Add a test to reproduce a bug in the read DMA API of
`encrypted_file_impl` (the file implementation for Encryption-at-Rest).
The test creates an encrypted file that contains padding, and then
attempts to read from an offset within the padding area. Although this
offset is invalid on the decrypted file, the `encrypted_file_impl` makes
no checks and proceeds with the decryption of padding data, which
eventually leads to bogus results.
Refs #22236.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
(cherry picked from commit 8f936b2cbc)
(cherry picked from commit 2fb95e4e2f)
Fixes#22236
If reading a file and not stopping on block bounds returned by `size()`, we could
allow reading from (_file_size+1-15) (block boundary) and try to decrypt this
buffer (last one).
Check on last block in `transform` would wrap around size due to us being >=
file size (l).
Simplest example:
Actual data size: 4095
Physical file size: 4095 + key block size (typically 16)
Read from 4096: -> 15 bytes (padding) -> transform return _file_size - read offset
-> wraparound -> rather larger number than we expected
(not to mention the data in question is junk/zero).
Just do an early bounds check and return zero if we're past the actual data limit.
v2:
* Moved check to a min expression instead
* Added lengthy comment
* Added unit test
v3:
* Fixed read_dma_bulk handling of short, unaligned read
* Added test for unaligned read
v4:
* Added another unaligned test case
(cherry picked from commit e96cc52668)
