htpasswd.py: add optional MD5-APR1 and BCRYPT support via passlib.
- Update docstring for optional MD5-APR1/BCRYPT support via passlib. - Support the "md5" and "bcrypt" htpasswd_encryption config values. - Conditionally import the required passlib components if either "md5" or "bcrypt" is requested in the configuration file. - Test bcrypt backend availability upon import. - First define verification functions, then conditionally import external dependencies. - Consolidate: use context manager for reading credential file. - Consolidate: save one call to strip() while parsing. - Consolidate: break long lines, clarify comments and docstrings. - Consolidate: use verification function mapping for improving maintainability.
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@ -19,18 +19,44 @@
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# along with Radicale. If not, see <http://www.gnu.org/licenses/>.
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"""
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Htpasswd authentication.
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Implement htpasswd authentication.
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Load the list of login/password couples according a the configuration file
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created by Apache ``htpasswd`` command. Plain-text, crypt and sha1 are
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supported, but md5 is not (see ``htpasswd`` man page to understand why).
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Apache's htpasswd command (httpd.apache.org/docs/programs/htpasswd.html) manages
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a file for storing user credentials. It can encrypt passwords using different
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methods, e.g. BCRYPT, MD5-APR1 (a version of MD5 modified for Apache), SHA1, or
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by using the system's CRYPT routine. The CRYPT and SHA1 encryption methods
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implemented by htpasswd are considered as insecure. MD5-APR1 provides medium
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security as of 2015. Only BCRYPT can be considered secure by current standards.
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MD5-APR1-encrypted credentials can be written by all versions of htpasswd (its
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the default, in fact), whereas BCRYPT requires htpasswd 2.4.x or newer.
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The `is_authenticated(user, password)` function provided by this module
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verifies the user-given credentials by parsing the htpasswd credential file
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pointed to by the ``htpasswd_filename`` configuration value while assuming
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the password encryption method specified via the ``htpasswd_encryption``
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configuration value.
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The following htpasswd password encrpytion methods are supported by Radicale
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out-of-the-box:
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- plain-text (created by htpasswd -p...) -- INSECURE
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- CRYPT (created by htpasswd -d...) -- INSECURE
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- SHA1 (created by htpasswd -s...) -- INSECURE
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When passlib (https://pypi.python.org/pypi/passlib) is importable, the
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following significantly more secure schemes are parsable by Radicale:
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- MD5-APR1 (htpasswd -m...) -- htpasswd's default method
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- BCRYPT (htpasswd -B...) -- Requires htpasswd 2.4.x
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"""
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import base64
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import hashlib
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import os
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from .. import config
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@ -39,28 +65,30 @@ ENCRYPTION = config.get("auth", "htpasswd_encryption")
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def _plain(hash_value, password):
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"""Check if ``hash_value`` and ``password`` match using plain method."""
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"""Check if ``hash_value`` and ``password`` match, using plain method."""
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return hash_value == password
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def _crypt(hash_value, password):
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"""Check if ``hash_value`` and ``password`` match using crypt method."""
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# The ``crypt`` module is only present on Unix, import if needed
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import crypt
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"""Check if ``hash_value`` and ``password`` match, using crypt method."""
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return crypt.crypt(password, hash_value) == hash_value
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def _sha1(hash_value, password):
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"""Check if ``hash_value`` and ``password`` match using sha1 method."""
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"""Check if ``hash_value`` and ``password`` match, using sha1 method."""
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hash_value = hash_value.replace("{SHA}", "").encode("ascii")
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password = password.encode(config.get("encoding", "stock"))
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sha1 = hashlib.sha1() # pylint: disable=E1101
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sha1.update(password)
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return sha1.digest() == base64.b64decode(hash_value)
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def _ssha(hash_salt_value, password):
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"""Check if ``hash_salt_value`` and ``password`` match using salted sha1 method."""
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hash_salt_value = hash_salt_value.replace("{SSHA}", "").encode("ascii").decode('base64')
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"""Check if ``hash_salt_value`` and ``password`` match, using salted sha1
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method. This method is not directly supported by htpasswd, but it can be
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written with e.g. openssl, and nginx can parse it."""
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hash_salt_value = hash_salt_value.replace(
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"{SSHA}", "").encode("ascii").decode('base64')
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password = password.encode(config.get("encoding", "stock"))
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hash_value = hash_salt_value[:20]
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salt_value = hash_salt_value[20:]
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@ -69,11 +97,69 @@ def _ssha(hash_salt_value, password):
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sha1.update(salt_value)
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return sha1.digest() == hash_value
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def _bcrypt(hash_value, password):
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return _passlib_bcrypt.verify(password, hash_value)
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def _md5apr1(hash_value, password):
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return _passlib_md5apr1.verify(password, hash_value)
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# Prepare mapping between encryption names and verification functions.
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# Pre-fill with methods that do not have external dependencies.
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_verifuncs = {
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"ssha": _ssha,
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"sha1": _sha1,
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"plain": _plain
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}
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# Conditionally attempt to import external dependencies.
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if ENCRYPTION == "md5":
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try:
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from passlib.hash import apr_md5_crypt as _passlib_md5apr1
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except ImportError:
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raise RuntimeError(("The htpasswd_encryption method 'md5' requires "
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"availability of the passlib module."))
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_verifuncs["md5"] = _md5apr1
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elif ENCRYPTION == "bcrypt":
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try:
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from passlib.hash import bcrypt as _passlib_bcrypt
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except ImportError:
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raise RuntimeError(("The htpasswd_encryption method 'bcrypt' requires "
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"availability of the passlib module with bcrypt support."))
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# A call to `encrypt` raises passlib.exc.MissingBackendError with a good
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# error message if bcrypt backend is not available. Trigger this here.
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_passlib_bcrypt.encrypt("test-bcrypt-backend")
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_verifuncs["bcrypt"] = _bcrypt
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elif ENCRYPTION == "crypt":
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try:
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import crypt
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except ImportError:
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raise RuntimeError(("The htpasswd_encryption method 'crypt' requires "
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"crypt() system support."))
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_verifuncs["crypt"] = _crypt
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# Validate initial configuration.
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if ENCRYPTION not in _verifuncs:
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raise RuntimeError(("The htpasswd encryption method '%s' is not "
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"supported." % ENCRYPTION))
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def is_authenticated(user, password):
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"""Check if ``user``/``password`` couple is valid."""
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for line in open(FILENAME).readlines():
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if line.strip():
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login, hash_value = line.strip().split(":")
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if login == user:
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return globals()["_%s" % ENCRYPTION](hash_value, password)
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"""Validate credentials: iterate through htpasswd credential file until
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user matches, extract hash (encrypted password) and check hash against
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user-given password, using the method specified in the Radicale config.
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"""
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with open(FILENAME) as f:
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for line in f:
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strippedline = line.strip()
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if strippedline:
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login, hash_value = strippedline.split(":")
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if login == user:
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# Allow encryption method to be overridden at runtime.
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return _verifuncs[ENCRYPTION](hash_value, password)
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return False
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