android su源码

/***** Copyright 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.*/#define LOG_TAG "su"#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/types.h>#include <dirent.h>#include <errno.h>#include <unistd.h>#include <time.h>#include <pwd.h>#include <private/android_filesystem_config.h>/* * SU can be given a specific command to exec. UID _must_ be * specified for this (ie argc => 3). * * Usage: * su 1000 * su 1000 ls -l */int main(int argc, char **argv){    struct passwd *pw;    int uid, gid, myuid;    if(argc < 2) {        uid = gid = 0;    } else {        pw = getpwnam(argv[1]);        if(pw == 0) {            uid = gid = atoi(argv[1]);        } else {            uid = pw->pw_uid;            gid = pw->pw_gid;        }    }    /* Until we have something better, only root and the shell can use su. */    myuid = getuid();    if (myuid != AID_ROOT && myuid != AID_SHELL) {        fprintf(stderr,"su: uid %d not allowed to su\n", myuid);        return 1;    }        if(setgid(gid) || setuid(uid)) {        fprintf(stderr,"su: permission denied\n");        return 1;    }    /* User specified command for exec. */    if (argc == 3 ) {        if (execlp(argv[2], argv[2], NULL) < 0) {            fprintf(stderr, "su: exec failed for %s Error:%s\n", argv[2],                    strerror(errno));            return -errno;        }    } else if (argc > 3) {        /* Copy the rest of the args from main. */        char *exec_args[argc - 1];        memset(exec_args, 0, sizeof(exec_args));        memcpy(exec_args, &argv[2], sizeof(exec_args));        if (execvp(argv[2], exec_args) < 0) {            fprintf(stderr, "su: exec failed for %s Error:%s\n", argv[2],                    strerror(errno));            return -errno;        }    }    /* Default exec shell. */    execlp("/system/bin/sh", "sh", NULL);    fprintf(stderr, "su: exec failed\n");    return 1;}
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