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contentenc: catch integer underflow in file size calculation

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If you truncate a ciphertext file to 19 bytes, you could get the
impression that the plaintext is 18446744073709551585 bytes long,
as reported by "ls -l".

Fix it by clamping the value to zero.
This commit is contained in:
Jakob Unterwurzacher 2017-03-06 23:50:17 +01:00
parent efc88346be
commit 2f953fdb95
1 changed files with 5 additions and 0 deletions
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5
internal/contentenc/offsets.go
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@ -54,6 +54,11 @@ func (be *ContentEnc) CipherSizeToPlainSize(cipherSize uint64) uint64 {
overhead := be.BlockOverhead()*blockCount + HeaderLen overhead := be.BlockOverhead()*blockCount + HeaderLen
if overhead > cipherSize {
tlog.Warn.Printf("cipherSize %d < overhead %d: corrupt file\n", cipherSize, overhead)
return 0
}
return cipherSize - overhead return cipherSize - overhead
} }