On 06/17/2016 09:44 AM, Peter Krempa wrote:
> Since introduction of the DAC security driver we've documented that
> seclabels with a leading + can be used with numerical uid. This would
> not work though with the rest of libvirt if the uid was not actually
> used in the system as we'd fail when trying to get a list of
> supplementary groups for the given uid. Since a uid without entry in
> /etc/passwd (or other user database) will not have any supplementary
> groups we can treat the failure to obtain them as such.
>
> This patch modifies virGetGroupList to not report the error for missing
> users and makes it return an empty list or just the group specified in
> @gid.
>
> All callers will grand less permissions in case of failure and thus this
> change is safe.
"grand less"? did you mean "gain less"?
ACK series (just typed out loud below)
John
> ---
> src/util/virutil.c | 31 ++++++++++++++++---------------
> 1 file changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/src/util/virutil.c b/src/util/virutil.c
> index 392091b..60da17b 100644
> --- a/src/util/virutil.c
> +++ b/src/util/virutil.c
> @@ -1120,29 +1120,30 @@ virGetGroupID(const char *group, gid_t *gid)
>
> /* Compute the list of primary and supplementary groups associated
> * with @uid, and including @gid in the list (unless it is -1),
> - * storing a malloc'd result into @list. Return the size of the list
> - * on success, or -1 on failure with error reported and errno set. May
> - * not be called between fork and exec. */
> + * storing a malloc'd result into @list. If uid is -1 or doesn't exist in the
> + * system database querying of the supplementary groups is skipped.
> + *
> + * Returns the size of the list on success, or -1 on failure with error
> + * reported and errno set. May not be called between fork and exec.
> + * */
> int
> virGetGroupList(uid_t uid, gid_t gid, gid_t **list)
> {
> - int ret = -1;
> + int ret = 0;
> char *user = NULL;
> gid_t primary;
>
> *list = NULL;
> - if (uid == (uid_t)-1)
> - return 0;
>
> - if (virGetUserEnt(uid, &user, &primary, NULL, NULL, false) < 0)
> - return -1;
> -
> - ret = mgetgroups(user, primary, list);
> - if (ret < 0) {
> - sa_assert(!*list);
> - virReportSystemError(errno,
> - _("cannot get group list for '%s'"), user);
> - goto cleanup;
> + /* invalid users have no supplementary groups */
> + if (uid != (uid_t)-1 &&
> + virGetUserEnt(uid, &user, &primary, NULL, NULL, true) >= 0) {
> + if ((ret = mgetgroups(user, primary, list)) < 0) {
> + virReportSystemError(errno,
> + _("cannot get group list for '%s'"), user);
> + ret = -1;
> + goto cleanup;
> + }
> }
Playing the "what if" game here. If for some reason uid == -1 OR
virGetUserEnt fails, then
gid - still to be determined
ret = 0
>
> if (gid != (gid_t)-1) {
>
If we enter this "if", then the for loop will exit immediately and the
VIR_APPEND_ELEMENT will append that gid onto *list which is IIRC what we
want. Then ret will be set to 1 (i) and we return. Otherwise if gid ==
-1, then we return 0, which is still fine.
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