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crypt: check for maximum length before decrypting filename

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The EME Transform() method will panic if the input data is larger than
2048 bytes.

Fixes #2826
This commit is contained in:
Garry McNulty 2018-12-18 20:35:41 +00:00 • committed by Nick Craig-Wood
parent c1dd76788d
commit 9cb3a68c38
2 changed files with 9 additions and 0 deletions
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4
backend/crypt/cipher.go
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@ -41,6 +41,7 @@ var (
ErrorBadDecryptControlChar = errors.New("bad decryption - contains control chars")
ErrorNotAMultipleOfBlocksize = errors.New("not a multiple of blocksize")
ErrorTooShortAfterDecode = errors.New("too short after base32 decode")
ErrorTooLongAfterDecode = errors.New("too long after base32 decode")
ErrorEncryptedFileTooShort = errors.New("file is too short to be encrypted")
ErrorEncryptedFileBadHeader = errors.New("file has truncated block header")
ErrorEncryptedBadMagic = errors.New("not an encrypted file - bad magic string")
@ -284,6 +285,9 @@ func (c *cipher) decryptSegment(ciphertext string) (string, error) {
// not possible if decodeFilename() working correctly
return "", ErrorTooShortAfterDecode
}
if len(rawCiphertext) > 2048 {
return "", ErrorTooLongAfterDecode
}
paddedPlaintext := eme.Transform(c.block, c.nameTweak[:], rawCiphertext, eme.DirectionDecrypt)
plaintext, err := pkcs7.Unpad(nameCipherBlockSize, paddedPlaintext)
if err != nil {