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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
ADD_VALUE_TO_DIGEST = {
String => ->(val, digest) { digest << val },
FalseClass => ->(val, digest) { digest << 'FalseClass'.freeze },
TrueClass => ->(val, digest) { digest << 'TrueClass'.freeze },
NilClass => ->(val, digest) { digest << 'NilClass'.freeze },
Symbol => ->(val, digest) {
digest << 'Symbol'.freeze
digest << val.to_s
},
Fixnum => ->(val, digest) {
digest << 'Fixnum'.freeze
digest << val.to_s
},
Bignum => ->(val, digest) {
digest << 'Bignum'.freeze
digest << val.to_s
},
Array => ->(val, digest) {
digest << 'Array'.freeze
val.each do |element|
ADD_VALUE_TO_DIGEST[element.class].call(element, digest)
end
},
Hash => ->(val, digest) {
digest << 'Hash'.freeze
val.sort.each do |array|
ADD_VALUE_TO_DIGEST[Array].call(array, digest)
end
},
Set => ->(val, digest) {
digest << 'Set'.freeze
ADD_VALUE_TO_DIGEST[Array].call(val.to_a, digest)
},
Encoding => ->(val, digest) {
digest << 'Encoding'.freeze
digest << val.name
},
}
ADD_VALUE_TO_DIGEST.default_proc = ->(_, val) {
raise TypeError, "couldn't digest #{ val }"
}
private_constant :ADD_VALUE_TO_DIGEST
# 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
ADD_VALUE_TO_DIGEST[obj.class].call(obj, digest)
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: Unpack a hex encoded digest string into binary bytes.
#
# hex - String hex
#
# Returns binary String.
def unpack_hexdigest(hex)
[hex].pack('H*')
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 CSP hash algorithm name.
HASH_ALGORITHMS = {
Digest::SHA256 => 'sha256'.freeze,
Digest::SHA384 => 'sha384'.freeze,
Digest::SHA512 => 'sha512'.freeze
}
# Public: Generate hash 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.
#
# Returns a String or nil if hash algorithm is incompatible.
def integrity_uri(digest)
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 = HASH_ALGORITHMS[digest_class]
"#{hash_name}-#{pack_base64digest(digest)}"
end
end
# Public: Generate hash for use in the `integrity` attribute of an asset tag
# as per the subresource integrity specification.
#
# digest - The String hexbyte digest of the asset content.
#
# Returns a String or nil if hash algorithm is incompatible.
def hexdigest_integrity_uri(hexdigest)
integrity_uri(unpack_hexdigest(hexdigest))
end
end
end
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