2 * really.c - program for gaining privilege
4 * Copyright (C) 1992-3 Ian Jackson <ian@davenant.greenend.org.uk>
6 * This is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation; either version 3,
9 * or (at your option) any later version.
11 * This is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public
17 * License along with this file; if not, consult the Free Software
18 * Foundation's website at www.fsf.org, or the GNU Project website at
28 #include <sys/types.h>
33 void usagemessage(void) {
34 if (fputs("usage: really [<really-option> ...] [--]"
35 " [<command> [<argument/option> ...]]\n"
36 "really-options specifying the user:\n"
37 " if no options given, set the uid to 0;\n"
38 " -u|--user <username> also sets their default group list\n"
39 " -i|--useronly <username> } set the uid\n"
40 " -I|--uidonly <uid> } but inherits the group list\n"
41 "really-options specifying the group:\n"
42 " -z|--groupsclear only groups specified are to be used\n"
43 " -g|--group <groupname> } add this to\n"
44 " -G|--gid <gid> } the group list\n"
45 "other really-options:\n"
46 " -h|--help display this message\n"
47 " -R|--chroot <dir> chroot (but *not* chdir - danger!)\n",
48 stderr) == EOF) { perror("write usage"); exit(-1); }
51 static const char *opt_user, *opt_useronly, *opt_chroot;
52 static int opt_groupsclear= 0, opt_ngids= 0, opt_uidonly= -1;
53 static int opt_gids[512];
55 static void af_uidonly(const struct cmdinfo *cip, const char *value) {
59 ul= strtoul(value,&ep,10);
60 if (*ep) { fprintf(stderr,"bad uid `%s'\n",value); exit(-1); }
64 static void af_group(const struct cmdinfo *cip, const char *value) {
67 if (opt_ngids >= sizeof(opt_gids)/sizeof(opt_gids[0]))
68 badusage("too many groups specified");
70 if (!gr) { fprintf(stderr,"unknown group `%s'\n",value); exit(-1); }
71 opt_gids[opt_ngids++]= gr->gr_gid;
74 static void af_gid(const struct cmdinfo *cip, const char *value) {
78 if (opt_ngids >= sizeof(opt_gids)/sizeof(opt_gids[0]))
79 badusage("too many gids specified");
80 ul= strtoul(value,&ep,0);
81 if ((*ep) || (uid_t)ul != ul || ul>INT_MAX) badusage("bad gid `%s'",value);
82 opt_gids[opt_ngids++]= ul;
85 static void af_help(const struct cmdinfo *cip, const char *value) {
86 usagemessage(); exit(0);
89 static const struct cmdinfo cmdinfos[]= {
90 { "user", 'u', 1, 0, &opt_user, 0, },
91 { "useronly", 'i', 1, 0, &opt_useronly, 0 },
92 { "uidonly", 'I', 1, 0, 0, af_uidonly },
93 { "groupsclear", 'z', 0, &opt_groupsclear, 0, 0, 1 },
94 { "group", 'g', 1, 0, 0, af_group },
95 { "gid", 'G', 1, 0, 0, af_gid },
96 { "chroot", 'R', 1, 0, &opt_chroot, 0 },
97 { "help", 'h', 0, 0, 0, af_help },
101 #ifdef REALLY_CHECK_FILE
102 static int checkroot(void) {
104 r= access(REALLY_CHECK_FILE,W_OK);
109 #ifdef REALLY_CHECK_GID
110 static int checkroot(void) {
114 r= getgid(); if (r==REALLY_CHECK_GID) return 0;
115 if (r<0) { perror("getgid check"); exit(-1); }
116 r= getgroups(sizeof(groups)/sizeof(groups[0]),groups);
117 if (r<0) { perror("getgroups check"); exit(-1); }
119 if (groups[i] == REALLY_CHECK_GID) return 0;
123 #ifdef REALLY_CHECK_NONE
124 static int checkroot(void) {
129 int main(int argc, const char *const *argv) {
130 struct passwd *pw= 0;
132 int i, j, ngroups, ngroups_in, maingid, orgmaingid, mainuid, orgmainuid, r;
135 orgmainuid= getuid();
136 if (orgmainuid && checkroot()) { perror("sorry"); exit(-1); }
137 myopt(&argv,cmdinfos);
139 if (opt_groupsclear && !opt_ngids)
140 badusage("-z|--groupsclear must be accompanied by some groups");
141 if (opt_user && (opt_useronly || opt_uidonly!=-1))
142 badusage("-u|--user may not be used with -i|--useronly or -I|--uidonly");
143 if (opt_user && opt_groupsclear)
144 badusage("-u|--user may not be used with -z|--groupsclear");
145 if (opt_uidonly != -1 && (uid_t)opt_uidonly != opt_uidonly)
146 badusage("-I|--uidonly value %d is out of range for a uid",opt_uidonly);
148 if (!opt_user && !opt_useronly && opt_uidonly==-1 && !opt_ngids) {
151 if (opt_user || opt_useronly) {
152 cp= opt_user ? opt_user : opt_useronly;
154 if (!pw) { fprintf(stderr,"unknown user `%s'\n",cp); exit(-1); }
155 opt_uidonly= pw->pw_uid;
158 if (chroot(opt_chroot)) { perror("chroot failed"); exit(-1); }
160 orgmaingid= getgid();
161 if (orgmaingid<0) { perror("getgid failed"); exit(-1); }
163 r= initgroups(opt_user,pw->pw_gid);
164 if (r) { perror("initgroups failed"); exit(-1); }
169 if (opt_groupsclear) {
171 if (opt_ngids > sizeof(groups)/sizeof(groups[0])) {
172 fputs("too many groups to set\n",stderr);
176 ngroups= getgroups(0,0);
177 if (ngroups<0) { perror("getgroups(0,0) failed"); exit(-1); }
178 if (ngroups+opt_ngids > sizeof(groups)/sizeof(groups[0])) {
179 fputs("too many groups already set for total to fit\n",stderr);
182 ngroups= getgroups(ngroups,groups);
183 if (ngroups<0) { perror("getgroups failed"); exit(-1); }
186 maingid= opt_gids[0];
188 if (opt_ngids || opt_groupsclear) {
189 ngroups_in= ngroups; ngroups= 0;
190 for (i=0; i<ngroups_in; i++) {
191 for (j=0; j<ngroups && groups[j] != groups[i]; j++);
192 if (j<ngroups) continue;
193 groups[ngroups++]= groups[i];
195 for (i=0; i<opt_ngids; i++) {
196 for (j=0; j<ngroups && groups[j] != opt_gids[i]; j++);
197 if (j<ngroups) continue;
198 groups[ngroups++]= opt_gids[i];
200 r= setgroups(ngroups,groups);
201 if (r) { perror("setgroups failed"); exit(-1); }
204 r= setgid(maingid); if (r) { perror("setgid failed"); exit(-1); }
205 r= setgid(maingid); if (r) { perror("2nd setgid failed"); exit(-1); }
207 if (opt_uidonly != -1) {
208 mainuid= opt_uidonly;
212 r= setuid(mainuid); if (r) { perror("setuid failed"); exit(-1); }
213 r= setuid(mainuid); if (r) { perror("2nd setuid failed"); exit(-1); }
215 r= seteuid(0); if (r>=0) { fputs("could seteuid 0",stderr); exit(-1); }
216 if (errno != EPERM) {
217 perror("unexpected failure mode for seteuid 0"); exit(-1);
220 r= getuid(); if (r<0) { perror("getuid failed"); exit(-1); }
221 if (r != mainuid) { fputs("getuid mismatch",stderr); exit(-1); }
222 r= geteuid(); if (r<0) { perror("geteuid failed"); exit(-1); }
223 if (r != mainuid) { fputs("geteuid mismatch",stderr); exit(-1); }
225 for (i=0; i<ngroups && maingid != groups[i]; i++);
226 if (i>=ngroups && maingid != orgmaingid) {
227 r= setgid(orgmaingid);
228 if (r>=0) { fputs("could setgid back",stderr); exit(-1); }
229 if (errno != EPERM) {
230 perror("unexpected failure mode for setgid back"); exit(-1);
233 r= getgid(); if (r<0) { perror("getgid failed"); exit(-1); }
234 if (r != maingid) { fputs("getgid mismatch",stderr); exit(-1); }
235 r= getegid(); if (r<0) { perror("getegid failed"); exit(-1); }
236 if (r != maingid) { fputs("getegid mismatch",stderr); exit(-1); }
241 execlp(cp,cp,"-i",(const char*)0);
243 execvp(argv[0],(char**)argv);
245 perror("exec failed");