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acl.rb
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acl.rb
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module AWS
module S3
# By default buckets are private. This means that only the owner has access rights to the bucket and its objects.
# Objects in that bucket inherit the permission of the bucket unless otherwise specified. When an object is private, the owner can
# generate a signed url that exposes the object to anyone who has that url. Alternatively, buckets and objects can be given other
# access levels. Several canned access levels are defined:
#
# * <tt>:private</tt> - Owner gets FULL_CONTROL. No one else has any access rights. This is the default.
# * <tt>:public_read</tt> - Owner gets FULL_CONTROL and the anonymous principal is granted READ access. If this policy is used on an object, it can be read from a browser with no authentication.
# * <tt>:public_read_write</tt> - Owner gets FULL_CONTROL, the anonymous principal is granted READ and WRITE access. This is a useful policy to apply to a bucket, if you intend for any anonymous user to PUT objects into the bucket.
# * <tt>:authenticated_read</tt> - Owner gets FULL_CONTROL, and any principal authenticated as a registered Amazon S3 user is granted READ access.
#
# You can set a canned access level when you create a bucket or an object by using the <tt>:access</tt> option:
#
# S3Object.store(
# 'kiss.jpg',
# data,
# 'marcel',
# :access => :public_read
# )
#
# Since the image we created is publicly readable, we can access it directly from a browser by going to the corresponding bucket name
# and specifying the object's key without a special authenticated url:
#
# http://s3.amazonaws.com/marcel/kiss.jpg
#
# ==== Building custum access policies
#
# For both buckets and objects, you can use the <tt>acl</tt> method to see its access control policy:
#
# policy = S3Object.acl('kiss.jpg', 'marcel')
# pp policy.grants
# [#<AWS::S3::ACL::Grant FULL_CONTROL to noradio>,
# #<AWS::S3::ACL::Grant READ to AllUsers Group>]
#
# Policies are made up of one or more grants which grant a specific permission to some grantee. Here we see the default FULL_CONTROL grant
# to the owner of this object. There is also READ permission granted to the Allusers Group, which means anyone has read access for the object.
#
# Say we wanted to grant access to anyone to read the access policy of this object. The current READ permission only grants them permission to read
# the object itself (for example, from a browser) but it does not allow them to read the access policy. For that we will need to grant the AllUsers group the READ_ACP permission.
#
# First we'll create a new grant object:
#
# grant = ACL::Grant.new
# # => #<AWS::S3::ACL::Grant (permission) to (grantee)>
# grant.permission = 'READ_ACP'
#
# Now we need to indicate who this grant is for. In other words, who the grantee is:
#
# grantee = ACL::Grantee.new
# # => #<AWS::S3::ACL::Grantee (xsi not set yet)>
#
# There are three ways to specify a grantee: 1) by their internal amazon id, such as the one returned with an object's Owner,
# 2) by their Amazon account email address or 3) by specifying a group. As of this writing you can not create custom groups, but
# Amazon does provide three already: AllUsers, Authenticated and LogDelivery. In this case we want to provide the grant to all users.
# This effectively means "anyone".
#
# grantee.group = 'AllUsers'
#
# Now that our grantee is setup, we'll associate it with the grant:
#
# grant.grantee = grantee
# grant
# # => #<AWS::S3::ACL::Grant READ_ACP to AllUsers Group>
#
# Are grant has all the information we need. Now that it's ready, we'll add it on to the object's access control policy's list of grants:
#
# policy.grants << grant
# pp policy.grants
# [#<AWS::S3::ACL::Grant FULL_CONTROL to noradio>,
# #<AWS::S3::ACL::Grant READ to AllUsers Group>,
# #<AWS::S3::ACL::Grant READ_ACP to AllUsers Group>]
#
# Now that the policy has the new grant, we reuse the <tt>acl</tt> method to persist the policy change:
#
# S3Object.acl('kiss.jpg', 'marcel', policy)
#
# If we fetch the object's policy again, we see that the grant has been added:
#
# pp S3Object.acl('kiss.jpg', 'marcel').grants
# [#<AWS::S3::ACL::Grant FULL_CONTROL to noradio>,
# #<AWS::S3::ACL::Grant READ to AllUsers Group>,
# #<AWS::S3::ACL::Grant READ_ACP to AllUsers Group>]
#
# If we were to access this object's acl url from a browser:
#
# http://s3.amazonaws.com/marcel/kiss.jpg?acl
#
# we would be shown its access control policy.
#
# ==== Pre-prepared grants
#
# Alternatively, the ACL::Grant class defines a set of stock grant policies that you can fetch by name. In most cases, you can
# just use one of these pre-prepared grants rather than building grants by hand. Two of these stock policies are <tt>:public_read</tt>
# and <tt>:public_read_acp</tt>, which happen to be the two grants that we built by hand above. In this case we could have simply written:
#
# policy.grants << ACL::Grant.grant(:public_read)
# policy.grants << ACL::Grant.grant(:public_read_acp)
# S3Object.acl('kiss.jpg', 'marcel', policy)
#
# The full details can be found in ACL::Policy, ACL::Grant and ACL::Grantee.
module ACL
# The ACL::Policy class lets you inspect and modify access controls for buckets and objects.
# A policy is made up of one or more Grants which specify a permission and a Grantee to whom that permission is granted.
#
# Buckets and objects are given a default access policy which contains one grant permitting the owner of the bucket or object
# FULL_CONTROL over its contents. This means they can read the object, write to the object, as well as read and write its
# policy.
#
# The <tt>acl</tt> method for both buckets and objects returns the policy object for that entity:
#
# policy = Bucket.acl('some-bucket')
#
# The <tt>grants</tt> method of a policy exposes its grants. You can treat this collection as an array and push new grants onto it:
#
# policy.grants << grant
#
# Check the documentation for Grant and Grantee for more details on how to create new grants.
class Policy
include SelectiveAttributeProxy #:nodoc:
attr_accessor :owner, :grants
def initialize(attributes = {})
@attributes = attributes
@grants = [].extend(GrantListExtensions)
extract_owner! if owner?
extract_grants! if grants?
end
# The xml representation of the policy.
def to_xml
Builder.new(owner, grants).to_s
end
private
def owner?
attributes.has_key?('owner') || !owner.nil?
end
def grants?
(attributes.has_key?('access_control_list') && attributes['access_control_list']['grant']) || !grants.empty?
end
def extract_owner!
@owner = Owner.new(attributes.delete('owner'))
end
def extract_grants!
attributes['access_control_list']['grant'].each do |grant|
grants << Grant.new(grant)
end
end
module GrantListExtensions #:nodoc:
def include?(grant)
case grant
when Symbol
super(ACL::Grant.grant(grant))
else
super
end
end
def delete(grant)
case grant
when Symbol
super(ACL::Grant.grant(grant))
else
super
end
end
# Two grant lists are equal if they have identical grants both in terms of permission and grantee.
def ==(grants)
size == grants.size && all? {|grant| grants.include?(grant)}
end
end
class Builder < XmlGenerator #:nodoc:
attr_reader :owner, :grants
def initialize(owner, grants)
@owner = owner
@grants = grants.uniq # There could be some duplicate grants
super()
end
def build
xml.tag!('AccessControlPolicy', 'xmlns' => 'http://s3.amazonaws.com/doc/2006-03-01/') do
xml.Owner do
xml.ID owner.id
xml.DisplayName owner.display_name
end
xml.AccessControlList do
xml << grants.map {|grant| grant.to_xml}.join("\n")
end
end
end
end
end
# A Policy is made up of one or more Grant objects. A grant sets a specific permission and grants it to the associated grantee.
#
# When creating a new grant to add to a policy, you need only set its permission and then associate with a Grantee.
#
# grant = ACL::Grant.new
# => #<AWS::S3::ACL::Grant (permission) to (grantee)>
#
# Here we see that neither the permission nor the grantee have been set. Let's make this grant provide the READ permission.
#
# grant.permission = 'READ'
# grant
# => #<AWS::S3::ACL::Grant READ to (grantee)>
#
# Now let's assume we have a grantee to the AllUsers group already set up. Just associate that grantee with our grant.
#
# grant.grantee = all_users_group_grantee
# grant
# => #<AWS::S3::ACL::Grant READ to AllUsers Group>
#
# And now are grant is complete. It provides READ permission to the AllUsers group, effectively making this object publicly readable
# without any authorization.
#
# Assuming we have some object's policy available in a local variable called <tt>policy</tt>, we can now add this grant onto its
# collection of grants.
#
# policy.grants << grant
#
# And then we send the updated policy to the S3 servers.
#
# some_s3object.acl(policy)
class Grant
include SelectiveAttributeProxy #:nodoc:
constant :VALID_PERMISSIONS, %w(READ WRITE READ_ACP WRITE_ACP FULL_CONTROL)
attr_accessor :grantee
class << self
# Returns stock grants with name <tt>type</tt>.
#
# public_read_grant = ACL::Grant.grant :public_read
# => #<AWS::S3::ACL::Grant READ to AllUsers Group>
#
# Valid stock grant types are:
#
# * <tt>:authenticated_read</tt>
# * <tt>:authenticated_read_acp</tt>
# * <tt>:authenticated_write</tt>
# * <tt>:authenticated_write_acp</tt>
# * <tt>:logging_read</tt>
# * <tt>:logging_read_acp</tt>
# * <tt>:logging_write</tt>
# * <tt>:logging_write_acp</tt>
# * <tt>:public_read</tt>
# * <tt>:public_read_acp</tt>
# * <tt>:public_write</tt>
# * <tt>:public_write_acp</tt>
def grant(type)
case type
when *stock_grant_map.keys
build_stock_grant_for type
else
raise ArgumentError, "Unknown grant type `#{type}'"
end
end
private
def stock_grant_map
grant = lambda {|permission, group| {:permission => permission, :group => group}}
groups = {:public => 'AllUsers', :authenticated => 'Authenticated', :logging => 'LogDelivery'}
permissions = %w(READ WRITE READ_ACP WRITE_ACP)
stock_grants = {}
groups.each do |grant_group_name, group_name|
permissions.each do |permission|
stock_grants["#{grant_group_name}_#{permission.downcase}".to_sym] = grant[permission, group_name]
end
end
stock_grants
end
memoized :stock_grant_map
def build_stock_grant_for(type)
stock_grant = stock_grant_map[type]
grant = new do |g|
g.permission = stock_grant[:permission]
end
grant.grantee = Grantee.new do |gr|
gr.group = stock_grant[:group]
end
grant
end
end
def initialize(attributes = {})
attributes = {'permission' => nil}.merge(attributes)
@attributes = attributes
extract_grantee!
yield self if block_given?
end
# Set the permission for this grant.
#
# grant.permission = 'READ'
# grant
# => #<AWS::S3::ACL::Grant READ to (grantee)>
#
# If the specified permisison level is not valid, an <tt>InvalidAccessControlLevel</tt> exception will be raised.
def permission=(permission_level)
unless self.class.valid_permissions.include?(permission_level)
raise InvalidAccessControlLevel.new(self.class.valid_permissions, permission_level)
end
attributes['permission'] = permission_level
end
# The xml representation of this grant.
def to_xml
Builder.new(permission, grantee).to_s
end
def inspect #:nodoc:
"#<%s:0x%s %s>" % [self.class, object_id, self]
end
def to_s #:nodoc:
[permission || '(permission)', 'to', grantee ? grantee.type_representation : '(grantee)'].join ' '
end
def eql?(grant) #:nodoc:
# This won't work for an unposted AmazonCustomerByEmail because of the normalization
# to CanonicalUser but it will work for groups.
to_s == grant.to_s
end
alias_method :==, :eql?
def hash #:nodoc:
to_s.hash
end
private
def extract_grantee!
@grantee = Grantee.new(attributes['grantee']) if attributes['grantee']
end
class Builder < XmlGenerator #:nodoc:
attr_reader :grantee, :permission
def initialize(permission, grantee)
@permission = permission
@grantee = grantee
super()
end
def build
xml.Grant do
xml << grantee.to_xml
xml.Permission permission
end
end
end
end
# Grants bestow a access permission to grantees. Each grant of some access control list Policy is associated with a grantee.
# There are three ways of specifying a grantee at the time of this writing.
#
# * By canonical user - This format uses the <tt>id</tt> of a given Amazon account. The id value for a given account is available in the
# Owner object of a bucket, object or policy.
#
# grantee.id = 'bb2041a25975c3d4ce9775fe9e93e5b77a6a9fad97dc7e00686191f3790b13f1'
#
# Often the id will just be fetched from some owner object.
#
# grantee.id = some_object.owner.id
#
# * By amazon email address - You can specify an email address for any Amazon account. The Amazon account need not be signed up with the S3 service.
# though it must be unique across the entire Amazon system. This email address is normalized into a canonical user representation once the grant
# has been sent back up to the S3 servers.
#
# grantee.email_address = 'joe@example.org'
#
# * By group - As of this writing you can not create custom groups, but Amazon provides three group that you can use. See the documentation for the
# Grantee.group= method for details.
#
# grantee.group = 'Authenticated'
class Grantee
include SelectiveAttributeProxy #:nodoc:
undef_method :id if method_defined?(:id) # Get rid of Object#id
def initialize(attributes = {})
# Set default values for attributes that may not be passed in but we still want the object
# to respond to
attributes = {'id' => nil, 'display_name' => nil, 'email_address' => nil, 'uri' => nil}.merge(attributes)
@attributes = attributes
extract_type!
yield self if block_given?
end
# The xml representation of the current grantee object.
def to_xml
Builder.new(self).to_s
end
# Returns the type of grantee. Will be one of <tt>CanonicalUser</tt>, <tt>AmazonCustomerByEmail</tt> or <tt>Group</tt>.
def type
return attributes['type'] if attributes['type']
# Lookups are in order of preference so if, for example, you set the uri but display_name and id are also
# set, we'd rather go with the canonical representation.
if display_name && id
'CanonicalUser'
elsif email_address
'AmazonCustomerByEmail'
elsif uri
'Group'
end
end
# Sets the grantee's group by name.
#
# grantee.group = 'AllUsers'
#
# Currently, valid groups defined by S3 are:
#
# * <tt>AllUsers</tt>: This group represents anyone. In other words, an anonymous request.
# * <tt>Authenticated</tt>: Any authenticated account on the S3 service.
# * <tt>LogDelivery</tt>: The entity that delivers bucket access logs.
def group=(group_name)
section = %w(AllUsers Authenticated).include?(group_name) ? 'global' : 's3'
self.uri = "http://acs.amazonaws.com/groups/#{section}/#{group_name}"
end
# Returns the grantee's group. If the grantee is not a group, <tt>nil</tt> is returned.
def group
return unless uri
uri[%r([^/]+$)]
end
def type_representation #:nodoc:
case type
when 'CanonicalUser' then display_name || id
when 'AmazonCustomerByEmail' then email_address
when 'Group' then "#{group} Group"
end
end
def inspect #:nodoc:
"#<%s:0x%s %s>" % [self.class, object_id, type_representation || '(type not set yet)']
end
private
def extract_type!
attributes['type'] = attributes.delete('xsi:type')
end
class Builder < XmlGenerator #:nodoc:
def initialize(grantee)
@grantee = grantee
super()
end
def build
xml.tag!('Grantee', attributes) do
representation
end
end
private
attr_reader :grantee
def representation
case grantee.type
when 'CanonicalUser'
xml.ID grantee.id
xml.DisplayName grantee.display_name
when 'AmazonCustomerByEmail'
xml.EmailAddress grantee.email_address
when 'Group'
xml.URI grantee.uri
end
end
def attributes
{'xsi:type' => grantee.type, 'xmlns:xsi' => 'http://www.w3.org/2001/XMLSchema-instance'}
end
end
end
module Bucket
def self.included(klass) #:nodoc:
klass.extend(ClassMethods)
end
module ClassMethods
# The acl method is the single point of entry for reading and writing access control list policies for a given bucket.
#
# # Fetch the acl for the 'marcel' bucket
# policy = Bucket.acl 'marcel'
#
# # Modify the policy ...
# # ...
#
# # Send updated policy back to the S3 servers
# Bucket.acl 'marcel', policy
def acl(name = nil, policy = nil)
if name.is_a?(ACL::Policy)
policy = name
name = nil
end
path = path(name) << '?acl'
respond_with ACL::Policy::Response do
policy ? put(path, {}, policy.to_xml) : ACL::Policy.new(get(path(name) << '?acl').policy)
end
end
end
# The acl method returns and updates the acl for a given bucket.
#
# # Fetch a bucket
# bucket = Bucket.find 'marcel'
#
# # Add a grant to the bucket's policy
# bucket.acl.grants << some_grant
#
# # Write the changes to the policy
# bucket.acl(bucket.acl)
def acl(reload = false)
policy = reload.is_a?(ACL::Policy) ? reload : nil
expirable_memoize(reload) do
self.class.acl(name, policy) if policy
self.class.acl(name)
end
end
end
module S3Object
def self.included(klass) #:nodoc:
klass.extend(ClassMethods)
end
module ClassMethods
# The acl method is the single point of entry for reading and writing access control list policies for a given object.
#
# # Fetch the acl for the 'kiss.jpg' object in the 'marcel' bucket
# policy = S3Object.acl 'kiss.jpg', 'marcel'
#
# # Modify the policy ...
# # ...
#
# # Send updated policy back to the S3 servers
# S3Object.acl 'kiss.jpg', 'marcel', policy
def acl(name, bucket = nil, policy = nil)
# We're using the second argument as the ACL::Policy
if bucket.is_a?(ACL::Policy)
policy = bucket
bucket = nil
end
bucket = bucket_name(bucket)
path = path!(bucket, name) << '?acl'
respond_with ACL::Policy::Response do
policy ? put(path, {}, policy.to_xml) : ACL::Policy.new(get(path).policy)
end
end
end
# The acl method returns and updates the acl for a given s3 object.
#
# # Fetch a the object
# object = S3Object.find 'kiss.jpg', 'marcel'
#
# # Add a grant to the object's
# object.acl.grants << some_grant
#
# # Write the changes to the policy
# object.acl(object.acl)
def acl(reload = false)
policy = reload.is_a?(ACL::Policy) ? reload : nil
expirable_memoize(reload) do
self.class.acl(key, bucket.name, policy) if policy
self.class.acl(key, bucket.name)
end
end
end
class OptionProcessor #:nodoc:
attr_reader :options
class << self
def process!(options)
new(options).process!
end
end
def initialize(options)
options.to_normalized_options!
@options = options
@access_level = extract_access_level
end
def process!
return unless access_level_specified?
validate!
options['x-amz-acl'] = access_level
end
private
def extract_access_level
options.delete('access') || options.delete('x-amz-acl')
end
def validate!
raise InvalidAccessControlLevel.new(valid_levels, access_level) unless valid?
end
def valid?
valid_levels.include?(access_level)
end
def access_level_specified?
!@access_level.nil?
end
def valid_levels
%w(private public-read public-read-write authenticated-read)
end
def access_level
@normalized_access_level ||= @access_level.to_header
end
end
end
end
end