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Re: [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gi
From: |
Stefano Stabellini |
Subject: |
Re: [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gid> facility |
Date: |
Thu, 26 Oct 2017 15:29:24 -0700 (PDT) |
User-agent: |
Alpine 2.10 (DEB 1266 2009-07-14) |
CC'ing the maintainers (scripts/get_maintainer.pl is your friend)
On Fri, 20 Oct 2017, Ian Jackson wrote:
> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry. This will be useful in certain
> Xen configurations.
>
> We don't support just -runas <uid> because: (i) deprivileging without
> calling setgroups would be ineffective (ii) given only a uid we don't
> know what gid we ought to use (since uids may eppear in multiple
> passwd file entries with different gids).
>
> Signed-off-by: Ian Jackson <address@hidden>
> ---
> v5: Use : rather than . to separate uid from gid
> v4: Changed to reuse option -runas
> v3: Error messages fixed. Thanks to Peter Maydell and Ross Lagerwall.
> v2: Coding style fixes.
>
> squash! os-posix: Provide new -runas <uid>.<gid> facility
> ---
> os-posix.c | 64
> +++++++++++++++++++++++++++++++++++++++++++++++----------
> qemu-options.hx | 3 ++-
> 2 files changed, 55 insertions(+), 12 deletions(-)
>
> diff --git a/os-posix.c b/os-posix.c
> index 92e9d85..f95b7bf 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -43,6 +43,8 @@
> #endif
>
> static struct passwd *user_pwd;
> +static uid_t user_uid = (uid_t)-1;
> +static gid_t user_gid = (gid_t)-1;
> static const char *chroot_dir;
> static int daemonize;
> static int daemon_pipe;
> @@ -128,6 +130,34 @@ void os_set_proc_name(const char *s)
> #endif
> }
>
> +
> +static bool os_parse_runas_uid_gid(const char *optarg)
> +{
> + unsigned long lv;
> + char *ep;
> + uid_t got_uid;
> + gid_t got_gid;
> + int rc;
> +
> + errno = 0;
> + lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep==':' */
> + got_uid = lv; /* overflow here is ID in C99 */
> + if (errno || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
> + return false;
> + }
> +
> + lv = 0;
> + rc = qemu_strtoul(ep + 1, 0, 0, &lv);
> + got_gid = lv; /* overflow here is ID in C99 */
> + if (rc || got_gid != lv || got_gid == (gid_t)-1) {
> + return false;
> + }
> +
> + user_uid = got_uid;
> + user_gid = got_gid;
> + return true;
> +}
> +
> /*
> * Parse OS specific command line options.
> * return 0 if option handled, -1 otherwise
> @@ -145,8 +175,10 @@ void os_parse_cmd_args(int index, const char *optarg)
> #endif
> case QEMU_OPTION_runas:
> user_pwd = getpwnam(optarg);
> - if (!user_pwd) {
> - fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
> + if (!user_pwd && !os_parse_runas_uid_gid(optarg)) {
> + fprintf(stderr,
> + "User \"%s\" doesn't exist (and is not <uid>.<gid>)\n",
> + optarg);
> exit(1);
> }
> break;
> @@ -166,18 +198,28 @@ void os_parse_cmd_args(int index, const char *optarg)
>
> static void change_process_uid(void)
> {
> - if (user_pwd) {
> - if (setgid(user_pwd->pw_gid) < 0) {
> - fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> + if (user_pwd || user_uid != (uid_t)-1) {
> + gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
> + uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
> + if (setgid(intended_gid) < 0) {
> + fprintf(stderr, "Failed to setgid(%d)\n", intended_gid);
> exit(1);
> }
> - if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> - fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
> - user_pwd->pw_name, user_pwd->pw_gid);
> - exit(1);
> + if (user_pwd) {
> + if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> + fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
> + user_pwd->pw_name, user_pwd->pw_gid);
> + exit(1);
> + }
> + } else {
> + if (setgroups(1, &user_gid) < 0) {
> + fprintf(stderr, "Failed to setgroups(1, [%d])",
> + user_gid);
> + exit(1);
> + }
> }
> - if (setuid(user_pwd->pw_uid) < 0) {
> - fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
> + if (setuid(intended_uid) < 0) {
> + fprintf(stderr, "Failed to setuid(%d)\n", intended_uid);
> exit(1);
> }
> if (setuid(0) != -1) {
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9f6e2ad..f707197e 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3958,7 +3958,8 @@ ETEXI
>
> #ifndef _WIN32
> DEF("runas", HAS_ARG, QEMU_OPTION_runas, \
> - "-runas user change to user id user just before starting the VM\n",
> + "-runas user change to user id user just before starting the VM\n" \
> + " user can be numeric uid:gid instead\n",
> QEMU_ARCH_ALL)
> #endif
> STEXI
> --
> 2.1.4
>
- Re: [Qemu-devel] [PATCH v5.1 6/8] xen: destroy_hvm_domain: Try xendevicemodel_shutdown, (continued)
- [Qemu-devel] [PATCH v5.1 4/8] xen: destroy_hvm_domain: Move reason into a variable, Ian Jackson, 2017/10/20
- Re: [Qemu-devel] [PATCH v5.1 4/8] xen: destroy_hvm_domain: Move reason into a variable, Stefano Stabellini, 2017/10/26
- [Qemu-devel] [PATCH v5.1 2/8] xen: restrict: use xentoolcore_restrict_all, Ian Jackson, 2017/10/20
- Re: [Qemu-devel] [PATCH v5.1 2/8] xen: restrict: use xentoolcore_restrict_all, Stefano Stabellini, 2017/10/26
- Re: [Qemu-devel] [PATCH v5.1 2/8] xen: restrict: use xentoolcore_restrict_all, Ian Jackson, 2017/10/27
- [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gid> facility, Ian Jackson, 2017/10/20
- Re: [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gid> facility, Anthony PERARD, 2017/10/24
- Re: [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gid> facility, Ian Jackson, 2017/10/24
- Re: [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gid> facility,
Stefano Stabellini <=
- Re: [Qemu-devel] [PATCH v5.1 7/8] os-posix: Provide new -runas <uid>:<gid> facility, Ian Jackson, 2017/10/27
- [Qemu-devel] [PATCH v5.1 5/8] xen: move xc_interface compatibility fallback further up the file, Ian Jackson, 2017/10/20
- Re: [Qemu-devel] [PATCH v5.1 5/8] xen: move xc_interface compatibility fallback further up the file, Stefano Stabellini, 2017/10/26
- Re: [Qemu-devel] [PATCH v5.1 1/8] xen: link against xentoolcore, Stefano Stabellini, 2017/10/26
- Re: [Qemu-devel] [PATCH v5.1 1/8] xen: link against xentoolcore, Ian Jackson, 2017/10/27
Re: [Qemu-devel] [PATCH v5 0/8] xen: xen-domid-restrict improvements, no-reply, 2017/10/21