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property_contexts
policy.py 12.63 KiB
from ctypes import *
import re
import os
import sys
import platform
###
# Check whether the regex will match a file path starting with the provided
# prefix
#
# Compares regex entries in file_contexts with a path prefix. Regex entries
# are often more specific than this file prefix. For example, the regex could
# be /system/bin/foo\.sh and the prefix could be /system. This function
# loops over the regex removing characters from the end until
# 1) there is a match - return True or 2) run out of characters - return
# False.
#
def MatchPathPrefix(pathregex, prefix):
for i in range(len(pathregex), 0, -1):
try:
pattern = re.compile('^' + pathregex[0:i] + "$")
except:
continue
if pattern.match(prefix):
return True
return False
def MatchPathPrefixes(pathregex, Prefixes):
for Prefix in Prefixes:
if MatchPathPrefix(pathregex, Prefix):
return True
return False
class TERule:
def __init__(self, rule):
data = rule.split(',')
self.flavor = data[0]
self.sctx = data[1]
self.tctx = data[2]
self.tclass = data[3]
self.perms = set((data[4].strip()).split(' '))
self.rule = rule
class Policy:
__ExpandedRules = set()
__Rules = set()
__FcDict = None
__libsepolwrap = None
__policydbP = None
__BUFSIZE = 2048
# Check that path prefixes that match MatchPrefix, and do not Match
# DoNotMatchPrefix have the attribute Attr.
# For example assert that all types in /sys, and not in /sys/kernel/debugfs
# have the sysfs_type attribute.
def AssertPathTypesHaveAttr(self, MatchPrefix, DoNotMatchPrefix, Attr):
# Query policy for the types associated with Attr
TypesPol = self.QueryTypeAttribute(Attr, True)
# Search file_contexts to find paths/types that should be associated with
# Attr.
TypesFc = self.__GetTypesByFilePathPrefix(MatchPrefix, DoNotMatchPrefix)
violators = TypesFc.difference(TypesPol)
ret = ""
if len(violators) > 0:
ret += "The following types on "
ret += " ".join(str(x) for x in sorted(MatchPrefix))
ret += " must be associated with the "
ret += "\"" + Attr + "\" attribute: "
ret += " ".join(str(x) for x in sorted(violators)) + "\n"
return ret
# Return all file_contexts entries that map to the input Type.
def QueryFc(self, Type):
if Type in self.__FcDict:
return self.__FcDict[Type]
else:
return None
# Return all attributes associated with a type if IsAttr=False or
# all types associated with an attribute if IsAttr=True
def QueryTypeAttribute(self, Type, IsAttr):
TypeIterP = self.__libsepolwrap.init_type_iter(self.__policydbP,
create_string_buffer(Type), IsAttr)
if (TypeIterP == None):
sys.exit("Failed to initialize type iterator")
buf = create_string_buffer(self.__BUFSIZE)
TypeAttr = set()
while True:
ret = self.__libsepolwrap.get_type(buf, self.__BUFSIZE,
self.__policydbP, TypeIterP)
if ret == 0:
TypeAttr.add(buf.value)
continue
if ret == 1:
break;
# We should never get here.
sys.exit("Failed to import policy")
self.__libsepolwrap.destroy_type_iter(TypeIterP)
return TypeAttr
def __TERuleMatch(self, Rule, **kwargs):
# Match source type
if ("scontext" in kwargs and
len(kwargs['scontext']) > 0 and
Rule.sctx not in kwargs['scontext']):
return False
# Match target type
if ("tcontext" in kwargs and
len(kwargs['tcontext']) > 0 and
Rule.tctx not in kwargs['tcontext']):
return False
# Match target class
if ("tclass" in kwargs and
len(kwargs['tclass']) > 0 and
not bool(set([Rule.tclass]) & kwargs['tclass'])):
return False
# Match any perms
if ("perms" in kwargs and
len(kwargs['perms']) > 0 and
not bool(Rule.perms & kwargs['perms'])):
return False
return True
# resolve a type to its attributes or
# resolve an attribute to its types and attributes
# For example if scontext is the domain attribute, then we need to
# include all types with the domain attribute such as untrusted_app and
# priv_app and all the attributes of those types such as appdomain.
def ResolveTypeAttribute(self, Type):
types = self.GetAllTypes(False)
attributes = self.GetAllTypes(True)
if Type in types:
return self.QueryTypeAttribute(Type, False)
elif Type in attributes:
TypesAndAttributes = set()
Types = self.QueryTypeAttribute(Type, True)
TypesAndAttributes |= Types
for T in Types:
TypesAndAttributes |= self.QueryTypeAttribute(T, False)
return TypesAndAttributes
else:
return set()
# Return all TERules that match:
# (any scontext) or (any tcontext) or (any tclass) or (any perms),
# perms.
# Any unspecified paramenter will match all.
#
# Example: QueryTERule(tcontext=["foo", "bar"], perms=["entrypoint"])
# Will return any rule with:
# (tcontext="foo" or tcontext="bar") and ("entrypoint" in perms)
def QueryTERule(self, **kwargs):
if len(self.__Rules) == 0:
self.__InitTERules()
# add any matching types and attributes for scontext and tcontext
if ("scontext" in kwargs and len(kwargs['scontext']) > 0):
scontext = set()
for sctx in kwargs['scontext']:
scontext |= self.ResolveTypeAttribute(sctx)
kwargs['scontext'] = scontext
if ("tcontext" in kwargs and len(kwargs['tcontext']) > 0):
tcontext = set()
for tctx in kwargs['tcontext']:
tcontext |= self.ResolveTypeAttribute(tctx)
kwargs['tcontext'] = tcontext
for Rule in self.__Rules:
if self.__TERuleMatch(Rule, **kwargs):
yield Rule
# Same as QueryTERule but only using the expanded ruleset.
# i.e. all attributes have been expanded to their various types.
def QueryExpandedTERule(self, **kwargs):
if len(self.__ExpandedRules) == 0:
self.__InitExpandedTERules()
for Rule in self.__ExpandedRules:
if self.__TERuleMatch(Rule, **kwargs):
yield Rule
def GetAllTypes(self, isAttr):
TypeIterP = self.__libsepolwrap.init_type_iter(self.__policydbP, None, isAttr)
if (TypeIterP == None):
sys.exit("Failed to initialize type iterator")
buf = create_string_buffer(self.__BUFSIZE)
AllTypes = set()
while True:
ret = self.__libsepolwrap.get_type(buf, self.__BUFSIZE,
self.__policydbP, TypeIterP)
if ret == 0:
AllTypes.add(buf.value)
continue
if ret == 1:
break;
# We should never get here.
sys.exit("Failed to import policy")
self.__libsepolwrap.destroy_type_iter(TypeIterP)
return AllTypes
def __GetTypesByFilePathPrefix(self, MatchPrefixes, DoNotMatchPrefixes):
Types = set()
for Type in self.__FcDict:
for pathregex in self.__FcDict[Type]:
if not MatchPathPrefixes(pathregex, MatchPrefixes):
continue
if MatchPathPrefixes(pathregex, DoNotMatchPrefixes):
continue
Types.add(Type)
return Types
def __GetTERules(self, policydbP, avtabIterP, Rules):
if Rules is None:
Rules = set()
buf = create_string_buffer(self.__BUFSIZE)
ret = 0
while True:
ret = self.__libsepolwrap.get_allow_rule(buf, self.__BUFSIZE,
policydbP, avtabIterP)
if ret == 0:
Rule = TERule(buf.value)
Rules.add(Rule)
continue
if ret == 1:
break;
# We should never get here.
sys.exit("Failed to import policy")
def __InitTERules(self):
avtabIterP = self.__libsepolwrap.init_avtab(self.__policydbP)
if (avtabIterP == None):
sys.exit("Failed to initialize avtab")
self.__GetTERules(self.__policydbP, avtabIterP, self.__Rules)
self.__libsepolwrap.destroy_avtab(avtabIterP)
avtabIterP = self.__libsepolwrap.init_cond_avtab(self.__policydbP)
if (avtabIterP == None):
sys.exit("Failed to initialize conditional avtab")
self.__GetTERules(self.__policydbP, avtabIterP, self.__Rules)
self.__libsepolwrap.destroy_avtab(avtabIterP)
def __InitExpandedTERules(self):
avtabIterP = self.__libsepolwrap.init_expanded_avtab(self.__policydbP)
if (avtabIterP == None):
sys.exit("Failed to initialize avtab")
self.__GetTERules(self.__policydbP, avtabIterP, self.__ExpandedRules)
self.__libsepolwrap.destroy_expanded_avtab(avtabIterP)
avtabIterP = self.__libsepolwrap.init_expanded_cond_avtab(self.__policydbP)
if (avtabIterP == None):
sys.exit("Failed to initialize conditional avtab")
self.__GetTERules(self.__policydbP, avtabIterP, self.__ExpandedRules)
self.__libsepolwrap.destroy_expanded_avtab(avtabIterP)
# load ctypes-ified libsepol wrapper
def __InitLibsepolwrap(self, LibPath):
lib = CDLL(LibPath)
# int get_allow_rule(char *out, size_t len, void *policydbp, void *avtab_iterp);
lib.get_allow_rule.restype = c_int
lib.get_allow_rule.argtypes = [c_char_p, c_size_t, c_void_p, c_void_p];
# void *load_policy(const char *policy_path);
lib.load_policy.restype = c_void_p
lib.load_policy.argtypes = [c_char_p]
# void destroy_policy(void *policydbp);
lib.destroy_policy.argtypes = [c_void_p]
# void *init_expanded_avtab(void *policydbp);
lib.init_expanded_avtab.restype = c_void_p
lib.init_expanded_avtab.argtypes = [c_void_p]
# void *init_expanded_cond_avtab(void *policydbp);
lib.init_expanded_cond_avtab.restype = c_void_p
lib.init_expanded_cond_avtab.argtypes = [c_void_p]
# void destroy_expanded_avtab(void *avtab_iterp);
lib.destroy_expanded_avtab.argtypes = [c_void_p]
# void *init_avtab(void *policydbp);
lib.init_avtab.restype = c_void_p
lib.init_avtab.argtypes = [c_void_p]
# void *init_cond_avtab(void *policydbp);
lib.init_cond_avtab.restype = c_void_p
lib.init_cond_avtab.argtypes = [c_void_p]
# void destroy_avtab(void *avtab_iterp);
lib.destroy_avtab.argtypes = [c_void_p]
# int get_type(char *out, size_t max_size, void *policydbp, void *type_iterp);
lib.get_type.restype = c_int
lib.get_type.argtypes = [c_char_p, c_size_t, c_void_p, c_void_p]
# void *init_type_iter(void *policydbp, const char *type, bool is_attr);
lib.init_type_iter.restype = c_void_p
lib.init_type_iter.argtypes = [c_void_p, c_char_p, c_bool]
# void destroy_type_iter(void *type_iterp);
lib.destroy_type_iter.argtypes = [c_void_p]
self.__libsepolwrap = lib
# load file_contexts
def __InitFC(self, FcPaths):
if FcPaths is None:
return
fc = []
for path in FcPaths:
if not os.path.exists(path):
sys.exit("file_contexts file " + path + " does not exist.")
fd = open(path, "r")
fc += fd.readlines()
fd.close()
self.__FcDict = {}
for i in fc:
rec = i.split()
try:
t = rec[-1].split(":")[2]
if t in self.__FcDict:
self.__FcDict[t].append(rec[0])
else:
self.__FcDict[t] = [rec[0]]
except:
pass
# load policy
def __InitPolicy(self, PolicyPath):
cPolicyPath = create_string_buffer(PolicyPath)
self.__policydbP = self.__libsepolwrap.load_policy(cPolicyPath)
if (self.__policydbP is None):
sys.exit("Failed to load policy")
def __init__(self, PolicyPath, FcPaths, LibPath):
self.__InitLibsepolwrap(LibPath)
self.__InitFC(FcPaths)
self.__InitPolicy(PolicyPath)
def __del__(self):
if self.__policydbP is not None:
self.__libsepolwrap.destroy_policy(self.__policydbP)