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1 | /* This file is part of the IPCop Firewall.\r |
2 | *\r | |
3 | * IPCop is free software; you can redistribute it and/or modify\r | |
4 | * it under the terms of the GNU General Public License as published by\r | |
5 | * the Free Software Foundation; either version 2 of the License, or\r | |
6 | * (at your option) any later version.\r | |
7 | *\r | |
8 | * IPCop is distributed in the hope that it will be useful,\r | |
9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of\r | |
10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the\r | |
11 | * GNU General Public License for more details.\r | |
12 | *\r | |
13 | * You should have received a copy of the GNU General Public License\r | |
14 | * along with IPCop; if not, write to the Free Software\r | |
15 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA\r | |
16 | *\r | |
17 | * Copyright (C) 2003-04-22 Robert Kerr <rkerr@go.to>\r | |
18 | *\r | |
19 | * $Id: setuid.c,v 1.2.2.1 2005/11/18 14:51:43 franck78 Exp $\r | |
20 | *\r | |
21 | */\r | |
22 | \r | |
23 | #include <stdio.h>\r | |
24 | #include <string.h>\r | |
25 | #include <errno.h>\r | |
26 | #include <unistd.h>\r | |
27 | #include <stdlib.h>\r | |
28 | #include <sys/types.h>\r | |
29 | #include <limits.h>\r | |
30 | #include <sys/time.h>\r | |
31 | #include <sys/resource.h>\r | |
32 | #include <sys/stat.h>\r | |
33 | #include <fcntl.h>\r | |
34 | #include <grp.h>\r | |
35 | #include <signal.h>\r | |
36 | #include <sys/wait.h>\r | |
37 | #include <glob.h>\r | |
38 | #include "setuid.h"\r | |
39 | \r | |
40 | #ifndef OPEN_MAX\r | |
41 | #define OPEN_MAX 256\r | |
42 | #endif\r | |
43 | \r | |
44 | /* Trusted environment for executing commands */\r | |
45 | char * trusted_env[4]={\r | |
46 | "PATH=/usr/bin:/usr/sbin:/sbin:/bin",\r | |
47 | "SHELL=/bin/sh",\r | |
48 | "TERM=dumb",\r | |
49 | NULL};\r | |
50 | \r | |
51 | /* Spawns a child process that uses /bin/sh to interpret a command.\r | |
52 | * This is much the same in use and purpose as system(), yet as it uses execve\r | |
53 | * to pass a trusted environment it's immune to attacks based upon changing\r | |
54 | * IFS, ENV, BASH_ENV and other such variables.\r | |
55 | * Note this does NOT guard against any other attacks, inparticular you MUST\r | |
56 | * validate the command you are passing. If the command is formed from user\r | |
57 | * input be sure to check this input is what you expect. Nasty things can\r | |
58 | * happen if a user can inject ; or `` into your command for example */\r | |
59 | int safe_system(char* command)\r | |
60 | {\r | |
61 | return system_core( command, 0, 0, "safe_system" );\r | |
62 | }\r | |
63 | \r | |
64 | /* Much like safe_system but lets you specify a non-root uid and gid to run\r | |
65 | * the command as */\r | |
66 | int unpriv_system(char* command, uid_t uid, gid_t gid)\r | |
67 | {\r | |
68 | return system_core(command, uid, gid, "unpriv_system" );\r | |
69 | }\r | |
70 | \r | |
71 | int system_core(char* command, uid_t uid, gid_t gid, char *error)\r | |
72 | {\r | |
73 | int pid, status;\r | |
74 | \r | |
75 | if(!command)\r | |
76 | return 1;\r | |
77 | \r | |
78 | switch( pid = fork() )\r | |
79 | {\r | |
80 | case -1:\r | |
81 | return -1;\r | |
82 | case 0: /* child */\r | |
83 | {\r | |
84 | char * argv[4];\r | |
85 | if (gid && setgid(gid)) \r | |
86 | {\r | |
87 | fprintf(stderr, "%s: ", error);\r | |
88 | perror("Couldn't setgid");\r | |
89 | exit(127);\r | |
90 | }\r | |
91 | if (uid && setuid(uid))\r | |
92 | {\r | |
93 | fprintf(stderr, "%s: ", error);\r | |
94 | perror("Couldn't setuid");\r | |
95 | exit(127);\r | |
96 | }\r | |
97 | argv[0] = "sh";\r | |
98 | argv[1] = "-c";\r | |
99 | argv[2] = command;\r | |
100 | argv[3] = NULL;\r | |
101 | execve("/bin/sh", argv, trusted_env);\r | |
102 | fprintf(stderr, "%s: ", error);\r | |
103 | perror("execve failed");\r | |
104 | exit(127);\r | |
105 | }\r | |
106 | default: /* parent */\r | |
107 | do {\r | |
108 | if( waitpid(pid, &status, 0) == -1 ) {\r | |
109 | if( errno != EINTR )\r | |
110 | return -1;\r | |
111 | } else\r | |
112 | return status;\r | |
113 | } while (1);\r | |
114 | }\r | |
115 | \r | |
116 | }\r | |
117 | \r | |
118 | /* BSD style safe strcat; from the secure programming cookbook */\r | |
119 | size_t strlcat(char *dst, const char *src, size_t len) {\r | |
120 | char *dstptr = dst;\r | |
121 | size_t dstlen, tocopy = len;\r | |
122 | const char *srcptr = src;\r | |
123 | \r | |
124 | while (tocopy-- && *dstptr) dstptr++;\r | |
125 | dstlen = dstptr - dst;\r | |
126 | if (!(tocopy = len - dstlen)) return (dstlen + strlen(src));\r | |
127 | while (*srcptr) {\r | |
128 | if (tocopy != 1) {\r | |
129 | *dstptr++ = *srcptr;\r | |
130 | tocopy--;\r | |
131 | }\r | |
132 | srcptr++;\r | |
133 | }\r | |
134 | *dstptr = 0;\r | |
135 | \r | |
136 | return (dstlen + (srcptr - src));\r | |
137 | }\r | |
138 | \r | |
139 | /* General routine to initialise a setuid root program, and put the\r | |
140 | * environment in a known state. Returns 1 on success, if initsetuid() returns\r | |
141 | * 0 then you should exit(1) immediately, DON'T attempt to recover from the\r | |
142 | * error */\r | |
143 | int initsetuid(void)\r | |
144 | {\r | |
145 | int fds,i;\r | |
146 | struct stat st;\r | |
147 | struct rlimit rlim;\r | |
148 | \r | |
149 | /* Prevent signal tricks by ignoring all except SIGKILL and SIGCHILD */\r | |
150 | for( i = 0; i < NSIG; i++ ) {\r | |
151 | if( i != SIGKILL && i != SIGCHLD )\r | |
152 | signal(i, SIG_IGN);\r | |
153 | }\r | |
154 | \r | |
155 | /* dump all non-standard file descriptors (a full descriptor table could\r | |
156 | * lead to DoS by preventing us opening files) */\r | |
157 | if ((fds = getdtablesize()) == -1) fds = OPEN_MAX;\r | |
158 | for( i = 3; i < fds; i++ ) close(i);\r | |
159 | \r | |
160 | /* check stdin, stdout & stderr are open before going any further */\r | |
161 | for( i = 0; i < 3; i++ )\r | |
162 | if( fstat(i, &st) == -1 && ((errno != EBADF) || (close(i), open("/dev/null", O_RDWR, 0)) != i ))\r | |
163 | return 0;\r | |
164 | \r | |
165 | /* disable core dumps in case we're processing sensitive information */\r | |
166 | rlim.rlim_cur = rlim.rlim_max = 0;\r | |
167 | if(setrlimit(RLIMIT_CORE, &rlim))\r | |
168 | { perror("Couldn't disable core dumps"); return 0; }\r | |
169 | \r | |
170 | /* drop any supplementary groups, set uid & gid to root */\r | |
171 | if (setgroups(0, NULL)) { perror("Couldn't clear group list"); return 0; }\r | |
172 | if (setgid(0)) { perror("Couldn't setgid(0)"); return 0; }\r | |
173 | if (setuid(0)) { perror("Couldn't setuid(0)"); return 0; }\r | |
174 | \r | |
175 | return 1;\r | |
176 | }\r | |
177 | \r | |
178 | /* check whether a file exists */\r | |
179 | int file_exists(const char *fname) {\r | |
180 | struct stat st;\r | |
181 | stat(fname, &st);\r | |
182 | return S_ISREG(st.st_mode) ? 1 : 0;\r | |
183 | }\r | |
184 | \r | |
185 | /* check whether a file exists. fname is wildcard eg: file_exists (/tmp/foo*) */\r | |
186 | int file_exists_w(const char *fname)\r | |
187 | {\r | |
188 | /* do a quick check first */\r | |
189 | struct stat st;\r | |
190 | stat(fname, &st);\r | |
191 | if (S_ISREG(st.st_mode))\r | |
192 | return 1;\r | |
193 | \r | |
194 | /* check for possible wild cards in name */\r | |
195 | glob_t globbuf;\r | |
196 | int retval=0;\r | |
197 | if (glob(fname, GLOB_ERR, NULL, &globbuf)==0) {\r | |
198 | if (globbuf.gl_pathc>0) {\r | |
199 | retval=1;\r | |
200 | }\r | |
201 | }\r | |
202 | globfree(&globbuf);\r | |
203 | return retval;\r | |
204 | }\r |