Support otherName in subAltName in CSR for UTF8 strings (#53)

* Support otherName in subAltName in CSR for UTF8 strings

* Remove uneeded docs and added changelog fragment

* Missed a merge conflict

* Fix up sanity issues and added test expectation

* Rename function

plugins/module_utils/crypto/_asn1.py

@@ -0,0 +1,153 @@
+# -*- coding: utf-8 -*-
+
+# (c) 2020, Jordan Borean <jborean93@gmail.com>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+import re
+
+from ansible.module_utils._text import to_bytes
+
+
+"""
+An ASN.1 serialized as a string in the OpenSSL format:
+    [modifier,]type[:value]
+
+modifier:
+    The modifier can be 'IMPLICIT:<tag_number><tag_class>,' or 'EXPLICIT:<tag_number><tag_class>' where IMPLICIT
+    changes the tag of the universal value to encode and EXPLICIT prefixes its tag to the existing universal value.
+    The tag_number must be set while the tag_class can be 'U', 'A', 'P', or 'C" for 'Universal', 'Application',
+    'Private', or 'Context Specific' with C being the default.
+
+type:
+    The underlying ASN.1 type of the value specified. Currently only the following have been implemented:
+        UTF8: The value must be a UTF-8 encoded string.
+
+value:
+    The value to encode, the format of this value depends on the <type> specified.
+"""
+ASN1_STRING_REGEX = re.compile(r'^((?P<tag_type>IMPLICIT|EXPLICIT):(?P<tag_number>\d+)(?P<tag_class>U|A|P|C)?,)?'
+                               r'(?P<value_type>[\w\d]+):(?P<value>.*)')
+
+
+class TagClass:
+    universal = 0
+    application = 1
+    context_specific = 2
+    private = 3
+
+
+# Universal tag numbers that can be encoded.
+class TagNumber:
+    utf8_string = 12
+
+
+def _pack_octet_integer(value):
+    """ Packs an integer value into 1 or multiple octets. """
+    # NOTE: This is *NOT* the same as packing an ASN.1 INTEGER like value.
+    octets = bytearray()
+
+    # Continue to shift the number by 7 bits and pack into an octet until the
+    # value is fully packed.
+    while value:
+        octet_value = value & 0b01111111
+
+        # First round (last octet) must have the MSB set.
+        if len(octets):
+            octet_value |= 0b10000000
+
+        octets.append(octet_value)
+        value >>= 7
+
+    # Reverse to ensure the higher order octets are first.
+    octets.reverse()
+    return bytes(octets)
+
+
+def serialize_asn1_string_as_der(value):
+    """ Deserializes an ASN.1 string to a DER encoded byte string. """
+    asn1_match = ASN1_STRING_REGEX.match(value)
+    if not asn1_match:
+        raise ValueError("The ASN.1 serialized string must be in the format [modifier,]type[:value]")
+
+    tag_type = asn1_match.group('tag_type')
+    tag_number = asn1_match.group('tag_number')
+    tag_class = asn1_match.group('tag_class') or 'C'
+    value_type = asn1_match.group('value_type')
+    asn1_value = asn1_match.group('value')
+
+    if value_type != 'UTF8':
+        raise ValueError('The ASN.1 serialized string is not a known type "{0}", only UTF8 types are '
+                         'supported'.format(value_type))
+
+    b_value = to_bytes(asn1_value, encoding='utf-8', errors='surrogate_or_strict')
+
+    # We should only do a universal type tag if not IMPLICITLY tagged or the tag class is not universal.
+    if not tag_type or (tag_type == 'EXPLICIT' and tag_class != 'U'):
+        b_value = pack_asn1(TagClass.universal, False, TagNumber.utf8_string, b_value)
+
+    if tag_type:
+        tag_class = {
+            'U': TagClass.universal,
+            'A': TagClass.application,
+            'P': TagClass.private,
+            'C': TagClass.context_specific,
+        }[tag_class]
+
+        # When adding support for more types this should be looked into further. For now it works with UTF8Strings.
+        constructed = tag_type == 'EXPLICIT' and tag_class != TagClass.universal
+        b_value = pack_asn1(tag_class, constructed, int(tag_number), b_value)
+
+    return b_value
+
+
+def pack_asn1(tag_class, constructed, tag_number, b_data):
+    """Pack the value into an ASN.1 data structure.
+
+    The structure for an ASN.1 element is
+
+    | Identifier Octet(s) | Length Octet(s) | Data Octet(s) |
+    """
+    b_asn1_data = bytearray()
+
+    if tag_class < 0 or tag_class > 3:
+        raise ValueError("tag_class must be between 0 and 3 not %s" % tag_class)
+
+    # Bit 8 and 7 denotes the class.
+    identifier_octets = tag_class << 6
+    # Bit 6 denotes whether the value is primitive or constructed.
+    identifier_octets |= ((1 if constructed else 0) << 5)
+
+    # Bits 5-1 contain the tag number, if it cannot be encoded in these 5 bits
+    # then they are set and another octet(s) is used to denote the tag number.
+    if tag_number < 31:
+        identifier_octets |= tag_number
+        b_asn1_data.append(identifier_octets)
+    else:
+        identifier_octets |= 31
+        b_asn1_data.append(identifier_octets)
+        b_asn1_data.extend(_pack_octet_integer(tag_number))
+
+    length = len(b_data)
+
+    # If the length can be encoded in 7 bits only 1 octet is required.
+    if length < 128:
+        b_asn1_data.append(length)
+
+    else:
+        # Otherwise the length must be encoded across multiple octets
+        length_octets = bytearray()
+        while length:
+            length_octets.append(length & 0b11111111)
+            length >>= 8
+
+        length_octets.reverse()  # Reverse to make the higher octets first.
+
+        # The first length octet must have the MSB set alongside the number of
+        # octets the length was encoded in.
+        b_asn1_data.append(len(length_octets) | 0b10000000)
+        b_asn1_data.extend(length_octets)
+
+    return bytes(b_asn1_data) + b_data

plugins/module_utils/crypto/cryptography_support.py

@@ -24,6 +24,7 @@ import binascii
 import re
 
 from ansible.module_utils._text import to_text
+from ._asn1 import serialize_asn1_string_as_der
 
 try:
     import cryptography
@@ -205,10 +206,22 @@ def cryptography_get_name(name):
                 raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}"'.format(name))
             return x509.RegisteredID(x509.oid.ObjectIdentifier(m.group(1)))
         if name.startswith('otherName:'):
+            # otherName can either be a raw ASN.1 hex string or in the format that OpenSSL works with.
             m = re.match(r'^([0-9]+(?:\.[0-9]+)*);([0-9a-fA-F]{1,2}(?::[0-9a-fA-F]{1,2})*)$', to_text(name[10:]))
-            if not m:
-                raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}"'.format(name))
-            return x509.OtherName(x509.oid.ObjectIdentifier(m.group(1)), _parse_hex(m.group(2)))
+            if m:
+                return x509.OtherName(x509.oid.ObjectIdentifier(m.group(1)), _parse_hex(m.group(2)))
+
+            # See https://www.openssl.org/docs/man1.0.2/man5/x509v3_config.html - Subject Alternative Name for more
+            # defailts on the format expected.
+            name = to_text(name[10:], errors='surrogate_or_strict')
+            if ';' not in name:
+                raise OpenSSLObjectError('Cannot parse Subject Alternative Name otherName "{0}", must be in the '
+                                         'format "otherName:<OID>;<ASN.1 OpenSSL Encoded String>" or '
+                                         '"otherName:<OID>;<hex string>"'.format(name))
+
+            oid, value = name.split(';', 1)
+            b_value = serialize_asn1_string_as_der(value)
+            return x509.OtherName(x509.ObjectIdentifier(oid), b_value)
         if name.startswith('dirName:'):
             return x509.DirectoryName(x509.Name(_parse_dn(to_text(name[8:]))))
     except Exception as e: