64 lines
1.3 KiB
Go
64 lines
1.3 KiB
Go
package nano
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import (
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"bytes"
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"crypto/sha512"
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"github.com/pkg/errors"
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)
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const (
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App = 0x80
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Init = 0x00
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Update = 0x01
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Digest = 0x02
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MaxChunk = 253
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KeyLength = 32
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SigLength = 64
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)
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var separator = []byte{0, 0xCA, 0xFE, 0}
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func generateSignRequests(payload []byte) [][]byte {
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// nice one-shot
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digest := []byte{App, Digest}
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if len(payload) < MaxChunk {
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return [][]byte{append(digest, payload...)}
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}
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// large payload is multi-chunk
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result := [][]byte{{App, Init}}
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update := []byte{App, Update}
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for len(payload) > MaxChunk {
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msg := append(update, payload[:MaxChunk]...)
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payload = payload[MaxChunk:]
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result = append(result, msg)
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}
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result = append(result, append(update, payload...))
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result = append(result, digest)
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return result
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}
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func parseDigest(resp []byte) (key, sig []byte, err error) {
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if resp[0] != App || resp[1] != Digest {
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return nil, nil, errors.New("Invalid header")
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}
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resp = resp[2:]
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if len(resp) != KeyLength+SigLength+len(separator) {
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return nil, nil, errors.Errorf("Incorrect length: %d", len(resp))
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}
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key, resp = resp[:KeyLength], resp[KeyLength:]
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if !bytes.Equal(separator, resp[:len(separator)]) {
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return nil, nil, errors.New("Cannot find 0xCAFE")
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}
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sig = resp[len(separator):]
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return key, sig, nil
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}
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func hashMsg(data []byte) []byte {
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res := sha512.Sum512(data)
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return res[:]
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}
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