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contentenc: update comments 

Also, replace one open-coded calculation with a
helper function.
This commit is contained in:
Jakob Unterwurzacher 2021-05-25 13:24:18 +02:00
parent 2a5ac3e9ba
commit bebd7ed81f
1 changed files with 5 additions and 3 deletions
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8
internal/contentenc/content.go
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@ -43,9 +43,11 @@ const (
type ContentEnc struct { type ContentEnc struct {
// Cryptographic primitives // Cryptographic primitives
cryptoCore *cryptocore.CryptoCore cryptoCore *cryptocore.CryptoCore
// Plaintext block size // plainBS is the plaintext block size. Usually 4096 bytes.
plainBS uint64 plainBS uint64
// Ciphertext block size // cipherBS is the ciphertext block size. Usually 4128 bytes.
// `cipherBS - plainBS`is the per-block overhead
// (use BlockOverhead() to calculate it for you!)
cipherBS uint64 cipherBS uint64
// All-zero block of size cipherBS, for fast compares // All-zero block of size cipherBS, for fast compares
allZeroBlock []byte allZeroBlock []byte
@ -302,7 +304,7 @@ func (be *ContentEnc) doEncryptBlock(plaintext []byte, blockNo uint64, fileID []
cBlock = cBlock[0:len(nonce)] cBlock = cBlock[0:len(nonce)]
// Encrypt plaintext and append to nonce // Encrypt plaintext and append to nonce
ciphertext := be.cryptoCore.AEADCipher.Seal(cBlock, nonce, plaintext, aData) ciphertext := be.cryptoCore.AEADCipher.Seal(cBlock, nonce, plaintext, aData)
overhead := int(be.cipherBS - be.plainBS) overhead := int(be.BlockOverhead())
if len(plaintext)+overhead != len(ciphertext) { if len(plaintext)+overhead != len(ciphertext) {
log.Panicf("unexpected ciphertext length: plaintext=%d, overhead=%d, ciphertext=%d", log.Panicf("unexpected ciphertext length: plaintext=%d, overhead=%d, ciphertext=%d",
len(plaintext), overhead, len(ciphertext)) len(plaintext), overhead, len(ciphertext))