/
digest_utils.rb
156 lines (142 loc) · 4.25 KB
/
digest_utils.rb
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require 'digest/md5'
require 'digest/sha1'
require 'digest/sha2'
require 'set'
module Sprockets
# Internal: Hash functions and digest related utilities. Mixed into
# Environment.
module DigestUtils
extend self
# Internal: Default digest class.
#
# Returns a Digest::Base subclass.
def digest_class
Digest::SHA256
end
# Internal: Maps digest bytesize to the digest class.
DIGEST_SIZES = {
16 => Digest::MD5,
20 => Digest::SHA1,
32 => Digest::SHA256,
48 => Digest::SHA384,
64 => Digest::SHA512
}
# Internal: Detect digest class hash algorithm for digest bytes.
#
# While not elegant, all the supported digests have a unique bytesize.
#
# Returns Digest::Base or nil.
def detect_digest_class(bytes)
DIGEST_SIZES[bytes.bytesize]
end
# Internal: Generate a hexdigest for a nested JSON serializable object.
#
# This is used for generating cache keys, so its pretty important its
# wicked fast. Microbenchmarks away!
#
# obj - A JSON serializable object.
#
# Returns a String digest of the object.
def digest(obj)
digest = digest_class.new
queue = [obj]
while queue.length > 0
obj = queue.shift
klass = obj.class
if klass == String
digest << obj
elsif klass == Symbol
digest << 'Symbol'
digest << obj.to_s
elsif klass == Fixnum
digest << 'Fixnum'
digest << obj.to_s
elsif klass == Bignum
digest << 'Bignum'
digest << obj.to_s
elsif klass == TrueClass
digest << 'TrueClass'
elsif klass == FalseClass
digest << 'FalseClass'
elsif klass == NilClass
digest << 'NilClass'
elsif klass == Array
digest << 'Array'
queue.concat(obj)
elsif klass == Hash
digest << 'Hash'
queue.concat(obj.sort)
elsif klass == Set
digest << 'Set'
queue.concat(obj.to_a)
elsif klass == Encoding
digest << 'Encoding'
digest << obj.name
else
raise TypeError, "couldn't digest #{klass}"
end
end
digest.digest
end
# Internal: Pack a binary digest to a hex encoded string.
#
# bin - String bytes
#
# Returns hex String.
def pack_hexdigest(bin)
bin.unpack('H*').first
end
# Internal: Pack a binary digest to a base64 encoded string.
#
# bin - String bytes
#
# Returns base64 String.
def pack_base64digest(bin)
[bin].pack('m0')
end
# Internal: Pack a binary digest to a urlsafe base64 encoded string.
#
# bin - String bytes
#
# Returns urlsafe base64 String.
def pack_urlsafe_base64digest(bin)
str = pack_base64digest(bin)
str.tr!('+/'.freeze, '-_'.freeze)
str.tr!('='.freeze, ''.freeze)
str
end
# Internal: Maps digest class to the named information hash algorithm name.
#
# http://www.iana.org/assignments/named-information/named-information.xhtml
NI_HASH_ALGORITHMS = {
Digest::SHA256 => 'sha-256'.freeze,
Digest::SHA384 => 'sha-384'.freeze,
Digest::SHA512 => 'sha-512'.freeze
}
# Internal: Generate a "named information" URI for use in the `integrity`
# attribute of an asset tag as per the subresource integrity specification.
#
# digest - The String byte digest of the asset content.
# content_type - The content-type the asset will be served with. This *must*
# be accurate if provided. Otherwise, subresource integrity
# will block the loading of the asset.
#
# Returns a String or nil if hash algorithm is incompatible.
def integrity_uri(digest, content_type = nil)
case digest
when Digest::Base
digest_class = digest.class
digest = digest.digest
when String
digest_class = DIGEST_SIZES[digest.bytesize]
else
raise TypeError, "unknown digest: #{digest.inspect}"
end
if hash_name = NI_HASH_ALGORITHMS[digest_class]
uri = "ni:///#{hash_name};#{pack_urlsafe_base64digest(digest)}"
uri << "?ct=#{content_type}" if content_type
uri
end
end
end
end