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/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <errno.h>
#include <error.h>
#include <getopt.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <private/android_filesystem_config.h>
void pwtoid(const char* tok, uid_t* uid, gid_t* gid) {
struct passwd* pw = getpwnam(tok);
if (pw) {
if (uid) *uid = pw->pw_uid;
if (gid) *gid = pw->pw_gid;
} else {
char* end;
errno = 0;
uid_t tmpid = strtoul(tok, &end, 10);
if (errno != 0 || end == tok) error(1, errno, "invalid uid/gid '%s'", tok);
if (uid) *uid = tmpid;
if (gid) *gid = tmpid;
}
}
void extract_uidgids(const char* uidgids, uid_t* uid, gid_t* gid, gid_t* gids, int* gids_count) {
char *clobberablegids;
char *nexttok;
char *tok;
int gids_found;
if (!uidgids || !*uidgids) {
*gid = *uid = 0;
*gids_count = 0;
return;
}
clobberablegids = strdup(uidgids);
strcpy(clobberablegids, uidgids);
nexttok = clobberablegids;
tok = strsep(&nexttok, ",");
pwtoid(tok, uid, gid);
tok = strsep(&nexttok, ",");
if (!tok) {
/* gid is already set above */
*gids_count = 0;
free(clobberablegids);
return;
}
pwtoid(tok, NULL, gid);
gids_found = 0;
while ((gids_found < *gids_count) && (tok = strsep(&nexttok, ","))) {
pwtoid(tok, NULL, gids);
gids_found++;
gids++;
}
if (nexttok && gids_found == *gids_count) {
fprintf(stderr, "too many group ids\n");
}
*gids_count = gids_found;
free(clobberablegids);
}
int main(int argc, char** argv) {
uid_t current_uid = getuid();
if (current_uid != AID_ROOT && current_uid != AID_SHELL) error(1, 0, "not allowed");
// Handle -h and --help.
++argv;
if (*argv && (strcmp(*argv, "--help") == 0 || strcmp(*argv, "-h") == 0)) {
fprintf(stderr,
"usage: su [WHO [COMMAND...]]\n"
"\n"
"Switch to WHO (default 'root') and run the given COMMAND (default sh).\n"
"\n"
"WHO is a comma-separated list of user, group, and supplementary groups\n"
"in that order.\n"
"\n");
return 0;
}
// The default user is root.
uid_t uid = 0;
gid_t gid = 0;
// If there are any arguments, the first argument is the uid/gid/supplementary groups.
if (*argv) {
gid_t gids[10];
int gids_count = sizeof(gids)/sizeof(gids[0]);
extract_uidgids(*argv, &uid, &gid, gids, &gids_count);
if (gids_count) {
if (setgroups(gids_count, gids)) {
error(1, errno, "setgroups failed");
}
}
++argv;
}
if (setgid(gid)) error(1, errno, "setgid failed");
if (setuid(uid)) error(1, errno, "setuid failed");
// Reset parts of the environment.
setenv("PATH", _PATH_DEFPATH, 1);
unsetenv("IFS");
struct passwd* pw = getpwuid(uid);
if (pw) {
setenv("LOGNAME", pw->pw_name, 1);
setenv("USER", pw->pw_name, 1);
} else {
unsetenv("LOGNAME");
unsetenv("USER");
}
// Set up the arguments for exec.
char* exec_args[argc + 1]; // Having too much space is fine.
size_t i = 0;
for (; *argv != NULL; ++i) {
exec_args[i] = *argv++;
}
// Default to the standard shell.
if (i == 0) exec_args[i++] = const_cast<char*>("/system/bin/sh");
exec_args[i] = NULL;
execvp(exec_args[0], exec_args);
error(1, errno, "failed to exec %s", exec_args[0]);
}
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