su.c revision d198c429f50e1cad98e989d6212508adb45d7919 
1/*
2**
3** Copyright 2008, The Android Open Source Project
4**
5** Licensed under the Apache License, Version 2.0 (the "License");
6** you may not use this file except in compliance with the License.
7** You may obtain a copy of the License at
8**
9**     http://www.apache.org/licenses/LICENSE-2.0
10**
11** Unless required by applicable law or agreed to in writing, software
12** distributed under the License is distributed on an "AS IS" BASIS,
13** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14** See the License for the specific language governing permissions and
15** limitations under the License.
16*/
17
18#define LOG_TAG "su"
19
20#include <stdio.h>
21#include <stdlib.h>
22#include <string.h>
23#include <sys/types.h>
24#include <dirent.h>
25#include <errno.h>
26
27#include <unistd.h>
28#include <time.h>
29
30#include <pwd.h>
31
32#include <private/android_filesystem_config.h>
33
34
35void pwtoid(const char *tok, uid_t *uid, gid_t *gid)
36{
37    struct passwd *pw;
38    pw = getpwnam(tok);
39    if (pw) {
40        if (uid) *uid = pw->pw_uid;
41        if (gid) *gid = pw->pw_gid;
42    } else {
43        uid_t tmpid = atoi(tok);
44        if (uid) *uid = tmpid;
45        if (gid) *gid = tmpid;
46    }
47}
48
49void extract_uidgids(const char *uidgids, uid_t *uid, gid_t *gid, gid_t *gids,
50                     int *gids_count)
51{
52    char *clobberablegids;
53    char *nexttok;
54    char *tok;
55    int gids_found;
56
57    if (!uidgids || !*uidgids) {
58        *gid = *uid = 0;
59        *gids_count = 0;
60        return;
61    }
62    clobberablegids = strdup(uidgids);
63    strcpy(clobberablegids, uidgids);
64    nexttok = clobberablegids;
65    tok = strsep(&nexttok, ",");
66    pwtoid(tok, uid, gid);
67    tok = strsep(&nexttok, ",");
68    if (!tok) {
69        /* gid is already set above */
70        *gids_count = 0;
71        free(clobberablegids);
72        return;
73    }
74    pwtoid(tok, NULL, gid);
75    gids_found = 0;
76    while ((gids_found < *gids_count) && (tok = strsep(&nexttok, ","))) {
77        pwtoid(tok, NULL, gids);
78        gids_found++;
79        gids++;
80    }
81    if (nexttok && gids_found == *gids_count) {
82        fprintf(stderr, "too many group ids\n");
83    }
84    *gids_count = gids_found;
85    free(clobberablegids);
86}
87
88/*
89 * SU can be given a specific command to exec. UID _must_ be
90 * specified for this (ie argc => 3).
91 *
92 * Usage:
93 *   su 1000
94 *   su 1000 ls -l
95 *  or
96 *   su [uid[,gid[,group1]...] [cmd]]
97 *  E.g.
98 *  su 1000,shell,net_bw_acct,net_bw_stats id
99 * will return
100 *  uid=1000(system) gid=2000(shell) groups=3006(net_bw_stats),3007(net_bw_acct)
101 */
102int main(int argc, char **argv)
103{
104    struct passwd *pw;
105    uid_t uid, myuid;
106    gid_t gid, gids[10];
107
108    /* Until we have something better, only root and the shell can use su. */
109    myuid = getuid();
110    if (myuid != AID_ROOT && myuid != AID_SHELL) {
111        fprintf(stderr,"su: uid %d not allowed to su\n", myuid);
112        return 1;
113    }
114
115    if(argc < 2) {
116        uid = gid = 0;
117    } else {
118        int gids_count = sizeof(gids)/sizeof(gids[0]);
119        extract_uidgids(argv[1], &uid, &gid, gids, &gids_count);
120        if(gids_count) {
121            if(setgroups(gids_count, gids)) {
122                fprintf(stderr, "su: failed to set groups\n");
123                return 1;
124            }
125        }
126    }
127
128    if(setgid(gid) || setuid(uid)) {
129        fprintf(stderr,"su: permission denied\n");
130        return 1;
131    }
132
133    /* User specified command for exec. */
134    if (argc == 3 ) {
135        if (execlp(argv[2], argv[2], NULL) < 0) {
136            int saved_errno = errno;
137            fprintf(stderr, "su: exec failed for %s Error:%s\n", argv[2],
138                    strerror(errno));
139            return -saved_errno;
140        }
141    } else if (argc > 3) {
142        /* Copy the rest of the args from main. */
143        char *exec_args[argc - 1];
144        memset(exec_args, 0, sizeof(exec_args));
145        memcpy(exec_args, &argv[2], sizeof(exec_args));
146        if (execvp(argv[2], exec_args) < 0) {
147            int saved_errno = errno;
148            fprintf(stderr, "su: exec failed for %s Error:%s\n", argv[2],
149                    strerror(errno));
150            return -saved_errno;
151        }
152    }
153
154    /* Default exec shell. */
155    execlp("/system/bin/sh", "sh", NULL);
156
157    fprintf(stderr, "su: exec failed\n");
158    return 1;
159}
160