67 lines
1.4 KiB
Go
67 lines
1.4 KiB
Go
package concatkdf
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import (
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"crypto"
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"encoding/binary"
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"fmt"
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)
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type KDF struct {
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buf []byte
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otherinfo []byte
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z []byte
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hash crypto.Hash
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}
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func ndata(src []byte) []byte {
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buf := make([]byte, 4+len(src))
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binary.BigEndian.PutUint32(buf, uint32(len(src)))
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copy(buf[4:], src)
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return buf
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}
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func New(hash crypto.Hash, alg, Z, apu, apv, pubinfo, privinfo []byte) *KDF {
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algbuf := ndata(alg)
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apubuf := ndata(apu)
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apvbuf := ndata(apv)
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concat := make([]byte, len(algbuf)+len(apubuf)+len(apvbuf)+len(pubinfo)+len(privinfo))
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n := copy(concat, algbuf)
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n += copy(concat[n:], apubuf)
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n += copy(concat[n:], apvbuf)
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n += copy(concat[n:], pubinfo)
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copy(concat[n:], privinfo)
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return &KDF{
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hash: hash,
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otherinfo: concat,
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z: Z,
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}
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}
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func (k *KDF) Read(out []byte) (int, error) {
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var round uint32 = 1
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h := k.hash.New()
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for len(out) > len(k.buf) {
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h.Reset()
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if err := binary.Write(h, binary.BigEndian, round); err != nil {
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return 0, fmt.Errorf(`failed to write round using kdf: %w`, err)
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}
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if _, err := h.Write(k.z); err != nil {
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return 0, fmt.Errorf(`failed to write z using kdf: %w`, err)
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}
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if _, err := h.Write(k.otherinfo); err != nil {
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return 0, fmt.Errorf(`failed to write other info using kdf: %w`, err)
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}
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k.buf = append(k.buf, h.Sum(nil)...)
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round++
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}
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n := copy(out, k.buf[:len(out)])
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k.buf = k.buf[len(out):]
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return n, nil
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}
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