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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: chrootsh.c,v 1.3 1999/04/21 22:52:43 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 1.3 1999/04/21 22:52:43 mdw |
31 | * Added a pile of syslog stuff, so that admins can see what this thing is |
32 | * doing. |
33 | * |
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34 | * Revision 1.2 1999/04/21 09:07:55 mdw |
35 | * Fiddle with copyright messages so that they're correct. |
36 | * |
37 | * Revision 1.1.1.1 1999/04/20 00:19:04 mdw |
38 | * Initial versions. |
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39 | * |
40 | */ |
41 | |
42 | /*----- Header files ------------------------------------------------------*/ |
43 | |
44 | #include <errno.h> |
45 | #include <stdio.h> |
46 | #include <stdlib.h> |
47 | #include <string.h> |
48 | |
49 | #include <sys/types.h> |
50 | #include <unistd.h> |
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51 | #include <syslog.h> |
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52 | #include <pwd.h> |
53 | |
54 | extern char **environ; |
55 | |
56 | /*----- Main code ---------------------------------------------------------*/ |
57 | |
58 | #ifndef CHROOTSH_PATH |
59 | # define CHROOTSH_PATH "/usr/bin/chrootsh" |
60 | #endif |
61 | |
62 | static const char *quis = "chrootsh"; |
63 | |
64 | static void *xmalloc(size_t sz) |
65 | { |
66 | void *p = malloc(sz); |
67 | if (!p) { |
68 | fprintf(stderr, "%s: not enough memory\n", quis); |
69 | exit(EXIT_FAILURE); |
70 | } |
71 | return (p); |
72 | } |
73 | |
74 | static char *xstrdup(const char *p) |
75 | { |
76 | size_t sz = strlen(p) + 1; |
77 | char *q = xmalloc(sz); |
78 | memcpy(q, p, sz); |
79 | return (q); |
80 | } |
81 | |
82 | int main(int argc, char *argv[]) |
83 | { |
84 | struct passwd *pw; |
85 | uid_t me = getuid(); |
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86 | char *myname; |
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87 | char **env; |
88 | char **av; |
89 | |
90 | /* --- Resolve the program name --- */ |
91 | |
92 | { |
93 | char *p, *q; |
94 | p = argv[0]; |
95 | for (q = argv[0]; *q; q++) { |
96 | if (*q == '/') |
97 | p = q + 1; |
98 | } |
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99 | if (*p == '-') |
100 | p++; |
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101 | quis = p; |
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102 | openlog(quis, LOG_PID | LOG_NDELAY, LOG_DAEMON); |
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103 | } |
104 | |
105 | /* --- Check the user is meant to be chrooted --- */ |
106 | |
107 | pw = getpwuid(me); |
108 | if (!pw) { |
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109 | syslog(LOG_ERR, "executed by non-existant user (uid = %i)", (int)me); |
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110 | fprintf(stderr, "%s: you don't exist. Go away.\n", quis); |
111 | exit(EXIT_FAILURE); |
112 | } |
113 | if (strcmp(pw->pw_shell, CHROOTSH_PATH) != 0) { |
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114 | syslog(LOG_ERR, "executed by non-chrooted user `%s'", pw->pw_name); |
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115 | fprintf(stderr, "%s: you aren't a chrooted user\n", quis); |
116 | exit(EXIT_FAILURE); |
117 | } |
118 | endpwent(); |
119 | |
120 | /* --- Chroot the user --- */ |
121 | |
122 | { |
123 | char *p = xstrdup(pw->pw_dir); |
124 | char *q = strstr(p, "/./"); |
125 | if (q) |
126 | *q = 0; |
127 | |
128 | if (chdir(p) || chroot(p)) { |
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129 | syslog(LOG_ERR, "error entering chroot gaol: %m"); |
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130 | fprintf(stderr, "%s: couldn't call chroot: %s", quis, strerror(errno)); |
131 | exit(EXIT_FAILURE); |
132 | } |
133 | setuid(me); |
134 | free(p); |
135 | } |
136 | |
137 | /* --- Read the new password block --- */ |
138 | |
139 | { |
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140 | myname = xstrdup(pw->pw_name); |
141 | pw = getpwnam(myname); |
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142 | if (!pw) { |
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143 | syslog(LOG_ERR, |
144 | "configuration error: user `%s' not defined in gaol", myname); |
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145 | fprintf(stderr, "%s: you don't exist in the gaol\n", quis); |
146 | exit(EXIT_FAILURE); |
147 | } |
148 | endpwent(); |
149 | } |
150 | |
151 | /* --- Now fiddle with environment strings and suchlike --- */ |
152 | |
153 | { |
154 | size_t n; |
155 | for (n = 0; environ[n]; n++) |
156 | ; |
157 | env = xmalloc((n + 1) * sizeof(char *)); |
158 | |
159 | for (n = 0; environ[n]; n++) { |
160 | if (strncmp(environ[n], "HOME=", 5) == 0) { |
161 | char *p = xmalloc(6 + strlen(pw->pw_dir)); |
162 | sprintf(p, "HOME=%s", pw->pw_dir); |
163 | env[n] = p; |
164 | } else if (strncmp(environ[n], "SHELL=", 6) == 0) { |
165 | char *p = xmalloc(7 + strlen(pw->pw_shell)); |
166 | sprintf(p, "SHELL=%s", pw->pw_shell); |
167 | env[n] = p; |
168 | } else |
169 | env[n] = environ[n]; |
170 | } |
171 | env[n] = 0; |
172 | } |
173 | |
174 | /* --- Finally, sort the argument list --- */ |
175 | |
176 | { |
177 | char *p, *q; |
178 | int i; |
179 | |
180 | av = xmalloc((argc + 1) * sizeof(char *)); |
181 | p = pw->pw_shell; |
182 | for (q = p; *q; q++) { |
183 | if (*q == '/') |
184 | p = q + 1; |
185 | } |
186 | if (argv[0][0] == '-') { |
187 | q = xmalloc(2 + strlen(p)); |
188 | *q = '-'; |
189 | strcpy(q + 1, p); |
190 | av[0] = q; |
191 | } else |
192 | av[0] = p; |
193 | |
194 | for (i = 1; i <= argc; i++) |
195 | av[i] = argv[i]; |
196 | } |
197 | |
198 | /* --- Change directory (again) --- */ |
199 | |
200 | if (chdir(pw->pw_dir)) |
201 | fprintf(stderr, "No directory, logging in with HOME=/\n"); |
202 | |
203 | /* --- Run the real shell --- */ |
204 | |
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205 | syslog(LOG_INFO, "chroot user `%s' logged in ok", myname); |
206 | closelog(); |
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207 | execve(pw->pw_shell, av, env); |
208 | fprintf(stderr, "%s: couldn't exec `%s': %s", |
209 | quis, pw->pw_shell, strerror(errno)); |
210 | return (EXIT_FAILURE); |
211 | } |
212 | |
213 | /*----- That's all, folks -------------------------------------------------*/ |