# Copyright 2003 Ben Escoto
#
# This file is part of rdiff-backup.
#
# rdiff-backup is free software; you can redistribute it and/or modify
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#
# rdiff-backup is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with rdiff-backup; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
# USA

"""Store and retrieve extended attributes and access control lists

Not all file systems will have EAs and ACLs, but if they do, store
this information in separate files in the rdiff-backup-data directory,
called extended_attributes.<time>.snapshot and
access_control_lists.<time>.snapshot.

"""

from __future__ import generators
import base64, errno, re
try: import posix1e
except ImportError: pass
import static, Globals, metadata, connection, rorpiter, log, C, \
	   rpath, user_group

# When an ACL gets dropped, put name in dropped_acl_names.  This is
# only used so that only the first dropped ACL for any given name
# triggers a warning.
dropped_acl_names = {}

class ExtendedAttributes:
	"""Hold a file's extended attribute information"""
	def __init__(self, index, attr_dict = None):
		"""Initialize EA object with no attributes"""
		self.index = index
		if attr_dict is None: self.attr_dict = {}
		else: self.attr_dict = attr_dict

	def __eq__(self, ea):
		"""Equal if all attributes and index are equal"""
		assert isinstance(ea, ExtendedAttributes)
		return ea.index == self.index and ea.attr_dict == self.attr_dict
	def __ne__(self, ea): return not self.__eq__(ea)

	def get_indexpath(self): return self.index and '/'.join(self.index) or '.'

	def read_from_rp(self, rp):
		"""Set the extended attributes from an rpath"""
		try: attr_list = rp.conn.xattr.listxattr(rp.path)
		except IOError, exc:
			if exc[0] == errno.EOPNOTSUPP: return # if not sup, consider empty
			raise
		for attr in attr_list:
			if not attr.startswith('user.'):
				# Only preserve user extended attributes
				continue
			try: self.attr_dict[attr] = rp.conn.xattr.getxattr(rp.path, attr)
			except IOError, exc:
				# File probably modified while reading, just continue
				if exc[0] == errno.ENODATA: continue
				elif exc[0] == errno.ENOENT: break
				else: raise

	def clear_rp(self, rp):
		"""Delete all the extended attributes in rpath"""
		for name in rp.conn.xattr.listxattr(rp.path):
			rp.conn.xattr.removexattr(rp.path, name)

	def write_to_rp(self, rp):
		"""Write extended attributes to rpath rp"""
		self.clear_rp(rp)
		for (name, value) in self.attr_dict.iteritems():
			rp.conn.xattr.setxattr(rp.path, name, value)

	def get(self, name):
		"""Return attribute attached to given name"""
		return self.attr_dict[name]

	def set(self, name, value = ""):
		"""Set given name to given value.  Does not write to disk"""
		self.attr_dict[name] = value

	def delete(self, name):
		"""Delete value associated with given name"""
		del self.attr_dict[name]

	def empty(self):
		"""Return true if no extended attributes are set"""
		return not self.attr_dict

def ea_compare_rps(rp1, rp2):
	"""Return true if rp1 and rp2 have same extended attributes"""
	ea1 = ExtendedAttributes(rp1.index)
	ea1.read_from_rp(rp1)
	ea2 = ExtendedAttributes(rp2.index)
	ea2.read_from_rp(rp2)
	return ea1 == ea2


def EA2Record(ea):
	"""Convert ExtendedAttributes object to text record"""
	str_list = ['# file: %s' % C.acl_quote(ea.get_indexpath())]
	for (name, val) in ea.attr_dict.iteritems():
		if not val: str_list.append(name)
		else:
			encoded_val = base64.encodestring(val).replace('\n', '')
			str_list.append('%s=0s%s' % (C.acl_quote(name), encoded_val))
	return '\n'.join(str_list)+'\n'

def Record2EA(record):
	"""Convert text record to ExtendedAttributes object"""
	lines = record.split('\n')
	first = lines.pop(0)
	if not first[:8] == "# file: ":
		raise metadata.ParsingError("Bad record beginning: " + first[:8])
	filename = first[8:]
	if filename == '.': index = ()
	else: index = tuple(C.acl_unquote(filename).split('/'))
	ea = ExtendedAttributes(index)

	for line in lines:
		line = line.strip()
		if not line: continue
		assert line[0] != '#', line
		eq_pos = line.find('=')
		if eq_pos == -1: ea.set(line)
		else:
			name = line[:eq_pos]
			assert line[eq_pos+1:eq_pos+3] == '0s', \
				   "Currently only base64 encoding supported"
			encoded_val = line[eq_pos+3:]
			ea.set(name, base64.decodestring(encoded_val))
	return ea


class EAExtractor(metadata.FlatExtractor):
	"""Iterate ExtendedAttributes objects from the EA information file"""
	record_boundary_regexp = re.compile('(?:\\n|^)(# file: (.*?))\\n')
	record_to_object = staticmethod(Record2EA)
	def filename_to_index(self, filename):
		"""Convert possibly quoted filename to index tuple"""
		if filename == '.': return ()
		else: return tuple(C.acl_unquote(filename).split('/'))

class ExtendedAttributesFile(metadata.FlatFile):
	"""Store/retrieve EAs from extended_attributes file"""
	_prefix = "extended_attributes"
	_extractor = EAExtractor
	_object_to_record = staticmethod(EA2Record)

	def join(cls, rorp_iter, rbdir, time, restrict_index):
		"""Add extended attribute information to existing rorp_iter"""
		def helper(rorp_iter, ea_iter):
			"""Add EA information in ea_iter to rorp_iter"""
			collated = rorpiter.CollateIterators(rorp_iter, ea_iter)
			for rorp, ea in collated:
				assert rorp, (rorp, (ea.index, ea.attr_dict), time)
				if not ea: ea = ExtendedAttributes(rorp.index)
				rorp.set_ea(ea)
				yield rorp
			
		ea_iter = cls.get_objects_at_time(rbdir, time, restrict_index)
		if not ea_iter:
			log.Log("Warning: Extended attributes file not found", 2)
			ea_iter = iter([])
		return helper(rorp_iter, ea_iter)

static.MakeClass(ExtendedAttributesFile)


class AccessControlLists:
	"""Hold a file's access control list information

	Since posix1e.ACL objects cannot be picked, and because they lack
	user/group name information, store everything in self.entry_list
	and self.default_entry_list.

	"""
	def __init__(self, index, acl_text = None):
		"""Initialize object with index and possibly acl_text"""
		self.index = index
		if acl_text: self.set_from_text(acl_text)
		else: self.entry_list = self.default_entry_list = None

	def set_from_text(self, text):
		"""Set self.entry_list and self.default_entry_list from text"""
		self.entry_list, self.default_entry_list = [], []
		for line in text.split('\n'):
			comment_pos = text.find('#')
			if comment_pos >= 0: line = line[:comment_pos]
			line = line.strip()
			if not line: continue

			if line.startswith('default:'):
				entrytuple = self.text_to_entrytuple(line[8:])
				self.default_entry_list.append(entrytuple)
			else: self.entry_list.append(self.text_to_entrytuple(line))

	def __str__(self):
		"""Return text version of acls"""
		slist = map(self.entrytuple_to_text, self.entry_list)
		if self.default_entry_list:
			slist.extend(map(lambda e: "default:" + self.entrytuple_to_text(e),
							 self.default_entry_list))
		return "\n".join(slist)

	def entrytuple_to_text(self, entrytuple):
		"""Return text version of entrytuple, as in getfacl"""
		type, name_pair, perms = entrytuple
		if type == posix1e.ACL_USER_OBJ:
			text = 'user::'
		elif type == posix1e.ACL_USER:
			uid, uname = name_pair
			text = 'user:%s:' % (uname or uid)
		elif type == posix1e.ACL_GROUP_OBJ:
			text = 'group::'
		elif type == posix1e.ACL_GROUP:
			gid, gname = name_pair
			text = 'group:%s:' % (gname or gid)
		elif type == posix1e.ACL_MASK:
			text = 'mask::'
		else:
			assert type == posix1e.ACL_OTHER, type
			text = 'other::'

		permstring = '%s%s%s' % (perms & 4 and 'r' or '-',
								 perms & 2 and 'w' or '-',
								 perms & 1 and 'x' or '-')
		return text+permstring

	def text_to_entrytuple(self, text):
		"""Return entrytuple given text like 'user:foo:r--'"""
		typetext, qualifier, permtext = text.split(':')
		if qualifier:
			try: id = int(qualifier)
			except ValueError: namepair = (None, qualifier)
			else: namepair = (uid, None)

			if typetext == 'user': type = posix1e.ACL_USER
			else:
				assert typetext == 'group', (typetext, text)
				type = posix1e.ACL_GROUP
		else:
			namepair = None
			if typetext == 'user': type = posix1e.ACL_USER_OBJ
			elif typetext == 'group': type = posix1e.ACL_GROUP_OBJ
			elif typetext == 'mask': type = posix1e.ACL_MASK
			else:
				assert typetext == 'other', (typetext, text)
				type = posix1e.ACL_OTHER

		assert len(permtext) == 3, (permtext, text)
		read, write, execute = permtext
		perms = ((read == 'r') << 2 |
				 (write == 'w') << 1 |
				 (execute == 'x'))
		return (type, namepair, perms)

	def cmp_entry_list(self, l1, l2):
		"""True if the lists have same entries.  Assume preordered"""
		if not l1: return l1 == l2
		if not l2 or len(l1) != len(l2): return 0
		for i in range(len(l1)):
			type1, namepair1, perms1 = l1[i]
			type2, namepair2, perms2 = l2[i]
			if type1 != type2 or perms1 != perms2: return 0
			if namepair1 == namepair2: continue
			if not namepair1 or not namepair2: return 0
			(id1, name1), (id2, name2) = namepair1, namepair2
			if name1:
				if name1 == name2: continue
				else: return 0
			if name2: return 0
			if id1 != id2: return 0
		return 1

	def __eq__(self, acl):
		"""Compare self and other access control list

		Basic acl permissions are considered equal to an empty acl
		object.

		"""
		assert isinstance(acl, self.__class__)
		if self.index != acl.index: return 0
		if self.is_basic(): return acl.is_basic()
		return (self.cmp_entry_list(self.entry_list, acl.entry_list) and
				self.cmp_entry_list(self.default_entry_list,
									acl.default_entry_list))
	
	def __ne__(self, acl): return not self.__eq__(acl)
	
	def eq_verbose(self, acl):
		"""Returns same as __eq__ but print explanation if not equal"""
		if self.index != acl.index:
			print "index %s not equal to index %s" % (self.index, acl.index)
			return 0
		if not self.cmp_entry_list(self.entry_list, acl.entry_list):
			print "ACL entries for %s compare differently" % (self.index,)
			return 0
		if not self.cmp_entry_list(self.default_entry_list,
								   acl.default_entry_list):
			print "Default ACL entries for %s do not compare" % (self.index,)
			return 0
		return 1

	def get_indexpath(self): return self.index and '/'.join(self.index) or '.'

	def is_basic(self):
		"""True if acl can be reduced to standard unix permissions

		Assume that if they are only three entries, they correspond to
		user, group, and other, and thus don't use any special ACL
		features.

		"""
		if not self.entry_list and not self.default_entry_list: return 1
		assert len(self.entry_list) >= 3, self.entry_list
		return len(self.entry_list) == 3 and not self.default_entry_list

	def read_from_rp(self, rp):
		"""Set self.ACL from an rpath, or None if not supported"""
		self.entry_list, self.default_entry_list = \
						 rp.conn.eas_acls.get_acl_lists_from_rp(rp)

	def write_to_rp(self, rp, map_names = 1):
		"""Write current access control list to RPath rp"""
		rp.conn.eas_acls.set_rp_acl(rp, self.entry_list,
									self.default_entry_list, map_names)


def set_rp_acl(rp, entry_list = None, default_entry_list = None,
			   map_names = 1):
	"""Set given rp with ACL that acl_text defines.  rp should be local"""
	assert rp.conn is Globals.local_connection
	if entry_list: acl = list_to_acl(entry_list, map_names)
	else: acl = posix1e.ACL()
	acl.applyto(rp.path)

	if rp.isdir():
		if default_entry_list:
			def_acl = list_to_acl(default_entry_list, map_names)
		else: def_acl = posix1e.ACL()
		def_acl.applyto(rp.path, posix1e.ACL_TYPE_DEFAULT)

def get_acl_lists_from_rp(rp):
	"""Returns (acl_list, def_acl_list) from an rpath.  Call locally"""
	assert rp.conn is Globals.local_connection
	try: acl = posix1e.ACL(file=rp.path)
	except IOError, exc:
		if exc[0] == errno.EOPNOTSUPP: acl = None
		else: raise
	if rp.isdir():
		try: def_acl = posix1e.ACL(filedef=rp.path)
		except IOError, exc:
			if exc[0] == errno.EOPNOTSUPP: def_acl = None
			else: raise
	else: def_acl = None
	return (acl and acl_to_list(acl), def_acl and acl_to_list(def_acl))

def acl_to_list(acl):
	"""Return list representation of posix1e.ACL object

	ACL objects cannot be pickled, so this representation keeps
	the structure while adding that option.  Also we insert the
	username along with the id, because that information will be
	lost when moved to another system.

	The result will be a list of tuples.  Each tuple will have the
	form (acltype, (uid or gid, uname or gname) or None,
	permissions as an int).

	"""
	def entry_to_tuple(entry):
		if entry.tag_type == posix1e.ACL_USER:
			uid = entry.qualifier
			owner_pair = (uid, user_group.uid2uname(uid))
		elif entry.tag_type == posix1e.ACL_GROUP:
			gid = entry.qualifier
			owner_pair = (gid, user_group.gid2gname(gid))
		else: owner_pair = None

		perms = (entry.permset.read << 2 | 
				 entry.permset.write << 1 |
				 entry.permset.execute)
		return (entry.tag_type, owner_pair, perms)
	return map(entry_to_tuple, acl)

def list_to_acl(entry_list, map_names = 1):
	"""Return posix1e.ACL object from list representation

	If map_names is true, use user_group to update the names for the
	current system, and drop if not available.  Otherwise just use the
	same id.

	"""
	def warn_drop(name):
		"""Warn about acl with name getting dropped"""
		global dropped_acl_names
		if Globals.never_drop_acls:
			log.Log.FatalError(
"--never-drop-acls specified but cannot map name\n"
"%s occurring inside an ACL." % (name,))
		if dropped_acl_names.has_key(name): return
		log.Log("Warning: name %s not found on system, dropping ACL entry.\n"
				"Further ACL entries dropped with this name will not "
				"trigger further warnings" % (name,), 2)
		dropped_acl_names[name] = name

	def map_id_name(owner_pair, group = None):
		"""Return id of mapped id and user given original owner_pair"""
		id, name = owner_pair
		Map = group and user_group.GroupMap or user_group.UserMap
		if name: return Map.get_id_from_name(name)
		else:
			assert id is not None
			return Map.get_id_from_id(id)

	acl = posix1e.ACL()
	for tag, owner_pair, perms in entry_list:
		id = None
		if owner_pair:
			if map_names:
				if tag == posix1e.ACL_USER: id = map_id_name(owner_pair, 0)
				else:
					assert tag == posix1e.ACL_GROUP, (tag, owner_pair, perms)
					id = map_id_name(owner_pair, 1)
				if id is None:
					warn_drop(owner_pair[1])
					continue
			else:
				assert owner_pair[0] is not None, (tag, owner_pair, perms)
				id = owner_pair[0]

		entry = posix1e.Entry(acl)
		entry.tag_type = tag
		if id is not None: entry.qualifier = id
		entry.permset.read = perms >> 2
		entry.permset.write = perms >> 1 & 1
		entry.permset.execute = perms & 1
	return acl

def acl_compare_rps(rp1, rp2):
	"""Return true if rp1 and rp2 have same acl information"""
	acl1 = AccessControlLists(rp1.index)
	acl1.read_from_rp(rp1)
	acl2 = AccessControlLists(rp2.index)
	acl2.read_from_rp(rp2)
	return acl1 == acl2


def ACL2Record(acl):
	"""Convert an AccessControlLists object into a text record"""
	return '# file: %s\n%s\n' % (C.acl_quote(acl.get_indexpath()), str(acl))

def Record2ACL(record):
	"""Convert text record to an AccessControlLists object"""
	newline_pos = record.find('\n')
	first_line = record[:newline_pos]
	if not first_line.startswith('# file: '):
		raise metadata.ParsingError("Bad record beginning: "+ first_line)
	filename = first_line[8:]
	if filename == '.': index = ()
	else: index = tuple(C.acl_unquote(filename).split('/'))
	return AccessControlLists(index, record[newline_pos:])

class ACLExtractor(EAExtractor):
	"""Iterate AccessControlLists objects from the ACL information file

	Except for the record_to_object method, we can reuse everything in
	the EAExtractor class because the file formats are so similar.

	"""
	record_to_object = staticmethod(Record2ACL)

class AccessControlListFile(metadata.FlatFile):
	"""Store/retrieve ACLs from extended attributes file"""
	_prefix = 'access_control_lists'
	_extractor = ACLExtractor
	_object_to_record = staticmethod(ACL2Record)

	def join(cls, rorp_iter, rbdir, time, restrict_index):
		"""Add access control list information to existing rorp_iter"""
		def helper(rorp_iter, acl_iter):
			"""Add ACL information in acl_iter to rorp_iter"""
			collated = rorpiter.CollateIterators(rorp_iter, acl_iter)
			for rorp, acl in collated:
				assert rorp, "Missing rorp for index %s" % (acl.index,)
				if not acl: acl = AccessControlLists(rorp.index)
				rorp.set_acl(acl)
				yield rorp

		acl_iter = cls.get_objects_at_time(rbdir, time, restrict_index)
		if not acl_iter:
			log.Log("Warning: Access Control List file not found", 2)
			acl_iter = iter([])
		return helper(rorp_iter, acl_iter)

static.MakeClass(AccessControlListFile)


def GetCombinedMetadataIter(rbdir, time, restrict_index = None,
							acls = None, eas = None):
	"""Return iterator of rorps from metadata and related files

	None will be returned if the metadata file is absent.  If acls or
	eas is true, access control list or extended attribute information
	will be added.

	"""
	metadata_iter = metadata.MetadataFile.get_objects_at_time(
		rbdir, time, restrict_index)
	if not metadata_iter:
		log.Log("Warning, metadata file not found.\n"
				"Metadata will be read from filesystem.", 2)
		return None
	if eas:
		metadata_iter = ExtendedAttributesFile.join(
			metadata_iter, rbdir, time, restrict_index)
	if acls:
		metadata_iter = AccessControlListFile.join(
			metadata_iter, rbdir, time, restrict_index)
	return metadata_iter


def rpath_acl_get(rp):
	"""Get acls of given rpath rp.

	This overrides a function in the rpath module.

	"""
	acl = AccessControlLists(rp.index)
	if not rp.issym(): acl.read_from_rp(rp)
	return acl
rpath.acl_get = rpath_acl_get

def rpath_ea_get(rp):
	"""Get extended attributes of given rpath

	This overrides a function in the rpath module.

	"""
	ea = ExtendedAttributes(rp.index)
	if not rp.issym(): ea.read_from_rp(rp)
	return ea
rpath.ea_get = rpath_ea_get