Richard Weinberger <richard@xxxxxx> writes:
> Using -S (--setuid) and -G (--setgid) one can select
> the uid/gid which will be used in the entered user namespace.
There is definitely utility here. I don't have a strong preference but
I am inclined to suggest that you remove the set_uid and set_gid
variables, and unconditionally call setuid and setgid when entering
a user namespace.
The only case where setting the uid and gid in a user namespace could be
problematic is where the uid/gid mapping has not been set. And entering
or running a user namespace with a mapping not setup is very unlikely to
be the common practice.
Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>
> Signed-off-by: Richard Weinberger <richard@xxxxxx>
> ---
> sys-utils/nsenter.c | 28 +++++++++++++++++++++++++++-
> 1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/sys-utils/nsenter.c b/sys-utils/nsenter.c
> index 106349c..7b2255c 100644
> --- a/sys-utils/nsenter.c
> +++ b/sys-utils/nsenter.c
> @@ -72,6 +72,8 @@ static void usage(int status)
> fputs(_(" -n, --net [=<file>] enter network namespace\n"), out);
> fputs(_(" -p, --pid [=<file>] enter pid namespace\n"), out);
> fputs(_(" -U, --user [=<file>] enter user namespace\n"), out);
> + fputs(_(" -S, --setuid <uid> set uid in user namespace\n"), out);
> + fputs(_(" -G, --setgid <gid> set gid in user namespace\n"), out);
> fputs(_(" -r, --root [=<dir>] set the root directory\n"), out);
> fputs(_(" -w, --wd [=<dir>] set the working directory\n"), out);
> fputs(_(" -F, --no-fork do not fork before exec'ing <program>\n"), out);
> @@ -169,6 +171,8 @@ int main(int argc, char *argv[])
> { "net", optional_argument, NULL, 'n' },
> { "pid", optional_argument, NULL, 'p' },
> { "user", optional_argument, NULL, 'U' },
> + { "setuid", required_argument, NULL, 'S' },
> + { "setgid", required_argument, NULL, 'G' },
> { "root", optional_argument, NULL, 'r' },
> { "wd", optional_argument, NULL, 'w' },
> { "no-fork", no_argument, NULL, 'F' },
> @@ -179,6 +183,10 @@ int main(int argc, char *argv[])
> int c, namespaces = 0;
> bool do_rd = false, do_wd = false;
> int do_fork = -1; /* unknown yet */
> + bool set_uid = false;
> + bool set_gid = false;
> + uid_t uid = 0;
> + gid_t gid = 0;
>
> setlocale(LC_MESSAGES, "");
> bindtextdomain(PACKAGE, LOCALEDIR);
> @@ -186,7 +194,7 @@ int main(int argc, char *argv[])
> atexit(close_stdout);
>
> while ((c =
> - getopt_long(argc, argv, "hVt:m::u::i::n::p::U::r::w::F",
> + getopt_long(argc, argv, "hVt:m::u::i::n::p::U::S:G:r::w::F",
> longopts, NULL)) != -1) {
> switch (c) {
> case 'h':
> @@ -234,6 +242,14 @@ int main(int argc, char *argv[])
> else
> namespaces |= CLONE_NEWUSER;
> break;
> + case 'S':
> + uid = strtoul_or_err(optarg, _("failed to parse uid"));
> + set_uid = true;
> + break;
> + case 'G':
> + gid = strtoul_or_err(optarg, _("failed to parse gid"));
> + set_gid = true;
> + break;
> case 'F':
> do_fork = 0;
> break;
> @@ -319,5 +335,15 @@ int main(int argc, char *argv[])
> execvp(argv[optind], argv + optind);
> err(EXIT_FAILURE, _("failed to execute %s"), argv[optind]);
> }
> +
> + if (namespaces & CLONE_NEWUSER) {
> + if (set_uid)
> + if (setuid(uid) < 0)
> + err(EXIT_FAILURE, _("setuid failed"));
> + if (set_gid)
> + if (setgid(gid) < 0)
> + err(EXIT_FAILURE, _("setgid failed"));
> + }
> +
> exec_shell();
> }
--
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