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