2 Unix SMB/Netbios implementation.
5 Copyright (C) Andrew Tridgell 1992-1998
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 extern int DEBUGLEVEL;
26 static int initial_uid;
27 static int initial_gid;
29 /* what user is current? */
30 struct current_user current_user;
34 /****************************************************************************
35 initialise the uid routines
36 ****************************************************************************/
39 initial_uid = current_user.uid = geteuid();
40 initial_gid = current_user.gid = getegid();
42 if (initial_gid != 0 && initial_uid == 0)
52 initial_uid = geteuid();
53 initial_gid = getegid();
55 current_user.cnum = -1;
56 current_user.vuid = UID_FIELD_INVALID;
62 /****************************************************************************
63 become the specified uid
64 ****************************************************************************/
65 static BOOL become_uid(int uid)
70 if (uid == -1 || uid == 65535) {
71 DEBUG(1,("WARNING: using uid %d is a security risk\n",uid));
76 /* AIX 3 stuff - inspired by a code fragment in wu-ftpd */
77 /* MWW: This is all undocumented, of course. There's a patch to WU-ftpd
78 in the AIX FAQ which does the setpriv, then sets the gid stuff, then
79 sets uid. Since Samba separates setting the gid and setting the uid,
80 I've duplicated the setpriv code in become_gid. I've also made the
81 requisite changes to become_gid to match the WU-ftpd patch.
83 I believe we'll still get errors in the Samba logs. This setpriv
84 call is supposed to disable "trapdooring" on AIX - ie. normally
85 once a seteuid / setegid is done, the effective ID can't be set back
86 to what it was before. See the comments in become_root / unbecome_root.
87 I *think* that we may have to do something additional here to prevent
88 the "Can't set uid (AIX3)" messages, though - possibly change the
89 values of priv.pv_priv to keep the SET_PROC_DAC privilege, and
90 possibly SET_OBJ_DAC and SET_OBJ_STAT as well.
92 The pv_priv array is two longwords, and the constants in sys/priv.h
93 have values between 1 and 64, according to the comments in priv.h.
94 This strongly suggests a bit vector - but does BYPASS_DAC_WRITE
95 (#define'd to 1) mean 1<<0 or 1<<1? Unfortunately, nothing's
96 defined to 0 or 64, which would be a dead giveaway. Also, what's the
97 fullword-boundary endianness? That is, is pv_priv[0] the high or
98 the low 32 bits? Fortunately, the values used by "su" (see below)
99 don't make much sense if pv_priv[0] is the high bits. Also, based
100 on analysis of the values used by su, I concluded that, for example,
101 BYPASS_DAC_READ (defined to 2) is bit "2" counting from 1 - ie.
102 if (pv_priv[0] & (1 << (BYPASS_DAC_READ - 1))) then BYPASS_DAC_READ
103 is on. That's a bit odd, but it makes more sense than if the
104 privilege constants are meant to be taken as exponents of 2.
106 For analysis, I ran "su" as root under dbx, and stopped in setpriv.
107 The first argument to setpriv can be examined using
109 print $r3 (eg. "0x30009" = PRIV_SET|PRIV_MAXIMUM|PRIV_EFFECTIV)
111 the contents of the pv_priv array can be examined using
117 setpriv(PRIV_SET | PRIV_INHERITED | PRIV_BEQUEATH, {0,0})
118 setpriv(PRIV_SET | PRIV_EFFECTIVE | PRIV_MAXIMUM,
119 {0x02800006, 0x00040000})
120 0x02800006 = SET_PROC_AUDIT | SET_PROC_ENV |
121 BYPASS_DAC_EXEC | BYPASS_DAC_READ
122 0x00040000 = TPATH_CONFIG
123 setpriv(PRIV_SET | PRIV_EFFECTIVE, {0, 0})
127 Reduce inherited privileges to none, so the child doesn't inherit
129 Change su's privileges so it can execute the shell even if someone
130 has goofed up the permissions to it or to directories on the
131 search path; so it can set the process auditing characteristics
132 and privileged environment (stuff in /etc/security/environ with
133 the sysenv attribute); and so that it can set the trusted path
134 characteristics for this login.
135 Zap those privileges back off when we don't need them any more.
137 I'm guessing we want to keep SET_PROC_DAC in the current priv set,
138 but not in the inherited one. That is, set PRIV_INHERITED and
139 PRIV_BEQUEATH to 0. We also probably want to set PRIV_MAXIMUM and
140 PRIV_EFFECTIVE to only the privs we need, which at this point would
141 appear to be just SET_PROC_DAC. *Note*: setting PRIV_MAXIMUM
142 with any of the privilege sets higher than what you're trying to
143 set the maximum to will produce an EINVAL. For example, if we
144 try to set PRIV_MAXIMUM to SET_PROC_DAC *before* we reduce
145 PRIV_INHERITED and PRIV_BEQUEATH, it won't work. Zero out the
146 inherited privileges first.
148 Some experimentation with simple programs confirms that if we're
149 running with an EUID of 0 we can switch our UID/EUID back and
150 forth with setuidx - *unless* we call setpriv({0,0}, ...) first.
151 In other words, by default root has SET_PROC_DAT set, but we can
152 remove it from our privilege set. This is what we want to do for
153 child processes, I believe.
155 Also, calling setpriv(PRIV_SUB|PRIV_EFFECTIVE,...) with pv_priv[0]
156 set to SET_PROC_DAC (1 << (SET_PROC_DAC - 1)) will prevent an
157 EUID-root process from switching its EUID back with setuidx.
159 In other words, setuidx on AIX is *not* trapdoor. setuid is
160 trapdoor. We need a non-trapdoor setuid function, but we don't
161 want processes we fork to have access to it. Thus we use setuidx
162 but first we disable it for our children.
164 Note, however, that we can only increase our privileges (as we
165 do in the first call to setpriv) if we're EUID-root. If we
166 started out as root, and then switched to a non-root user ID,
167 that's OK; we've already set them. Just don't try to set them
170 Also, I suspect that after using setpriv / setuidx / etc. here in
171 the AIX-specific code we DON'T want to fall through to the code that
172 calls setuid, etc. However, I haven't noticed any more problems with
173 the code the way it is here.
180 if (setpriv(PRIV_SET|PRIV_INHERITED|PRIV_BEQUEATH,
181 &priv, sizeof(priv_t)) < 0) {
182 DEBUG(1, ("Can't set child privileges (AIX3): %s\n", strerror(errno)));
185 priv.pv_priv[0] = (1 << (SET_PROC_DAC - 1));
186 if (setpriv(PRIV_SET|PRIV_EFFECTIVE|PRIV_MAXIMUM,
187 &priv, sizeof(priv_t)) < 0) {
188 DEBUG(1, ("Can't set own privileges (AIX3): %s\n", strerror(errno)));
191 if (setuidx(ID_REAL|ID_EFFECTIVE, (uid_t)uid) < 0 ||
192 seteuid((uid_t)uid) < 0) {
193 DEBUG(1,("Can't set uid (AIX3)\n"));
199 if (setresuid(-1,uid,-1) != 0)
200 #elif defined(USE_SETFS)
201 if (setfsuid(uid) != 0)
203 if ((seteuid(uid) != 0) &&
207 DEBUG(0,("Couldn't set uid %d currently set to (%d,%d)\n",
208 uid,getuid(), geteuid()));
210 DEBUG(0,("Looks like your OS doesn't like high uid values - try using a different account\n"));
214 if (((uid == -1) || (uid == 65535)) && geteuid() != uid) {
215 DEBUG(0,("Invalid uid -1. perhaps you have a account with uid 65535?\n"));
219 current_user.uid = uid;
225 /****************************************************************************
226 become the specified gid
227 ****************************************************************************/
228 static BOOL become_gid(int gid)
230 if (initial_uid != 0)
233 if (gid == -1 || gid == 65535) {
234 DEBUG(1,("WARNING: using gid %d is a security risk\n",gid));
239 /* MWW: See comment above in become_uid. */
244 if (setpriv(PRIV_SET|PRIV_INHERITED|PRIV_EFFECTIVE|PRIV_BEQUEATH,
245 &priv, sizeof(priv_t)) < 0) {
246 DEBUG(1, ("Can't set privilege (AIX3)\n"));
248 if (setgidx(ID_REAL|ID_EFFECTIVE, (gid_t)gid) < 0 ||
249 setegid((gid_t)gid) < 0) {
250 DEBUG(1,("Can't set gid (AIX3)\n"));
256 if (setresgid(-1,gid,-1) != 0)
257 #elif defined(USE_SETFS)
258 if (setfsgid(gid) != 0)
260 if (setgid(gid) != 0)
263 DEBUG(0,("Couldn't set gid %d currently set to (%d,%d)\n",
264 gid,getgid(),getegid()));
266 DEBUG(0,("Looks like your OS doesn't like high gid values - try using a different account\n"));
270 current_user.gid = gid;
276 /****************************************************************************
277 become the specified uid and gid
278 ****************************************************************************/
279 static BOOL become_id(int uid,int gid)
281 return(become_gid(gid) && become_uid(uid));
284 /****************************************************************************
285 become the guest user
286 ****************************************************************************/
287 BOOL become_guest(void)
290 static struct passwd *pass=NULL;
292 if (initial_uid != 0)
296 pass = Get_Pwnam(lp_guestaccount(-1),True);
297 if (!pass) return(False);
300 /* MWW: From AIX FAQ patch to WU-ftpd: call initgroups before setting IDs */
301 initgroups(pass->pw_name, (gid_t)pass->pw_gid);
303 ret = become_id(pass->pw_uid,pass->pw_gid);
306 DEBUG(1,("Failed to become guest. Invalid guest account?\n"));
308 current_user.cnum = -2;
309 current_user.vuid = UID_FIELD_INVALID;
314 /*******************************************************************
315 check if a username is OK
316 ********************************************************************/
317 static BOOL check_user_ok(connection_struct *conn, user_struct *vuser,int snum)
320 for (i=0;i<conn->uid_cache.entries;i++)
321 if (conn->uid_cache.list[i] == vuser->uid) return(True);
323 if (!user_ok(vuser->name,snum)) return(False);
325 i = conn->uid_cache.entries % UID_CACHE_SIZE;
326 conn->uid_cache.list[i] = vuser->uid;
328 if (conn->uid_cache.entries < UID_CACHE_SIZE)
329 conn->uid_cache.entries++;
335 /****************************************************************************
336 become the user of a connection number
337 ****************************************************************************/
338 BOOL become_user(connection_struct *conn, int cnum, uint16 vuid)
340 user_struct *vuser = get_valid_user_struct(vuid);
344 if ((current_user.cnum == cnum) && (vuser != 0) && (current_user.vuid == vuid) &&
345 (current_user.uid == vuser->uid)) {
346 DEBUG(4,("Skipping become_user - already user\n"));
352 if (!(VALID_CNUM(cnum) && conn->open)) {
353 DEBUG(2,("Connection %d not open\n",cnum));
357 snum = conn->service;
359 if((vuser != NULL) && !check_user_ok(conn, vuser, snum))
362 if (conn->force_user ||
363 lp_security() == SEC_SHARE ||
364 !(vuser) || (vuser->guest)
369 current_user.groups = conn->groups;
370 current_user.igroups = conn->igroups;
371 current_user.ngroups = conn->ngroups;
376 DEBUG(2,("Invalid vuid used %d\n",vuid));
380 if(!*lp_force_group(snum))
384 current_user.ngroups = vuser->n_groups;
385 current_user.groups = vuser->groups;
386 current_user.igroups = vuser->igroups;
389 if (initial_uid == 0)
391 if (!become_gid(gid)) return(False);
394 if (!(VALID_CNUM(cnum) && conn->ipc)) {
395 /* groups stuff added by ih/wreu */
396 if (current_user.ngroups > 0)
397 if (setgroups(current_user.ngroups,current_user.groups)<0)
398 DEBUG(0,("setgroups call failed!\n"));
402 if (!conn->admin_user && !become_uid(uid))
406 current_user.cnum = cnum;
407 current_user.vuid = vuid;
409 DEBUG(5,("become_user uid=(%d,%d) gid=(%d,%d)\n",
410 getuid(),geteuid(),getgid(),getegid()));
415 /****************************************************************************
416 unbecome the user of a connection number
417 ****************************************************************************/
418 BOOL unbecome_user(void )
420 if (current_user.cnum == -1)
425 if (initial_uid == 0)
428 setresuid(-1,getuid(),-1);
429 setresgid(-1,getgid(),-1);
430 #elif defined(USE_SETFS)
431 setfsuid(initial_uid);
432 setfsgid(initial_gid);
434 if (seteuid(initial_uid) != 0)
440 if (initial_uid == 0)
441 DEBUG(2,("Running with no EID\n"));
442 initial_uid = getuid();
443 initial_gid = getgid();
445 if (geteuid() != initial_uid)
447 DEBUG(0,("Warning: You appear to have a trapdoor uid system\n"));
448 initial_uid = geteuid();
450 if (getegid() != initial_gid)
452 DEBUG(0,("Warning: You appear to have a trapdoor gid system\n"));
453 initial_gid = getegid();
457 current_user.uid = initial_uid;
458 current_user.gid = initial_gid;
460 if (ChDir(OriginalDir) != 0)
461 DEBUG(0,("%s chdir(%s) failed in unbecome_user\n",
462 timestring(),OriginalDir));
464 DEBUG(5,("unbecome_user now uid=(%d,%d) gid=(%d,%d)\n",
465 getuid(),geteuid(),getgid(),getegid()));
467 current_user.cnum = -1;
468 current_user.vuid = UID_FIELD_INVALID;
474 /****************************************************************************
475 This is a utility function of smbrun(). It must be called only from
476 the child as it may leave the caller in a privilaged state.
477 ****************************************************************************/
478 static BOOL setup_stdout_file(char *outfile,BOOL shared)
482 mode_t mode = S_IWUSR|S_IRUSR|S_IRGRP|S_IROTH;
483 int flags = O_RDWR|O_CREAT|O_TRUNC|O_EXCL;
488 /* become root - unprivilaged users can't delete these files */
498 if(stat(outfile, &st) == 0) {
499 /* Check we're not deleting a device file. */
500 if(st.st_mode & S_IFREG)
505 /* now create the file */
506 fd = open(outfile,flags,mode);
508 if (fd == -1) return False;
511 if (dup2(fd,1) != 0) {
512 DEBUG(2,("Failed to create stdout file descriptor\n"));
522 /****************************************************************************
523 run a command being careful about uid/gid handling and putting the output in
524 outfile (or discard it if outfile is NULL).
526 if shared is True then ensure the file will be writeable by all users
527 but created such that its owned by root. This overcomes a security hole.
529 if shared is not set then open the file with O_EXCL set
530 ****************************************************************************/
531 int smbrun(char *cmd,char *outfile,BOOL shared)
534 int uid = current_user.uid;
535 int gid = current_user.gid;
540 char *path = lp_smbrun();
542 /* in the old method we use system() to execute smbrun which then
543 executes the command (using system() again!). This involves lots
544 of shell launches and is very slow. It also suffers from a
545 potential security hole */
546 if (!file_exist(path,NULL))
548 DEBUG(0,("SMBRUN ERROR: Can't find %s. Installation problem?\n",path));
552 slprintf(syscmd,sizeof(syscmd)-1,"%s %d %d \"(%s 2>&1) > %s\"",
554 outfile?outfile:"/dev/null");
556 DEBUG(5,("smbrun - running %s ",syscmd));
557 ret = system(syscmd);
558 DEBUG(5,("gave %d\n",ret));
561 /* in this newer method we will exec /bin/sh with the correct
562 arguments, after first setting stdout to point at the file */
566 /* the parent just waits for the child to exit */
567 if (sys_waitpid(pid,&status,0) != pid) {
568 DEBUG(2,("waitpid(%d) : %s\n",pid,strerror(errno)));
575 /* we are in the child. we exec /bin/sh to do the work for us. we
576 don't directly exec the command we want because it may be a
577 pipeline or anything else the config file specifies */
579 /* point our stdout at the file we want output to go into */
580 if (outfile && !setup_stdout_file(outfile,shared)) {
584 /* now completely lose our privilages. This is a fairly paranoid
585 way of doing it, but it does work on all systems that I know of */
589 setresgid(gid,gid,gid);
590 setresuid(uid,uid,uid);
600 if (getuid() != uid || geteuid() != uid ||
601 getgid() != gid || getegid() != gid) {
602 /* we failed to lose our privilages - do not execute the command */
603 exit(81); /* we can't print stuff at this stage, instead use exit codes
607 /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
608 2 point to /dev/null from the startup code */
609 for (fd=3;fd<256;fd++) close(fd);
611 execl("/bin/sh","sh","-c",cmd,NULL);
619 static struct current_user current_user_saved;
620 static int become_root_depth;
621 static pstring become_root_dir;
623 /****************************************************************************
624 This is used when we need to do a privilaged operation (such as mucking
625 with share mode files) and temporarily need root access to do it. This
626 call should always be paired with an unbecome_root() call immediately
629 Set save_dir if you also need to save/restore the CWD
630 ****************************************************************************/
631 void become_root(BOOL save_dir)
633 if (become_root_depth) {
634 DEBUG(0,("ERROR: become root depth is non zero\n"));
637 GetWd(become_root_dir);
639 current_user_saved = current_user;
640 become_root_depth = 1;
646 /****************************************************************************
647 When the privilaged operation is over call this
649 Set save_dir if you also need to save/restore the CWD
650 ****************************************************************************/
651 void unbecome_root(BOOL restore_dir)
653 if (become_root_depth != 1) {
654 DEBUG(0,("ERROR: unbecome root depth is %d\n",
658 /* we might have done a become_user() while running as root,
659 if we have then become root again in order to become
661 if (current_user.uid != 0) {
665 /* restore our gid first */
666 if (!become_gid(current_user_saved.gid)) {
667 DEBUG(0,("ERROR: Failed to restore gid\n"));
668 exit_server("Failed to restore gid");
672 if (current_user_saved.ngroups > 0) {
673 if (setgroups(current_user_saved.ngroups,
674 current_user_saved.groups)<0)
675 DEBUG(0,("ERROR: setgroups call failed!\n"));
679 /* now restore our uid */
680 if (!become_uid(current_user_saved.uid)) {
681 DEBUG(0,("ERROR: Failed to restore uid\n"));
682 exit_server("Failed to restore uid");
686 ChDir(become_root_dir);
688 current_user = current_user_saved;
690 become_root_depth = 0;