_verify, signature, verify_cert): sig = signer['signature'].native signed_data = data_to_verify - if signed_attributes: + if signer['signed_attrs']: attr_dict = {} - for attr in signed_attributes.native: - attr_dict[attr['type']] = attr['values'] + for attr in signer['signed_attrs']: + try: + attr_dict[attr.native['type']] = attr.native['values'] + except (ValueError, KeyError): + continue message_digest = bytes() for d in attr_dict['message_digest']: @@ -371,7 +373,7 @@ def verify_message(data_to_verify, signature, verify_cert): raise IntegrityError( 'Failed to verify message signature: Message Digest does not match.') - signed_data = signed_attributes.untag().dump() + signed_data = signer['signed_attrs'].untag().dump() try: if sig_alg == 'rsassa_pkcs1v15': diff --git a/pyas2lib/tests/test_mdn.py b/pyas2lib/tests/test_mdn.py index 49f0f7a..9787841 100644 --- a/pyas2lib/tests/test_mdn.py +++ b/pyas2lib/tests/test_mdn.py @@ -77,6 +77,38 @@ def test_signed_mdn(self): ) self.assertEqual(status, 'processed') + def test_failed_mdn_parse(self): + """Test mdn parsing failures are captured.""" + # Build an As2 message to be transmitted to partner + self.partner.sign = True + self.partner.encrypt = True + self.partner.mdn_mode = as2.SYNCHRONOUS_MDN + self.partner.mdn_digest_alg = 'sha256' + self.out_message = as2.Message(self.org, self.partner) + self.out_message.build(self.test_data) + + # Parse the generated AS2 message as the partner + raw_out_message = \ + self.out_message.headers_str + b'\r\n' + self.out_message.content + in_message = as2.Message() + _, _, mdn = in_message.parse( + raw_out_message, + find_org_cb=self.find_org, + find_partner_cb=self.find_partner + ) + + out_mdn = as2.Mdn() + self.partner.verify_cert = self.mecas2_public_key + self.partner.validate_certs = False + status, detailed_status = out_mdn.parse( + mdn.headers_str + b'\r\n' + mdn.content, + find_message_cb=self.find_message + ) + self.assertEqual(status, 'failed/Failure') + self.assertEqual( + detailed_status, 'Failed to parse received MDN. Failed to verify message signature: ' + 'Message Digest does not match.') + def find_org(self, as2_id): return self.org diff --git a/pyas2lib/utils.py b/pyas2lib/utils.py index 72b33f0..94846e6 100644 --- a/pyas2lib/utils.py +++ b/pyas2lib/utils.py @@ -40,16 +40,22 @@ def quote_as2name(unquoted_name: str): class BinaryBytesGenerator(BytesGenerator): """Override the bytes generator to better handle binary data.""" - def _handle_application_pkcs7_mime(self, msg: email.message.Message): + def _handle_text(self, msg): """ Handle writing the binary messages to prevent default behaviour of newline replacements. """ - payload = msg.get_payload(decode=True) - if payload is None: - return + if msg.get('Content-Transfer-Encoding') == 'binary' and \ + msg.get_content_subtype() in ['pkcs7-mime', 'pkcs7-signature']: + payload = msg.get_payload(decode=True) + if payload is None: + return + else: + self._fp.write(payload) else: - self._fp.write(payload) + super()._handle_text(msg) + + _writeBody = _handle_text def mime_to_bytes(msg: message.Message, email_policy: policy.Policy = policy.HTTP):