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# -*- coding: utf-8 -*-
# Minio Python Library for Amazon S3 Compatible Cloud Storage, (C)
# 2015, 2016 Minio, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
minio.policy
This module implements policy management.
:copyright: (c) 2016 by Minio, Inc.
:license: Apache 2.0, see LICENSE for more details.
"""
import collections
import fnmatch
import itertools
from .compat import basestring
_AWS_RESOURCE_PREFIX = "arn:aws:s3:::"
_COMMON_BUCKET_ACTIONS = set(['s3:GetBucketLocation'])
_READ_ONLY_BUCKET_ACTIONS = set(['s3:ListBucket'])
_WRITE_ONLY_BUCKET_ACTIONS = set(['s3:ListBucketMultipartUploads'])
_READ_ONLY_OBJECT_ACTIONS = set(['s3:GetObject'])
_WRITE_ONLY_OBJECT_ACTIONS = set(['s3:AbortMultipartUpload',
's3:DeleteObject',
's3:ListMultipartUploadParts',
's3:PutObject'])
_READ_WRITE_OBJECT_ACTIONS = (_READ_ONLY_OBJECT_ACTIONS |
_WRITE_ONLY_OBJECT_ACTIONS)
# Policy Enums.
class Policy(object):
NONE = "none"
READ_ONLY = "readonly"
READ_WRITE = "readwrite"
WRITE_ONLY = "writeonly"
def _get_resource(statement):
"""
Always return resource as a list
"""
resource = statement.get('Resource')
if isinstance(resource, basestring):
resource = [resource]
return resource
def _get_action(statement):
"""
Always return action as a list
"""
action = statement.get('Action', [])
if isinstance(action, basestring):
action = [action]
return action
# Returns new statements with bucket actions.
def _new_bucket_statement(policy, bucket_name, prefix=''):
if policy == Policy.NONE:
return []
bucket_resource = _AWS_RESOURCE_PREFIX + bucket_name
rv = [{'Action': list(_COMMON_BUCKET_ACTIONS),
'Effect': 'Allow',
'Principal': {'AWS': '*'},
'Resource': bucket_resource,
'Sid': ''}]
if policy == Policy.READ_ONLY or policy == Policy.READ_WRITE:
s = {'Action': list(_READ_ONLY_BUCKET_ACTIONS),
'Effect': 'Allow',
'Principal': {'AWS': '*'},
'Resource': bucket_resource,
'Sid': ''}
if prefix:
s.update({'Condition': {'StringEquals': {
's3:prefix': prefix}}})
rv.append(s)
if policy == Policy.WRITE_ONLY or policy == Policy.READ_WRITE:
rv.append({'Action': list(_WRITE_ONLY_BUCKET_ACTIONS),
'Effect': 'Allow',
'Principal': {'AWS': '*'},
'Resource': bucket_resource,
'Sid': ''})
return rv
# Returns new statements contains object actions.
def _new_object_statement(policy, bucket_name, prefix=''):
rv = [{'Action': [],
'Effect': 'Allow',
'Principal': {'AWS': '*'},
'Resource': _AWS_RESOURCE_PREFIX + bucket_name + '/' + prefix + '*',
'Sid': ''}]
if policy == Policy.READ_ONLY:
rv[0]['Action'] = list(_READ_ONLY_OBJECT_ACTIONS)
elif policy == Policy.WRITE_ONLY:
rv[0]['Action'] = list(_WRITE_ONLY_OBJECT_ACTIONS)
elif policy == Policy.READ_WRITE:
rv[0]['Action'] = list(_READ_WRITE_OBJECT_ACTIONS)
else:
rv = []
return rv
# Returns new statements for given bucket and prefix.
def _new_statements(policy, bucket_name, prefix=''):
return (_new_bucket_statement(policy, bucket_name, prefix) +
_new_object_statement(policy, bucket_name, prefix))
def _filter_resources(prefix, resources):
"""
Returns a list of resources, which starts with given prefix
"""
return list(filter(lambda r: r.startswith(prefix), resources))
# Returns whether given bucket statements are used by other than given
# prefix statements.
def _get_in_use_policy(statements, bucket_name, prefix=''):
resource_prefix = _AWS_RESOURCE_PREFIX + bucket_name + '/'
object_resource = _AWS_RESOURCE_PREFIX + bucket_name + '/' + prefix + '*'
in_use = {Policy.READ_ONLY: False,
Policy.WRITE_ONLY: False}
for s in statements:
resource = _get_resource(s)
actions = set(_get_action(s))
if (resource != object_resource and
_filter_resources(resource_prefix, resource)):
if (not in_use[Policy.READ_ONLY] and
actions & _READ_ONLY_OBJECT_ACTIONS):
in_use[Policy.READ_ONLY] = True
if (not in_use[Policy.WRITE_ONLY] and
actions & _WRITE_ONLY_OBJECT_ACTIONS):
in_use[Policy.WRITE_ONLY] = True
return in_use
# Removes bucket actions for given policy in given statement.
def _remove_bucket_actions(statement, policy, prefix=''):
def _remove_read_only(s, actions, cond_value):
if not (set(actions) & _READ_ONLY_BUCKET_ACTIONS ==
_READ_ONLY_BUCKET_ACTIONS):
return s, actions, cond_value
if not prefix and not cond_value:
actions = list(set(actions) - _READ_ONLY_BUCKET_ACTIONS)
return s, actions, cond_value
if prefix and cond_value:
string_equals_value = cond_value.get('StringEquals', {})
values = string_equals_value.get('s3:prefix', [])
if isinstance(values, basestring):
values = [values]
if prefix in values:
values.remove(prefix)
if not values and 's3:prefix' in string_equals_value:
del string_equals_value['s3:prefix']
if (not string_equals_value and
'StringEquals' in cond_value):
del cond_value['StringEquals']
if not cond_value and 'Condition' in s:
del s['Condition']
if not cond_value:
actions = list(set(actions) - _READ_ONLY_BUCKET_ACTIONS)
return s, actions, cond_value
def _remove_write_only(actions, cond_value):
if not cond_value:
actions = list(set(actions) - _WRITE_ONLY_BUCKET_ACTIONS)
return actions
actions = _get_action(statement)
cond_value = statement.get('Condition', {})
if (statement.get('Effect') == 'Allow' and
statement.get('Principal') == {'AWS': '*'}):
if policy == Policy.READ_ONLY:
statement, actions, cond_value = _remove_read_only(statement,
actions,
cond_value)
elif policy == Policy.WRITE_ONLY:
actions = _remove_write_only(actions, cond_value)
elif policy == Policy.READ_WRITE or policy == Policy.NONE:
statement, actions, cond_value = _remove_read_only(statement,
actions,
cond_value)
actions = _remove_write_only(actions, cond_value)
if actions:
statement['Action'] = actions
else:
statement = {}
return statement
# Removes object actions in given statement for given policy.
def _remove_object_actions(statement, policy):
actions = _get_action(statement)
if (statement.get('Effect') == 'Allow' and
statement.get('Principal') == {'AWS': '*'} and
not statement.get('Condition')):
if policy == Policy.READ_ONLY:
actions = list(set(actions) - _READ_ONLY_OBJECT_ACTIONS)
elif policy == Policy.WRITE_ONLY:
actions = list(set(actions) - _WRITE_ONLY_OBJECT_ACTIONS)
elif policy == Policy.READ_WRITE or policy == Policy.NONE:
actions = list(set(actions) - _READ_WRITE_OBJECT_ACTIONS)
if actions:
statement['Action'] = actions
else:
statement = {}
return statement
# Returns statements containing removed actions/statements for given
# policy, bucket name and prefix.
def _remove_statements(statements, policy, bucket_name, prefix=''):
bucket_resource = _AWS_RESOURCE_PREFIX + bucket_name
object_resource = _AWS_RESOURCE_PREFIX + bucket_name + '/' + prefix + '*'
in_use = _get_in_use_policy(statements, bucket_name, prefix)
out = []
read_only_bucket_statements = []
s3_prefix_value = []
for s in statements:
if s['Resource'] == bucket_resource:
if s.get('Condition'):
s = _remove_bucket_actions(s, policy, prefix)
else:
if (policy == Policy.READ_ONLY or
policy == Policy.READ_WRITE and
not in_use[Policy.READ_ONLY]):
s = _remove_bucket_actions(s, Policy.READ_ONLY, prefix)
if (policy == Policy.WRITE_ONLY or
policy == Policy.READ_WRITE and
not in_use[Policy.WRITE_ONLY]):
s = _remove_bucket_actions(s, Policy.WRITE_ONLY, prefix)
elif s['Resource'] == object_resource:
s = _remove_object_actions(s, policy)
if s:
if (s['Resource'] == bucket_resource and
set(_get_action(s)) & _READ_ONLY_BUCKET_ACTIONS and
s.get('Effect') == 'Allow' and
s.get('Principal') == {'AWS': '*'}):
cond_value = s.get('Condition', {})
string_equals_value = cond_value.get('StringEquals', {})
values = string_equals_value.get('s3:prefix', [])
if isinstance(values, basestring):
values = [values]
s3_prefix_value += [(bucket_resource + '/' + v + '*')
for v in values]
if s3_prefix_value or not cond_value:
read_only_bucket_statements.append(s)
continue
out.append(s)
skip_bucket_statement = True
resource_prefix = _AWS_RESOURCE_PREFIX + bucket_name + '/'
for s in out:
resource = s['Resource']
if (_filter_resources(resource_prefix, resource) and
resource not in s3_prefix_value):
skip_bucket_statement = False
break
for s in read_only_bucket_statements:
if (skip_bucket_statement and
s['Resource'] == bucket_resource and
s.get('Effect') == 'Allow' and
s.get('Principal') == {'AWS': '*'} and
not s.get('Condition')):
continue
_append_statement(out, s)
if len(out) == 1:
s = out[0]
if (s['Resource'] == bucket_resource and
s.get('Action') == list(_COMMON_BUCKET_ACTIONS) and
s.get('Effect') == 'Allow' and
s.get('Principal') == {'AWS': '*'} and
not s.get('Condition')):
out = []
return out
# Returns a dictionary containing values as list for same keys in
# given two dictionaries.
#
# Example:
# d1 = {'s3:prefix': 'hello',
# 's3:x-amz-acl': 'public-read',
# 'aws:SourceIp': '192.168.143.0/24'}
#
# d2 = {'s3:prefix': 'world',
# 's3:x-amz-acl': 'public-read'}
#
# _merge_dict(d1, d2) == {'s3:prefix': ['hello', 'world'],
# 's3:x-amz-acl': ['public-read'],
# 'aws:SourceIp': ['192.168.143.0/24']}
#
def _merge_dict(d1, d2):
out = collections.defaultdict(list)
for k, v in itertools.chain(d1.iteritems(), d2.iteritems()):
out[k] = list(set(out[k] + [v] if isinstance(v, basestring) else v))
return dict(out)
# Returns a dictionary containing merged conditions for given two dictionaries.
#
# Example:
# c1 = {'Condition': {'StringEquals': {'s3:prefix': 'hello'}}}
#
# c2 = {'Condition': {'StringEquals': {'s3:prefix': 'world'},
# 'StringNotEquals': {'s3:prefix': 'foo'}}}
#
# _merge_condition(c1, c2) == {'Condition': {
# 'StringEquals': {
# 's3:prefix': ['hello', 'world']},
# {'StringNotEquals': {
# 's3:prefix': ['foo']}}}
#
def _merge_condition(c1, c2):
out = collections.defaultdict(dict)
for k, v in itertools.chain(c1.iteritems(), c2.iteritems()):
out.update({k: _merge_dict(out[k], v)})
return dict(out)
# Appends given statement into statement list to have unique statements.
# - If statement already exists in statement list, it ignores.
# - If statement exists with different conditions, they are merged.
# - Else the statement is appended to statement list.
def _append_statement(statements, statement):
for s in statements:
if (s.get('Resource') == statement.get('Resource') and
_get_action(s) == _get_action(statement) and
s.get('Effect') == statement.get('Effect') and
s.get('Principal') == statement.get('Principal')):
if s.get('Condition') == statement.get('Condition'):
return
if s.get('Condition') and statement.get('Condition'):
s['Condition'] = _merge_condition(s['Condition'],
statement['Condition'])
return
statements.append(statement)
# Appends two statement lists.
def append_statements(statements, append_statements):
for s in append_statements:
_append_statement(statements, s)
# Checks whether given prefix starts with given s3 prefix list.
def _match_prefix(prefix, s3_prefix):
if isinstance(s3_prefix, basestring):
return prefix.startswith(s3_prefix)
matched = False
for p in s3_prefix:
matched = prefix.startswith(p)
if matched:
break
return matched
# Returns policy of given bucket statement.
def _get_bucket_policy(statement, prefix=''):
common_found = False
read_only = False
write_only = False
actions = set(_get_action(statement))
cond_value = statement.get('Condition', {})
if (statement.get('Effect') == 'Allow' and
statement.get('Principal') == {'AWS': '*'}):
if actions & _COMMON_BUCKET_ACTIONS and not cond_value:
common_found = True
if actions & _WRITE_ONLY_BUCKET_ACTIONS and not cond_value:
write_only = True
if actions & _READ_ONLY_BUCKET_ACTIONS:
if prefix and cond_value:
string_equals_value = cond_value.get('StringEquals', {})
if string_equals_value:
s3_prefix_value = string_equals_value.get('s3:prefix', [])
if isinstance(s3_prefix_value, basestring):
s3_prefix_value = [s3_prefix_value]
if _match_prefix(prefix, s3_prefix_value):
read_only = True
else:
string_not_equals_value = cond_value.get('StringNotEquals',
{})
if string_not_equals_value:
s3_prefix_value = string_not_equals_value.get(
's3:prefix', [])
if not _match_prefix(prefix, s3_prefix_value):
read_only = True
elif not prefix and not cond_value:
read_only = True
elif prefix and not cond_value:
read_only = True
return common_found, read_only, write_only
# Returns policy of given object statement.
def _get_object_policy(statement):
read_only = False
write_only = False
actions = set(_get_action(statement))
if (statement.get('Effect') == 'Allow' and
statement.get('Principal') == {'AWS': '*'} and
not statement.get('Condition')):
if actions & _READ_ONLY_OBJECT_ACTIONS:
read_only = True
if actions & _WRITE_ONLY_OBJECT_ACTIONS:
write_only = True
return read_only, write_only
# Returns policy of given bucket name, prefix in given statements.
def get_policy(statements, bucket_name, prefix=''):
bucket_resource = _AWS_RESOURCE_PREFIX + bucket_name
object_resource = _AWS_RESOURCE_PREFIX + bucket_name + '/' + prefix + '*'
bucket_common_found = False
bucket_read_only = False
bucket_write_only = False
matched_resource = ''
obj_read_only = False
obj_write_only = False
for s in statements:
resource = s['Resource']
if (resource == object_resource or
fnmatch.fnmatch(object_resource, resource)):
read_only, write_only = _get_object_policy(s)
if len(matched_resource) < len(resource):
obj_read_only = read_only
obj_write_only = write_only
matched_resource = resource
elif len(matched_resource) == len(resource):
obj_read_only = obj_read_only or read_only
obj_write_only = obj_write_only or write_only
matched_resource = resource
elif resource == bucket_resource:
common_found, read_only, write_only = _get_bucket_policy(s, prefix)
bucket_common_found = bucket_common_found or common_found
bucket_read_only = bucket_read_only or read_only
bucket_write_only = bucket_write_only or write_only
policy = Policy.NONE
if bucket_common_found:
if (bucket_read_only and bucket_write_only and
obj_read_only and obj_write_only):
policy = Policy.READ_WRITE
elif bucket_read_only and obj_read_only:
policy = Policy.READ_ONLY
elif bucket_write_only and obj_write_only:
policy = Policy.WRITE_ONLY
return policy
# Returns new statements containing policy of given bucket name and
# prefix are appended.
def set_policy(statements, policy, bucket_name, prefix=''):
out = _remove_statements(statements, Policy.READ_WRITE,
bucket_name, prefix)
ns = _new_statements(policy, bucket_name, prefix)
append_statements(out, ns)
return out