From patchwork Thu Apr 19 16:45:13 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Jackson X-Patchwork-Id: 10351355 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id D20BA602B7 for ; Thu, 19 Apr 2018 16:57:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C080720CCF for ; Thu, 19 Apr 2018 16:57:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B41A4212D8; Thu, 19 Apr 2018 16:57:49 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0997320CCF for ; Thu, 19 Apr 2018 16:57:49 +0000 (UTC) Received: from localhost ([::1]:60560 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f9CsW-0003D1-50 for patchwork-qemu-devel@patchwork.kernel.org; Thu, 19 Apr 2018 12:57:48 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60646) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f9Ch1-0002Hx-71 for qemu-devel@nongnu.org; Thu, 19 Apr 2018 12:45:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f9Cgz-0006HL-Bg for qemu-devel@nongnu.org; Thu, 19 Apr 2018 12:45:55 -0400 Received: from smtp03.citrix.com ([162.221.156.55]:53478) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f9Cgz-0006C9-0d for qemu-devel@nongnu.org; Thu, 19 Apr 2018 12:45:53 -0400 X-IronPort-AV: E=Sophos;i="5.48,469,1517875200"; d="scan'208";a="52102003" From: Ian Jackson To: Date: Thu, 19 Apr 2018 17:45:13 +0100 Message-ID: <1524156319-11465-11-git-send-email-ian.jackson@eu.citrix.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1524156319-11465-1-git-send-email-ian.jackson@eu.citrix.com> References: <1524156319-11465-1-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: 162.221.156.55 Subject: [Qemu-devel] [PATCH 10/16] 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 , Michael Tokarev , Ian Jackson , Markus Armbruster , Ross Lagerwall , Paolo Bonzini , Anthony PERARD , xen-devel@lists.xenproject.org Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP 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 Reviewed-by: Anthony PERARD CC: Paolo Bonzini CC: Markus Armbruster CC: Daniel P. Berrange CC: Michael Tokarev Reviewed-by: Markus Armbruster --- v7: Be much more explicit about legal combinations of user_{pwd,uid,gid}. Rely more on qemu_stroul being sane, dropping pointless pre-assignments of errno and lv. Retain optarg in error message about -runas argument. Rebase over introduction of error_report in change_process_uid. v6.1: Fix constness of qemu_strtoul end pointer parameter. v6: Use qemu_strtoul for the first strtoul. Use error_report rather than fprintf to print usage error message. Fix an error message which still referred to . rather than : 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. --- os-posix.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++--------- qemu-options.hx | 3 ++- 2 files changed, 67 insertions(+), 13 deletions(-) diff --git a/os-posix.c b/os-posix.c index 560db95..0f59566 100644 --- a/os-posix.c +++ b/os-posix.c @@ -41,7 +41,14 @@ #include #endif -static struct passwd *user_pwd; +/* + * Must set all three of these at once. + * Legal combinations are unset by name by uid + */ +static struct passwd *user_pwd; /* NULL non-NULL NULL */ +static uid_t user_uid = (uid_t)-1; /* -1 -1 >=0 */ +static gid_t user_gid = (gid_t)-1; /* -1 -1 >=0 */ + static const char *chroot_dir; static int daemonize; static int daemon_pipe; @@ -127,6 +134,33 @@ void os_set_proc_name(const char *s) #endif } + +static bool os_parse_runas_uid_gid(const char *optarg) +{ + unsigned long lv; + const char *ep; + uid_t got_uid; + gid_t got_gid; + int rc; + + rc = qemu_strtoul(optarg, &ep, 0, &lv); + got_uid = lv; /* overflow here is ID in C99 */ + if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) { + return false; + } + + 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_pwd = NULL; + user_uid = got_uid; + user_gid = got_gid; + return true; +} + /* * Parse OS specific command line options. * return 0 if option handled, -1 otherwise @@ -144,8 +178,13 @@ 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) { + user_uid = -1; + user_gid = -1; + } else if (!os_parse_runas_uid_gid(optarg)) { + error_report("User \"%s\" doesn't exist" + " (and is not :)", + optarg); exit(1); } break; @@ -165,18 +204,32 @@ 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) { - error_report("Failed to setgid(%d)", user_pwd->pw_gid); + assert((user_uid == (uid_t)-1) || user_pwd == NULL); + assert((user_uid == (uid_t)-1) == + (user_gid == (gid_t)-1)); + + 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) { + error_report("Failed to setgid(%d)", intended_gid); exit(1); } - if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) { - error_report("Failed to initgroups(\"%s\", %d)", - user_pwd->pw_name, user_pwd->pw_gid); - exit(1); + if (user_pwd) { + if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) { + error_report("Failed to initgroups(\"%s\", %d)", + user_pwd->pw_name, user_pwd->pw_gid); + exit(1); + } + } else { + if (setgroups(1, &user_gid) < 0) { + error_report("Failed to setgroups(1, [%d])", + user_gid); + exit(1); + } } - if (setuid(user_pwd->pw_uid) < 0) { - error_report("Failed to setuid(%d)", user_pwd->pw_uid); + if (setuid(intended_uid) < 0) { + error_report("Failed to setuid(%d)", intended_uid); exit(1); } if (setuid(0) != -1) { diff --git a/qemu-options.hx b/qemu-options.hx index ca4e412..5fbf966 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -3765,7 +3765,8 @@ 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