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# Copyright (C) 2015 Custodia Project Contributors - see LICENSE file
import errno
import os
import shutil
import socket
import struct
import six
try:
# pylint: disable=import-error
from BaseHTTPServer import BaseHTTPRequestHandler
from SocketServer import ForkingMixIn, UnixStreamServer
from urlparse import urlparse, parse_qs
from urllib import unquote
except ImportError:
# pylint: disable=import-error,no-name-in-module
from http.server import BaseHTTPRequestHandler
from socketserver import ForkingMixIn, UnixStreamServer
from urllib.parse import urlparse, parse_qs, unquote
from custodia import log
SO_PEERCRED = getattr(socket, 'SO_PEERCRED', 17)
SO_PEERSEC = getattr(socket, 'SO_PEERSEC', 31)
SELINUX_CONTEXT_LEN = 256
MAX_REQUEST_SIZE = 10 * 1024 * 1024 # For now limit body to 10MiB
class HTTPError(Exception):
def __init__(self, code=None, message=None):
self.code = code if code is not None else 500
self.mesg = message
errstring = '%d: %s' % (self.code, self.mesg)
log.debug(errstring)
super(HTTPError, self).__init__(errstring)
class ForkingLocalHTTPServer(ForkingMixIn, UnixStreamServer):
"""
A forking HTTP Server.
Each request runs into a forked server so that the whole environment
is clean and isolated, and parallel requests cannot unintentionally
influence one another.
When a request is received it is parsed by the handler_class provided
at server initialization.
"""
server_string = "Custodia/0.1"
allow_reuse_address = True
socket_file = None
def __init__(self, server_address, handler_class, config):
UnixStreamServer.__init__(self, server_address, handler_class)
if 'consumers' not in config:
raise ValueError('Configuration does not provide any consumer')
self.config = config
if 'server_string' in self.config:
self.server_string = self.config['server_string']
self._auditlog = log.AuditLog(self.config)
def server_bind(self):
oldmask = os.umask(000)
UnixStreamServer.server_bind(self)
os.umask(oldmask)
self.socket_file = self.socket.getsockname()
class LocalHTTPRequestHandler(BaseHTTPRequestHandler):
"""
This request handler is a slight modification of BaseHTTPRequestHandler
where the per-request handler is replaced.
When a request comes in it is parsed and the 'request' dictionary is
populated accordingly. Additionally a 'creds' structure is added to the
request.
The 'creds' structure contains the data retrieved via a call to
getsockopt with the SO_PEERCRED option. This retrieves via kernel assist
the uid,gid and pid of the process on the other side of the unix socket
on which the request has been made. This can be used for authentication
and/or authorization purposes.
The 'creds' structure is further augmented with a 'context' option
containing the Selinux Context string for the calling process, if
available.
after the request is parsed the server's pipeline() function is invoked
in order to handle it. The pipeline() should return a response object,
where te return 'code', the 'output' and 'headers' may be found.
If no 'code' is present the request is assumed to be successful and a
'200 OK' status code will be sent back to the client.
The 'output' parameter can be a string or a file like object.
The 'headers' objct must be a dictionary where keys are headers names.
By default we assume HTTP1.0
"""
protocol_version = "HTTP/1.0"
def __init__(self, *args, **kwargs):
BaseHTTPRequestHandler.__init__(self, *args, **kwargs)
self.requestline = ''
self.request_version = ''
self.command = ''
self.raw_requestline = None
self.close_connection = 0
self.path = None
self.query = None
self.url = None
self.body = None
self.loginuid = None
def version_string(self):
return self.server.server_string
def _get_loginuid(self, pid):
loginuid = None
try:
with open("/proc/" + str(pid) + "/loginuid", "r") as f:
loginuid = int(f.read(), 10)
except IOError as e:
if e.errno != errno.ENOENT:
raise
if loginuid == -1:
loginuid = None
return loginuid
@property
def peer_creds(self):
creds = self.request.getsockopt(socket.SOL_SOCKET, SO_PEERCRED,
struct.calcsize('3i'))
pid, uid, gid = struct.unpack('3i', creds)
try:
creds = self.request.getsockopt(socket.SOL_SOCKET, SO_PEERSEC,
SELINUX_CONTEXT_LEN)
context = creds.decode('utf-8')
except Exception as e:
log.debug("Couldn't retrieve SELinux Context: (%s)" % str(e))
context = None
return {'pid': pid, 'uid': uid, 'gid': gid, 'context': context}
def parse_request(self, *args, **kwargs):
if not BaseHTTPRequestHandler.parse_request(self, *args, **kwargs):
return False
# grab the loginuid from `/proc` as soon as possible
creds = self.peer_creds
self.loginuid = self._get_loginuid(creds['pid'])
# after basic parsing also use urlparse to retrieve individual
# elements of a request.
url = urlparse(self.path)
# Yes, override path with the path part only
self.path = unquote(url.path)
# Create dict out of query
self.query = parse_qs(url.query)
# keep the rest into the 'url' element in case someone needs it
self.url = url
return True
def parse_body(self):
length = int(self.headers.get('content-length', 0))
if length > MAX_REQUEST_SIZE:
raise HTTPError(413)
if length == 0:
self.body = None
else:
self.body = self.rfile.read(length)
def handle_one_request(self):
# Set a fake client address to make log functions happy
self.client_address = ['127.0.0.1', 0]
try:
if not self.server.config:
self.close_connection = 1
return
self.raw_requestline = self.rfile.readline(65537)
if not self.raw_requestline:
self.close_connection = 1
return
if len(self.raw_requestline) > 65536:
self.requestline = ''
self.request_version = ''
self.command = ''
self.send_error(414)
self.wfile.flush()
return
if not self.parse_request():
self.close_connection = 1
return
try:
self.parse_body()
except HTTPError as e:
self.send_error(e.code, e.mesg)
self.wfile.flush()
return
request = {'creds': self.peer_creds,
'command': self.command,
'path': self.path,
'query': self.query,
'url': self.url,
'version': self.request_version,
'headers': self.headers,
'body': self.body}
try:
response = self.pipeline(self.server.config, request)
if response is None:
raise HTTPError(500)
except HTTPError as e:
self.send_error(e.code, e.mesg)
self.wfile.flush()
return
except socket.timeout as e:
self.log_error("Request timed out: %r", e)
self.close_connection = 1
return
except Exception as e: # pylint: disable=broad-except
self.log_error("Handler failed: %r", e)
self.log_traceback()
self.send_error(500)
self.wfile.flush()
return
self.send_response(response.get('code', 200))
for header, value in six.iteritems(response.get('headers', {})):
self.send_header(header, value)
self.end_headers()
output = response.get('output', None)
if hasattr(output, 'read'):
shutil.copyfileobj(output, self.wfile)
output.close()
elif output is not None:
self.wfile.write(str(output).encode('utf-8'))
else:
self.close_connection = 1
self.wfile.flush()
return
except socket.timeout as e:
self.log_error("Request timed out: %r", e)
self.close_connection = 1
return
def log_traceback(self):
self.log_error('Traceback:\n%s' % log.stacktrace())
def pipeline(self, config, request):
"""
The pipeline() function handles authentication and invocation of
the correct consumer based on the server configuration, that is
provided at initialization time.
When authentication is performed all the authenticators are
executed. If any returns False, authentication fails and a 403
error is raised. If none of them positively succeeds and they all
return None then also authentication fails and a 403 error is
raised. Authentication plugins can add attributes to the request
object for use of authorization or other plugins.
When authorization is performed and positive result will cause the
operation to be accepted and any negative result will cause it to
fail. If no authorization plugin returns a positive result a 403
error is returned.
Once authentication and authorization are successful the pipeline
will parse the path component and find the consumer plugin that
handles the provided path walking up the path component by
component until a consumer is found.
Paths are walked up from the leaf to the root, so if two consumers
hang on the same tree, the one closer to the leaf will be used. If
there is a trailing path when the conumer is selected then it will
be stored in the request dicstionary named 'trail'. The 'trail' is
an ordered list of the path components below the consumer entry
point.
"""
# auth framework here
authers = config.get('authenticators')
if authers is None:
raise HTTPError(403)
valid_once = False
for auth in authers:
valid = authers[auth].handle(request)
if valid is False:
raise HTTPError(403)
elif valid is True:
valid_once = True
if valid_once is not True:
self.server._auditlog.svc_access(log.AUDIT_SVC_AUTH_FAIL,
request['creds']['pid'], "MAIN",
'No auth')
raise HTTPError(403)
# auhz framework here
authzers = config.get('authorizers')
if authzers is None:
raise HTTPError(403)
for authz in authzers:
valid = authzers[authz].handle(request)
if valid is not None:
break
if valid is not True:
self.server._auditlog.svc_access(log.AUDIT_SVC_AUTHZ_FAIL,
request['creds']['pid'], "MAIN",
request.get('path', '/'))
raise HTTPError(403)
# Select consumer
path = request.get('path', '')
if not os.path.isabs(path):
raise HTTPError(400)
trail = []
while path != '':
if path in config['consumers']:
con = config['consumers'][path]
if len(trail) != 0:
request['trail'] = trail
return con.handle(request)
if path == '/':
path = ''
else:
head, tail = os.path.split(path)
trail.insert(0, tail)
path = head
raise HTTPError(404)
class LocalHTTPServer(object):
def __init__(self, address, config):
if address[0] != '/':
raise ValueError('Must use absolute unix socket name')
if os.path.exists(address):
os.remove(address)
self.httpd = ForkingLocalHTTPServer(address, LocalHTTPRequestHandler,
config)
def get_socket(self):
return (self.httpd.socket, self.httpd.socket_file)
def serve(self):
return self.httpd.serve_forever()
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