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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: chrootsh.c,v 1.4 1999/04/22 00:30:27 mdw Exp $ |
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4 | * |
5 | * Chroot gaol shell |
6 | * |
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7 | * (c) 1999 Mark Wooding |
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8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
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12 | * This program is free software; you can redistribute it and/or modify |
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13 | * it under the terms of the GNU General Public License as published by |
14 | * the Free Software Foundation; either version 2 of the License, or |
15 | * (at your option) any later version. |
16 | * |
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17 | * This program is distributed in the hope that it will be useful, |
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18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU General Public License for more details. |
21 | * |
22 | * You should have received a copy of the GNU General Public License |
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23 | * along with this program; if not, write to the Free Software Foundation, |
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24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
25 | */ |
26 | |
27 | /*----- Revision history --------------------------------------------------* |
28 | * |
29 | * $Log: chrootsh.c,v $ |
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30 | * Revision 1.4 1999/04/22 00:30:27 mdw |
31 | * Miscellanous tidying and security fixes. Lots of thanks due to Clive |
32 | * Jones. |
33 | * |
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34 | * Revision 1.3 1999/04/21 22:52:43 mdw |
35 | * Added a pile of syslog stuff, so that admins can see what this thing is |
36 | * doing. |
37 | * |
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38 | * Revision 1.2 1999/04/21 09:07:55 mdw |
39 | * Fiddle with copyright messages so that they're correct. |
40 | * |
41 | * Revision 1.1.1.1 1999/04/20 00:19:04 mdw |
42 | * Initial versions. |
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43 | * |
44 | */ |
45 | |
46 | /*----- Header files ------------------------------------------------------*/ |
47 | |
48 | #include <errno.h> |
49 | #include <stdio.h> |
50 | #include <stdlib.h> |
51 | #include <string.h> |
52 | |
53 | #include <sys/types.h> |
54 | #include <unistd.h> |
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55 | #include <syslog.h> |
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56 | #include <pwd.h> |
57 | |
58 | extern char **environ; |
59 | |
60 | /*----- Main code ---------------------------------------------------------*/ |
61 | |
62 | #ifndef CHROOTSH_PATH |
63 | # define CHROOTSH_PATH "/usr/bin/chrootsh" |
64 | #endif |
65 | |
66 | static const char *quis = "chrootsh"; |
67 | |
68 | static void *xmalloc(size_t sz) |
69 | { |
70 | void *p = malloc(sz); |
71 | if (!p) { |
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72 | setuid(getuid()); |
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73 | fprintf(stderr, "%s: not enough memory\n", quis); |
74 | exit(EXIT_FAILURE); |
75 | } |
76 | return (p); |
77 | } |
78 | |
79 | static char *xstrdup(const char *p) |
80 | { |
81 | size_t sz = strlen(p) + 1; |
82 | char *q = xmalloc(sz); |
83 | memcpy(q, p, sz); |
84 | return (q); |
85 | } |
86 | |
87 | int main(int argc, char *argv[]) |
88 | { |
89 | struct passwd *pw; |
90 | uid_t me = getuid(); |
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91 | char *myname; |
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92 | char **env; |
93 | char **av; |
94 | |
95 | /* --- Resolve the program name --- */ |
96 | |
97 | { |
98 | char *p, *q; |
99 | p = argv[0]; |
100 | for (q = argv[0]; *q; q++) { |
101 | if (*q == '/') |
102 | p = q + 1; |
103 | } |
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104 | if (*p == '-') |
105 | p++; |
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106 | quis = p; |
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107 | openlog(quis, LOG_PID | LOG_NDELAY, LOG_DAEMON); |
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108 | } |
109 | |
110 | /* --- Check the user is meant to be chrooted --- */ |
111 | |
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112 | { |
113 | uid_t eff = geteuid(); |
114 | |
115 | setreuid(eff, me); |
116 | pw = getpwuid(me); |
117 | if (!pw) { |
118 | syslog(LOG_ERR, "executed by non-existant user (uid = %i)", (int)me); |
119 | fprintf(stderr, "%s: you don't exist. Go away.\n", quis); |
120 | exit(EXIT_FAILURE); |
121 | } |
122 | if (strcmp(pw->pw_shell, CHROOTSH_PATH) != 0) { |
123 | syslog(LOG_ERR, "executed by non-chrooted user `%s'", pw->pw_name); |
124 | fprintf(stderr, "%s: you aren't a chrooted user\n", quis); |
125 | exit(EXIT_FAILURE); |
126 | } |
127 | endpwent(); |
128 | setreuid(me, eff); |
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129 | } |
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130 | |
131 | /* --- Chroot the user --- */ |
132 | |
133 | { |
134 | char *p = xstrdup(pw->pw_dir); |
135 | char *q = strstr(p, "/./"); |
136 | if (q) |
137 | *q = 0; |
138 | |
139 | if (chdir(p) || chroot(p)) { |
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140 | int e = errno; |
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141 | syslog(LOG_ERR, "error entering chroot gaol: %m"); |
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142 | setuid(me); |
143 | fprintf(stderr, "%s: couldn't call chroot: %s\n", quis, strerror(e)); |
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144 | exit(EXIT_FAILURE); |
145 | } |
146 | setuid(me); |
147 | free(p); |
148 | } |
149 | |
150 | /* --- Read the new password block --- */ |
151 | |
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152 | myname = xstrdup(pw->pw_name); |
153 | pw = getpwnam(myname); |
154 | if (!pw) { |
155 | syslog(LOG_ERR, |
156 | "configuration error: user `%s' not defined in gaol", myname); |
157 | fprintf(stderr, "%s: you don't exist in the gaol\n", quis); |
158 | exit(EXIT_FAILURE); |
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159 | } |
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160 | endpwent(); |
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161 | |
162 | /* --- Now fiddle with environment strings and suchlike --- */ |
163 | |
164 | { |
165 | size_t n; |
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166 | char **homevar = 0; |
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167 | for (n = 0; environ[n]; n++) |
168 | ; |
169 | env = xmalloc((n + 1) * sizeof(char *)); |
170 | |
171 | for (n = 0; environ[n]; n++) { |
172 | if (strncmp(environ[n], "HOME=", 5) == 0) { |
173 | char *p = xmalloc(6 + strlen(pw->pw_dir)); |
174 | sprintf(p, "HOME=%s", pw->pw_dir); |
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175 | homevar = &env[n]; |
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176 | env[n] = p; |
177 | } else if (strncmp(environ[n], "SHELL=", 6) == 0) { |
178 | char *p = xmalloc(7 + strlen(pw->pw_shell)); |
179 | sprintf(p, "SHELL=%s", pw->pw_shell); |
180 | env[n] = p; |
181 | } else |
182 | env[n] = environ[n]; |
183 | } |
184 | env[n] = 0; |
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185 | |
186 | /* --- Change directory (again) --- */ |
187 | |
188 | if (chdir(pw->pw_dir)) { |
189 | if (homevar) { |
190 | free(*homevar); |
191 | *homevar = "HOME=/"; |
192 | } |
193 | fprintf(stderr, "No directory, logging in with HOME=/\n"); |
194 | } |
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195 | } |
196 | |
197 | /* --- Finally, sort the argument list --- */ |
198 | |
199 | { |
200 | char *p, *q; |
201 | int i; |
202 | |
203 | av = xmalloc((argc + 1) * sizeof(char *)); |
204 | p = pw->pw_shell; |
205 | for (q = p; *q; q++) { |
206 | if (*q == '/') |
207 | p = q + 1; |
208 | } |
209 | if (argv[0][0] == '-') { |
210 | q = xmalloc(2 + strlen(p)); |
211 | *q = '-'; |
212 | strcpy(q + 1, p); |
213 | av[0] = q; |
214 | } else |
215 | av[0] = p; |
216 | |
217 | for (i = 1; i <= argc; i++) |
218 | av[i] = argv[i]; |
219 | } |
220 | |
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221 | /* --- Run the real shell --- */ |
222 | |
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223 | syslog(LOG_INFO, "chroot user `%s' logged in ok", myname); |
224 | closelog(); |
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225 | execve(pw->pw_shell, av, env); |
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226 | fprintf(stderr, "%s: couldn't exec `%s': %s\n", |
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227 | quis, pw->pw_shell, strerror(errno)); |
228 | return (EXIT_FAILURE); |
229 | } |
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230 | |
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231 | /*----- That's all, folks -------------------------------------------------*/ |