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Re: [Libguestfs] [PATCH] lib: update inspect_list_applications to return app_arch (RHBZ#859949)



On Mon, Oct 15, 2012 at 04:30:24PM -0400, John Eckersberg wrote:
> (Work in progress)
> 
> For now this only works for RPM, the others just return an empty string.
> ---
>  generator/structs.ml |  1 +
>  src/inspect-apps.c   | 88 +++++++++++++++++++++++++++++-----------------------
>  2 files changed, 51 insertions(+), 38 deletions(-)
> 
> diff --git a/generator/structs.ml b/generator/structs.ml
> index d62fcc5..8ac9fc5 100644
> --- a/generator/structs.ml
> +++ b/generator/structs.ml
> @@ -183,6 +183,7 @@ let structs = [
>      "app_epoch", FInt32;
>      "app_version", FString;
>      "app_release", FString;
> +    "app_arch", FString;
>      "app_install_path", FString;
>      "app_trans_path", FString;
>      "app_publisher", FString;

Unfortunately (and this a rather serious shortcoming of the generator)
you cannot add fields to an existing struct and maintain backwards
binary compatibility.  Let's not worry about this bit right now
though, I need to think about what to do a bit more.

> diff --git a/src/inspect-apps.c b/src/inspect-apps.c
> index f65c70a..3dbfb5b 100644
> --- a/src/inspect-apps.c
> +++ b/src/inspect-apps.c
> @@ -31,6 +31,7 @@
>  #ifdef HAVE_ENDIAN_H
>  #include <endian.h>
>  #endif
> +#include <arpa/inet.h>

Don't need this -- see below.

>  #include <pcre.h>
>  
> @@ -46,7 +47,7 @@ static struct guestfs_application_list *list_applications_rpm (guestfs_h *g, str
>  #endif
>  static struct guestfs_application_list *list_applications_deb (guestfs_h *g, struct inspect_fs *fs);
>  static struct guestfs_application_list *list_applications_windows (guestfs_h *g, struct inspect_fs *fs);
> -static void add_application (guestfs_h *g, struct guestfs_application_list *, const char *name, const char *display_name, int32_t epoch, const char *version, const char *release, const char *install_path, const char *publisher, const char *url, const char *description);
> +static void add_application (guestfs_h *g, struct guestfs_application_list *, const char *name, const char *display_name, int32_t epoch, const char *version, const char *release, const char *arch, const char *install_path, const char *publisher, const char *url, const char *description);
>  static void sort_applications (struct guestfs_application_list *);
>  
>  /* Unlike the simple inspect-get-* calls, this one assumes that the
> @@ -181,6 +182,37 @@ read_rpm_name (guestfs_h *g,
>    return 0;
>  }
>  
> +/* tag constants, see rpmtag.h in RPM for complete list */
> +#define RPMTAG_VERSION 1001
> +#define RPMTAG_RELEASE 1002
> +#define RPMTAG_ARCH    1022
> +
> +static char *
> +get_rpm_header_tag (guestfs_h *g, const void *header_start, size_t header_len, uint32_t tag)
> +{
> +  uint32_t num_fields, offset;
> +  const void *cursor = header_start + 8, *store;
> +
> +  /* This function parses the RPM header structure to pull out various
> +   * tag strings (version, release, arch, etc.).  For more detail on the
> +   * header format, see:
> +   * http://www.rpm.org/max-rpm/s1-rpm-file-format-rpm-file-format.html#S2-RPM-FILE-FORMAT-HEADER
> +   */
> +
> +  num_fields = ntohl (*(uint32_t *) header_start);

It's probably better to use the functions from <endian.h> like
'be32toh', 'le32toh' etc.  We already use them, eg. in
src/inspect-fs-windows.c.

> +  store = header_start + 8 + (16 * num_fields);
> +
> +  while (cursor < store ){
> +    if (ntohl (*(uint32_t *) cursor) == tag){
> +      offset = ntohl(*(uint32_t *) (cursor + 8));
> +      return safe_strdup(g, store + offset);
> +    }
> +    cursor += 16;

Can a malicious RPM in the guest cause an infinite loop in the host?

> +  }
> +
> +  return NULL;
> +}
> +
>  struct read_package_data {
>    struct rpm_names_list *list;
>    struct guestfs_application_list *apps;
> @@ -194,16 +226,13 @@ read_package (guestfs_h *g,
>  {
>    struct read_package_data *data = datav;
>    struct rpm_name nkey, *entry;
> -  char *p;
> -  size_t len;
> -  ssize_t max;
> -  char *nul_name_nul, *version, *release;
> +  char *version, *release, *arch;
>  
>    /* This function reads one (key, value) pair from the Packages
>     * database.  The key is the link field (see struct rpm_name).  The
> -   * value is a long binary string, but we can extract the version
> -   * number from it as below.  First we have to look up the link field
> -   * in the list of links (which is sorted by link field).
> +   * value is a long binary string, but we can extract the header data
> +   * from it as below.  First we have to look up the link field in the
> +   * list of links (which is sorted by link field).
>     */
>  
>    /* Ignore bogus entries. */
> @@ -219,41 +248,23 @@ read_package (guestfs_h *g,
>  
>    /* We found a matching link entry, so that gives us the application
>     * name (entry->name).  Now we can get other data for this
> -   * application out of the binary value string.  XXX This is a real
> -   * hack.
> +   * application out of the binary value string.
>     */
>  
> -  /* Look for \0<name>\0 */
> -  len = strlen (entry->name);
> -  nul_name_nul = safe_malloc (g, len + 2);
> -  nul_name_nul[0] = '\0';
> -  memcpy (&nul_name_nul[1], entry->name, len);
> -  nul_name_nul[len+1] = '\0';
> -  p = memmem (value, valuelen, nul_name_nul, len+2);
> -  free (nul_name_nul);
> -  if (!p)
> -    return 0;
> -
> -  /* Following that are \0-delimited version and release fields. */
> -  p += len + 2; /* Note we have to skip \0 + name + \0. */
> -  max = valuelen - (p - (char *) value);
> -  if (max < 0)
> -    max = 0;
> -  version = safe_strndup (g, p, max);
> -
> -  len = strlen (version);
> -  p += len + 1;
> -  max = valuelen - (p - (char *) value);
> -  if (max < 0)
> -    max = 0;
> -  release = safe_strndup (g, p, max);
> +  version = get_rpm_header_tag(g, value, valuelen, RPMTAG_VERSION);
> +  release = get_rpm_header_tag(g, value, valuelen, RPMTAG_RELEASE);
> +  arch = get_rpm_header_tag(g, value, valuelen, RPMTAG_ARCH);

Good, this seems like a considerable improvement.

>    /* Add the application and what we know. */
>    add_application (g, data->apps, entry->name, "", 0, version, release,
> -                   "", "", "", "");
> +                   arch ? arch : "(none)", "", "", "", "");

Don't use "(none)".  If you need a special value, use either "" or
"unknown" (I suspect in this case empty string), and document it in
the API (generator/actions.ml).

>    free (version);
>    free (release);
> +  if (arch)
> +    /* arch will occasionally be NULL, because some packages
> +     * (e.g. "gpgkeys") do not have an arch */
> +    free (arch);
>  
>    return 0;
>  }
> @@ -378,7 +389,7 @@ list_applications_deb (guestfs_h *g, struct inspect_fs *fs)
>      else if (STREQ (line, "")) {
>        if (installed_flag && name && version)
>          add_application (g, apps, name, "", 0, version, release ? : "",
> -                         "", "", "", "");
> +                         "", "", "", "", "");
>        free (name);
>        free (version);
>        free (release);
> @@ -519,7 +530,7 @@ list_applications_windows_from_path (guestfs_h *g,
>  
>          add_application (g, apps, name, display_name, 0,
>                           version ? : "",
> -                         "",
> +                         "", "",
>                           install_path ? : "",
>                           publisher ? : "",
>                           url ? : "",
> @@ -542,7 +553,7 @@ list_applications_windows_from_path (guestfs_h *g,
>  static void
>  add_application (guestfs_h *g, struct guestfs_application_list *apps,
>                   const char *name, const char *display_name, int32_t epoch,
> -                 const char *version, const char *release,
> +                 const char *version, const char *release, const char *arch,
>                   const char *install_path,
>                   const char *publisher, const char *url,
>                   const char *description)
> @@ -555,6 +566,7 @@ add_application (guestfs_h *g, struct guestfs_application_list *apps,
>    apps->val[apps->len-1].app_epoch = epoch;
>    apps->val[apps->len-1].app_version = safe_strdup (g, version);
>    apps->val[apps->len-1].app_release = safe_strdup (g, release);
> +  apps->val[apps->len-1].app_arch = safe_strdup (g, arch);
>    apps->val[apps->len-1].app_install_path = safe_strdup (g, install_path);
>    /* XXX Translated path is not implemented yet. */
>    apps->val[apps->len-1].app_trans_path = safe_strdup (g, "");
> -- 
> 1.7.11.4

Does it work?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v


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