forked from hardcoresushi/DroidFS
30 lines
827 B
Go
30 lines
827 B
Go
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package cryptocore
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import (
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"crypto/sha256"
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"log"
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"golang.org/x/crypto/hkdf"
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)
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const (
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// "info" data that HKDF mixes into the generated key to make it unique.
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// For convenience, we use a readable string.
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HkdfInfoEMENames = "EME filename encryption"
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hkdfInfoGCMContent = "AES-GCM file content encryption"
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hkdfInfoSIVContent = "AES-SIV file content encryption"
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)
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// hkdfDerive derives "outLen" bytes from "masterkey" and "info" using
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// HKDF-SHA256 (RFC 5869).
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// It returns the derived bytes or panics.
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func HkdfDerive(masterkey []byte, info string, outLen int) (out []byte) {
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h := hkdf.New(sha256.New, masterkey, nil, []byte(info))
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out = make([]byte, outLen)
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n, err := h.Read(out)
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if n != outLen || err != nil {
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log.Panicf("hkdfDerive: hkdf read failed, got %d bytes, error: %v", n, err)
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}
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return out
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}
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