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