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# coding: utf-8
"""
Encoding DER to PEM and decoding PEM to DER. Exports the following items:
- armor()
- detect()
- unarmor()
"""
from __future__ import unicode_literals, division, absolute_import, print_function
import base64
import re
import sys
from ._errors import unwrap
from ._types import type_name as _type_name, str_cls, byte_cls
if sys.version_info < (3,):
from cStringIO import StringIO as BytesIO
else:
from io import BytesIO
def detect(byte_string):
"""
Detect if a byte string seems to contain a PEM-encoded block
:param byte_string:
A byte string to look through
:return:
A boolean, indicating if a PEM-encoded block is contained in the byte
string
"""
if not isinstance(byte_string, byte_cls):
raise TypeError(unwrap(
'''
byte_string must be a byte string, not %s
''',
_type_name(byte_string)
))
return byte_string.find(b'-----BEGIN') != -1 or byte_string.find(b'---- BEGIN') != -1
def armor(type_name, der_bytes, headers=None):
"""
Armors a DER-encoded byte string in PEM
:param type_name:
A unicode string that will be capitalized and placed in the header
and footer of the block. E.g. "CERTIFICATE", "PRIVATE KEY", etc. This
will appear as "-----BEGIN CERTIFICATE-----" and
"-----END CERTIFICATE-----".
:param der_bytes:
A byte string to be armored
:param headers:
An OrderedDict of the header lines to write after the BEGIN line
:return:
A byte string of the PEM block
"""
if not isinstance(der_bytes, byte_cls):
raise TypeError(unwrap(
'''
der_bytes must be a byte string, not %s
''' % _type_name(der_bytes)
))
if not isinstance(type_name, str_cls):
raise TypeError(unwrap(
'''
type_name must be a unicode string, not %s
''',
_type_name(type_name)
))
type_name = type_name.upper().encode('ascii')
output = BytesIO()
output.write(b'-----BEGIN ')
output.write(type_name)
output.write(b'-----\n')
if headers:
for key in headers:
output.write(key.encode('ascii'))
output.write(b': ')
output.write(headers[key].encode('ascii'))
output.write(b'\n')
output.write(b'\n')
b64_bytes = base64.b64encode(der_bytes)
b64_len = len(b64_bytes)
i = 0
while i < b64_len:
output.write(b64_bytes[i:i + 64])
output.write(b'\n')
i += 64
output.write(b'-----END ')
output.write(type_name)
output.write(b'-----\n')
return output.getvalue()
def _unarmor(pem_bytes):
"""
Convert a PEM-encoded byte string into one or more DER-encoded byte strings
:param pem_bytes:
A byte string of the PEM-encoded data
:raises:
ValueError - when the pem_bytes do not appear to be PEM-encoded bytes
:return:
A generator of 3-element tuples in the format: (object_type, headers,
der_bytes). The object_type is a unicode string of what is between
"-----BEGIN " and "-----". Examples include: "CERTIFICATE",
"PUBLIC KEY", "PRIVATE KEY". The headers is a dict containing any lines
in the form "Name: Value" that are right after the begin line.
"""
if not isinstance(pem_bytes, byte_cls):
raise TypeError(unwrap(
'''
pem_bytes must be a byte string, not %s
''',
_type_name(pem_bytes)
))
# Valid states include: "trash", "headers", "body"
state = 'trash'
headers = {}
base64_data = b''
object_type = None
found_start = False
found_end = False
for line in pem_bytes.splitlines(False):
if line == b'':
continue
if state == "trash":
# Look for a starting line since some CA cert bundle show the cert
# into in a parsed format above each PEM block
type_name_match = re.match(b'^(?:---- |-----)BEGIN ([A-Z0-9 ]+)(?: ----|-----)', line)
if not type_name_match:
continue
object_type = type_name_match.group(1).decode('ascii')
found_start = True
state = 'headers'
continue
if state == 'headers':
if line.find(b':') == -1:
state = 'body'
else:
decoded_line = line.decode('ascii')
name, value = decoded_line.split(':', 1)
headers[name] = value.strip()
continue
if state == 'body':
if line[0:5] in (b'-----', b'---- '):
der_bytes = base64.b64decode(base64_data)
yield (object_type, headers, der_bytes)
state = 'trash'
headers = {}
base64_data = b''
object_type = None
found_end = True
continue
base64_data += line
if not found_start or not found_end:
raise ValueError(unwrap(
'''
pem_bytes does not appear to contain PEM-encoded data - no
BEGIN/END combination found
'''
))
def unarmor(pem_bytes, multiple=False):
"""
Convert a PEM-encoded byte string into a DER-encoded byte string
:param pem_bytes:
A byte string of the PEM-encoded data
:param multiple:
If True, function will return a generator
:raises:
ValueError - when the pem_bytes do not appear to be PEM-encoded bytes
:return:
A 3-element tuple (object_name, headers, der_bytes). The object_name is
a unicode string of what is between "-----BEGIN " and "-----". Examples
include: "CERTIFICATE", "PUBLIC KEY", "PRIVATE KEY". The headers is a
dict containing any lines in the form "Name: Value" that are right
after the begin line.
"""
generator = _unarmor(pem_bytes)
if not multiple:
return next(generator)
return generator
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