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Editing: asn1.py
# -*- coding: ascii -*- # # Util/asn1.py : Minimal support for ASN.1 DER binary encoding. # # =================================================================== # The contents of this file are dedicated to the public domain. To # the extent that dedication to the public domain is not available, # everyone is granted a worldwide, perpetual, royalty-free, # non-exclusive license to exercise all rights associated with the # contents of this file for any purpose whatsoever. # No rights are reserved. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS # BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN # ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE # SOFTWARE. # =================================================================== import struct from Crypto.Util.py3compat import byte_string, bchr, bord from Crypto.Util.number import long_to_bytes, bytes_to_long __all__ = ['DerObject', 'DerInteger', 'DerBoolean', 'DerOctetString', 'DerNull', 'DerSequence', 'DerObjectId', 'DerBitString', 'DerSetOf'] # Useful references: # - https://luca.ntop.org/Teaching/Appunti/asn1.html # - https://letsencrypt.org/docs/a-warm-welcome-to-asn1-and-der/ # - https://www.zytrax.com/tech/survival/asn1.html # - https://www.oss.com/asn1/resources/books-whitepapers-pubs/larmouth-asn1-book.pdf # - https://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf # - https://misc.daniel-marschall.de/asn.1/oid-converter/online.php def _is_number(x, only_non_negative=False): test = 0 try: test = x + test except TypeError: return False return not only_non_negative or x >= 0 class BytesIO_EOF(object): """This class differs from BytesIO in that a ValueError exception is raised whenever EOF is reached.""" def __init__(self, initial_bytes): self._buffer = initial_bytes self._index = 0 self._bookmark = None def set_bookmark(self): self._bookmark = self._index def data_since_bookmark(self): assert self._bookmark is not None return self._buffer[self._bookmark:self._index] def remaining_data(self): return len(self._buffer) - self._index def read(self, length): new_index = self._index + length if new_index > len(self._buffer): raise ValueError("Not enough data for DER decoding: expected %d bytes and found %d" % (new_index, len(self._buffer))) result = self._buffer[self._index:new_index] self._index = new_index return result def read_byte(self): return bord(self.read(1)[0]) class DerObject(object): """Base class for defining a single DER object. This class should never be directly instantiated. """ def __init__(self, asn1Id=None, payload=b'', implicit=None, constructed=False, explicit=None): """Initialize the DER object according to a specific ASN.1 type. :Parameters: asn1Id : integer or byte The universal DER tag number for this object (e.g. 0x10 for a SEQUENCE). If None, the tag is not known yet. payload : byte string The initial payload of the object (that it, the content octets). If not specified, the payload is empty. implicit : integer or byte The IMPLICIT tag number (< 0x1F) to use for the encoded object. It overrides the universal tag *asn1Id*. It cannot be combined with the ``explicit`` parameter. By default, there is no IMPLICIT tag. constructed : bool True when the ASN.1 type is *constructed*. False when it is *primitive* (default). explicit : integer or byte The EXPLICIT tag number (< 0x1F) to use for the encoded object. It cannot be combined with the ``implicit`` parameter. By default, there is no EXPLICIT tag. """ if asn1Id is None: # The tag octet will be read in with ``decode`` self._tag_octet = None return asn1Id = self._convertTag(asn1Id) self.payload = payload # In a BER/DER identifier octet: # * bits 4-0 contain the tag value # * bit 5 is set if the type is 'constructed' # and unset if 'primitive' # * bits 7-6 depend on the encoding class # # Class | Bit 7, Bit 6 # ---------------------------------- # universal | 0 0 # application | 0 1 # context-spec | 1 0 (default for IMPLICIT/EXPLICIT) # private | 1 1 # constructed_bit = 0x20 if constructed else 0x00 if None not in (explicit, implicit): raise ValueError("Explicit and implicit tags are" " mutually exclusive") if implicit is not None: # IMPLICIT tag overrides asn1Id self._tag_octet = 0x80 | constructed_bit | self._convertTag(implicit) elif explicit is not None: # 'constructed bit' is always asserted for an EXPLICIT tag self._tag_octet = 0x80 | 0x20 | self._convertTag(explicit) self._inner_tag_octet = constructed_bit | asn1Id else: # Neither IMPLICIT nor EXPLICIT self._tag_octet = constructed_bit | asn1Id def _convertTag(self, tag): """Check if *tag* is a real DER tag (5 bits). Convert it from a character to number if necessary. """ if not _is_number(tag): if len(tag) == 1: tag = bord(tag[0]) # Ensure that tag is a low tag if not (_is_number(tag) and 0 <= tag < 0x1F): raise ValueError("Wrong DER tag") return tag @staticmethod def _definite_form(length): """Build length octets according to BER/DER definite form. """ if length > 127: encoding = long_to_bytes(length) return bchr(len(encoding) + 128) + encoding return bchr(length) def encode(self): """Return this DER element, fully encoded as a binary byte string.""" # Concatenate identifier octets, length octets, # and contents octets output_payload = self.payload # In case of an EXTERNAL tag, first encode the inner # element. if hasattr(self, "_inner_tag_octet"): output_payload = (bchr(self._inner_tag_octet) + self._definite_form(len(self.payload)) + self.payload) return (bchr(self._tag_octet) + self._definite_form(len(output_payload)) + output_payload) def _decodeLen(self, s): """Decode DER length octets from a file.""" length = s.read_byte() if length > 127: encoded_length = s.read(length & 0x7F) if bord(encoded_length[0]) == 0: raise ValueError("Invalid DER: length has leading zero") length = bytes_to_long(encoded_length) if length <= 127: raise ValueError("Invalid DER: length in long form but smaller than 128") return length def decode(self, der_encoded, strict=False): """Decode a complete DER element, and re-initializes this object with it. Args: der_encoded (byte string): A complete DER element. Raises: ValueError: in case of parsing errors. """ if not byte_string(der_encoded): raise ValueError("Input is not a byte string") s = BytesIO_EOF(der_encoded) self._decodeFromStream(s, strict) # There shouldn't be other bytes left if s.remaining_data() > 0: raise ValueError("Unexpected extra data after the DER structure") return self def _decodeFromStream(self, s, strict): """Decode a complete DER element from a file.""" idOctet = s.read_byte() if self._tag_octet is not None: if idOctet != self._tag_octet: raise ValueError("Unexpected DER tag") else: self._tag_octet = idOctet length = self._decodeLen(s) self.payload = s.read(length) # In case of an EXTERNAL tag, further decode the inner # element. if hasattr(self, "_inner_tag_octet"): p = BytesIO_EOF(self.payload) inner_octet = p.read_byte() if inner_octet != self._inner_tag_octet: raise ValueError("Unexpected internal DER tag") length = self._decodeLen(p) self.payload = p.read(length) # There shouldn't be other bytes left if p.remaining_data() > 0: raise ValueError("Unexpected extra data after the DER structure") class DerInteger(DerObject): """Class to model a DER INTEGER. An example of encoding is:: >>> from Crypto.Util.asn1 import DerInteger >>> from binascii import hexlify, unhexlify >>> int_der = DerInteger(9) >>> print hexlify(int_der.encode()) which will show ``020109``, the DER encoding of 9. And for decoding:: >>> s = unhexlify(b'020109') >>> try: >>> int_der = DerInteger() >>> int_der.decode(s) >>> print int_der.value >>> except ValueError: >>> print "Not a valid DER INTEGER" the output will be ``9``. :ivar value: The integer value :vartype value: integer """ def __init__(self, value=0, implicit=None, explicit=None): """Initialize the DER object as an INTEGER. :Parameters: value : integer The value of the integer. implicit : integer The IMPLICIT tag to use for the encoded object. It overrides the universal tag for INTEGER (2). """ DerObject.__init__(self, 0x02, b'', implicit, False, explicit) self.value = value # The integer value def encode(self): """Return the DER INTEGER, fully encoded as a binary string.""" number = self.value self.payload = b'' while True: self.payload = bchr(int(number & 255)) + self.payload if 128 <= number <= 255: self.payload = bchr(0x00) + self.payload if -128 <= number <= 255: break number >>= 8 return DerObject.encode(self) def decode(self, der_encoded, strict=False): """Decode a DER-encoded INTEGER, and re-initializes this object with it. Args: der_encoded (byte string): A complete INTEGER DER element. Raises: ValueError: in case of parsing errors. """ return DerObject.decode(self, der_encoded, strict=strict) def _decodeFromStream(self, s, strict): """Decode a complete DER INTEGER from a file.""" # Fill up self.payload DerObject._decodeFromStream(self, s, strict) if strict: if len(self.payload) == 0: raise ValueError("Invalid encoding for DER INTEGER: empty payload") if len(self.payload) >= 2 and struct.unpack('>H', self.payload[:2])[0] < 0x80: raise ValueError("Invalid encoding for DER INTEGER: leading zero") # Derive self.value from self.payload self.value = 0 bits = 1 for i in self.payload: self.value *= 256 self.value += bord(i) bits <<= 8 if self.payload and bord(self.payload[0]) & 0x80: self.value -= bits class DerBoolean(DerObject): """Class to model a DER-encoded BOOLEAN. An example of encoding is:: >>> from Crypto.Util.asn1 import DerBoolean >>> bool_der = DerBoolean(True) >>> print(bool_der.encode().hex()) which will show ``0101ff``, the DER encoding of True. And for decoding:: >>> s = bytes.fromhex('0101ff') >>> try: >>> bool_der = DerBoolean() >>> bool_der.decode(s) >>> print(bool_der.value) >>> except ValueError: >>> print "Not a valid DER BOOLEAN" the output will be ``True``. :ivar value: The boolean value :vartype value: boolean """ def __init__(self, value=False, implicit=None, explicit=None): """Initialize the DER object as a BOOLEAN. Args: value (boolean): The value of the boolean. Default is False. implicit (integer or byte): The IMPLICIT tag number (< 0x1F) to use for the encoded object. It overrides the universal tag for BOOLEAN (1). It cannot be combined with the ``explicit`` parameter. By default, there is no IMPLICIT tag. explicit (integer or byte): The EXPLICIT tag number (< 0x1F) to use for the encoded object. It cannot be combined with the ``implicit`` parameter. By default, there is no EXPLICIT tag. """ DerObject.__init__(self, 0x01, b'', implicit, False, explicit) self.value = value # The boolean value def encode(self): """Return the DER BOOLEAN, fully encoded as a binary string.""" self.payload = b'\xFF' if self.value else b'\x00' return DerObject.encode(self) def decode(self, der_encoded, strict=False): """Decode a DER-encoded BOOLEAN, and re-initializes this object with it. Args: der_encoded (byte string): A DER-encoded BOOLEAN. Raises: ValueError: in case of parsing errors. """ return DerObject.decode(self, der_encoded, strict) def _decodeFromStream(self, s, strict): """Decode a DER-encoded BOOLEAN from a file.""" # Fill up self.payload DerObject._decodeFromStream(self, s, strict) if len(self.payload) != 1: raise ValueError("Invalid encoding for DER BOOLEAN: payload is not 1 byte") if bord(self.payload[0]) == 0: self.value = False elif bord(self.payload[0]) == 0xFF: self.value = True else: raise ValueError("Invalid payload for DER BOOLEAN") class DerSequence(DerObject): """Class to model a DER SEQUENCE. This object behaves like a dynamic Python sequence. Sub-elements that are INTEGERs behave like Python integers. Any other sub-element is a binary string encoded as a complete DER sub-element (TLV). An example of encoding is: >>> from Crypto.Util.asn1 import DerSequence, DerInteger >>> from binascii import hexlify, unhexlify >>> obj_der = unhexlify('070102') >>> seq_der = DerSequence([4]) >>> seq_der.append(9) >>> seq_der.append(obj_der.encode()) >>> print hexlify(seq_der.encode()) which will show ``3009020104020109070102``, the DER encoding of the sequence containing ``4``, ``9``, and the object with payload ``02``. For decoding: >>> s = unhexlify(b'3009020104020109070102') >>> try: >>> seq_der = DerSequence() >>> seq_der.decode(s) >>> print len(seq_der) >>> print seq_der[0] >>> print seq_der[:] >>> except ValueError: >>> print "Not a valid DER SEQUENCE" the output will be:: 3 4 [4, 9, b'\x07\x01\x02'] """ def __init__(self, startSeq=None, implicit=None, explicit=None): """Initialize the DER object as a SEQUENCE. :Parameters: startSeq : Python sequence A sequence whose element are either integers or other DER objects. implicit : integer or byte The IMPLICIT tag number (< 0x1F) to use for the encoded object. It overrides the universal tag for SEQUENCE (16). It cannot be combined with the ``explicit`` parameter. By default, there is no IMPLICIT tag. explicit : integer or byte The EXPLICIT tag number (< 0x1F) to use for the encoded object. It cannot be combined with the ``implicit`` parameter. By default, there is no EXPLICIT tag. """ DerObject.__init__(self, 0x10, b'', implicit, True, explicit) if startSeq is None: self._seq = [] else: self._seq = startSeq # A few methods to make it behave like a python sequence def __delitem__(self, n): del self._seq[n] def __getitem__(self, n): return self._seq[n] def __setitem__(self, key, value): self._seq[key] = value def __setslice__(self, i, j, sequence): self._seq[i:j] = sequence def __delslice__(self, i, j): del self._seq[i:j] def __getslice__(self, i, j): return self._seq[max(0, i):max(0, j)] def __len__(self): return len(self._seq) def __iadd__(self, item): self._seq.append(item) return self def append(self, item): self._seq.append(item) return self def insert(self, index, item): self._seq.insert(index, item) return self def hasInts(self, only_non_negative=True): """Return the number of items in this sequence that are integers. Args: only_non_negative (boolean): If ``True``, negative integers are not counted in. """ items = [x for x in self._seq if _is_number(x, only_non_negative)] return len(items) def hasOnlyInts(self, only_non_negative=True): """Return ``True`` if all items in this sequence are integers or non-negative integers. This function returns False is the sequence is empty, or at least one member is not an integer. Args: only_non_negative (boolean): If ``True``, the presence of negative integers causes the method to return ``False``.""" return self._seq and self.hasInts(only_non_negative) == len(self._seq) def encode(self): """Return this DER SEQUENCE, fully encoded as a binary string. Raises: ValueError: if some elements in the sequence are neither integers nor byte strings. """ self.payload = b'' for item in self._seq: if byte_string(item): self.payload += item elif _is_number(item): self.payload += DerInteger(item).encode() else: self.payload += item.encode() return DerObject.encode(self) def decode(self, der_encoded, strict=False, nr_elements=None, only_ints_expected=False): """Decode a complete DER SEQUENCE, and re-initializes this object with it. Args: der_encoded (byte string): A complete SEQUENCE DER element. nr_elements (None or integer or list of integers): The number of members the SEQUENCE can have only_ints_expected (boolean): Whether the SEQUENCE is expected to contain only integers. strict (boolean): Whether decoding must check for strict DER compliancy. Raises: ValueError: in case of parsing errors. DER INTEGERs are decoded into Python integers. Any other DER element is not decoded. Its validity is not checked. """ self._nr_elements = nr_elements result = DerObject.decode(self, der_encoded, strict=strict) if only_ints_expected and not self.hasOnlyInts(): raise ValueError("Some members are not INTEGERs") return result def _decodeFromStream(self, s, strict): """Decode a complete DER SEQUENCE from a file.""" self._seq = [] # Fill up self.payload DerObject._decodeFromStream(self, s, strict) # Add one item at a time to self.seq, by scanning self.payload p = BytesIO_EOF(self.payload) while p.remaining_data() > 0: p.set_bookmark() der = DerObject() der._decodeFromStream(p, strict) # Parse INTEGERs differently if der._tag_octet != 0x02: self._seq.append(p.data_since_bookmark()) else: derInt = DerInteger() data = p.data_since_bookmark() derInt.decode(data, strict=strict) self._seq.append(derInt.value) ok = True if self._nr_elements is not None: try: ok = len(self._seq) in self._nr_elements except TypeError: ok = len(self._seq) == self._nr_elements if not ok: raise ValueError("Unexpected number of members (%d)" " in the sequence" % len(self._seq)) class DerOctetString(DerObject): """Class to model a DER OCTET STRING. An example of encoding is: >>> from Crypto.Util.asn1 import DerOctetString >>> from binascii import hexlify, unhexlify >>> os_der = DerOctetString(b'\\xaa') >>> os_der.payload += b'\\xbb' >>> print hexlify(os_der.encode()) which will show ``0402aabb``, the DER encoding for the byte string ``b'\\xAA\\xBB'``. For decoding: >>> s = unhexlify(b'0402aabb') >>> try: >>> os_der = DerOctetString() >>> os_der.decode(s) >>> print hexlify(os_der.payload) >>> except ValueError: >>> print "Not a valid DER OCTET STRING" the output will be ``aabb``. :ivar payload: The content of the string :vartype payload: byte string """ def __init__(self, value=b'', implicit=None): """Initialize the DER object as an OCTET STRING. :Parameters: value : byte string The initial payload of the object. If not specified, the payload is empty. implicit : integer The IMPLICIT tag to use for the encoded object. It overrides the universal tag for OCTET STRING (4). """ DerObject.__init__(self, 0x04, value, implicit, False) class DerNull(DerObject): """Class to model a DER NULL element.""" def __init__(self): """Initialize the DER object as a NULL.""" DerObject.__init__(self, 0x05, b'', None, False) class DerObjectId(DerObject): """Class to model a DER OBJECT ID. An example of encoding is: >>> from Crypto.Util.asn1 import DerObjectId >>> from binascii import hexlify, unhexlify >>> oid_der = DerObjectId("1.2") >>> oid_der.value += ".840.113549.1.1.1" >>> print hexlify(oid_der.encode()) which will show ``06092a864886f70d010101``, the DER encoding for the RSA Object Identifier ``1.2.840.113549.1.1.1``. For decoding: >>> s = unhexlify(b'06092a864886f70d010101') >>> try: >>> oid_der = DerObjectId() >>> oid_der.decode(s) >>> print oid_der.value >>> except ValueError: >>> print "Not a valid DER OBJECT ID" the output will be ``1.2.840.113549.1.1.1``. :ivar value: The Object ID (OID), a dot separated list of integers :vartype value: string """ def __init__(self, value='', implicit=None, explicit=None): """Initialize the DER object as an OBJECT ID. :Parameters: value : string The initial Object Identifier (e.g. "1.2.0.0.6.2"). implicit : integer The IMPLICIT tag to use for the encoded object. It overrides the universal tag for OBJECT ID (6). explicit : integer The EXPLICIT tag to use for the encoded object. """ DerObject.__init__(self, 0x06, b'', implicit, False, explicit) self.value = value def encode(self): """Return the DER OBJECT ID, fully encoded as a binary string.""" comps = [int(x) for x in self.value.split(".")] if len(comps) < 2: raise ValueError("Not a valid Object Identifier string") if comps[0] > 2: raise ValueError("First component must be 0, 1 or 2") if comps[0] < 2 and comps[1] > 39: raise ValueError("Second component must be 39 at most") subcomps = [40 * comps[0] + comps[1]] + comps[2:] encoding = [] for v in reversed(subcomps): encoding.append(v & 0x7F) v >>= 7 while v: encoding.append((v & 0x7F) | 0x80) v >>= 7 self.payload = b''.join([bchr(x) for x in reversed(encoding)]) return DerObject.encode(self) def decode(self, der_encoded, strict=False): """Decode a complete DER OBJECT ID, and re-initializes this object with it. Args: der_encoded (byte string): A complete DER OBJECT ID. strict (boolean): Whether decoding must check for strict DER compliancy. Raises: ValueError: in case of parsing errors. """ return DerObject.decode(self, der_encoded, strict) def _decodeFromStream(self, s, strict): """Decode a complete DER OBJECT ID from a file.""" # Fill up self.payload DerObject._decodeFromStream(self, s, strict) # Derive self.value from self.payload p = BytesIO_EOF(self.payload) subcomps = [] v = 0 while p.remaining_data(): c = p.read_byte() v = (v << 7) + (c & 0x7F) if not (c & 0x80): subcomps.append(v) v = 0 if len(subcomps) == 0: raise ValueError("Empty payload") if subcomps[0] < 40: subcomps[:1] = [0, subcomps[0]] elif subcomps[0] < 80: subcomps[:1] = [1, subcomps[0] - 40] else: subcomps[:1] = [2, subcomps[0] - 80] self.value = ".".join([str(x) for x in subcomps]) class DerBitString(DerObject): """Class to model a DER BIT STRING. An example of encoding is: >>> from Crypto.Util.asn1 import DerBitString >>> bs_der = DerBitString(b'\\xAA') >>> bs_der.value += b'\\xBB' >>> print(bs_der.encode().hex()) which will show ``030300aabb``, the DER encoding for the bit string ``b'\\xAA\\xBB'``. For decoding: >>> s = bytes.fromhex('030300aabb') >>> try: >>> bs_der = DerBitString() >>> bs_der.decode(s) >>> print(bs_der.value.hex()) >>> except ValueError: >>> print "Not a valid DER BIT STRING" the output will be ``aabb``. :ivar value: The content of the string :vartype value: byte string """ def __init__(self, value=b'', implicit=None, explicit=None): """Initialize the DER object as a BIT STRING. :Parameters: value : byte string or DER object The initial, packed bit string. If not specified, the bit string is empty. implicit : integer The IMPLICIT tag to use for the encoded object. It overrides the universal tag for BIT STRING (3). explicit : integer The EXPLICIT tag to use for the encoded object. """ DerObject.__init__(self, 0x03, b'', implicit, False, explicit) # The bitstring value (packed) if isinstance(value, DerObject): self.value = value.encode() else: self.value = value def encode(self): """Return the DER BIT STRING, fully encoded as a byte string.""" # Add padding count byte self.payload = b'\x00' + self.value return DerObject.encode(self) def decode(self, der_encoded, strict=False): """Decode a complete DER BIT STRING, and re-initializes this object with it. Args: der_encoded (byte string): a complete DER BIT STRING. strict (boolean): Whether decoding must check for strict DER compliancy. Raises: ValueError: in case of parsing errors. """ return DerObject.decode(self, der_encoded, strict) def _decodeFromStream(self, s, strict): """Decode a complete DER BIT STRING DER from a file.""" # Fill-up self.payload DerObject._decodeFromStream(self, s, strict) if self.payload and bord(self.payload[0]) != 0: raise ValueError("Not a valid BIT STRING") # Fill-up self.value self.value = b'' # Remove padding count byte if self.payload: self.value = self.payload[1:] class DerSetOf(DerObject): """Class to model a DER SET OF. An example of encoding is: >>> from Crypto.Util.asn1 import DerBitString >>> from binascii import hexlify, unhexlify >>> so_der = DerSetOf([4,5]) >>> so_der.add(6) >>> print hexlify(so_der.encode()) which will show ``3109020104020105020106``, the DER encoding of a SET OF with items 4,5, and 6. For decoding: >>> s = unhexlify(b'3109020104020105020106') >>> try: >>> so_der = DerSetOf() >>> so_der.decode(s) >>> print [x for x in so_der] >>> except ValueError: >>> print "Not a valid DER SET OF" the output will be ``[4, 5, 6]``. """ def __init__(self, startSet=None, implicit=None): """Initialize the DER object as a SET OF. :Parameters: startSet : container The initial set of integers or DER encoded objects. implicit : integer The IMPLICIT tag to use for the encoded object. It overrides the universal tag for SET OF (17). """ DerObject.__init__(self, 0x11, b'', implicit, True) self._seq = [] # All elements must be of the same type (and therefore have the # same leading octet) self._elemOctet = None if startSet: for e in startSet: self.add(e) def __getitem__(self, n): return self._seq[n] def __iter__(self): return iter(self._seq) def __len__(self): return len(self._seq) def add(self, elem): """Add an element to the set. Args: elem (byte string or integer): An element of the same type of objects already in the set. It can be an integer or a DER encoded object. """ if _is_number(elem): eo = 0x02 elif isinstance(elem, DerObject): eo = self._tag_octet else: eo = bord(elem[0]) if self._elemOctet != eo: if self._elemOctet is not None: raise ValueError("New element does not belong to the set") self._elemOctet = eo if elem not in self._seq: self._seq.append(elem) def decode(self, der_encoded, strict=False): """Decode a complete SET OF DER element, and re-initializes this object with it. DER INTEGERs are decoded into Python integers. Any other DER element is left undecoded; its validity is not checked. Args: der_encoded (byte string): a complete DER BIT SET OF. strict (boolean): Whether decoding must check for strict DER compliancy. Raises: ValueError: in case of parsing errors. """ return DerObject.decode(self, der_encoded, strict) def _decodeFromStream(self, s, strict): """Decode a complete DER SET OF from a file.""" self._seq = [] # Fill up self.payload DerObject._decodeFromStream(self, s, strict) # Add one item at a time to self.seq, by scanning self.payload p = BytesIO_EOF(self.payload) setIdOctet = -1 while p.remaining_data() > 0: p.set_bookmark() der = DerObject() der._decodeFromStream(p, strict) # Verify that all members are of the same type if setIdOctet < 0: setIdOctet = der._tag_octet else: if setIdOctet != der._tag_octet: raise ValueError("Not all elements are of the same DER type") # Parse INTEGERs differently if setIdOctet != 0x02: self._seq.append(p.data_since_bookmark()) else: derInt = DerInteger() derInt.decode(p.data_since_bookmark(), strict) self._seq.append(derInt.value) # end def encode(self): """Return this SET OF DER element, fully encoded as a binary string. """ # Elements in the set must be ordered in lexicographic order ordered = [] for item in self._seq: if _is_number(item): bys = DerInteger(item).encode() elif isinstance(item, DerObject): bys = item.encode() else: bys = item ordered.append(bys) ordered.sort() self.payload = b''.join(ordered) return DerObject.encode(self)
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