Date: Sun, 17 Feb 2013 03:41:28 GMT From: Danny Warren <danny@dannywarren.com> To: freebsd-gnats-submit@FreeBSD.org Subject: ports/176203: [patch] devel/gamin: Drop privileges to effective user and group Message-ID: <201302170341.r1H3fSB4034750@red.freebsd.org> Resent-Message-ID: <201302170350.r1H3o0j2086275@freefall.freebsd.org>
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>Number: 176203 >Category: ports >Synopsis: [patch] devel/gamin: Drop privileges to effective user and group >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-ports-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: change-request >Submitter-Id: current-users >Arrival-Date: Sun Feb 17 03:50:00 UTC 2013 >Closed-Date: >Last-Modified: >Originator: Danny Warren >Release: 9.1-RELEASE >Organization: >Environment: 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec 4 09:23:10 UTC 2012 root@farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64 >Description: The base release of gamin uses the current real uid to determine the location of the socket and during the security routines. It also forks off a copy of "gam_server" as the current real uid as well. This breaks gamin functionality with any application that uses effective an uid/gid for privilege separation, such as samba. Samba runs as root, but always sets the effective uid/gid to that of the connecting user. Since gamin is only aware of the real uid, it always creates a root-owned gamin socket that the effective user can't touch (gamin's own security checks refuse it). For a description of the problem with samba, see: https://bugzilla.samba.org/show_bug.cgi?id=9558 A similar bug has already been filed against gamin, but has gone unanswered by gamin's maintainer for years: https://bugzilla.gnome.org/show_bug.cgi?id=345244 This patch adds a "RUN_AS_EUID" definition which will enable the following behavior at compile time: * use the effective uid to determine the name of user socket to create * use the effective uid when verifying ownership for security * runs setuid/setgid to change to the effective uid/gid after forking but before starting a copy of gam_server when run via libgamin * refuses to escalate privileges to root during setuid/setgid, only dropping privileges (though it would be easy to change that if someone needed it, but I'm erring on the side of caution here since setuid is involved) I'm not sure which effect this will have on other applications that use gamin, so I leave it up to you to determine the right behavior for the Makefile. Right now it is provided as a "Drop privileges to effective user" but it may make sense to have it always on by default for security reasons. It works great on my system so far, though. This is the first time I have seen samba's file alteration monitoring work on freebsd. (NOTE: My patch to gam_api.c includes the existing patches, I wasn't sure whether to give you something you can just slap in place that would match svn or provide a patch-of-a-patch) >How-To-Repeat: >Fix: Patch attached with submission follows: --- Makefile.orig 2013-02-16 19:09:52.507178348 -0800 +++ Makefile 2013-02-16 16:18:30.230098850 -0800 @@ -27,9 +27,10 @@ GNU_CONFIGURE= yes .if !defined(GAMIN_SLAVE) -OPTIONS_DEFINE= GAM_POLLER LIBINOTIFY +OPTIONS_DEFINE= GAM_POLLER LIBINOTIFY RUN_AS_EUID GAM_POLLER_DESC=Use gamin's poller instead of kqueue's LIBINOTIFY_DESC=Use libinotify as the FAM backend +RUN_AS_EUID_DESC=Drop privileges to effective user .endif .include <bsd.port.options.mk> @@ -48,6 +49,10 @@ .endif .endif +.if ${PORT_OPTIONS:MRUN_AS_EUID} +CPPFLAGS+= -DRUN_AS_EUID=1 +.endif + post-patch: @${REINPLACE_CMD} "s|/etc|${PREFIX}/etc|g" ${WRKSRC}/server/gam_conf.c --- libgamin/gam_api.c.orig 2007-08-27 03:21:03.000000000 -0700 +++ libgamin/gam_api.c 2013-02-16 15:51:11.927100135 -0800 @@ -14,6 +14,7 @@ #include <sys/socket.h> #include <sys/un.h> #include <sys/uio.h> +#include <string.h> #include "fam.h" #include "gam_protocol.h" #include "gam_data.h" @@ -117,7 +118,11 @@ if (user_name[0] != 0) return (user_name); +#ifdef RUN_AS_EUID + pw = getpwuid(geteuid()); +#else pw = getpwuid(getuid()); +#endif if (pw != NULL) { strncpy(user_name, pw->pw_name, 99); @@ -224,7 +229,11 @@ free(dir); return(0); } +#ifdef RUN_AS_EUID + if (st.st_uid != geteuid()) { +#else if (st.st_uid != getuid()) { +#endif gam_error(DEBUG_INFO, "Socket directory %s has different owner\n", dir); @@ -301,7 +310,11 @@ if (ret < 0) return(0); +#ifdef RUN_AS_EUID + if (st.st_uid != geteuid()) { +#else if (st.st_uid != getuid()) { +#endif gam_error(DEBUG_INFO, "Socket %s has different owner\n", path); @@ -428,10 +441,10 @@ { char data[2] = { 0, 0 }; int written; -#if defined(HAVE_CMSGCRED) && !defined(LOCAL_CREDS) - struct { +#if defined(HAVE_CMSGCRED) && (!defined(LOCAL_CREDS) || defined(__FreeBSD__)) + union { struct cmsghdr hdr; - struct cmsgcred cred; + char cred[CMSG_SPACE (sizeof (struct cmsgcred))]; } cmsg; struct iovec iov; struct msghdr msg; @@ -443,16 +456,16 @@ msg.msg_iov = &iov; msg.msg_iovlen = 1; - msg.msg_control = &cmsg; - msg.msg_controllen = sizeof (cmsg); + msg.msg_control = (caddr_t) &cmsg; + msg.msg_controllen = CMSG_SPACE (sizeof (struct cmsgcred)); memset (&cmsg, 0, sizeof (cmsg)); - cmsg.hdr.cmsg_len = sizeof (cmsg); + cmsg.hdr.cmsg_len = CMSG_LEN (sizeof (struct cmsgcred)); cmsg.hdr.cmsg_level = SOL_SOCKET; cmsg.hdr.cmsg_type = SCM_CREDS; #endif retry: -#if defined(HAVE_CMSGCRED) && !defined(LOCAL_CREDS) +#if defined(HAVE_CMSGCRED) && (!defined(LOCAL_CREDS) || defined(__FreeBSD__)) written = sendmsg(fd, &msg, 0); #else written = write(fd, &data[0], 1); @@ -654,15 +667,20 @@ gid_t c_gid; #ifdef HAVE_CMSGCRED - struct { + struct cmsgcred *cred; + union { struct cmsghdr hdr; - struct cmsgcred cred; + char cred[CMSG_SPACE (sizeof (struct cmsgcred))]; } cmsg; #endif +#ifdef RUN_AS_EUID + s_uid = geteuid(); +#else s_uid = getuid(); +#endif -#if defined(LOCAL_CREDS) && defined(HAVE_CMSGCRED) +#if defined(LOCAL_CREDS) && defined(HAVE_CMSGCRED) && !defined(__FreeBSD__) /* Set the socket to receive credentials on the next message */ { int on = 1; @@ -683,8 +701,8 @@ #ifdef HAVE_CMSGCRED memset(&cmsg, 0, sizeof(cmsg)); - msg.msg_control = &cmsg; - msg.msg_controllen = sizeof(cmsg); + msg.msg_control = (caddr_t) &cmsg; + msg.msg_controllen = CMSG_SPACE (sizeof (struct cmsgcred)); #endif retry: @@ -701,7 +719,7 @@ goto failed; } #ifdef HAVE_CMSGCRED - if (cmsg.hdr.cmsg_len < sizeof(cmsg) || cmsg.hdr.cmsg_type != SCM_CREDS) { + if (cmsg.hdr.cmsg_len < CMSG_LEN (sizeof (struct cmsgcred)) || cmsg.hdr.cmsg_type != SCM_CREDS) { GAM_DEBUG(DEBUG_INFO, "Message from recvmsg() was not SCM_CREDS\n"); goto failed; @@ -727,9 +745,10 @@ goto failed; } #elif defined(HAVE_CMSGCRED) - c_pid = cmsg.cred.cmcred_pid; - c_uid = cmsg.cred.cmcred_euid; - c_gid = cmsg.cred.cmcred_groups[0]; + cred = (struct cmsgcred *) CMSG_DATA (&cmsg); + c_pid = cred->cmcred_pid; + c_uid = cred->cmcred_euid; + c_gid = cred->cmcred_groups[0]; #else /* !SO_PEERCRED && !HAVE_CMSGCRED */ GAM_DEBUG(DEBUG_INFO, "Socket credentials not supported on this OS\n"); @@ -1288,14 +1307,17 @@ // FIXME: drop and reacquire lock while blocked? gamin_data_lock(conn); - if (!gamin_data_event_ready(conn)) { + while ((ret = gamin_data_event_ready(conn)) == 0) { if (gamin_read_data(conn, fc->fd, 1) < 0) { gamin_try_reconnect(conn, fc->fd); FAMErrno = FAM_CONNECT; return (-1); } } - ret = gamin_data_read_event(conn, fe); + + if (ret > 0) + ret = gamin_data_read_event(conn, fe); + gamin_data_unlock(conn); if (ret < 0) { --- libgamin/gam_fork.c.orig 2007-07-04 06:36:48.000000000 -0700 +++ libgamin/gam_fork.c 2013-02-16 19:02:46.360093751 -0800 @@ -42,6 +42,82 @@ return NULL; } +#ifdef RUN_AS_EUID +/** + * gamin_drop_privileges + * + * Attempt to drop privileges to the effective uid and gid before + * forking a copy of the gamin server + * + * Return 0 in case of success or -1 in case of detected error. + */ +int +gamin_drop_privileges(void) +{ + GAM_DEBUG(DEBUG_INFO, "Dropping privileges to effective user and group\n"); + + /* get the current real user and group */ + int from_uid = getuid(); + int from_gid = getgid(); + + /* get the effective user and group */ + int to_uid = geteuid(); + int to_gid = getegid(); + + /* make sure we were able to get the user and group values */ + if ( from_uid == -1 || to_uid == -1 || from_gid == -1 || to_gid == -1 ) { + gam_error(DEBUG_INFO, "failed to get user or group info, unable to drop privileges\n"); + return(-1); + } + + /* refuse to run setuid if it would escalate privileges */ + if ( from_uid != 0 && to_uid == 0 ) + { + gam_error(DEBUG_INFO, "refusing to escalate user privileges from=%d to=%d\n", from_uid, to_uid); + return(-1); + } + + /* refuse to run setgid if it would escalate privileges */ + if ( from_gid != 0 && to_gid == 0 ) + { + gam_error(DEBUG_INFO, "refusing to escalate group privileges from=%d to=%d\n", from_gid, to_gid); + return(-1); + } + + /* run setuid to drop privileges to the effective user */ + if ( from_uid != to_uid ) { + GAM_DEBUG(DEBUG_INFO, "Attempting setuid from=%d to=%d\n", from_uid, to_uid); + + /* run setuid and check for errors */ + if (setuid(to_uid) == -1) { + gam_error(DEBUG_INFO, "failed to run setuid from=%d to=%d\n", from_uid, to_uid); + return(-1); + } + } + else { + GAM_DEBUG(DEBUG_INFO, "Already running as effective user, skipping setuid\n"); + } + + /* run setgid to drop privileges to the effective group */ + if ( from_gid != to_gid ) { + GAM_DEBUG(DEBUG_INFO, "Attempting setgid from=%d to=%d\n", from_gid, to_gid); + + /* run setuid and check for errors */ + if (setgid(to_gid) == -1) { + gam_error(DEBUG_INFO, "failed to run setgid from=%d to=%d\n", from_uid, to_uid); + return(-1); + } + } + else { + GAM_DEBUG(DEBUG_INFO, "Already running as effective group, skipping setgid\n"); + } + + GAM_DEBUG(DEBUG_INFO, "Succeeded in dropping privileges from %d:%d to %d:%d\n", from_uid, from_gid, to_uid, to_gid); + + return(0); +} +#endif + /** * gamin_fork_server: * @fam_client_id: the client ID string to use @@ -71,6 +147,14 @@ long open_max; long i; +#ifdef RUN_AS_EUID + /* Drop privileges to the current uid/gid and return on failure */ + if(gamin_drop_privileges() == -1) + { + return(-1); + } +#endif + /* don't hold open fd opened from the client of the library */ open_max = sysconf (_SC_OPEN_MAX); for (i = 0; i < open_max; i++) --- libgamin/gam_api.c.orig 2007-08-27 03:21:03.000000000 -0700 +++ libgamin/gam_api.c 2013-02-16 15:51:11.927100135 -0800 @@ -14,6 +14,7 @@ #include <sys/socket.h> #include <sys/un.h> #include <sys/uio.h> +#include <string.h> #include "fam.h" #include "gam_protocol.h" #include "gam_data.h" @@ -117,7 +118,11 @@ if (user_name[0] != 0) return (user_name); +#ifdef RUN_AS_EUID + pw = getpwuid(geteuid()); +#else pw = getpwuid(getuid()); +#endif if (pw != NULL) { strncpy(user_name, pw->pw_name, 99); @@ -224,7 +229,11 @@ free(dir); return(0); } +#ifdef RUN_AS_EUID + if (st.st_uid != geteuid()) { +#else if (st.st_uid != getuid()) { +#endif gam_error(DEBUG_INFO, "Socket directory %s has different owner\n", dir); @@ -301,7 +310,11 @@ if (ret < 0) return(0); +#ifdef RUN_AS_EUID + if (st.st_uid != geteuid()) { +#else if (st.st_uid != getuid()) { +#endif gam_error(DEBUG_INFO, "Socket %s has different owner\n", path); @@ -428,10 +441,10 @@ { char data[2] = { 0, 0 }; int written; -#if defined(HAVE_CMSGCRED) && !defined(LOCAL_CREDS) - struct { +#if defined(HAVE_CMSGCRED) && (!defined(LOCAL_CREDS) || defined(__FreeBSD__)) + union { struct cmsghdr hdr; - struct cmsgcred cred; + char cred[CMSG_SPACE (sizeof (struct cmsgcred))]; } cmsg; struct iovec iov; struct msghdr msg; @@ -443,16 +456,16 @@ msg.msg_iov = &iov; msg.msg_iovlen = 1; - msg.msg_control = &cmsg; - msg.msg_controllen = sizeof (cmsg); + msg.msg_control = (caddr_t) &cmsg; + msg.msg_controllen = CMSG_SPACE (sizeof (struct cmsgcred)); memset (&cmsg, 0, sizeof (cmsg)); - cmsg.hdr.cmsg_len = sizeof (cmsg); + cmsg.hdr.cmsg_len = CMSG_LEN (sizeof (struct cmsgcred)); cmsg.hdr.cmsg_level = SOL_SOCKET; cmsg.hdr.cmsg_type = SCM_CREDS; #endif retry: -#if defined(HAVE_CMSGCRED) && !defined(LOCAL_CREDS) +#if defined(HAVE_CMSGCRED) && (!defined(LOCAL_CREDS) || defined(__FreeBSD__)) written = sendmsg(fd, &msg, 0); #else written = write(fd, &data[0], 1); @@ -654,15 +667,20 @@ gid_t c_gid; #ifdef HAVE_CMSGCRED - struct { + struct cmsgcred *cred; + union { struct cmsghdr hdr; - struct cmsgcred cred; + char cred[CMSG_SPACE (sizeof (struct cmsgcred))]; } cmsg; #endif +#ifdef RUN_AS_EUID + s_uid = geteuid(); +#else s_uid = getuid(); +#endif -#if defined(LOCAL_CREDS) && defined(HAVE_CMSGCRED) +#if defined(LOCAL_CREDS) && defined(HAVE_CMSGCRED) && !defined(__FreeBSD__) /* Set the socket to receive credentials on the next message */ { int on = 1; @@ -683,8 +701,8 @@ #ifdef HAVE_CMSGCRED memset(&cmsg, 0, sizeof(cmsg)); - msg.msg_control = &cmsg; - msg.msg_controllen = sizeof(cmsg); + msg.msg_control = (caddr_t) &cmsg; + msg.msg_controllen = CMSG_SPACE (sizeof (struct cmsgcred)); #endif retry: @@ -701,7 +719,7 @@ goto failed; } #ifdef HAVE_CMSGCRED - if (cmsg.hdr.cmsg_len < sizeof(cmsg) || cmsg.hdr.cmsg_type != SCM_CREDS) { + if (cmsg.hdr.cmsg_len < CMSG_LEN (sizeof (struct cmsgcred)) || cmsg.hdr.cmsg_type != SCM_CREDS) { GAM_DEBUG(DEBUG_INFO, "Message from recvmsg() was not SCM_CREDS\n"); goto failed; @@ -727,9 +745,10 @@ goto failed; } #elif defined(HAVE_CMSGCRED) - c_pid = cmsg.cred.cmcred_pid; - c_uid = cmsg.cred.cmcred_euid; - c_gid = cmsg.cred.cmcred_groups[0]; + cred = (struct cmsgcred *) CMSG_DATA (&cmsg); + c_pid = cred->cmcred_pid; + c_uid = cred->cmcred_euid; + c_gid = cred->cmcred_groups[0]; #else /* !SO_PEERCRED && !HAVE_CMSGCRED */ GAM_DEBUG(DEBUG_INFO, "Socket credentials not supported on this OS\n"); @@ -1288,14 +1307,17 @@ // FIXME: drop and reacquire lock while blocked? gamin_data_lock(conn); - if (!gamin_data_event_ready(conn)) { + while ((ret = gamin_data_event_ready(conn)) == 0) { if (gamin_read_data(conn, fc->fd, 1) < 0) { gamin_try_reconnect(conn, fc->fd); FAMErrno = FAM_CONNECT; return (-1); } } - ret = gamin_data_read_event(conn, fe); + + if (ret > 0) + ret = gamin_data_read_event(conn, fe); + gamin_data_unlock(conn); if (ret < 0) { >Release-Note: >Audit-Trail: >Unformatted:
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