From mboxrd@z Thu Jan 1 00:00:00 1970 From: Markus Armbruster Subject: Re: [Qemu-devel] [PATCH 08/12] os-posix: Provide new -runas : facility Date: Fri, 13 Apr 2018 17:51:42 +0200 Message-ID: <874lkfxfxt.fsf@dusky.pond.sub.org> References: <1520535787-6223-1-git-send-email-ian.jackson@eu.citrix.com> <1520535787-6223-9-git-send-email-ian.jackson@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from all-amaz-eas1.inumbo.com ([34.197.232.57]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1f70zJ-0000vQ-Gd for xen-devel@lists.xenproject.org; Fri, 13 Apr 2018 15:51:45 +0000 In-Reply-To: <1520535787-6223-9-git-send-email-ian.jackson@eu.citrix.com> (Ian Jackson's message of "Thu, 8 Mar 2018 19:03:03 +0000") List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" To: Ian Jackson Cc: Juergen Gross , Stefano Stabellini , 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SQoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRl dmVsIG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVucHJvamVjdC5vcmcKaHR0cHM6Ly9s aXN0cy54ZW5wcm9qZWN0Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL3hlbi1kZXZlbA== From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37696) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f70zJ-0000Ff-M6 for qemu-devel@nongnu.org; Fri, 13 Apr 2018 11:51:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f70zI-000141-BJ for qemu-devel@nongnu.org; Fri, 13 Apr 2018 11:51:45 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38332 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f70zI-00012U-5K for qemu-devel@nongnu.org; Fri, 13 Apr 2018 11:51:44 -0400 From: Markus Armbruster References: <1520535787-6223-1-git-send-email-ian.jackson@eu.citrix.com> <1520535787-6223-9-git-send-email-ian.jackson@eu.citrix.com> Date: Fri, 13 Apr 2018 17:51:42 +0200 In-Reply-To: <1520535787-6223-9-git-send-email-ian.jackson@eu.citrix.com> (Ian Jackson's message of "Thu, 8 Mar 2018 19:03:03 +0000") Message-ID: <874lkfxfxt.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH 08/12] os-posix: Provide new -runas : facility List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Ian Jackson Cc: qemu-devel@nongnu.org, Juergen Gross , Stefano Stabellini , Ross Lagerwall , Paolo Bonzini , Anthony PERARD , xen-devel@lists.xenproject.org Ian Jackson writes: > 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 > --- > 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. > v2: Coding style fixes. > > Signed-off-by: Ian Jackson > --- > os-posix.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++---------- > qemu-options.hx | 3 ++- > 2 files changed, 53 insertions(+), 12 deletions(-) > > diff --git a/os-posix.c b/os-posix.c > index b9c2343..214f8fb 100644 > --- a/os-posix.c > +++ b/os-posix.c > @@ -42,6 +42,8 @@ > #endif > > static struct passwd *user_pwd; > +static uid_t user_uid = (uid_t)-1; > +static gid_t user_gid = (gid_t)-1; As we'll see below, @user_pwd->pw_uid, @user_pwd_pw_gid take precedence over @user_uid, @user_gid. Awkward. > static const char *chroot_dir; > static int daemonize; > static int daemon_pipe; > @@ -127,6 +129,34 @@ 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; > + > + errno = 0; > + 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; > + } > + > + lv = 0; Either zero lv before both qemu_strtoul() or neither one. > + 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 > @@ -144,8 +174,8 @@ 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)) { > + error_report("User doesn't exist (and is not :)"); The error message no longer includes the offending value. Intentional? Note for later: @user_uid and @user_gid get set only when @user_pwd remains null. > exit(1); > } > break; > @@ -165,18 +195,28 @@ 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); error_report(), please. More of the same below. > 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) { This function is the only user of @user_pwd, @user_uid, @user_gid. Have you considered replacing global @user_pwd by @user_uid, @user_gid and @user_name? --runas with numeric uid and gid would leave @user_name null. > diff --git a/qemu-options.hx b/qemu-options.hx > index 6585058..211f2a6 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -3763,7 +3763,8 @@ 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