From patchwork Thu Oct 19 16:51:55 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Jackson X-Patchwork-Id: 828277 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3yHwdw49d0z9t3B for ; Fri, 20 Oct 2017 04:19:32 +1100 (AEDT) Received: from localhost ([::1]:50379 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e5ETi-00049z-Kw for incoming@patchwork.ozlabs.org; Thu, 19 Oct 2017 13:19:30 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39013) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e5E3k-0006vv-14 for qemu-devel@nongnu.org; Thu, 19 Oct 2017 12:52:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e5E3g-0006pP-Ix for qemu-devel@nongnu.org; Thu, 19 Oct 2017 12:52:40 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:13261) by eggs.gnu.org with esmtps (TLS1.0:RSA_ARCFOUR_SHA1:16) (Exim 4.71) (envelope-from ) id 1e5E3g-0006oD-By for qemu-devel@nongnu.org; Thu, 19 Oct 2017 12:52:36 -0400 X-IronPort-AV: E=Sophos;i="5.43,402,1503360000"; d="scan'208";a="455062334" From: Ian Jackson To: Date: Thu, 19 Oct 2017 17:51:55 +0100 Message-ID: <1508431916-9412-8-git-send-email-ian.jackson@eu.citrix.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1508431916-9412-1-git-send-email-ian.jackson@eu.citrix.com> References: <1508431916-9412-1-git-send-email-ian.jackson@eu.citrix.com> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 66.165.176.63 Subject: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runas . facility X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Stefano Stabellini , Ian Jackson , Ross Lagerwall , Anthony PERARD , xen-devel@lists.xenproject.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" 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 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 --- v4: Changed to reuse option -runas v3: Error messages fixed. Thanks to Peter Maydell and Ross Lagerwall. v2: Coding style fixes. --- 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..9418bd4 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 .)\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..bdff99f 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