Re: [PATCH RESEND v3 05/10] crypto: Mark the payload_offset_sector invalid for detached LUKS header

[Daniel P . Berrangé]

On Mon, Dec 25, 2023 at 01:45:07PM +0800, Hyman Huang wrote:
> Set the payload_offset_sector to a value that is nearly never reached
> in order to mark it as invalid and indicate that 0 should be the offset
> of the read/write operation on the 'file' protocol blockdev node.
> 
> Signed-off-by: Hyman Huang <yong.huang@smartx.com>
> ---
>  crypto/block-luks.c | 41 +++++++++++++++++++++++++++++++----------
>  1 file changed, 31 insertions(+), 10 deletions(-)
> 
> diff --git a/crypto/block-luks.c b/crypto/block-luks.c
> index fb01ec38bb..48443ffcae 100644
> --- a/crypto/block-luks.c
> +++ b/crypto/block-luks.c
> @@ -34,6 +34,8 @@
>  
>  #include "qemu/bitmap.h"
>  
> +#define INVALID_SECTOR_OFFSET UINT32_MAX
> +
>  /*
>   * Reference for the LUKS format implemented here is
>   *
> @@ -136,6 +138,13 @@ struct QCryptoBlockLUKS {
>  };
>  
>  
> +static inline uint32_t
> +qcrypto_block_luks_payload_offset(uint32_t sector)
> +{
> +    return sector == INVALID_SECTOR_OFFSET ? 0 :
> +        sector * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
> +}
> +
>  static int qcrypto_block_luks_cipher_name_lookup(const char *name,
>                                                   QCryptoCipherMode mode,
>                                                   uint32_t key_bytes,
> @@ -1255,8 +1264,8 @@ qcrypto_block_luks_open(QCryptoBlock *block,
>      }
>  
>      block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
> -    block->payload_offset = luks->header.payload_offset_sector *
> -        block->sector_size;
> +    block->payload_offset =
> +        
> qcrypto_block_luks_payload_offset(luks->header.payload_offset_sector);
>  
>      return 0;
>  
> @@ -1529,16 +1538,28 @@ qcrypto_block_luks_create(QCryptoBlock *block,
>          slot->stripes = QCRYPTO_BLOCK_LUKS_STRIPES;
>      }
>  
> -    /* The total size of the LUKS headers is the partition header + key
> -     * slot headers, rounded up to the nearest sector, combined with
> -     * the size of each master key material region, also rounded up
> -     * to the nearest sector */
> -    luks->header.payload_offset_sector = header_sectors +
> -            QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS * split_key_sectors;
> +    if (block->detached_header) {
> +        /*
> +         * Set the payload_offset_sector to a value that is nearly never
> +         * reached in order to mark it as invalid and indicate that 0 should
> +         * be the offset of the read/write operation on the 'file' protocol
> +         * blockdev node. Here the UINT32_MAX is choosed
> +         */
> +        luks->header.payload_offset_sector = INVALID_SECTOR_OFFSET;

We should be setting payload offset to 0 when using a detached header
to match behaviour of 'cryptsetup' tools.

> +    } else {
> +        /*
> +         * The total size of the LUKS headers is the partition header + key
> +         * slot headers, rounded up to the nearest sector, combined with
> +         * the size of each master key material region, also rounded up
> +         * to the nearest sector
> +         */
> +        luks->header.payload_offset_sector = header_sectors +
> +                QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS * split_key_sectors;
> +    }
>  
>      block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
> -    block->payload_offset = luks->header.payload_offset_sector *
> -        block->sector_size;
> +    block->payload_offset =
> +        
> qcrypto_block_luks_payload_offset(luks->header.payload_offset_sector);
>  
>      /* Reserve header space to match payload offset */
>      initfunc(block, block->payload_offset, opaque, &local_err);
> -- 
> 2.39.1
> 

With regards,
Daniel
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