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Re: [Libguestfs] [PATCH 3/3] lib: Add support for creating nodes (keys) and values with UTF-16LE-encoded names



On Sun, Nov 24, 2013 at 11:25:53PM +0100, Hilko Bengen wrote:
> ---
>  lib/write.c | 49 ++++++++++++++++++++++++++++++++++---------------
>  1 file changed, 34 insertions(+), 15 deletions(-)
> 
> diff --git a/lib/write.c b/lib/write.c
> index dbb8292..72b1f8a 100644
> --- a/lib/write.c
> +++ b/lib/write.c
> @@ -608,9 +608,17 @@ hivex_node_add_child (hive_h *h, hive_node_h parent, const char *name)
>      return 0;
>    }
>  
> +  size_t recoded_name_len;
> +  int use_utf16 = 0;
> +  char* recoded_name = _hivex_encode_string (name, &recoded_name_len, &use_utf16);
> +  if (recoded_name == NULL) {
> +    SET_ERRNO (EINVAL, "malformed name");
> +    return 0;
> +  }
> +
>    /* Create the new nk-record. */
>    static const char nk_id[2] = { 'n', 'k' };
> -  size_t seg_len = sizeof (struct ntreg_nk_record) + strlen (name);
> +  size_t seg_len = sizeof (struct ntreg_nk_record) + recoded_name_len;
>    hive_node_h nkoffset = allocate_block (h, seg_len, nk_id);
>    if (nkoffset == 0)
>      return 0;
> @@ -619,14 +627,18 @@ hivex_node_add_child (hive_h *h, hive_node_h parent, const char *name)
>  
>    struct ntreg_nk_record *nk =
>      (struct ntreg_nk_record *) ((char *) h->addr + nkoffset);
> -  nk->flags = htole16 (0x0020); /* key is ASCII. */
> +  if (use_utf16)
> +    nk->flags = htole16 (0x0000);
> +  else
> +    nk->flags = htole16 (0x0020);
>    nk->parent = htole32 (parent - 0x1000);
>    nk->subkey_lf = htole32 (0xffffffff);
>    nk->subkey_lf_volatile = htole32 (0xffffffff);
>    nk->vallist = htole32 (0xffffffff);
>    nk->classname = htole32 (0xffffffff);
> -  nk->name_len = htole16 (strlen (name));
> -  strcpy (nk->name, name);
> +  nk->name_len = htole16 (recoded_name_len);
> +  memcpy (nk->name, recoded_name, recoded_name_len);
> +  free(recoded_name);

Please put spaces after function names!  It improves readability:

http://www1.psych.purdue.edu/~zpizlo/rsteinma/Bob-FOR%20CV/Epelboim%20et%20al%201997%20Fillers%20in%20Reading.pdf

>    /* Inherit parent sk. */
>    struct ntreg_nk_record *parent_nk =
> @@ -719,9 +731,9 @@ hivex_node_add_child (hive_h *h, hive_node_h parent, const char *name)
>    parent_nk->nr_subkeys = htole32 (nr_subkeys_in_parent_nk);
>  
>    /* Update max_subkey_name_len in parent nk. */
> -  uint16_t max = le16toh (parent_nk->max_subkey_name_len);
> -  if (max < strlen (name) * 2)  /* *2 because "recoded" in UTF16-LE. */
> -    parent_nk->max_subkey_name_len = htole16 (strlen (name) * 2);
> +  size_t utf16_len = use_utf16 ? recoded_name_len : recoded_name_len * 2;

* 2 is probably wrong here for non-BMP characters, but the original
code makes the same mistake ...  Could we get the true length from the
hivex_encode_string function?

> +  if (le16toh (parent_nk->max_subkey_name_len) < utf16_len)
> +    parent_nk->max_subkey_name_len = htole16 (utf16_len);
>    return nkoffset;
>  }
> @@ -942,7 +954,12 @@ hivex_node_set_values (hive_h *h, hive_node_h node,
>    for (i = 0; i < nr_values; ++i) {
>      /* Allocate vk record to store this (key, value) pair. */
>      static const char vk_id[2] = { 'v', 'k' };
> -    seg_len = sizeof (struct ntreg_vk_record) + strlen (values[i].key);
> +    size_t name_len = strlen (values[i].key);
> +    size_t recoded_name_len;
> +    int use_utf16;
> +    char* recoded_name = _hivex_encode_string (values[i].key, &recoded_name_len,
> +                                               &use_utf16);
> +    seg_len = sizeof (struct ntreg_vk_record) + recoded_name_len;
>      size_t vk_offs = allocate_block (h, seg_len, vk_id);
>      if (vk_offs == 0)
>        return -1;
> @@ -957,15 +974,17 @@ hivex_node_set_values (hive_h *h, hive_node_h node,
>  
>      struct ntreg_vk_record *vk =
>        (struct ntreg_vk_record *) ((char *) h->addr + vk_offs);
> -    size_t name_len = strlen (values[i].key);
> -    vk->name_len = htole16 (name_len);
> -    strcpy (vk->name, values[i].key);
> +    vk->name_len = htole16 (recoded_name_len);
> +    memcpy (vk->name, recoded_name, recoded_name_len);
>      vk->data_type = htole32 (values[i].t);
>      uint32_t len = values[i].len;
>      if (len <= 4)               /* store it inline => set MSB flag */
>        len |= 0x80000000;
>      vk->data_len = htole32 (len);
> -    vk->flags = name_len == 0 ? 0 : 1;
> +    if (recoded_name_len == 0)
> +      vk->flags = 0;
> +    else
> +      vk->flags = htole16 (!use_utf16);
>      if (values[i].len <= 4)     /* store it inline */
>        memcpy (&vk->data_offset, values[i].value, values[i].len);
> @@ -985,9 +1004,9 @@ hivex_node_set_values (hive_h *h, hive_node_h node,
>        vk->data_offset = htole32 (offs - 0x1000);
>      }
>  
> -    if (name_len * 2 > le32toh (nk->max_vk_name_len))
> -      /* * 2 for UTF16-LE "reencoding" */
> -      nk->max_vk_name_len = htole32 (name_len * 2);
> +    size_t utf16_len = use_utf16 ? recoded_name_len : recoded_name_len * 2;

* 2 - see above.

> +    if (utf16_len > le32toh (nk->max_vk_name_len))
> +      nk->max_vk_name_len = htole32 (utf16_len);
>      if (values[i].len > le32toh (nk->max_vk_data_len))
>        nk->max_vk_data_len = htole32 (values[i].len);
>    }
> -- 
> 1.8.4.4

2/3 & 3/3 are generally good, so ACK.  Any comment on *2 issue above?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
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