77 lines
1.5 KiB
C
77 lines
1.5 KiB
C
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// For privilege separation
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#include <clone3.h>
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#include <linux/wait.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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// This program
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#include <stdint.h>
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#include <stdio.h>
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uint64_t fib(uint64_t i) {
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uint64_t a = 0;
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uint64_t b = 1;
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for (; i > 0; i--) {
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uint64_t old_b = b;
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b = b + a;
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a = old_b;
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}
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return a;
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}
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int real_main(int argc, char **argv);
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int main(int argc, char **argv) {
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int pid_fd;
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struct clone_args cl_args = {
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.flags = CLONE_NEWIPC | CLONE_NEWNET | CLONE_NEWNS | CLONE_NEWPID |
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CLONE_NEWUSER | CLONE_NEWUTS | CLONE_PIDFD,
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.pidfd = (uint64_t)&pid_fd,
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.child_tid = (uint64_t)NULL,
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.parent_tid = (uint64_t)NULL,
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.exit_signal = SIGCHLD,
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.stack = (uint64_t)NULL,
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.stack_size = 0,
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.tls = (uint64_t)NULL,
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};
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pid_t child = clone3(&cl_args);
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if (child < 0) {
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perror("clone3");
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exit(-1);
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} else if (child == 0) {
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int code = real_main(argc, argv);
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exit(code);
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} else {
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siginfo_t status;
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if (waitid(P_PIDFD, pid_fd, &status, WEXITED) == -1) {
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perror("waitid");
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return -1;
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}
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exit(status.si_status);
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}
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}
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int real_main(int argc, char **argv) {
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if (argc != 2) {
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fprintf(stderr, "expected 1 argument\n");
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return -1;
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}
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uint64_t i = 0;
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if (sscanf(argv[1], "%lu", &i) != 1) {
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fprintf(stderr, "sscanf failed\n");
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return -1;
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}
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uint64_t fib_result = fib(i);
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printf("fib(%lu) = %lu\n", i, fib_result);
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return 0;
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}
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