76 lines
1.8 KiB
Go
76 lines
1.8 KiB
Go
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/*-
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* Copyright 2014 Square Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package josecipher
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import (
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"crypto"
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"encoding/binary"
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"hash"
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"io"
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)
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type concatKDF struct {
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z, info []byte
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i uint32
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cache []byte
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hasher hash.Hash
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}
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// NewConcatKDF builds a KDF reader based on the given inputs.
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func NewConcatKDF(hash crypto.Hash, z, algID, ptyUInfo, ptyVInfo, supPubInfo, supPrivInfo []byte) io.Reader {
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buffer := make([]byte, len(algID)+len(ptyUInfo)+len(ptyVInfo)+len(supPubInfo)+len(supPrivInfo))
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n := 0
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n += copy(buffer, algID)
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n += copy(buffer[n:], ptyUInfo)
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n += copy(buffer[n:], ptyVInfo)
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n += copy(buffer[n:], supPubInfo)
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copy(buffer[n:], supPrivInfo)
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hasher := hash.New()
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return &concatKDF{
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z: z,
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info: buffer,
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hasher: hasher,
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cache: []byte{},
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i: 1,
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}
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}
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func (ctx *concatKDF) Read(out []byte) (int, error) {
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copied := copy(out, ctx.cache)
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ctx.cache = ctx.cache[copied:]
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for copied < len(out) {
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ctx.hasher.Reset()
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// Write on a hash.Hash never fails
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_ = binary.Write(ctx.hasher, binary.BigEndian, ctx.i)
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_, _ = ctx.hasher.Write(ctx.z)
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_, _ = ctx.hasher.Write(ctx.info)
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hash := ctx.hasher.Sum(nil)
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chunkCopied := copy(out[copied:], hash)
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copied += chunkCopied
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ctx.cache = hash[chunkCopied:]
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ctx.i++
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}
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return copied, nil
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}
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