Source code for certbot.crypto_util

"""Certbot client crypto utility functions.

.. todo:: Make the transition to use PSS rather than PKCS1_v1_5 when the server
    is capable of handling the signatures.

"""
import hashlib
import logging
import os

import OpenSSL
import pyrfc3339
import six
import zope.component
from cryptography.hazmat.backends import default_backend
from cryptography import x509

from acme import crypto_util as acme_crypto_util
from acme import jose

from certbot import errors
from certbot import interfaces
from certbot import util


logger = logging.getLogger(__name__)


# High level functions
[docs]def init_save_key(key_size, key_dir, keyname="key-certbot.pem"): """Initializes and saves a privkey. Inits key and saves it in PEM format on the filesystem. .. note:: keyname is the attempted filename, it may be different if a file already exists at the path. :param int key_size: RSA key size in bits :param str key_dir: Key save directory. :param str keyname: Filename of key :returns: Key :rtype: :class:`certbot.util.Key` :raises ValueError: If unable to generate the key given key_size. """ try: key_pem = make_key(key_size) except ValueError as err: logger.exception(err) raise err config = zope.component.getUtility(interfaces.IConfig) # Save file util.make_or_verify_dir(key_dir, 0o700, os.geteuid(), config.strict_permissions) key_f, key_path = util.unique_file( os.path.join(key_dir, keyname), 0o600, "wb") with key_f: key_f.write(key_pem) logger.debug("Generating key (%d bits): %s", key_size, key_path) return util.Key(key_path, key_pem)
[docs]def init_save_csr(privkey, names, path): """Initialize a CSR with the given private key. :param privkey: Key to include in the CSR :type privkey: :class:`certbot.util.Key` :param set names: `str` names to include in the CSR :param str path: Certificate save directory. :returns: CSR :rtype: :class:`certbot.util.CSR` """ config = zope.component.getUtility(interfaces.IConfig) csr_pem = acme_crypto_util.make_csr( privkey.pem, names, must_staple=config.must_staple) # Save CSR util.make_or_verify_dir(path, 0o755, os.geteuid(), config.strict_permissions) csr_f, csr_filename = util.unique_file( os.path.join(path, "csr-certbot.pem"), 0o644, "wb") with csr_f: csr_f.write(csr_pem) logger.debug("Creating CSR: %s", csr_filename) return util.CSR(csr_filename, csr_pem, "pem")
# WARNING: the csr and private key file are possible attack vectors for TOCTOU # We should either... # A. Do more checks to verify that the CSR is trusted/valid # B. Audit the parsing code for vulnerabilities
[docs]def valid_csr(csr): """Validate CSR. Check if `csr` is a valid CSR for the given domains. :param str csr: CSR in PEM. :returns: Validity of CSR. :rtype: bool """ try: req = OpenSSL.crypto.load_certificate_request( OpenSSL.crypto.FILETYPE_PEM, csr) return req.verify(req.get_pubkey()) except OpenSSL.crypto.Error as error: logger.debug(error, exc_info=True) return False
[docs]def csr_matches_pubkey(csr, privkey): """Does private key correspond to the subject public key in the CSR? :param str csr: CSR in PEM. :param str privkey: Private key file contents (PEM) :returns: Correspondence of private key to CSR subject public key. :rtype: bool """ req = OpenSSL.crypto.load_certificate_request( OpenSSL.crypto.FILETYPE_PEM, csr) pkey = OpenSSL.crypto.load_privatekey(OpenSSL.crypto.FILETYPE_PEM, privkey) try: return req.verify(pkey) except OpenSSL.crypto.Error as error: logger.debug(error, exc_info=True) return False
[docs]def import_csr_file(csrfile, data): """Import a CSR file, which can be either PEM or DER. :param str csrfile: CSR filename :param str data: contents of the CSR file :returns: (`OpenSSL.crypto.FILETYPE_PEM`, util.CSR object representing the CSR, list of domains requested in the CSR) :rtype: tuple """ PEM = OpenSSL.crypto.FILETYPE_PEM load = OpenSSL.crypto.load_certificate_request try: # Try to parse as DER first, then fall back to PEM. csr = load(OpenSSL.crypto.FILETYPE_ASN1, data) except OpenSSL.crypto.Error: try: csr = load(PEM, data) except OpenSSL.crypto.Error: raise errors.Error("Failed to parse CSR file: {0}".format(csrfile)) domains = _get_names_from_loaded_cert_or_req(csr) # Internally we always use PEM, so re-encode as PEM before returning. data_pem = OpenSSL.crypto.dump_certificate_request(PEM, csr) return PEM, util.CSR(file=csrfile, data=data_pem, form="pem"), domains
[docs]def make_key(bits): """Generate PEM encoded RSA key. :param int bits: Number of bits, at least 1024. :returns: new RSA key in PEM form with specified number of bits :rtype: str """ assert bits >= 1024 # XXX key = OpenSSL.crypto.PKey() key.generate_key(OpenSSL.crypto.TYPE_RSA, bits) return OpenSSL.crypto.dump_privatekey(OpenSSL.crypto.FILETYPE_PEM, key)
[docs]def valid_privkey(privkey): """Is valid RSA private key? :param str privkey: Private key file contents in PEM :returns: Validity of private key. :rtype: bool """ try: return OpenSSL.crypto.load_privatekey( OpenSSL.crypto.FILETYPE_PEM, privkey).check() except (TypeError, OpenSSL.crypto.Error): return False
[docs]def verify_renewable_cert(renewable_cert): """For checking that your certs were not corrupted on disk. Several things are checked: 1. Signature verification for the cert. 2. That fullchain matches cert and chain when concatenated. 3. Check that the private key matches the certificate. :param `.storage.RenewableCert` renewable_cert: cert to verify :raises errors.Error: If verification fails. """ verify_renewable_cert_sig(renewable_cert) verify_fullchain(renewable_cert) verify_cert_matches_priv_key(renewable_cert.cert, renewable_cert.privkey)
[docs]def verify_renewable_cert_sig(renewable_cert): """ Verifies the signature of a `.storage.RenewableCert` object. :param `.storage.RenewableCert` renewable_cert: cert to verify :raises errors.Error: If signature verification fails. """ try: with open(renewable_cert.chain, 'rb') as chain: chain, _ = pyopenssl_load_certificate(chain.read()) with open(renewable_cert.cert, 'rb') as cert: cert = x509.load_pem_x509_certificate(cert.read(), default_backend()) hash_name = cert.signature_hash_algorithm.name OpenSSL.crypto.verify(chain, cert.signature, cert.tbs_certificate_bytes, hash_name) except (IOError, ValueError, OpenSSL.crypto.Error) as e: error_str = "verifying the signature of the cert located at {0} has failed. \ Details: {1}".format(renewable_cert.cert, e) logger.exception(error_str) raise errors.Error(error_str)
[docs]def verify_cert_matches_priv_key(cert_path, key_path): """ Verifies that the private key and cert match. :param str cert_path: path to a cert in PEM format :param str key_path: path to a private key file :raises errors.Error: If they don't match. """ try: context = OpenSSL.SSL.Context(OpenSSL.SSL.SSLv23_METHOD) context.use_certificate_file(cert_path) context.use_privatekey_file(key_path) context.check_privatekey() except (IOError, OpenSSL.SSL.Error) as e: error_str = "verifying the cert located at {0} matches the \ private key located at {1} has failed. \ Details: {2}".format(cert_path, key_path, e) logger.exception(error_str) raise errors.Error(error_str)
[docs]def verify_fullchain(renewable_cert): """ Verifies that fullchain is indeed cert concatenated with chain. :param `.storage.RenewableCert` renewable_cert: cert to verify :raises errors.Error: If cert and chain do not combine to fullchain. """ try: with open(renewable_cert.chain) as chain: chain = chain.read() with open(renewable_cert.cert) as cert: cert = cert.read() with open(renewable_cert.fullchain) as fullchain: fullchain = fullchain.read() if (cert + chain) != fullchain: error_str = "fullchain does not match cert + chain for {0}!" error_str = error_str.format(renewable_cert.lineagename) raise errors.Error(error_str) except IOError as e: error_str = "reading one of cert, chain, or fullchain has failed: {0}".format(e) logger.exception(error_str) raise errors.Error(error_str) except errors.Error as e: raise e
[docs]def pyopenssl_load_certificate(data): """Load PEM/DER certificate. :raises errors.Error: """ openssl_errors = [] for file_type in (OpenSSL.crypto.FILETYPE_PEM, OpenSSL.crypto.FILETYPE_ASN1): try: return OpenSSL.crypto.load_certificate(file_type, data), file_type except OpenSSL.crypto.Error as error: # TODO: other errors? openssl_errors.append(error) raise errors.Error("Unable to load: {0}".format(",".join( str(error) for error in openssl_errors)))
def _load_cert_or_req(cert_or_req_str, load_func, typ=OpenSSL.crypto.FILETYPE_PEM): try: return load_func(typ, cert_or_req_str) except OpenSSL.crypto.Error as error: logger.exception(error) raise def _get_sans_from_cert_or_req(cert_or_req_str, load_func, typ=OpenSSL.crypto.FILETYPE_PEM): # pylint: disable=protected-access return acme_crypto_util._pyopenssl_cert_or_req_san(_load_cert_or_req( cert_or_req_str, load_func, typ))
[docs]def get_sans_from_cert(cert, typ=OpenSSL.crypto.FILETYPE_PEM): """Get a list of Subject Alternative Names from a certificate. :param str cert: Certificate (encoded). :param typ: `OpenSSL.crypto.FILETYPE_PEM` or `OpenSSL.crypto.FILETYPE_ASN1` :returns: A list of Subject Alternative Names. :rtype: list """ return _get_sans_from_cert_or_req( cert, OpenSSL.crypto.load_certificate, typ)
def _get_names_from_cert_or_req(cert_or_req, load_func, typ): loaded_cert_or_req = _load_cert_or_req(cert_or_req, load_func, typ) return _get_names_from_loaded_cert_or_req(loaded_cert_or_req) def _get_names_from_loaded_cert_or_req(loaded_cert_or_req): common_name = loaded_cert_or_req.get_subject().CN # pylint: disable=protected-access sans = acme_crypto_util._pyopenssl_cert_or_req_san(loaded_cert_or_req) if common_name is None: return sans else: return [common_name] + [d for d in sans if d != common_name]
[docs]def get_names_from_cert(csr, typ=OpenSSL.crypto.FILETYPE_PEM): """Get a list of domains from a cert, including the CN if it is set. :param str cert: Certificate (encoded). :param typ: `OpenSSL.crypto.FILETYPE_PEM` or `OpenSSL.crypto.FILETYPE_ASN1` :returns: A list of domain names. :rtype: list """ return _get_names_from_cert_or_req( csr, OpenSSL.crypto.load_certificate, typ)
[docs]def dump_pyopenssl_chain(chain, filetype=OpenSSL.crypto.FILETYPE_PEM): """Dump certificate chain into a bundle. :param list chain: List of `OpenSSL.crypto.X509` (or wrapped in `acme.jose.ComparableX509`). """ # XXX: returns empty string when no chain is available, which # shuts up RenewableCert, but might not be the best solution... def _dump_cert(cert): if isinstance(cert, jose.ComparableX509): # pylint: disable=protected-access cert = cert.wrapped return OpenSSL.crypto.dump_certificate(filetype, cert) # assumes that OpenSSL.crypto.dump_certificate includes ending # newline character return b"".join(_dump_cert(cert) for cert in chain)
[docs]def notBefore(cert_path): """When does the cert at cert_path start being valid? :param str cert_path: path to a cert in PEM format :returns: the notBefore value from the cert at cert_path :rtype: :class:`datetime.datetime` """ return _notAfterBefore(cert_path, OpenSSL.crypto.X509.get_notBefore)
[docs]def notAfter(cert_path): """When does the cert at cert_path stop being valid? :param str cert_path: path to a cert in PEM format :returns: the notAfter value from the cert at cert_path :rtype: :class:`datetime.datetime` """ return _notAfterBefore(cert_path, OpenSSL.crypto.X509.get_notAfter)
[docs]def _notAfterBefore(cert_path, method): """Internal helper function for finding notbefore/notafter. :param str cert_path: path to a cert in PEM format :param function method: one of ``OpenSSL.crypto.X509.get_notBefore`` or ``OpenSSL.crypto.X509.get_notAfter`` :returns: the notBefore or notAfter value from the cert at cert_path :rtype: :class:`datetime.datetime` """ # pylint: disable=redefined-outer-name with open(cert_path) as f: x509 = OpenSSL.crypto.load_certificate(OpenSSL.crypto.FILETYPE_PEM, f.read()) # pyopenssl always returns bytes timestamp = method(x509) reformatted_timestamp = [timestamp[0:4], b"-", timestamp[4:6], b"-", timestamp[6:8], b"T", timestamp[8:10], b":", timestamp[10:12], b":", timestamp[12:]] timestamp_str = b"".join(reformatted_timestamp) # pyrfc3339 uses "native" strings. That is, bytes on Python 2 and unicode # on Python 3 if six.PY3: timestamp_str = timestamp_str.decode('ascii') return pyrfc3339.parse(timestamp_str)
[docs]def sha256sum(filename): """Compute a sha256sum of a file. :param str filename: path to the file whose hash will be computed :returns: sha256 digest of the file in hexadecimal :rtype: str """ sha256 = hashlib.sha256() with open(filename, 'rb') as f: sha256.update(f.read()) return sha256.hexdigest()