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// Copyright 2016 Google LLC. All Rights Reserved.
//
// 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.
package fixchain
import (
"crypto/sha256"
"sort"
"github.com/google/certificate-transparency-go/x509"
)
const hashSize = sha256.Size
var newHash = sha256.New
func hash(c *x509.Certificate) (hash [hashSize]byte) {
copy(hash[:], newHash().Sum(c.Raw))
return
}
func hashChain(ch []*x509.Certificate) (hash [hashSize]byte) {
h := newHash()
for _, c := range ch {
h.Write(newHash().Sum(c.Raw))
}
copy(hash[:], h.Sum(nil))
return
}
// hashBag hashes all of the certs in the chain, irrespective of their order.
// Chains containing the same certs in the same order with no duplicates will
// result in the same hash. Chains containing the same certs in different orders
// with no duplicates will result in the same hash. Chains containing the same
// certs (either in the same order or in different orders) that contain exactly
// the same duplicated certs, will result in the same hash. If chains contain
// the same certs (either in the same order or in different orders) and some
// certs are duplicated, but the specific certs that are duplicated differ
// and/or the number of times they are duplicated differ, these chains will
// result in different hashes.
func hashBag(chain []*x509.Certificate) [hashSize]byte {
b := bag{certs: make([]*x509.Certificate, len(chain))}
copy(b.certs, chain)
sort.Sort(b)
return hashChain(b.certs)
}
// bag is a collection of certificates that can contain duplicates.
// Applying sort will order them by their raw representation.
type bag struct {
certs []*x509.Certificate
}
// Len implements sort.Sort(data Interface) for bag.
func (b bag) Len() int { return len(b.certs) }
// Less implements sort.Sort(data Interface) for bag.
func (b bag) Less(i, j int) bool {
ci := b.certs[i].Raw
cj := b.certs[j].Raw
if len(ci) != len(cj) {
return len(ci) < len(cj)
}
for n := range ci {
if ci[n] < cj[n] {
return true
}
if ci[n] > cj[n] {
return false
}
}
return false
}
// Swap implements sort.Sort(data Interface) for bag.
func (b bag) Swap(i, j int) {
t := b.certs[i]
b.certs[i] = b.certs[j]
b.certs[j] = t
}
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