Re: [PATCH] Implement checksum verification for gunzip

[Andrei Borzenkov <arvidjaar@gmail.com>]

01.05.2016 15:32, Stefan Fritsch пишет:
> This implements the crc32 check for the gzip format. Support for zlib's
> adler checksum is not included, yet.
>     

That looks fine, but it is something for post 2.02. Ping if it gets forgot.

> diff --git a/contrib/grub2/grub-core/io/gzio.c b/contrib/grub2/grub-core/io/gzio.c
> index 0f2ea6b..432f0aa 100644
> --- a/contrib/grub2/grub-core/io/gzio.c
> +++ b/contrib/grub2/grub-core/io/gzio.c
> @@ -43,6 +43,7 @@
>  #include <grub/dl.h>
>  #include <grub/deflate.h>
>  #include <grub/i18n.h>
> +#include <grub/crypto.h>
>  
>  GRUB_MOD_LICENSE ("GPLv3+");
>  
> @@ -94,6 +95,14 @@ struct grub_gzio
>    struct huft *tl;
>    /* The distance code table.  */
>    struct huft *td;
> +  /* The checksum algorithm */
> +  const gcry_md_spec_t *hdesc;

Are different algorithms possible?

> +  /* The wanted checksum */
> +  grub_uint32_t orig_checksum;
> +  /* The uncompressed length */
> +  grub_size_t orig_len;
> +  /* Context for checksum calculation */
> +  grub_uint8_t *hcontext;
>    /* The lookup bits for the literal/length code table. */
>    int bl;
>    /* The lookup bits for the distance code table.  */
> @@ -180,7 +189,7 @@ test_gzip_header (grub_file_t file)
>      grub_uint8_t os_type;
>    } hdr;
>    grub_uint16_t extra_len;
> -  grub_uint32_t orig_len;
> +  grub_uint32_t crc32;
>    grub_gzio_t gzio = file->data;
>  
>    if (grub_file_tell (gzio->file) != 0)
> @@ -215,12 +224,15 @@ test_gzip_header (grub_file_t file)
>  
>    /* FIXME: don't do this on not easily seekable files.  */
>    {
> -    grub_file_seek (gzio->file, grub_file_size (gzio->file) - 4);
> -    if (grub_file_read (gzio->file, &orig_len, 4) != 4)
> +    grub_file_seek (gzio->file, grub_file_size (gzio->file) - 8);
> +    if (grub_file_read (gzio->file, &crc32, 4) != 4)
> +      return 0;
> +    gzio->orig_checksum = grub_le_to_cpu32 (crc32);
> +    if (grub_file_read (gzio->file, &gzio->orig_len, 4) != 4)
>        return 0;
>      /* FIXME: this does not handle files whose original size is over 4GB.
>         But how can we know the real original size?  */
> -    file->size = grub_le_to_cpu32 (orig_len);
> +    file->size = grub_le_to_cpu32 (gzio->orig_len);
>    }
>  
>    initialize_tables (gzio);
> @@ -1095,7 +1107,23 @@ inflate_window (grub_gzio_t gzio)
>  
>    gzio->saved_offset += gzio->wp;
>  
> -  /* XXX do CRC calculation here! */
> +  if (gzio->hcontext)
> +    {
> +      gzio->hdesc->write (gzio->hcontext, gzio->slide, gzio->wp);
> +
> +      if (gzio->saved_offset == gzio->orig_len)
> +	{
> +	  grub_uint32_t csum;
> +
> +	  gzio->hdesc->final (gzio->hcontext);
> +	  csum = *(grub_uint32_t *)gzio->hdesc->read (gzio->hcontext);
> +	  csum = grub_be_to_cpu32 (csum);
> +	  if (csum != gzio->orig_checksum)
> +	    grub_error (GRUB_ERR_BAD_COMPRESSED_DATA,
> +			"checksum mismatch %08x/%08x",
> +			gzio->orig_checksum, csum);
> +	}
> +    }
>  }
>  
>  
> @@ -1118,6 +1146,9 @@ initialize_tables (grub_gzio_t gzio)
>    huft_free (gzio->td);
>    gzio->tl = NULL;
>    gzio->td = NULL;
> +
> +  if (gzio->hcontext)
> +    gzio->hdesc->init(gzio->hcontext);
>  }
>  
>  
> @@ -1143,6 +1174,9 @@ grub_gzio_open (grub_file_t io, const char *name __attribute__ ((unused)))
>  
>    gzio->file = io;
>  
> +  gzio->hdesc = GRUB_MD_CRC32;
> +  gzio->hcontext = grub_malloc(gzio->hdesc->contextsize);
> +
>    file->device = io->device;
>    file->data = gzio;
>    file->fs = &grub_gzio_fs;
> @@ -1151,6 +1185,7 @@ grub_gzio_open (grub_file_t io, const char *name __attribute__ ((unused)))
>    if (! test_gzip_header (file))
>      {
>        grub_errno = GRUB_ERR_NONE;
> +      grub_free (gzio->hcontext);
>        grub_free (gzio);
>        grub_free (file);
>        grub_file_seek (io, 0);
> @@ -1287,6 +1322,7 @@ grub_gzio_close (grub_file_t file)
>    grub_file_close (gzio->file);
>    huft_free (gzio->tl);
>    huft_free (gzio->td);
> +  grub_free (gzio->hcontext);
>    grub_free (gzio);
>  
>    /* No need to close the same device twice.  */
> 
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