Re: [PATCH v1 3/3] lib: aes: reject an unciphered size larger than the ciphertext

On 2026-08-15T22:07:52, Pranav Rajendran <[email protected]> wrote:
> lib: aes: reject an unciphered size larger than the ciphertext
>
> image_aes_decrypt() allocates cipher_len bytes, decrypts into them, and
> then reports the plaintext length to its caller as
> info->size_unciphered, without relating the two. size_unciphered comes
> from the image's 'data-size-unciphered' property, so an image can claim
> a plaintext larger than the buffer that was allocated for it.
>
> fit_image_uncipher() propagates that length as the image size, and
> everything downstream - the load, the copy to the entry point - works
> from it, reading up to 4 GiB past the end of the decrypted buffer.
>
> Unlike the image data itself, 'data-size-unciphered' is not covered by
> the per-image hash or signature, so this is reachable on a signed FIT
> whose signature still verifies.
>
> Decryption produces exactly cipher_len bytes, so require the claimed
> size to fit within that.
>
> Fixes: 4df3578119b0 ("u-boot: fit: add support to decrypt fit with aes")
> Signed-off-by: Pranav Rajendran <[email protected]>
>
> lib/aes/aes-decrypt.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Reviewed-by: Simon Glass <[email protected]>